Yesterday I stopped by a friends house where he was putting heads back onto his 1955 Pontiac with 287 V8. This engine is untouched other than the top end. With the intake still off I noticed how nicely the lifter sat forward of the lobes on the cam (back edge of lobes to back edge of lifters with the lifters overhanging forward of lobes). This had me thinking back to what's talked about here a lot. Early cam failure with SBC's. Also what crossed my mind, all the aftermarket cams I've put into SBC's the lobes tend to be centered in the lifter bores more than I'd like to see. Now I'll admit, I've lost a couple of cam's but what I seen yesterday with the Pontiac, I haven't seen with any SBC with an aftermarket cam. So, it's a big so, could there be lobe positioning issue's with today's cam shafts? Since I do not have an early unmolested SBC to make a comparison with I thought I'd bring this up to see what others have to say about this outside of "you broke it in wrong", "no zinc in oil today" or "china crap". Oh, to add to this. Anyone ever place a spacer between cam and timing sprocket so cam can set back further "if" do able?
Do you suppose there's any chance that some of the cam companies might be trying to grind flat tappet AND roller lifter cams on the same core casting?
No idea. Just something I'm throwing out there. It'll be a while before I tear into another SBC to experiment with alignment. But knowing good and well I'll need to see where distributor gear , fuel pump lobe end up and how much spacer could be placed between cam and sprocket and still index well enough.
How much would you say cam lobe off center of lifter bore? Cam & crank can be shimed. Sbc/Bbc. There can be factors that can cause issues with cam location . timing gear faces / thickness ,timing chain flex leading to cam walk with out cam button ,lobs being cut in wrong location, then would need to look @ cam gear teeth incorrect size to mesh with distributor gear & size . If looks that Quality control is so bad that all needs to be check. Maybe most all company's even name brand are focused on roller's that flat tapped set up have a different go or no go spec then Roller machining specs. Cam change seem not the same as it use to be since 2000, So can it be oil blend , cheap material, no quality control? Cam change Should be Straight & forward.
i have noticed that the lifters are not centered on the cam lobe in my sbc possibly to promote lifter rotation
Im sure there is a limit to off set before Lifter will not Rotate, I will try to get my Reher Morrison books read & see .
Yes. You'll have to trust me on what I said about the Pontiac at the top of the page. The 287 lifter bosses are not like that of a SBC. One can see what's happening without X-Ray glasses per this sample photo of a 287.
I wasn't trying to say I didn't believe you. I just thought it would be nice to compare it to Chevy visually.
I think offsetting the lifter changes the contact on the cam lobe, but not the lifter contact relative to the lifter CenterLine. I think the offset of the lifter contact relative to the lifter CenterLine. is what tries to rotate the lifter, and does not change no matter where the cam lobe CL is..
I should have worded differently. Main reason for reply was to show how easy it is to see things in the Pontiac 287 vs SBC especially when lifter are in place.
^^^^^ When he states "cam is too far back" he had timing sprocket off. Still video at 1:41 (sprocket still on) and tell me that cam lobes are a full 3/16" too far back?
Came across these: However where mark should be is very vague per description of marking tool. COMP Cams Camshaft Lobe Center Marking Tools "COMP Cams camshaft lobe center marking tools are constructed of aluminum and available in three sizes for all common lifter bore diameters. With these tools, the user marks the cam lobe with a type of marking fluid, installs the cam, and then places the tool in the lifter bore. Next, the cam is turned over to mark a line around the cam lobe. The cam is then removed, and the distance from the edge of the lobe is measured. Finally, shims are changed to achieve the correct lobe to lifter alignment. The marking tools are available in three sizes for all common lifter bore diameters: .842 in., .875 in., and .904 in. They have 1/4-20 threads for the bolt in the top."
What Johnny Gee posted in post 9 was what I was taught in the 60's in auto mechanics class both in High school and in trade school. That maybe not visible to the naked eye bevel is what spins the lifter. I don't have one laying around but if you look at the wear pattern on an old stock cam it works it's way in as the lifter rises on the ramp to a point at the lobe tip and then has a matching pattern on the back ramp. Thinking about it I don't remember seeing the wear patterns on any stock sbc cams looked at I have go full side to side.
In my early or younger self messing with engines I never payed attention to where lobes were to lifter bore. That said, those that built and tore down way more engines than I ever will would show me stock cams they removed and I recall contact pattern being at three fourths to rear of lobe.
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