| Author | Message | ||
| matt (Matthewmag)
New member Username: Matthewmag Post Number: 17 Registered: 11-2002 |
I have now updated the list of standard jet settings at http://www.catalanvilla.com/ferrari/jets There's still plenty of gaps to fill if anyone can help. Thanks for the info on your Weber book Paul. Likewise Bill for the explanation on your advance curve. Like you say, it would be nice if there were more break points. | ||
| Paul Newman (Newman)
Intermediate Member Username: Newman Post Number: 1118 Registered: 12-2001 |
Matt, the book is called Weber carburetors, HPBooks-774 on the binding and Pat Braden is the author. It gives alot of detail about weber conversions, rebuilding and modifying. Also, since the rebuild of my engine with high compression pistons and head work, I found it wouldnt idle with the original idle settings. I have my idle mixture screws set at about 6 turns out. It runs great but I figure the engine requirements have now changed and a step to the .6 idle jets are now needed so the idle screws can be returned to a more reasonable 3 turns so they dont vibrate and fall out. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 412 Registered: 5-2001 |
Matt, I replied before I saw your last post. The initial advance for the HPV-1, 6 ATDC, was driven by wanting to provide flexibility in setting the 400-1000 rpm plateau for anticipated emissions reasons. In reality, I lucked out in that CT suspended emissions testing because of vendor fraud. My car is now exempt from testing because it is 25 years old. The remaining settings are pretty much driven by adjustment limitations. In reality, the only adjustment to play with at this time is the 400-1000 rpm plateau. This adjustment controls advance at idle and because all remaining settings are derived from it, overall advance. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 411 Registered: 5-2001 |
John, Thanks for pointing out the need to account for the static advance. One can see the effects when comparing the OM advance curves in the 78 OM to the transformed curves found in the Predicted HPV-1 Advance Compared to Factory Specification plot. When setting ignition timing for a 78 model, static advance is set at idle to 3 crank degrees ATDC, when it is designed to run off the R2 point set. One can see that at 5000 engine rpm, R1 nominal is 34 degrees BTDC, assuming your advance mechanism is working perfectly. In the case of the HPV-1, note there are severe constraints in what one could dial in for possible advance curves. The initial plateau shown in the example, 0-400 engine rpm, reflects the static positioning of the trigger wheel, in this case 6 degrees ATDC. Normally this first level is set to 0 degrees BTDC but does no harm where I currently have it set. The next plateau is the initial advance in HPV-1 speak and is adjustable by a potentiometer or pot between 2-25 crank degrees. The example reflects 14 degrees advance over the range of 400-1000 engine rpm. The next possible adjustment by pot is an additional advance between 1000-3000 rpm. The break point setting is maxed out at 25 out of a possible 6-25 crank degrees. Similarly, the final break point adjustment, at 8000 rpm is maxed out at 10 degrees out of a possible -7 to 10 crank degrees. My experience is that the HPV-1 advance curve works reasonably well as shown. It would be nice if additional break points were provided. The biggest limitation in my mind is the initial advance plateau between 400-1000 rpm. I would like to see this range extended to perhaps 400-1200 rpm where at idle, the advance would be fixed. Having a break point at the nominal idle speed of 1000 rpm can be detrimental to a steady idle. | ||
| matt (Matthewmag)
New member Username: Matthewmag Post Number: 14 Registered: 11-2002 |
Bill, thanks for those figures, I've added them to the chart but as people might notice, my server's down so no-one can see them. I'll try to post again when the revised list is up there. Re. the ignition timing etc. Yes, the 78 USA car has twin distributors with points, the 78 Euro cars have a single distributor with electronic ignition. How did you arrive at your current settings for ignition advance? John, Yes, those graphs are for distributor advance only. As you say, you need to add on the static advance figure of 3 degrees (6 crankshaft degrees). I believe that 6 degrees is correct for all models, whether single or twin distributor, points or electronic...... | ||
| John_Miles (John_miles)
New member Username: John_miles Post Number: 39 Registered: 7-2001 |
Note that when you're obtaining overall timing info from those those distributor graphs, you have to add the distributor's static mechanical advance figure to the value you're looking up. The dual-distributor 308s seem to use a 3-degree static offset. For example, looking at the R1 (advanced) point graph below, about 14 degrees distributor advance is called for at 2,500 RPM, or 28 degrees at the crank at 5,000 RPM (since the crankshaft turns twice as fast as the camshafts). But the standard 5,000-RPM timing mark on the flywheel (A5 34) is at 34 degrees! So you need to add 3 degrees of advance to anything you read on the distributor graph before multiplying by two to obtain the actual total advance. Needless to say this can be confusing to people looking to dial in their new computer-controlled ignition with the distributor data from the 308GT4 shop manual. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 410 Registered: 5-2001 |
Matt, Good info on the jetting. Please update your table with the following for a 78 GTS US spec. dcnf model: 72,73,74,75 main jet: 1.25 idle jet: .55 idle air corrector: 1.40 emulsion tube: F36 main air corrector: 2.00 pump jet: .35 pump valve: .50 pump discharge: .40 float height: 48 without gasket progression holes: 1.50, 1.15, 1.50, 1.60, 1.80 With regard to ignition advance, the 78 was fitted with 2 distributors, both of which had R1 and R2 point sets. The following advance curves come from my OM.  The two distributor setup was replaced with an Electromotive HPV-1 system. The factory advance curves are compared below with the HPV-1 advance curve as it is currently set.  | ||
| Steve (Steve)
Member Username: Steve Post Number: 313 Registered: 2-2001 |
Don I've just done my WP and will do the belts but after I restarted the 77 I went to do a vacuum check and although the engine seems to run good (a little rich) it idles rock solid at 1000rpm. But if I put a vacuum gage on the rear left (back of the car side) carb. I get a 5"-15"flxuation on the gage. Needle is jumpin. Also the large vacuum line going to the brake boster is pulseing a lot. What kind of vacuum readings are you getting and what is your base idle mixture screw # of turns on set up. My plugs were black but the car has been sitting since the Christmas snow started. I did a hot comp. test and got around 180 psi on all but 1 cyl.Don't think I have leaking valves but I can't get the vacuum issue. Any thoughts out there?????? | ||
| matt (Matthewmag)
New member Username: Matthewmag Post Number: 12 Registered: 11-2002 |
This is an interesting thread indeed and I reckon there's some really useful experiences on jetting a 308 here. And I certainly agree with the consensus that improvements can be made. I thought I'd throw in the following information which might clarify some things and confuse others: Jetting is always a compromise. Carb'd 308s have been fitted with quite a number of different jet combinations from the factory - sometimes this is because of different engine specs for different markets - sometimes not. Here are just some of the jet settings that 308s left the factory with. There are some blanks in the table below, can anyone help fill them in? www.catalanvilla.com/ferrari/jets Important differences are as follows: Different cars have different float heights. Some cars have F36 emulsion tubes, others F24. It's relatively unusual for any given engine to have different em. tubes specified - this obviously has a pretty big bearing on everything else. Also, progression holes are very different on different models - this will have a pretty big bearing on the idle jets needed (and the idle air corrector bush). Some USA spec cars have a .70 pump pleedback in place of a .40 This will affect the progression (and even idle) requirements as the larger bleedback means less enrichment on slower (more gradual) throttle opening. If I had the .70 on my car, I'd try changing it before anything else jet wise. It might explain why one or two people seem to need really big idle jets but IMO if you need very big idles, something else needs looking at first. And now to confuse things. These engines came with different ignition advance curves! The picture below needs some explanation. The red curve is, I believe, the advance curve for R1 on usa cars with twin points. It is also the advance curve for later european cars with a single distributor. The black curves are for R1 and R2 for early Euro cars with twin distributors. Some Euro cars only have the R1 curve. I haven't shown the R2 curve for USA spec. cars either. The graduations are in DISTRIBUTOR rpm and advance - i.e. x2 for engine figures. There is a pretty huge difference in these curves that will affect the carb jetting required.  And then of course there are the different cams on earlier euro cars....... and the emissions gear and different exhaust on usa cars which is often not present.......... The upshot in my opinion is that it's kind of difficult to say that a certain jetting will work on one car because it's worked on another unless you're sure all the specs are exactly the same........(And strictly speaking, it would be useful if you stated air pressure and temperature, or at least altitude where you're setting the car up.) On the other hand, 308s had to pass emissions testing they weren't really conceived for and so, in most cases, the factory jetting will be in favour of emissions rather than smoothness and power. I know that in the UK during the period of new carburettored cars and emissions testing, lots of cars (not specifically F-cars) were prepared for press test-drives, with richer jetting than standard. Finally, the really troublesome area is the progression which can often cause the apparent "cornering" flat spot or hiccough on an increasing light throttle. If there's a problem, it's not easy to set up on a rolling road because it doesn't recreate the real transient conditions you encounter. I use in-car exhaust gas analysis kit with remote guages on the dash...... useful for testing other things too - you can hold full power on the road for a lot longer than you can on a rolling road dyno for example. Does anyone else use this or am I the only one? BTW, James, Matt, is the 38 DCOE the same casting as the 40 but with a different bore? Hmm, maybe not or someone else would have pointed that out. Even if it's a different casting, most bits from the 40 will fit - if you're rebuilding a 38 with a 40 rebuild kit, then at worst I guess you'd just have to make a couple of gaskets. The butterflies would be a tight fit though! : ) Paul - Which Weber book was that? I have a couple of weber books but the one I really want, I can't remember the name of the author - I think he had an Italian sounding name. I photocopied half the book years ago - it's basically lots of this guy's experiences in setting up weber carbs on a whole variety of cars over the years...... I think it's out of print but I didn't photocopy the pages with the book's name or author. | ||
| Paul Newman (Newman)
Intermediate Member Username: Newman Post Number: 1117 Registered: 12-2001 |
Regarding emulsion tubes, I have a book on webers called "weber carburetors", go figure. It mentions rebuiling step by step and modifications to the carbs themselves. It states, "Dont change emulsion tubes unless you have access to a chassis dynometer and an HC/CO meter. For your needs, the air correction jets control top-end mixture strength". I decided to leave them alone rather than come to the conclusion that I should have listened to what I read. Im running 140 mains, 200AC and 55 idles. I will be going to .60 idle and 195 AC this spring. I saw a noticable gain going to the 140's in mid range torque. | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2546 Registered: 12-2000 |
Mike P.: Guy Dellavechia on the F'List is/has changed over to F24 Emulsion tubes (as per Euro GT4 spec). He's also running 135 mains and 200 A.C.'s. Sorry, that's all I know... For more info on Emulsion tubes, get a copy of Pierce Manifolds Tuning Manual (P/N: 95.0000.54PM). It lists all emulsion tubes specs and drawings. | ||
| Philip Airey (Pma1010)
Junior Member Username: Pma1010 Post Number: 153 Registered: 7-2002 |
For general interest: 1974 Ferrari GT Competition Dino Specs: 4 Weber DC(N)F 35-36-37-38 Venturi - 36 mm. Vel stack #105736 Main Jet 160 Main air bleed 175 idle jet 60 Float level 48 mm Emulsion tube F6 Pump jet 45 And, for further interest: Cam timing: Intake opens 51 BTDC, closes 58 ABDC Exhaust: opens 64 BBDC, closes 44 ATDC CR: 9.7:1 | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 136 Registered: 10-2002 |
Regarding emulsion tubes, it seems that nobody ever plays with these--my sense is that the the stock tubes are fine with a range of jetting... I've never spoken with anyone running changed tubes (other than F36, IIRC). | ||
| Mitch Alsup (Mitch_alsup)
Member Username: Mitch_alsup Post Number: 366 Registered: 4-2002 |
Emulsion tubes are also tunable: a properly jetted carb can still be sick in the mid range unless the proper emulsion tube is installed. Anyone played around with these? | ||
| Russ Turner (Snj5)
New member Username: Snj5 Post Number: 2 Registered: 2-2003 |
This is a great discussion. Has anyone tried different venturis while re-jetting? | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 919 Registered: 4-2002 |
Philip: Yeah, I'm a little lean. The performance books published by Chevrolet used to say to aim for 12.8:1. I think a little lean at the lower rpm is not a bad idea, but I'm going to shoot for richer than I've got now at high rpm. | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 131 Registered: 10-2002 |
OK, that's it. It's 10:18 Albuquerque time, I've gotta get some "fresh" air. I'm outta here for ride! Thinking of you all, --Mike ...........VAROOM!! | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 130 Registered: 10-2002 |
Let me just say, boys-- How bout them CARBS! | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 129 Registered: 10-2002 |
John, Will post my gas mileage and exact jetting at next fill up... Early next week. Before my recent rejetting, I was getting 15MPG solid in the city. The car's running better now, I expect to get at least that (if the lower hydrocarbon count is to be trusted, anyway!). These cars are more fuel efficient than many SUVs, and most suburbans! | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2538 Registered: 12-2000 |
John, I noticed no one has answered your previous question about gas mileage: I haven't done any precise calculations, but an example would be with stock jets, I used about a 1/2 tank to go from Vancouver to Seattle travelling at around 70-75 MPH. Same trip with larger jets took around 5/8 of a tank... | ||
| Don McCormick (Dandy_don)
Junior Member Username: Dandy_don Post Number: 51 Registered: 2-2002 |
Well, I could just not leave well enough alone. After I got the carbs running correctly I decided to get into the ignition. My 79 has (had) the 2 sets of points for each distributor and I thought to get in there and disable the R2 setup (the retarded points) and dress up the R1 points. Well after much filing and setting (actually bought a cheap dwell meter) of points I finally gave up when I realized that it is next to impossible to set the point gap (or adjust the dwell angle) accurately with the distributors in the car. Initially I set the point gap at .35mm as listed in the shop manual. When installed in the car this gave me a dwell angle of about 22 to 25 degrees (at least according to my cheap dwell meter). Problem is that the specs for the car as printed on the data plate in the engine compartment list a dwell angle of 39 degrees (plus or minus) Since dwell angle and point gap are functions of each other (greater dwell angle yields smaller gap and vice versa) one of these values would appear to be inconsistent. I think that the dwell angle of 39 degrees is correct as setting it at 39 results in a much smaller point gap than .35 and closer to what I remember (by eyeball) it was before I started in (many hours ago) to dress up the points. I realized then that the points had to go. Not wanting to invest in the $1500 direct fire or even a $5-600 pertronix I decided that the best was to try the Crane XR-700 (2 each) and a set of their coils. I plan to install them this weekend and see if I can't get the ignition back to at least what it was before I started monkeying with it. Any thoughts about plug wires and where I can get some reasonably priced? The caps and rotors look good as well at the fittings at the end of the plug wires so I am thinking that I could buy some bulk wire (red, I hope ) and make up my own. I know this is a carb rebuild and rejet thread but I kind of got sidetracked with this ignition thing. Once I get it corrected and running right I will come back with my experience with the jet sizes I have installed. The car seemed to run fine and eliminated the stumbling prior to tinkering with the ignition. I can report that my gas mileage has always been terrible and I guess that it is about 15 mpg which is terrible for an engine of this displacement, but hey I guess I did not buy it for an economy vehicle. The plugs continue to be a nice gray color even with the upsized idle jets (which is all I am using sitting in the garage)and prolonged idling. Only the exhaust pipes are sooty and black | ||
| Philip Airey (Pma1010)
Junior Member Username: Pma1010 Post Number: 150 Registered: 7-2002 |
Hans In my experience, most tuners suggest 13.5:1 or richer (to say 12.5:1) for optimal power and some detonation "insurance' through a richer mixture. Depending on the AF across the RPM range, either a larger main jet or a reduced AC jet might be worth trying. Thanks for posting the data. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 375 Registered: 6-2002 |
Matt - this thread made me think about doing my C4 carbs (Manufactured December 1971, sold March 1972). I have the technical documents, but did not see parts available at Pierce Manifolds. Thanks. Jim S. | ||
| Matt Lemus (Mlemus)
Intermediate Member Username: Mlemus Post Number: 2432 Registered: 8-2002 |
Ooops... James, What year is your c4. I might have it. | ||
| Matt Lemus (Mlemus)
Intermediate Member Username: Mlemus Post Number: 2431 Registered: 8-2002 |
40 or 38 represents the barrel diameter | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 374 Registered: 6-2002 |
I just found the answer to my own question regarding the difference between a 38 and 40 DCOE - barrel diameter. (I have a Technical document published by E. Weber - circa 1974, 4th edition. Has all the information one would want to know about Webers). Now, where can I find parts for a 38? Jim S. | ||
| James Selevan (Jselevan)
Member Username: Jselevan Post Number: 373 Registered: 6-2002 |
This has been an excellent thread to follow. However, it has generated a question. I visited Pierce Manifolds web site, and tried to find the parts blowup for my C4 carbs - "Weber 38 DCOE 59/60". They did not list this carburettor in their extensive catalog of documents. They do list a Weber 40 DCOE. Here are the questions: Where can I find data and parts for the 38 DCOE, and what is the difference between the 38 DCOE and 40 DCOE? Thanks for your help. Jim S. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 916 Registered: 4-2002 |
Philip: I had my car dyno'd with the stock carb setup. '75 GT4 w/K&N, Euro Ansa exhaust, 135 mains, 220 A/C. My main reason for the dyno test was to check the A/F ratio. (BTW, I got 196 corrected RWHP) A/F was about 13:1 at 3500rpm, and gradually leaned out to 14:1 at 7000rpm. This, of course, was all at full throttle. FWIW. | ||
| Philip Airey (Pma1010)
Junior Member Username: Pma1010 Post Number: 149 Registered: 7-2002 |
John Thanks for the advice. Actually I am in Chicago where the snow sits on the ground and the Ferrari waits in the garage. Oh for warmer weather. | ||
| John_Miles (John_miles)
New member Username: John_miles Post Number: 38 Registered: 7-2001 |
Yeah, you'll have the same setup I do, so the jet combination I posted should work for you. I found that in general: - 140 mains need 57 or 60 idles to drive smoothly at the low end. If your car's like mine you'll experience lurchiness around 3K RPM if you don't bump up the idles when you do the mains. - Similarly, richer idle jets seem to need richer accelerator pump jets to perform well under acceleration. The 140/60 combination I'm using now still felt a little lumpy before I switched to the .55 pump jets. So it seems that you really need to swap out all 3, or none at all, if you want to maintain smooth drivability throughout the range. - Fuel starvation on corners seemed to improve substantially with the 0.55 pump jets. It appears that as you add gas to compensate for tire scrub in a corner, the bigger pump jets prevent the engine from leaning out so badly. I suspect you'll want to install richer pump jets even though it's kind of a pain (you have to pull the carb tops off). This will also be a good time to check your float levels. - I originally got 195 RWHP with 140 mains, without changing the 220 AC jets. I dropped to 200 AC to try to get more high-end power out of the 135 mains. It may have helped some -- I never made it to the dyno with the 135/200 combination -- but in the end the car still feels quite a bit stronger with 140s regardless of the AC jet. On Saturday I'll hook up the AF meter and see if I'm actually running too rich now with the 140/200 combo. If so, I'll go back to the previously-proven 140/220. Edit: Philip, you're in the Seattle area, aren't you? If so, you need to bring your car to Carburetor Connection on Saturday! Even if the dyno slots are full (and they usually don't fill up) it's still a blast to watch all the cars go. | ||
| Philip Airey (Pma1010)
Junior Member Username: Pma1010 Post Number: 148 Registered: 7-2002 |
Having just put on a Tubi on my 77, (intake is K&N) I have ordered 140 mains from Pierce, so am venturing down the path others have followed. The stock set up on my car is 135/55/F36/220 (main/idle/emulsion/AC jets) and, given the design (and noise) of the Tubi, I am sure it will flow more than stock suggesting a richening of the jets is needed. The experience of others above supports this. The real answer to testing the AF ratio "under fire" is on a dyno. Short of this for the moment, I'll do a few "plug cuts" to see how the plugs look. My question is this: has anyone tried to tune using a wide band O2 sensor and readout on the street? Elsewhere on this forum, a contributor opined that some ULEV cars use a wideband O2 sensor. I am wondering if one will fit in the inspection/sampling holes in the rear exhaust manifold and if a voltmeter can be connected to the output leads (and this reading then converted to AF ratio). Raises two questions: - would a wideband sensor fit in the manifold holes? - anyone know which ULEV cars use a wideband? Philip | ||
| Rob Schermerhorn (Rexrcr)
Member Username: Rexrcr Post Number: 267 Registered: 11-2002 |
Excellent thread guys!! | ||
| John_Miles (John_miles)
New member Username: John_miles Post Number: 37 Registered: 7-2001 |
Don, Mike, and Peter: what kind of highway MPG are you guys getting with those 140 mains? I seem to have finally settled on a combination I like: 140 main, 200 AC, .55 pump jet (up from .45 stock) and 60 idle. The car pulls strong from idle and I don't see any of the stumbling during progression that I get with any idle jet sizes under 60. (I tried 52 earlier today just for grins, and the car ran like crap). But with all those rich jets, I'm only getting around 15.5 MPG highway now (gas up, go 35 miles at 65-70 MPH, turn around, go 35 miles back at the same speed, gas up again at the same pump). This car has previously done as well as 19 on the highway with 135 mains and 55 idles. It certainly runs stronger now, so I'm going to leave this combination alone at least until the dyno session on Saturday. But is this typical of the mileage you guys are getting? | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2510 Registered: 12-2000 |
Hans, I used wheel bearing grease (specifically Esso Unirex). Nice and thick yet it doesn't slow down the opening/closing action (no resistance/drag). | ||
| Don McCormick (Dandy_don)
New member Username: Dandy_don Post Number: 49 Registered: 2-2002 |
During my rebuild, I cleaned out the bearings with a bit of carb cleaner and then blew out the fluid with compressed air. I regreased the bearings (rightly or wrongly) with white grease which I understand is somewhat waterproof. Anyway it seems to work fine and I don't have any air leaks at the spindles. However I did not check the carb bases as Kermit has done but then again I seem to have a stable idle. The best prices I found for jets and things were at Weber Carbs Direct but Pierce Manifolds gets the best marks for accuracy, availability, and timeliness. Don | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 894 Registered: 4-2002 |
Peter: What grease did you use? I'm assuming something really thick, but not sure what. Seems maybe silicone grease wouldn't dry out. Just gotta be careful not to use silicone sealer! Oops! | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 893 Registered: 4-2002 |
Yeah, Mike, if you want to see how serious, let me stuff you into the back seat of my GT4. There are still skeletons there from the last people that tried it. | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2502 Registered: 12-2000 |
Hey Mike, I wasn't being funny, I was serious!  | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2501 Registered: 12-2000 |
Yes, they have an online PDF catalog. Their tuning manual is great too. Although it re-iterates typical carburetor functions and tuning procedures, it does include an excellent table and cut-away diagrams of the emulsion tubes avaliable for ALL Webers. Plus other interesting stuff. Hans and Kermit: I experienced the vacuum-leaks-around-the-dry-bearings syndrome last year. Car drove like crap. Lots of grease and home-made teflon seals did the trick... | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 888 Registered: 4-2002 |
Oh, and PS: They have a web catalog. (or at least they did last I checked!) | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 887 Registered: 4-2002 |
Matt: Pierce Manifolds seems to have the best inventory, but not always the best price. I use them just for convenience, and the helpful tech advise. The guys that I have talked to seem familiar with the V8 Ferrari setup, i.e. the '5 screw' 40DCNF. | ||
| Matt Lemus (Mlemus)
Intermediate Member Username: Mlemus Post Number: 2260 Registered: 8-2002 |
Does anyone have a source and price for replacement jets? | ||
| Matt Morgan (Kermit)
Junior Member Username: Kermit Post Number: 109 Registered: 8-2001 |
Hans, As the bearings themselves showed no undue wear (binding, Looseness) the grease did the trick beautifully. There aren't any Seals in these. Hope that helps. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 882 Registered: 4-2002 |
Should the shaft bearings be replaced, or is greasing good enough? Is there a seal involved? | ||
| Matt Morgan (Kermit)
Junior Member Username: Kermit Post Number: 107 Registered: 8-2001 |
A couple of thing I found on Dialing in a "professionally" rebuilt set on Stuart's 308 was the base gasket surfaces weren't flat, easily sanded on a flat surface. And the throttle shaft bearings had not been looked at. The were dry as a bone. A quick bit of attention, and a dab of gease cured the leak there. As I was told that they were ready, "Just set the idle", I was going nuts trying to get them to smooth out. I now have a constant idle that I can tune from. The multiplicity of leaks were hard to detect as each was so small. | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 879 Registered: 4-2002 |
Mike: We HAVE to. | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 102 Registered: 10-2002 |
You GT4 guys have the coolest humor ;). | ||
| Hans E. Hansen (4re_gt4)
Member Username: 4re_gt4 Post Number: 877 Registered: 4-2002 |
Peter: 3 available seats? Oh, so THAT'S what those things in the back are. I've been wondering. | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2500 Registered: 12-2000 |
Sounds great Don... If you're bringing the family, the GT4 has three avaliable seats (and all-season tires if there's a chance there'll be snow on the ground...) if you want to be chauffeured up to Whistler!  | ||
| John_Miles (John_miles)
New member Username: John_miles Post Number: 36 Registered: 7-2001 |
I thought you fixed your hesitation problem? I did. That was a different issue (transition from idle to mains), while what I'm seeing now is more of an off-idle bog at much lower RPM. I am being EXTREMELY nitpicky at this point; I pretty much have to drive into Seattle and try to take off from one of the hilltop stoplights downtown to demonstrate the bog. It wouldn't bug me if I never tracked this problem down -- but I can't help but think it has something to do with either float levels or the accelerator pump jets. I may go ahead and order some .6 mm pump jets from Pierce and see what they do. | ||
| Don McCormick (Dandy_don)
New member Username: Dandy_don Post Number: 48 Registered: 2-2002 |
John and Mike I have a stock exhaust and have not yet gotten around to putting the air cleaner back on as it so much easier to work on the carbs with it off. When I do I will go for a K and N or something similar. Spent time Sunday rereading all of the past info on the board here about webers and timing and decided that I should make sure that the R2 points are deactivated and it is only running on the R1 points. Also found out that at 7 BTDC I should expect to have the idle at about 1100 rpm as I can't get it below that without the car stalling when the electric fans come on and the alternator is put to work. Peter, I have not found that the .6 idle jet is too rich at all. The car pulls nicely all the way to redline without a stumble. Maybe it is the change to the .6 acc pump jets that did that in addition to the bigger idle jets. I did use your pictures again as I spent Sunday rebuilding (cleaning and more ) the rear distributor and deactivating the R2 points in that dist. I also cleaned and filed the R1 points to get some added life out of them but know that I am going to do some sort of ignition upgrade and I don't want to spend $$$$ for something I won't need shortly. Anyway the pix helped as usual and I got the car to fire first time when I put the cleaned rear dist back in- beginners luck I guess. By the way my family and I are on our way to Whistler in mid March and I would like to stop by and see your car if you would like to show it off. We will be passing through Vancouver on March 15th driving north from Seattle. Perhaps we can rendez- vous. If this is of interest email me off-line. Don | ||
| '75 308 GT4 (Peter)
Intermediate Member Username: Peter Post Number: 2490 Registered: 12-2000 |
I've been experimenting with this set-up so far: -140 mains -210 air correctors -NGK BPR5EVX plugs gapped at 0.035" (w. Crane XR700's) -stock everything else I tried 60 idle jets but these were WAY TOO rich than the stock 55's. Car was sluggish and took forever to get into the main circuit. I'd switch to 57's but first I'll try this with my 55's (author: Matt Morgan from Nick's Forza in the thread: http://www.ferrarichat.com/discus/messages/112/180699.html): "Peter, one observation I have made in tuning Webers is an off idle problem is often due to the throttle plate position. The idle speed is often set by turning the screws, which is fine , but be watchful that the plate is in the correct position. The air bypass screws, usually used to balance must be taken into consideration. If the throttle plates are open too far from adjusting the idle speed screws alone, it allows them to feed from the intermediate circut (series of small holes). This can drive one crazy trying to jet." Makes sense since all my air by-pass screws are shut tight (carbs were that well balanced!). Since I'm flowing a typical 3.5kg/h rate on my STE-BK to achieve a normal 900RPM idle with only the throttle plates, this symptom is what may be happening. I can say that switching from the stock 135/220 mix to the 140/210's made a remarkable improvement! | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 99 Registered: 10-2002 |
Hey John, I thought you fixed your hesitation problem? I, too, had the exact same hesitation problem, low rpms, when applying medium throttle from a light throttle condition. Absurdly strong throttle (e.g. quick flooring the pelda) will cover up the problem. I have met many people a similar problem. Essentially, as I have researched and understood this problem occurs during a lean condition, specific to the weber carburators, created during the transition from the idle jets to the main jets. This happens under medium throttle application, enough to cause the transition to the main jets but not quite enough to have the accelerator pump jets cover up the problem. My solution was two fold. 1. Richen the idle jets. I went from stock (55) to 65. 2. Richen the accelerator pump jets. I went from stock (40 I believe), to 45. These two steps has elimated all hesitation on light to medium application of throttle. Also, I had a fuel starvation problem in corners, which is also no longer a problem. Don, John, my feeling is that 60 for the accelerator pump jets is quite rich! --Mike At 5000ft in Albuquerque | ||
| Matt Lemus (Mlemus)
Intermediate Member Username: Mlemus Post Number: 2189 Registered: 8-2002 |
DOH!! | ||
| John_Miles (John_miles)
New member Username: John_miles Post Number: 35 Registered: 7-2001 |
Don, do you have an aftermarket exhaust in this car, and/or freer-flowing (K&N, whatever) filter? I have both in my '76, and that's the optimal combination of jets I've found after much experimentation. However, I haven't changed my accelerator pump jets from stock (.55 if I remember right). I get a bit of a stumble when taking off (< 2000 RPM) uphill, but that's the only drivability complaint at this point. I'm wondering if the .6 pump jets would make a difference. Did you change the metering bushing on the pump jets as well? | ||
| Mike Procopio (Pupz308)
Junior Member Username: Pupz308 Post Number: 98 Registered: 10-2002 |
Absolutely. Try BP5ES plugs, .027" gap. Great emissions, no fouling. Many have recommended this setup. Most will recommend 7 degrees BTDC for single point, though I run 6. --Mike 78 308 GTS, US, Carbed My friend's has test pipes | ||
| F. Lee Ashley (Flashley)
New member Username: Flashley Post Number: 4 Registered: 10-2002 |
Will this configuration work for the 78 model 308 as well. | ||
| Bob Campen (Bob308gts)
Member Username: Bob308gts Post Number: 413 Registered: 9-2001 |
.66mm = .0259" | ||
| Matt Lemus (Mlemus)
Intermediate Member Username: Mlemus Post Number: 2185 Registered: 8-2002 |
gapped at .66mm? Shouldn't it be .23-.27? | ||
| Don McCormick (Dandy_don)
New member Username: Dandy_don Post Number: 47 Registered: 2-2002 |
Hello all, Thought I would update on the status of my carb rebuild and rejet. Also decided to put in the hotter spark plugs recommended on this board. The carb rebuild went well after I got all of the parts finally. Weber Carbs Direct 800 871 3619 has the best prices for Weber rebuild kits and jets that I found but they were hit and miss on availability and order accuracy and were so busy that orders got confused or misshipped (3 day vs overnite etc) Pierce Manifolds in California (408) 842 6667 is more expensive but they are extremely dependable. No mis picked orders and they seemingly have every piece in stock. I installed the following in the carbs .140 main jets 8 each .195 Air corrector jets 8 each .6 idle jet 8 each .6 Accelerator pump jets 4 each all new throttle return springs 4 each all new 5 bolt gaskets 4 each new phenolic base gaskets 4 each new O rings (at idle jets) new needle valves and seats 4 each new acc pump diaphrams 4 each new acc pump springs 4 each new gaskets at cold start mechanism 4 each adjusted floats to 46 mm regreased the "sealed" bearings 2 per carb Installed the carbs back on the engine and synched them with a new Synchrometer STE SK (standard air flow) ($41 from Weber carbs direct) in lieu of my old Uni Syn (with the red ball) which would not even work with the DCNF "shared" air horns. Took some time but the various postings on this chat board really guide one through with no problem. Replaced the BP6ES spark plugs with BP5ES gapped at .66mm and set both banks ignition timing to 7 degrees BTDC. 1 bank was set at 7 degrees BTDC while the other was at about 2 degrees BTDC. The idle got quite a bit more stable after that. The car appears to be running on just one set of points ( R2 ? )because fiddling with the microswitch while using the timing light does not seem to change the ignition advance at all. Do I really need the other set ( R1?) points at all? I have replaced the cats with test pipes and am running the engine at 7BTDC instead of the 3 ATDC which it was timed at with all of the emissions air pump and air injectors installed. Air pump and injectors are not longer on the car- no need, as there are no inspections of any kind here in KS. I set the idle mixture by leaning out each cylinder in turn, waiting for the engine to stumble and then richening it up until the engine returned to a steady idle. Probably not exact but I guess it is close enough. The plugs have a nice brown residue with little tendency to load up at idle. I even reconnected the fast idle mechanism and it seems to work just fine without any of the problems mentioned on this chat line. The car runs great now and I can't wait to get it out for an extended period once the weather warms up again here in KS. The car on my limited test runs seems to have a bit more power and certainly runs smoother at idle. Next step is some sort of electronic ignition Crane XR 700 or maybe the direct fire system ) although it seems to run fine as it is. |