| Author | Message | ||
| Verell Boaen (Verell)
Member Username: Verell Post Number: 833 Registered: 5-2001 |
Adjustable pulleys would sure make life easier. Of course, the risk of the adjustment mechanism vibrating loose & destroying a head/valves/pistons would come with it. The 308 pulleys are relatively small diameter compared to most of the Japanese V-6s you've been seeing adjustable pulleys for. Simple example of the implications: The adjusting mechanism ends up transfering the force from the belt to the cam. If the 3x8 mechanism were 1/2 the distance from the cam's center as the J-car pulley adj mechanism, it would have only 1/0 the leverage of the J-car mechanism. Therefore the force on the adjusting mechanism would be roughly 2x higher as the mechanism is closer to the center of the cam. On the newer 3x8 engines, there are enough pins so that you can come up with a set of holes that will get you within 0.8 degree which should be close enough. | ||
| '75 308 GT4 (Peter)
Advanced Member Username: Peter Post Number: 2839 Registered: 12-2000 |
I've noticed many performance companies offering adjustable, vernier cam pulleys to dial the cams dead-on for _OHC engines. Ferrari relies on this pin/hole arrangement. Is this just as accurate, or could the Ferrari benefit from using adjustable pulleys? I ask this since when I was last in there, I just lined-up the marks and the best hole and even with one cam (can't remember which one), it still was off a hair (the cam mark splitting the cap mark in half). No matter which hole I chose, it just wouldn't line up. I should add that my GT4 uses the three-hole arrangement... | ||
| Andrew A. Illes (Andyilles)
Junior Member Username: Andyilles Post Number: 98 Registered: 10-2002 |
Bill... yes, the P6s are marked with a file cut.. "supposedly". These guys are NOTORIOUS for being off-mark!! Besides, with their higher lift and duration, their timing can be tweaked quite a bit, so the best/surest way is with a degree wheel. Moreover, if you see 6 "authorities" quoting the "correct" timing for P6 cams, chances are good that you will see 6 different sets of "correct" figures. That merely reflects the flexibility of the cams. Many think degreeing cams is a daunting task, but it really isn't... it's just usually explained in overly complex terms. Affix the degree wheel to the crankshaft, doesn't matter how, or where it's pointing, except 0 should be near the wire/coathanger next described. Fasten coathanger wire, or whatever, somewhere on the engine to act as a pointer on the wheel. Turn the engine to precisely TDC (meaning insert a dial indicator[best]or a stick [next best] into the plug hole and rock the crank back and forth until you have TDC... then center the coathanger pointer between the ranges the degree wheel shows, set that to 0... Reason: There will be "play" due to bearing clearances. Place a dial indicator on the #1 I valve shim so you can note the precise point at which the cam lobe begins to move the shim as you rotate the engine (adding clearance, since cam specs are usually given at 0 clearance.. or leave the correct feeler guage in to effect it). That will be the I opening figure. If the number isn't right with the degree wheel at the precise number you want opening at, unpeg the cam-drive sprocket and rotate the cam until the dial indicator just moves.. then repeg the sprocket. Do the same with the #1 E valve. Then do the back bank. Rotate the engine a few times after setting each cam to recheck and make sure belt slack, etc., didn't change anything. You will have correctly timed cams. No-brainer, really. The valve closing figures are for all practical purposes really meaningless for timing since that's governed by the cam profile.. meaning you can't change it. Hope that helps someone, Andy | ||
| Andrew A. Illes (Andyilles)
Junior Member Username: Andyilles Post Number: 97 Registered: 10-2002 |
Bill... yes, the P6s are marked with a file cut.. "supposedly". These guys are NOTORIOUS for being off-mark!! Besides, with their higher lift and duration, their timing can be tweaked quite a bit, so the best/surest way is with a degree wheel. Moreover, if you see 6 "authorities" quoting the "correct" timing for P6 cams, chances are good that you will see 6 different sets of "correct" figures. That merely reflects the flexibility of the cams. Many think degreeing cams is a daunting task, but it really isn't... it's just usually explained in overly complex terms. Affix the degree wheel to the crankshaft, doesn't matter how, or where it's pointing, except 0 should be near the wire/coathanger next described. Fasten coathanger wire, or whatever, somewhere on the engine to act as a pointer on the wheel. Turn the engine to precisely TDC (meaning insert a dial indicator[best]or a stick [next best] into the plug hole and rock the crank back and forth until you have TDC... then center the coathanger pointer between the ranges the degree wheel shows, set that to 0... Reason: There will be "play" due to bearing clearances. Place a dial indicator on the #1 I valve shim so you can note the precise point at which the cam lobe begins to move the shim as you rotate the engine (adding clearance, since cam specs are usually given at 0 clearance.. or leave the correct feeler guage in to effect it). That will be the I opening figure. If the number isn't right with the degree wheel at the precise number you want opening at, unpeg the cam-drive sprocket and rotate the cam until the dial indicator just moves.. then repeg the sprocket. Do the same with the #1 E valve. Then do the back bank. Rotate the engine a few times after setting each cam to recheck and make sure belt slack, etc., didn't change anything. You will have correctly timed cams. No-brainer, really. The valve closing figures are for all practical purposes really meaningless for timing since that's governed by the cam profile.. meaning you can't change it. Hope that helps someone, Andy | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 471 Registered: 5-2001 |
Philip, Are the P6 cams marked for installation at TDC with a punch mark or are they installed only with the aid of a degree wheel and dial indicator with no punch mark. In either event, I concur that if you pay someone to really do it right, it is very labor intensive. Having the correct shims on hand can help a lot and patience is truly a virtue. I also think you have to confirm that the TDC mark on the flywheel is true. | ||
| Russ Turner (Snj5)
Junior Member Username: Snj5 Post Number: 184 Registered: 2-2003 |
Dave Thanks for the advice. Had run into that info a while back about reversion pulses confusing the sensor plate (a large airflow resistor in it's own right). Guess that's why I have a set of 4 cast weber dcnf manifolds to fit a qv/3.2 head with carbs on the way.  Had talked to Lori at Web Cam who suggested changing the cam timing to see if I liked it better before going to a more radical profile (P-6) with the carbs. Already have a tubi. thanks rt | ||
| Philip Airey (Pma1010)
Member Username: Pma1010 Post Number: 278 Registered: 7-2002 |
Bill I am in the middle of the P6 upgrade now. As you know, the cams are a fraction of the total cost - - the fitment is a multiple of the acquisition and checking/upgrade cost (multiple hours on the bench confirming opening/closing angles and lift. | ||
| Bill Sebestyen (Bill308)
Member Username: Bill308 Post Number: 470 Registered: 5-2001 |
Mark, With all due respect, the total cost to replace a set of cams is a real eye opener. One could get them reground domesticly for a small fraction of new ones. The limiting factor with this approach is there is not a lot of meat on the lobes to enable real perfomance grinds. Still, some potential gains are possible. With all the automotive expertise available in England, wouldn't it make sense to seek a local supplier of cam shaft blanks, and let the customer elect to have them ground locally to OEM or their own specs? Or how about reproducing some P6 cams. I suspect there is a lot more meat on these lobes and which could be used as is, or again reground to alternate specs. I'll bet there would be a lot of interest for sets of carb 308 cams. I'd think in terms of a set of 4-cams for say $1000 delivered. | ||
| David McAlexander (Stuttgartdavid)
New member Username: Stuttgartdavid Post Number: 19 Registered: 5-2003 |
Russ: You might be disappointed. I understand that the sensor for the Bosch FI can't tolerate much overlap or it gets confused. This is the primary reason for the drop in rated hp from the carb cars to the FI cars - they had to use a milder cam (thought FI has so many other advantages over carbs that I believe that it doesn't deserve the bad rap it gets). I suspect that the factory used just about the most aggressive cam possible with the FI and that there is little room for improvement without major changes in intake system. However, this was the accepted wisdom with Porsches for many years before the factory came out with the 964 cam used on the Carrera 2, which is supposed to be good for a slight performance increase over the cams used in the 911 SC and Carrera, so maybe I'm wrong... Still, I suspect that to have major improvement, you'd need to rip out the Bosch FI and go to a motec or other modern laptop programmable EFI in order to run a cam with significantly more aggressive specs, which would not only cost big bucks but would have a host of other problems - smog legality, reliability, and the fact that then you are running in a different rpm band and need to re-engineer both the cylinder head flow and the bottom end, which just ain't practical for most of us. | ||
| Russ Turner (Snj5)
Junior Member Username: Snj5 Post Number: 182 Registered: 2-2003 |
Mark Are there any performance cams available for the qv or 3.2? many thanks Russ | ||
| Mark Langfield (Ferrari_co_uk)
New member Username: Ferrari_co_uk Post Number: 30 Registered: 4-2003 |
Hi RC, We have the following NEW cams available: Euro GT4 and Early Euro 308 RH Cylinder Head (47)#108915 - �546.15 (approx $912.69) (45)#108977 - �546.15 LH Cylinder Head (45)#108990 - �546.15 (43)#108978 - �546.15 Early US 308 RH Cylinder Head (41)#108006 - �803.50 (approx $1342.76) (40)#107787 - �803.50 LH Cylinder Head (45)#108007 - �803.50 (43)#107118 - �546.15 (approx $912.69) The numbers in brackets refer to the locations on the parts diagrams in www.owners.ferrari.com Not all are available online so please email me: [email protected] for any enquiries Best Regards Mark | ||
| Philip Airey (Pma1010)
Member Username: Pma1010 Post Number: 277 Registered: 7-2002 |
Tom Shaughnessy has some cams for sale on eBay right now. Otherwise, suggest you try the usual sources - Maranello (TRutlands), GT Car Parts etc. They're around. | ||
| RC PEAK (Rc_peak)
New member Username: Rc_peak Post Number: 7 Registered: 5-2003 |
Does anyone know where to get either some used gt4 cams or early european 308 cams or even some early carburated 308 USA cams? |