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#3 exhaust lobe wipe prevention

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GNandTTA

Member
Joined
Jun 5, 2001
Messages
563
I remember someone had an idea about plumbing a dedicated oil line just for the #3 exhaust lobe. I looked but could not find it. So to whomever posted this, please elaborate. I pulled my cam a few weeks ago and all lobes were fine except the #3 exhaust was wiped. Was wondering if anyone had any thoughts on this. Would it help prevent wipage. Maybe tap off one of the oil cooler lines or the turbo feed line? Run a 3/16 or 1/8 metal line? You could tap a hole in the intake and have it dump right on the lobe. I guess you could drill a hole in the block for that matter.
 
That is an interesting idea and wonder if it has any merit?

How does the wear surface on your lifter look/feel? A wiped lope usually is due to the lifter not rotating. Other possibilities like cam hardening process inadaquate, lifter bore alignment problem and other theories.

No. 3 exhaust lobe seems to be a common problem on Buick turbo motors, but have a GN here now with no. 6 exhaust flat and no.2 intake getting there. No. 3 exhaust looks fine! [This is not a stock cam either.]
 
Comp cams has a tool to grove the lifter bore from the oil hole that will pressure feed the cam lobe. Did a couple "problem blocks" that way that seemed to eat cams and had no more problems
Mike
 
Interesting but how would this help on a block where the lifter bore is off causing the lifter to be centered on the lobe as opposed to offset and thus not spinning...not doubting or questioning here...just trying to understand...
 
Mike,

Would you only want to do this on the #3 problem lobe or on all lobes? Is this basically the same thing as running the "cam saver" lifters with the one flat side.
 
Originally posted by MSDGN
Interesting but how would this help on a block where the lifter bore is off causing the lifter to be centered on the lobe as opposed to offset and thus not spinning...not doubting or questioning here...just trying to understand...

Have heard about the lifter bores "not centered" in the past and have wondered what this means since they are not centered by design. Also, a stock cam will last over 100k miles and an aftermarket only a few thousand miles in the same block?
 
I had 2 pushrods that were contacting the head. I'm not sure if this caused a "lifter not rotating" problem for me or not, but when you say #2 and #6 Nick it makes me think of this.

It was on the 2nd pushrod in from the outside edge, both front and back, and on both heads. ie, if you numbered the pushrods on one side front to back 1-2-3-4-5-6-7-8, the contact was at numbers 2 and 7. One side had both touching, the other side had one *very* close with the other not so bad. I clearanced 3 spots and left the 4th alone. This was only at full lift, no contact when on the base circle of the cam. I just happened to notice it one time when I had the valve covers off and saw the 2nd pushrod touching the head. Then the light clicked on, and I said "oh! that's why there's that shiny spot on the pushrod!" Now, which cam was this with... I think I may have noticed it when running my PTE econo-roller. But it may have been with the MM 208/208 I had run before that, and which had 2 lifters obviously not spin (pulled that cam with about an hour run time on it). Unfortunately I don't remember if those lifters came from the holes that had the pushrod to head contact, I didn't notice that problem until much later.

John
 
oh yeah, Crower "cool face" lifters (I think that's them) have a tiny hole drilled in the face of the lifter to squirt oil right at the lifter/cam interface. Not sure if these are available in hydraulic lifters, TurboTR ran solid lifters modified as such I believe. Another option.

John
 
Normally, lifter bores are offset to one side of the lobe. Then the combination of the offset bore, the convexity of the lifter bottom, and the taper ground into the lobe in the crosswise direction serves to make the lifter rotate as it is swiped by the lobe rotation. This serves to keep the lifter from digging into the lobe and eroding the bottom with time.

The closer the bore comes to being centered on the lobe, the less it will tend to rotate.

The Club offered some Lunati grinds that were supposed to have about twice the crosswise taper ground into the lobe in an effort to promote greater rotation even when the bore was too close to being centered.

The grooved bore is an attempt to pour more oil onto the lobe and keep it cooler/as well as minimize wiping friction.

Factory springs were quite soft and matched the factory rpm range for the combination quite well. Many reported short spring life, tho', and it became popular to replace them with LT1 springs from the early chevies. These springs are closer to 100# and may have aggravated cam wear as they are 20-25% stronger than the factor units. Using the CC 979s or the 980s (without the cup) seems to keep the pressures in line with the original intent of the factor. Using higher lift cams with the attendant higher load on the lobe nose in combination of a centered bore probably shortens life in some cases.

More oil may well help lobe life. Plenty of cam break in lube, softer springs, and a properly executed break in period probably enhances the chance of long term success.

But, then, I had #5 fail after 20,000 miles on a Comp Cam, so who knows? :) I do think a worn front cam bearing which caused a drop in oil pressure was the probably culprit, but, I am not positive.
 
Actually, the cam saver lifter have machined flat spots on the side to put more oil on the cam lobe. similar to the "cool face" liters except they will work with hydraulic cams.
 
How does the wear surface on your lifter look/feel?
Nick, there is a noticable cup. Not severe, I have ssen worse.

Mike, do you have the exact name or part # of the Comp Cam tool?


The Club offered some Lunati grinds that were supposed to have about twice the crosswise taper ground into the lobe in an effort to promote greater rotation even when the bore was too close to being centered.
Steve, by the "club", do you mean the GSCA? I remember someone mentioning this.
 
I have the tool somewhere I will try to find it. I measured quite a few blocks and never really saw any problems with lifter bores. I did however figure out that there is at least 3 different cam blanks that all say they fit our motor but two of them have the #3 exhaust lobe in a slightly different place. At one time I was able to have cams ground only on the blank that I thought was closest to stock but now no cam company will guarantee that now that the volume is sales is not there.
Mike
 
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