HI all, I'm working on a major for a 1980 308 GTSI 2V and I'm in the process of doing valve lash adjustments/seal replacements/bearings/belts. I removed the intake cam on the rear bank (1-4) and noticed wear to the corners of the cam lobe. I measured the valve lift and it appears to be within 7.7mm specifications (per earlier fchat posts) and the lobe profile, while not new, seems to be acceptable. Should I replace this cam? Thanks Image Unavailable, Please Login
At the very least you should replace the shim as it is clearly not a flat shim (and hasn't been for a while) per the lobe wear pattern. I would send the cam to Elgin and have him professionally assess how to proceed as my assessment says it should be replaced whilst Elgin may be able to either repair the lobe and parkerise the thing or at least provide a more clear solution re how to proceed.
I'd characterize that more as edge chipping or flaking, but what did the shim surface look like (and versus the other shim surfaces)? If the shim is flat, but tilted, I believe it would generate a circular wear scar line, or maybe two circular wear scar lines (corresponding to the radii from the bucket axis where the edges of the lobe contact the shim face) as the bucket rotates. That's also the pattern you might get if the lobe was contacting the rim on the bucket -- any sign of contact there?
That edge chipping is of no consequence at all and could have been the original state of the cam. BUT...I'm confused re the lift you mentioned. 7.7mm is a huge amount of valve lift "difference" unless I'm misunderstanding the reference.
The lift on the US '78-'82 models was reduced. Agree with your assessment that the loss at the very nose of the lobe isn't so bad, but moving towards the top of the photo seems like it's more than 50% of the width
Cam is dead. That is the classic early failure pattern on Ferrari cams. Hard to see in the picture but it has a semi circular wear line extending down the ramp connecting the damaged edges. If a straight edge was put on the shim I bet it is not flat. I also bet the toe is similarly no longer flat. Very unusual for cams of that vintage. Dinos and Daytonas had a real reputation for it but they improved the cams and for the most part solved it. I wonder if that thing has or had a lubrication problem or maybe a cam follower that won't turn.
Thanks All. I'm now concerned about the causal relationship. Service records don't show lubrication issues, and the block was rebuilt in 2007 by Norwood Texas. Are there any other signs of low lubrication in the cam area I should look for? The rest of the cam lobes look fine. I will say that the valve clearance was .11 mm (out of tolerance by 45%). My rudimentary knowledge and logic suggests that would not cause this kind of wear. That said, my entire intake valve clearances were under .20, The buckets look fine, I'll have to re examine the shim with a straight edge. I have several sets of cams for this engine which came with it, and I found one in much better condition, but I didn't want to have to time the valves beyond the factory marks on the cams and TDC. My original idea of belt change turned into a serious education. . .
For a valve in a 308 to tighten up that much is unusual, particularly an intake valve. I don't suppose you know who did the last valve adjustment or how many miles ago? 90% of the time when a valve is off by more than 2 thousandths (inch)or so it is because it was adjusted wrong. People lose track and add instead of subtract, that sort of thing. What shim thickness will it take to get it right?
Don't laugh at me for asking this, but could this be the type of thing we can eventually expect by using oil without zinc
Rebuilds do weird things as stuff gets to limit of one spec while being in spec elsewhere. If you put the other cams in then you have to time the motor degree wheel blah blah. It is not that hard read about it. In the old days web cam in riverside would weld up stock cams and do a P6 grind for hot cams. Maybe look into that for the toasted cams. If you have to do work you may as well make it fast.
I don't think this is like unlead gas and hardened valve seats from the olden days. I don't see a curent formulation issue but if you don't mind risking your cats (controversial) you can run diesel motor oil cheaply or spend more for something like mobil 1 racing motor oil and get the zinc back.
I ordered a .305 for this shim. Previous owner was a DIY, like myself, until this car is done. Next car comes with FNA or Reputable Indy service records.
I assume you meant 3.05mm? That's pretty thin. I don't think they were ever made that thin. May not be possible. Makes me worry about what is going on with that valve.
Oh yeah, I have your tutorial bookmarked FBB. Without it I wouldn't attempt it. Now if you'd just share your secret about cam belt tensions, I'm all ears.
P6 cams are terrible on the street. It would never smog in California and CIS injection probably will not even run with them.
Yeah me too. I tried to order it from T Rutlands and found out the smallest factory shim was 3.25, I had to get it from Superformance UK. Guess this goes deeper than the camshaft.
Could it be that the cam lobe was hitting the edges of the bucket first and not the (thin) shim, when for some reason the valve sank too deep in the head?
this could be a problem or just lack of attention to detail on a past head rebuild. Past history would be great to know. There are volvo tablets that are the same diameter that can be had in 2.95 iirc. I had to use them once on an improperly rebuilt 308 head. Owner was in too much hurry to get it installed than either having seats redone or valve stem trimmed a bit.
Another "need a thinner shim" thread: http://www.ferrarichat.com/forum/308-328/443963-thinnest-usable-valve-shim.html
Agreed! But if you got some dinged cams and some extra smog cams what a fun toy to make. I did it to a carb car back in the day when a 20 year old could brib a younger smog tech with 100 bucks and a thrill ride around the block. Those days are long gone!
Awesome info on a topic I have zero experience with at present. Really appreciate people contributing the information!
