| Author | Message | ||
| Adelina Vallese (Dina)
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Thanks for the pics, Peter. Dom is not 100% happy with the setup. He said after driving the car, he wants to play with the accelerator pump springs some more (??). He said with the extractor system and exhaust,I have enough flow efficiency to cope with the 34mm chokes but has a friend with a Dyno and wants to have a go with that before changing anything else.You obviously understand more about webers than I do. All my previous sports cars were with S.U. carbs which are much easier to setup and tune. Regards - Dina | ||
| '75 308 GT4 (Peter)
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Thanks Dina for the info. It takes great skill and knowledge to start fiddling with those tiny progression holes, so Bravo to him! Progression holes (seen from the bottom of the carb):  Idle jet and holder:  Main venturis:  Top cover, float and float needle valve assembly:  | ||
| Adelina Vallese (Dina)
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OK GT4 Peter, finally after two weeks I was able to pin Dom down and he went through what he did to my webers. Some parts of this I do not fully understand, but hope it makes some sense to you.This is what he scribbled down as the webers were put together. Chokes replaced with 34mm ones. Main jet-1.35,Aux venturi 4.5, Idle jet .6, Emulsion jets were not changed. neddle valves unchanged, Starter jet 2.2, Acc pump jet .40, He said he altered the progression phase holes to get better low throttle response. Also the delivery valves and nozzles were modified (something to do with the angle and how far they sit in to the venturi)as were the air corrector jets. All the accel. pumps were renewed and he custom altered something on the return spring ( ??? ) One float was not floating properly, so it was replaced. All the floats were reset. When I asked him about float settings, he just said they are now correct !! Sorry I can't be more specific, but after spending 35 years tuning/racing webers on Alfas he just seems to know what works and what doesn't. He did however indicate my GTB will not pass CA smog next year. But he said we'll fix that up for the day, when the time comes . Good luck from Dina !! | ||
| Adelina Vallese (Dina)
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Sam: This Alfa friend, Dominic (nick name 'Dom')is in his 60's and was my late fathers best friend. They were always working on each others cars. He has no kids and treats me like his own daughter. GT4 Peter: I have yet to talk to him on exactly what he did to my webers. I'll see him next weekend and find out. He did explain as he put them together, but very confusing. | ||
| Sam NYCFERRARIS (Sam)
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Consider this Alfa friend,what a guy, he gets Alfa performance and Ferrari maintanence -- the worst of both worlds! Dina you must be some incredible compensating factor -- what brand of beer you providing him -- you'd think after the heater hose job the guy would have left the country. Dina with these skills he's a keeper. I guess who among us isn't a sucker for a woman in a ferrari. Go burn up the roads with the way that sexy Italian was meant to do. enjoy. | ||
| '75 308 GT4 (Peter)
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Please do post those set-ups | ||
| Adelina Vallese (Dina)
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I have learnt a lot over the last weekend and from all the posts this has bought out.My GTB was all ready switched to single point system.We found too much resistance in 3 plug wires. Replaced the lot using Alfa high performance leads. Changed plugs as well as checked valve clearances. My alfa friend removed webers put larger main venturis and replaced all jets/ needles resetting all specs etc. He wrote down all the specs and if anyone is interested, I will post them. Well my GTB absolutely flys.. Revs cleanly through all gears to redline. I have to be carefull I don't over rev or get booked in the process. What a change in performance ! I must confess apart from providing beer and support with tools, this was all done by my Alfa friend. Regards - Dina | ||
| '75 308 GT4 (Peter)
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When I first got my car, I initially had to go through emissions testing in order to get temporary licencing. I got these readings: HC: 2000 ppm (@idle, they state 400 a pass) CO: 8.3% (@idle, they state 4.5% a pass) NOx: 70 ppm (they state 2500 a pass, which I did) My car set-up at that time: - Single R1 points set at 7°BTDC - It had sat for many years, only occasionally driven. I will be installing Crane XR700's and everything else for the ignition system is new (wires, extenders, etc...). Plus my float levels were off the mark back then and now I've corrected that. Even though I'm exempt now from testing, I'd be curious to see how things will improve and wondering how all of this talk of the different points relates to my old readings. | ||
| Bill Sebestyen (Bill308)
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It is my understanding the retarded point set helps in the control of NOx emissions, but probably only near idle. As ignition timing becomes retarded from 7 BTDC, cylinder pressures should go down and so should NOx, but HC and CO are likely to go up and as Steve says you also have to increase throttle setting at idle. If you failed HC and CO, the more advanced spark setting resulting from R1, should help, but you now have a slightly more closed throttle. If one failed NOx, retarded ignition timing should help at the cost of HC and CO increases. This is probably why Ferrari chose to pair retarded timing for NOx control and 2-way cats to control HC and CO. Any other thoughts? | ||
| Steve Magnusson (91tr)
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Jeff -- indeed, the only reason for the R2 setup in the first place was for "emissions" at idle, and I agree with you that the R1-to-R2 setup can be tricky (basically impossible without a distributor machine IMHO); however, too many times I've heard the mis-statement that there's some performance advantage to be gained by removing the R2s -- which is just not true. | ||
| Jeff K (Jbk)
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Steve, while I agree with everything you said, I don't see any advantage in running with the R2 points unless they help pass idle emmissions (which I don't currently have to worry about here in upstate NY). The reason I removed them was to avoid the difficulty in timing them accurately at 5 degrees retarded from the R1 pts. This seemed to require moving the mounting plate under the hold down screws until it was right in relation to the R1 pts. If you don't get it right, it seemed like starting and idling would be rough. With just the R1 pts, the car starts and idles fine, and as you noted, there is no difference once you come off idle. The other reason I removed them was to avoid any chance of damaging the engine if the microswitch failed at high RPM's. Didn't want to risk the 23 year old switch shorting out and setting the spark back 10 degrees. I did keep the hardware though. Also fabricated a small plate to cover the hole to the advance mechanism so as not to get any grease on the pts. | ||
| Steve Magnusson (91tr)
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Actually, this single-point vs dual-point setup question does have some Weber effects. At anything above idle (i.e., the microswitch is open) the two set-ups are exactly the same as both are running on the R1 points at the same advance values (if the dual-point idle is set at 3 deg ATDC and the single-point idle is set at 7 deg BTDC). The difference is only at idle where my experience is that with the R2s working (i.e., the engine running at 3 deg ATDC and 1000 RPM) the corresponding Weber airflow is 3.75~4 Kg/hr per barrel. Whereas, when running on the R1s at idle (7 deg BTDC and 1000 RPM) the Webers must be "closed down" slightly to 3.25~3.5 Kg/hr per barrel airflow. This "closing down" of the Webers makes things more sensitive to the inevitable wear/instability of the mechanical bits in the throttle plate linkage system. The only downside to the dual-point setup is mechanical complexity/difficulty of adjustment -- not performance; the upsides are 1) more consistent idle (i.e., less sensitivity to throttle plate position variation), 2) helps reduce plug fouling (although less of an issue with NGK VX plugs), and 3) easier starting as David mentioned. If a car was/is completely missing the R2 hardware I'd deduct $1K-$2K -- if the seller still had all the R2 hardware (but it was not installed), I'd still deduct ~$500 for the labor to reinstall. JMHOs. PS When I restored the R2 stuff in my ex-308 I could only buy the (larger) R1 point plate. Consequently, I have a design to modify the R1 point plate into an R2 point plate (plus the insulators and other various hardware bits). If there's any interest, let me know and I'll see if I can scan/post some jpegs. PPS This is not to say that the single point setup can't work acceptably -- it obviously can. | ||
| david schirmer (David)
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I have been wondering about the single point vs. dual point set up. It seems to me that if you go with just the single set of points you are always running advanced. (no jokes about running retarded please). What are the advantages to this? Would this contribute to running a little hot at lower RPMs and possible difficulty starting and idling. When I first got my car, it was running single point. I re-engaged the microswitch and got it running reasonably well with dual points. I never got the idle perfect, but I was getting there. I then had to get the car though emissions, which it failed at low RPM. Not wanting to play the tune and test game, I took it to a good Ferrari mechanic and he got it through. When the car came back he had switched it back to single points. I had guessed that he did that to get it through emissions, but maybe he had another reason for this. Can anyone educate me on the pros and cons? Thank you, David PS. Sorry this has nothing to do with Weber setup but I saw H. Gault's post and it brought up something I been thinking about. I will discuss carbs in the camshaft forum. | ||
| Herbert E. Gault (Irfgt)
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The best thing you can do is switch to the single point system for the point type ignition. I agree completely. Plus one of the condensers is no longer available. | ||
| Jeff K (Jbk)
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I also had hesitation over 6000 rpm with my 77 308 GTB. Replaced the R1 pts, reset the distributor advance curves to balance them, and removed the R2 pts. Set the timing at 7 BTDC and now it pulls redline strongly in 4th. Haven't tried it in 5th yet though. | ||
| '75 308 GT4 (Peter)
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I had similar running symptoms you described (no good after 6500+), but blamed it on other things. After rebuilding my carbs, I was amazed at how off the float levels were. Could this be a problem (I don't know. After this engine rebuild, it'll be hard to pin-point what was really to blame for not-so-great performance)? The levels should be 48mm full / 58.5mm empty float bowl (measured from the bottom of the top cover to the bottom of the float - not the soldered seam!). I'd be curious to hear what measurements you read off of your carbs. | ||
| Adelina Vallese (Dina)
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Whoa girl!I spoke to my Alfa friend this afternoon and he said I have 'jumped the gun' with my hasty FerrariChat post. Also told me not to tell people he likes my GTB.LOL. He wants to initially retune the existing carbs and go over the ignition before we do anything drastic. He has some old Maserati Merak 44mm webers in his workshop attic, but says unless we change the cams plus head work, it would be a waste of time. Plus he says I can't afford it (don't you hate that). I have borrowed a Haynes weber carb workshop manual (bit like a webers for dummies guide)and am looking through it. Yes you were right, I should have 40mm webers on the car as standard. | ||
| '75 308 GT4 (Peter)
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Dina, even the competition upgrade kits from the factory years ago stuck with 40mm DCNF's, they upgraded them by installing 36mm main venturi's (our 308's use 32mm), as well as different jetting, but I don't know what sizes they used. If you want to play around with carbs, pick up Pat Braden's "Weber Carburetors", published by HPBooks, 1988. I'm in the middle of reading it now, very informative on how to set up carbs from scratch. Your Alfa guy would know who this guy is (well-known Alfa and Abarth collector). Any Ferrari won't have alot of power below 3000 RPM, but yours falling off after 6500? Hmmm... | ||
| Sam NYCFERRARIS (Sam)
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I think Herb is the specialist on this, on my maserati, I was told to set-up the Webers spec and then never touch them agian ( they also did carb type stuff that you describe) -just keep them clean and tip-toe around them softly, the other extreme is that Webers are the ultimate gadget for fiddling with --almost unlimited options -- have fun. | ||
| Adelina Vallese (Dina)
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OK, let's forget about alloy gear shift knobs and get down to some real Ferrari stuff! I am finding that the more I drive my 308GTB, the more urgent performance I need. At the moment the weber setup is standard. Believe that's 38mm. I find the car tends to bog down at low revs, clears out at about 3000 but runs out of breath over 6500. I have spoken to a few so called experts, but tend to get mixed comments. Some say leave it alone(nature of the beast),re-jet the existing carbs,or the one I like the sound of, put a 44mm setup on it. I have stainless extractor setup with custom 2 into 4 exhaust(no cats).The previous owner said it has a euro spec camshaft, but I do not know the specifications or if it is any different from the standard US one. Any one out there run a 308 with 44mm webers? Any help with jetting would also be appreciated. This is a step up from changing heater hoses, but my retired Alfa specialist friend is getting more and more excited with my car and can't keep away from it !.He suggested the bigger 44mm webers with an ignition upgrade. |