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| Russ Turner (Snj5)
Junior Member Username: Snj5 Post Number: 157 Registered: 2-2003 |
Brilliant presentation. would also look at setting to Euro specs. Talked to Lori at web cam and she reccomended closing the lobe centers on my injected 3.2, also with 244 durations. Ferraris were always known for close lobe centers in the 12 cyl cars (See Bishop's book). IMHO what really hurts the later cams is the duration. Again, very well done rt | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 17 Registered: 2-2003 |
Cam data posted to date. Sorry about the eye test, but it's all I can get in a 640 image. Makes one want to set the degraded '78 and later cams to European centers. Comments?      | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1826 Registered: 1-2001 |
Thanks Ted -- actually, those lift values match well with some Elgin Cam data for the "'78-'79 US cat version" so I'm convinced the '78-'79 US lifts were/are reduced from the values shown in the 308GT4 WSM. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 16 Registered: 2-2003 |
I measured both Intake and Exhaust lift at .303 to .304. Seems lower than others have measured. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1824 Registered: 1-2001 |
I forgot to ask if you measured the max intake lift... | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 15 Registered: 2-2003 |
Good question. The manual that came with the car may not represent the correct configuration. I suspect it's for an earlier model. I think I'll go create some graphics for the various timings that have been posted. It would also be interesting to create some timing diagrams using the US cams set to European specs.  | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1823 Registered: 1-2001 |
Nicely done Ted, but why don't you consider the values listed in the 150/78 B/S OM of 244 deg duration for both intake and exhaust as the corresponding the "Factory Specification" for your '79 B? | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 14 Registered: 2-2003 |
Steve -- Whoops! Good thinking Steve. After considering the measurement technique for a while, I realized that the point of contact between the cam and the lifter changes... therefore the proper way to measure the exact cam profile is to zero the clearance between the cam and lifter. I made the following measurements at the specified .020 lift using the correct thickness feeler gage inserted to zero the clearance. The measurements are actually taken on the bucket. The results are as you would expect. Here are the measurements for duration. I've intentionally not included the open and close degrees, as those can be set within the duration boundaries as we home in on optimum figures.
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| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 465 Registered: 5-2001 |
What would be really interresting is to do a plot of the #1 inlet and exhaust cams over 2-engine revolutions. Over the heel of the cam, perhaps a lifter measurement every 20 degress of engine would be sufficient. At the beginning of the ramps, perhaps every 5-10 degrees of rotation. In the area of maximum lift maybe every 2-5 degress. All measurements should be relative to TDC and in the motor running direction. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1821 Registered: 1-2001 |
Ted -- How can the duration at the cam lobe between the .020" lift points (over the peak side) be "shorter" than the duration measured at the bucket's .020" (+ working clearance) lift points (which would be like .029" lift at the cam lobe)? | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 520 Registered: 5-2002 |
Ted, I should add that I timed my cams to the euro spec to get a wider power banded for drivability. The performance is actually slightly better with the factory setting if you shift at redline. I figured with the blower a little less overlap would be good and I like a nice broad torque curve, which I got. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 13 Registered: 2-2003 |
Verell -- For clarification to add to your table, the initial measurements of 287 and 268 were at the first discernable opening of the valve: call it .001. The cylinder loses pressurization at this value, e.g., the valve is actually open a small amount. I've also measured the cam duration directly at .020 and found the duration to be slightly shorter than the .020 measurements at the bucket. After thinking this over a while, you would expect this phenomenon due to the lifter clearance of .009. In search of a consensus method, I've concluded there isn't one. Right now, I'm thinking of two alternate methodologies that seem to make sense. First, to measure the lift at various heights to find the duration at the specified value (my cams duration at 260 degrees occurs at .003 lift PLUS the valve lash), then set the cams to spec. Second, following Mark's approach, measure the duration at .020, then calibrate by bringing each end in by 1/2 the difference between the specification and the measured duration. I was hoping for a more elegant process. Thanks to all for the additional postings and cam data. What I'm hoping for is specs to set US cams for maximum performance. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2787 Registered: 12-2000 |
I don't know if this has any relevance to this, but, I noticed quite some time ago, in the parts list that Jeff of FofUK posted, included some unusual cams for sale. As it was written in the list (BTW - the "L" is UK Pounds... How do you write the Pounds symbol?):
Now, also in that list were "normal", street Euro cams (I call them Euro, since in my GT4 P.C., the same P/N's are listed for cars "Non vale per USA-AUS e J") with the same part numbers without the "/M" designation (note the difference in price!):
Now, what are the specs for the "/M" cams??? | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1819 Registered: 1-2001 |
Alan -- Those specs seem like nice HiPo road cam material. If the duration (at .050" lift measured at the cam lobe) gets greater than ~270 deg the low RPM behavior gets pretty lumpy due to the increased overlap so it's maxed out there, and the lift is pumped up +11% (+1mm) intake and +17% (+1.5mm) exhaust over the "good" US cams -- any valve spring changes req'd/recommended? (I've heard that the intake lift on the '78-'79 US 308 cams was also reduced below the ~9mm shown in the GT4 WSM so more reason for the 205hp rating.) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Alan Ing (Alan)
New member Username: Alan Post Number: 6 Registered: 2-2002 |
Hi Everyone, A cam source you might want to try is Modena Engineering in Australia. I bought a set of cams from Frank Capo (Owner) several years ago. Actually, I haven't installed them, but the specs are as follows. If anyone can give me their thoughts on the profiles I would appreciate it. Frank said they were his road profile (Whatever that means). Oh forgot to mention that I am increasing compression to 10:1 and adding a 328 crank in my 308 to get a little more stroke. My car is a 1977 2 valve 308. The cam specs are as follows: Intake Cam Lift 0.408 Duration Adv 303 Duration @050 262 Valve Clr 0.008 Valve Lift 0.4 Cam Lift Tdc 171 Phase <) 105 Exhaust Cam Lift 0.408 Duration Adv 303 Duration @ 050 262 Valve Clr 0.008 Valve Lift 0.4 Cam Lift Tdc 157 Exhaust: Timing Advance Open 78, Close 45 Timing @050 Open 57.5, Close 24 Intake: Timing Advance Open 48, Close 75 Timing @050 Open 28, Close 54.5 Sorry, I do not know how to format this post better. The cams were somewhere around $1200-$1500 US for the whole set if I recall. I also have some stock 308 cam specs from D. Elgin Cams who used to regrind Ferrari cams(1975-1977 are different from 1978-82). If anyone wants the data, I can attempt to provide it if someone would tell me how to include a table. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Don McCormick (Dandy_don)
Junior Member Username: Dandy_don Post Number: 80 Registered: 2-2002 |
I have a 79 GTS and it has run better since I removed the cats and richened up the jets and retimed the engine to 6 degrees BTDC instead of 3 ATDC. I have been following this cam thread rather closely as I am getting serious about installing a better cam. Especially since Verell's post showing how radically the 78 and 79's changed from earlier engines. Superperformance does indeed have a new set of cams for about $1500-1600 US but I have a question in to them about cam lift and duration etc and will compare to the data so very nicely compiled by Verell. I notice that Web Cams will weld and regrind your own cams for about $1350. Seems it would be better to have a completely new set of cams for just $200-300 more. I will continue investigating and check back from time to time. On the subject of rejetting I have upsized the main jets to 140 from the stock 125 and that works well although it now really has poor gas mileage. I have continued to experiment with the idle jets after finally getting it to run on all 8 cylinders (Thanx all for the help again) and have found that upsizing the idles from .55 stock to .60 makes the car run just that much better accelerating from low speed. Pulling the plugs however tells a different story in that with the .55 jets I am getting better combustion with a brown residue while with the .60 jets I have carbon buildup. Can't seem to resolve this except to say that the car really runs better with the bigger idle jets despite what the plugs say. Any reasons for this? Could it be linked to the poor cams in my 79? | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| david handa (Davehanda)
Member Username: Davehanda Post Number: 799 Registered: 5-2001 |
Well this is starting to make more sense why 78-79 308's (USA) only made 205hp. Different cams, cats, leaner jetting....damn EPA requirements! | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Verell Boaen (Verell)
Member Username: Verell Post Number: 783 Registered: 5-2001 |
Steve, Your preceding post is the 1st that I've ever heard that there was a 2nd set of specs. for the carb'd cars. It makse sense tho, the change to catalytic converters in 78 would have required changes in other areas. Thank you for pointing this out. I've downloaded the 150/78 US & Euro OMs from owners.ferrari.com & extracted the '78 specs. Also, the column headings have been corrected.
(a?),(b): I've heard & always assumed that the '75 Euro Exhaust closing spec of 28° was a miss-print & that intended value was 38°. However, the value was unchanged in the '78 OM as well. Anyone have access to the service manuals to verify these values? The specs in the table are from: 0)308GT4 Service manual 1)Original Ferrari V8 - '75 2V Euro & US numbers, QV specs.. 2) The 100/74, 150/78 Euro & US Owner's Manuals 3) 1982 Euro Owner's manuals 4) 1983 Euro & QV owner's manuals. 5) 308/328 Service Manual WOW! What radical difference between the '78 US specs & the '75 US specs!!! However, Tom's 0.5mm measurements are even shorter. We still missing something. Tom, do you have the open/close readings to add to the table? | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1813 Registered: 1-2001 |
Verell -- I think you're bringing some confusion to this issue by implying that there's a "single" 308-2V US cam spec. No disagreement that the US 2-valve cam numbers you're quoting match the numbers shown in the 100/74 OM ('75 308GT4 N.A. version F106A engine family), but the values in the 150/78 OM for the later '78-'79 US 308-2V (F106AE engine family) are much different -- (relative to the numbers in 100/74) the opening of the intake is much delayed (shortening the intake duration) and the exhaust opening and closing are both significantly advanced. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Verell Boaen (Verell)
Member Username: Verell Post Number: 782 Registered: 5-2001 |
- Thanx Peter, somehow I never noticed that button. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2779 Registered: 12-2000 |
Verell, in the "Help/Instructions" area of this site, under "Formating", there is a simple table formatting key: \ table{\ blue{BTDC},\ blue{ATDC},\ blue{Duration},\ red{BTDC},\ red{ATDC},\ red{Duration} 34,46,260,36,38,253 30,50,260,36,28,243} ...
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| Verell Boaen (Verell)
Member Username: Verell Post Number: 781 Registered: 5-2001 |
Damn, Sorry that the spec tables are messed up. I forgot that TABs don't get handled properly. There's just no good way to do column aligned stuff on this forum(sigh). Mark, I'm having trouble reconciling your timing wheel results with Charles Claussen's results (See last thread reference in my preceding post.) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Verell Boaen (Verell)
Member Username: Verell Post Number: 780 Registered: 5-2001 |
To summarize the specs vs meas'ts to date: Intake Exhaust --------------- ------------------------ ------------------------ BTDC ABDC Duration BTDC ABDC Duration SPECS: 2-Distrib 34 46 260 36 38 253 (aka US) Spec. 1-Distrib. 30 50 260 36 28(?) 243(?) (aka Euro) Spec. 38 (A) 253(A) F* P6 racing 48 62 290 64 44 288 grind MEASURMENTS: Initial meas't ? ? 287 ? ? 268 [email protected] ? ? 232 ? ? 228 valve lift: NOTES: 1) Sole Euro spec sourcs is Original Ferrari V8. Other specs have been verified by cross-checking Orig. F* V8, owners, service & 308GT4 manuals. 2)The Euro Exhaust spec of 28 must be a miss-print. Assumed (A) value of 38 is more likely the correct value. 3) P6 source is from a recent eBAY sale of a set, + F*Chat & other archives. BTW. P6 lift is 9.25mm. IMHO, Like the QV cams, the 2V Euro cams are identical to the US spec cams except that the intake cam's timing mark is shifted 4 degrees relative to the US spec. cam. Those are very interesting & somewhat confusing results. I've always interpreted the phrasing in the owners & FSMs as specifying the timing at the 5mm valve lift(clearance) points. The 308GT4 phrasing pretty strongly implies this, & it's also consistent with the differently phrased description in a '82 Euro owner's manual. I've dug up several prior posts and they seem to agree with this interpretation. See the last thread referenced below, It also describes two innovative ways of measuring the timing: - The use of a special 0.50mm thick shim to to find the 0.5mm lift points. - Pressurizing the cylinder & listening for the airflow beginning & ending while using a timing wheel. I just can't fit the 0.5mm measurements with the specs. It seems to come down to: one of the following: - Either the procedure interpretation is wrong, - the measurements are off, - the cam clearance is off, or - that's a very strange cam profile. I'd expect a high performance cam grind to have longer duration than stock at the 0.5mm points, not less. The cam's lift would be very interesting. If the lift matches stock, then it will be hard to believe that those aren't stock cams. References: ----------- eBay P6 auction(may not be there much longer!): http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2408704234&category=33614 F*chat discussion of P6 & Frank Capo's high perf. cam specs: http://www.ferrarichat.com/discus/messages/112/229316.html F*chat discussion ofP6 cams, Matt Morgan's flow bench work, other opinions: http://www.ferrarichat.com/discus/messages/112/206003.html?1045803934 F*chat discussion of cam timing adjustment/checking (Ric Rainbolt,Charles I Claussen): http://www.ferrarichat.com/discus/messages/112/17479.html | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Mark Eberhardt (Me_k)
Member Username: Me_k Post Number: 515 Registered: 5-2002 |
When I measured my QV at .020 lift, it came out 16 degrees under what the manual said...the lift was perfect so they weren't worn, but the duration was wrong. I was trying to set the cams with a degree wheel to the euro spec, since I noticed the only diffence between US and euro was the exhaust cam timing, not lift or duration. I called a couple dealers,since the manual said the best way to set the cams was with a degree wheel, but no one at any of the dealerships has ever tried and knew nothing about a mistake in the manual. I guessed maybe it was the 2v timing. Anyway, when I timed them using the marks on the cam, I found the lobe center was right, just 8 degrees off each side less than the manual said. So I rolled the exhaust to the euro lobe center and closed it up. I got the car on the dyno about a month later and sure enough peak torque was down at 5000 instead of 5500 and peak hp was still at 6800. Not that this helps your 2v problem I guess except that when it comes to documenting little things like cams timing ferrari doesn't seem to sweat a few degrees here or there. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1812 Registered: 1-2001 |
Ted -- After a while the light bulb goes on!  Measuring the cam lobe from the .020" lift point -to- the other .020" lift point would be equivalent to measuring the zero lift point -to- the other zero lift point of the bucket on a set-up with .020" clearance so the OMs are technically OK, but it sure isn't the clearest wording IMO (I'm sure they didn't expect people to swap out the whole valve shim set just to check/set the cam timing). Were you able to get some 308-2V "euro" cam specs out of the OMs on the Owner's Site for comparison? | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1811 Registered: 1-2001 |
Ted -- I believe/guess that the lift/duration F cam specs are for the camshaft lobe geometry itself (not how the camshaft lobe works thru the cold operating clearance to produce lift at the bucket -- which would explain why you're measuring less "duration" on the exhaust cam even though the duration spec in the 150/78 OM is 244 deg for both) -- can you get your dial indicator set-up measuring directly (or indirectly via a roller) on the cam lobe itself? Side note -- I sure wouldn't mind someone posting some actual '78~'79 US version 308 max int & ext cam lift measurements (i.e, peak of lobe -to- back of lobe) -- can you please include? TIA. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 12 Registered: 2-2003 |
Steve, As you predicated, measuring at .020 dramatically changed the results. I'm now reading Intake durations of 232 degrees and exhaust durations of 228 degrees. To make sure cylinder #1 wasn't different, I made measurements on #2 with the same results. As the cam duration data still doesn't match either of the US specs identified by you in the archives, I'm unable to define the "ideal" setting. I'm leaning toward calculating the cam center degrees and centering around that point. But which cam center point? If I had the data, I think I would calibrate using the European (not detuned US) standard. There's a lot of variation in the published specs. I found a nifty way to set an exact cam timing using the multiple holes in the gear and cam with an easy-to-make special tool. When I finally get everything defined, I'll publish a step-by-step for critique. I've attached a JPEG of the lift measurement for clarification, and just because I wanted to see if it works. Thank to all for the help.  | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Verell Boaen (Verell)
Member Username: Verell Post Number: 758 Registered: 5-2001 |
I didn't say it was a step by step. Here's the closest you'll get to a step by step: For valve service w/Photos, See the 'Online Service Manual' - 15K service procedure http://www.cameragear.com/ec/15k_service.htm This is the 2nd or 3rd time you've complained about not finding a step by step. I'm sorry, but mostly they don't exist for Ferraris. God knows, most of us would love to have them. If you want a car with 'step by step' instructions, go buy a high volume car & the factory or Haines manuals for it. The F*Chat & F*List members are doing the best we can to capture information we know isn't available anywhere else that will supplement the factory service manuals & other resources, including previous posts & online links(see below). There's a well known online repertoire of documented service procedures & technical resources. Many of them precede the FerrariChat's existance by several years, so we tend to forget that newbies aren't familiar with them & links to them. If a step by step you're looking for isn't in one of the following set of links, or the F*Chat Parts and Service topic. it probably doesn't exist, but you're welcome to write it & submit it for the Parts & Service topic: 'Online Service Manual' - http://www.cameragear.com/ec/ 308 GTB Register TechTips - http://www.r-design.net/308/index_e.html Ferrari Club of America:Northwest Region Site: FerrariFAQ - http://www.ferrariclub.com/faq/ (Click on Ferrari FAQ & scroll down) FerrariList.com: DIY and Mechnical information and instructions - http://www.ferrarilist.com/?query=docs&action=catlist&cat=5 Forum: Technical/DIY - http://www.ferrarilist.com/forum/list.php?f=3 Also the FerrariList archives are searchable. Ferrari 308 FAQ - http://home.att.net/~ferrari/308faq1.htm Technical Articles and Writings by Tony Palladino - http://www.modena-motors.com/Technical%20Articles.htm SERVICE & PARTS MANUALS, SPECS & SERVICE BULLETINS: Private Ferrari Document Collection - http://ferrari.jenkins.org/books/ | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 11 Registered: 2-2003 |
Verell, I've been through the archives and haven't been able to find a "step-by-step" process. If there were one, parking it in the Parts and Service link would be swell. All users of this board would benefit if tried and proven practices were posted in an easy to find place. I did find your travels of discovery while plowing this same ground. After visiting with James Patterson of Norwood (see Forza #43 and #44), there's a difference of interpretation (translation ?) in the .020 specifications. James believes, as does Steve Magnusson, that the .020 is the point where "Open" or "Closed" is set and refers to lift produced by the cam. James also verifies his setting by computing and measuring the crankshaft degree position of the cam "top", insuring that both banks are set the same. So perhaps there is something yet to learn of this topic through revisitation. Note that the act of increasing the lash, setting the timing, and then resetting to the desired clearance would achieve nearly the same results. I've also discovered that for the QV, at least, the European and American cams appear to be identical. Only the exhaust timing is specified differently. The exhaust timing is retarded in the US to help meet emission standards. This then leads to the question of the "best" setting of exhaust timing for the two-valve engine as well. Could anything be gained by inching toward the European timing for exhaust? I'm going to research the exhaust timing some more and try a couple of things. Results will be posted. Thanks to all for your responses. I'm learning a lot. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Andrew A. Illes (Andyilles)
New member Username: Andyilles Post Number: 33 Registered: 10-2002 |
Hey Verell..... that a Shady Grady you're waving? | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Verell Boaen (Verell)
Member Username: Verell Post Number: 751 Registered: 5-2001 |
We've been here before, Please search the archives. Ric Rainbolt among others spent a lot of time clarifying & describing the procedure. An alternate procedure using a timing wheel was also described & discussed in depth. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 9 Registered: 2-2003 |
Thanks all. I'll pick up some shims that provide the recommended clearance and give it a shot. Results to be posted. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| William Badurski (Billb)
Junior Member Username: Billb Post Number: 183 Registered: 6-2001 |
All the shop manuals I've used on 4-cam engines indicate that cam timing is done using .020" checking clearance on both inlet and exhaust cams, after which you install the correct shims for operating clearance. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1795 Registered: 1-2001 |
That's why I think it a mis-translation somewhere along the line (either meaning or language) -- it doesn't make sense to have two different mechanical set-ups, and there's no tolerance given in the OM for that 0.5mm "clearance". And just like you noted, by defining the "ends" of the open duration to have a little lift, the slope is not so near 0 so it's easier to resolve/pick the angle. If you want to compare your results to the published F stuff I think you should remeasure at .020" lift -- JMO. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 7 Registered: 2-2003 |
The exhaust clearance is set at .013 go and .014 no-go. The intake clearance is .009 go and .010 no-go. I believe this is in the center of the recommended range of .30-.35 mm exhaust, and .20-.25mm intake. I also took some measurements when the lift was about .003 (the point where the rate of lift changes dramatically). This if course brings the duration in toward the center. I suppose I could find the lift producing the proper duration. Would I then use those points as the "open" and "close" degree points? Addition clearance would also narrow the duration but would have out-of-spec valve lash. Even taking cam ramp-up into consideration, I do not believe that these cams are "standard" USA. Thanks for the help. Onward through the fog. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Steve Magnusson (91tr)
Intermediate Member Username: 91tr Post Number: 1794 Registered: 1-2001 |
Ted -- the ends of the cam angular "specs", I believe, are determined at a little lift (0.5mm = .020"), not zero lift -- was this included in your duration calculations? (I personally think the way it's called out in the OM as a "clearance" is a bit of a language mis-translation -- although it works in a similar direction.) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2764 Registered: 12-2000 |
Are you taking measurements with 0.020" valve lash? The greater clearance eliminates the vagueness of the beginning of the cam ramp and will define a definite opening/closing point of the cam. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Ted Gage (Tedmac)
New member Username: Tedmac Post Number: 6 Registered: 2-2003 |
Using a degree wheel and a digital dial indicator to measure lift, I'm discovering the the duration of the factory cams is significantly longer than the catalog specs which are Intake 34 BTDC, 46 ABDC, duration 260, Exhaust 36 BBDC, 38 ATDC, duration 254. I'm beginning to wonder if this car has European cams. Does anyone have the factory specs and timing recommendations for European cams? I'm measuring durations of 287 for intake and 268 for exhaust. The car is a 1979 308 GTB. This engine has only 6800 miles and otherwise the cams measure within factory specs. I'm performing the valve job due to a timing belt failure. Thanks. |