Misaligned tappet bore?

[chuckfryer]

'87 GN 3.8L

I've wiped the #3 exhaust cam lobe three times. I read somewhere that GM put out a number of 3.8L turbo Buick blocks with a misaligned tappet bore(s). I read that Buick solved the problem by using specially built cams that had lobes positioned to deal with the offset(s) from spec.

Of course, all aftermarket cams are built to factory spec., so they fail pretty regularly.

Comp Cams (at least the tech. I spoke with) has never heard of this issue.

Question: Is this real? Or just some mechanic's excuse for another wiped cam lobe?

I have a set of roller cams to install, but wonder if a bad block (if I have one) will destroy them, too.

 

[getchasum]

There is a lot of info here about the misaligned #3. Some have had it corrected but most choose to go roller and never look back.

 

[turbo2nr]

My friend had a GN that the factory had re-ground that lifter hole and installed a plug/shim(?) to relocate the hole a little. Low mile GN that seems like it's never been opened up. For sure a real thing that affects some engines IMO. Never affected my GNs that I know of.

 

[Chuck Leeper]

Powerhouse tools has a tool to check for off location lifter bores.[Incorrect angles, ft to back, and side to side.]
I use my version of it, and I also use the Goodsen bore sizing tool on all engines I do.. Buick and otherwise.
The ball is an exact size for the OEM bore size. I made a slide hammer for it. The ball is driven thru the bore, then the slide hammer is used to retract it. Once done, the bore is very smooth, and to the OEM dimension.
I also use the Comp Cams slotting tool, to cut a small slot in the bores, to direct pressure oil onto the cam lobe, in ft of the lifter.
Lastly, I NEVER use assy lube on the sides of the lifters... Engine oil, ONLY. Assy lube is thick, and some is grease. This slows/ stops the initial lifter rotation, on startup. NOT GOOD!
Prior to putting the intake on, I mark all lifters, and then rotate the engine w/ a bar, 10 revs. Every lifter has to make at least 1 rev, or I start looking for the cause.
Once buttoned up, I have a remote oil filter/and line setup, that I install, and then prime the engine. Once this is done, that filter setup is removed, and the running filter is installed. After break-in, I cut both open to see what I've got.

Works for me.. never had 1 go flat.

 

[bison]

You can visually see how far its off when looking at it. Its centered too much over the lobe. Cheaper and easier to go ductile roller and forget it was ever a problem. The cam lobe spacing does not accommodate the out of position lifter bore. Comp tech can kiss our asses. This problem has been known about since 1977 when the even fire v-6 engine was first produced. Its wrong in the f'in blueprints. 853 lifters were problematic for a while too. They seem to have corrected their problems since then. Obviously they should come on this forum and get informed.

 

[bison]

Powerhouse tools has a tool to check for off location lifter bores.[Incorrect angles, ft to back, and side to side.]
I use my version of it, and I also use the Goodsen bore sizing tool on all engines I do.. Buick and otherwise.
The ball is an exact size for the OEM bore size. I made a slide hammer for it. The ball is driven thru the bore, then the slide hammer is used to retract it. Once done, the bore is very smooth, and to the OEM dimension.
I also use the Comp Cams slotting tool, to cut a small slot in the bores, to direct pressure oil onto the cam lobe, in ft of the lifter.
Lastly, I NEVER use assy lube on the sides of the lifters... Engine oil, ONLY. Assy lube is thick, and some is grease. This slows/ stops the initial lifter rotation, on startup. NOT GOOD!
Prior to putting the intake on, I mark all lifters, and then rotate the engine w/ a bar, 10 revs. Every lifter has to make at least 1 rev, or I start looking for the cause.
Once buttoned up, I have a remote oil filter/and line setup, that I install, and then prime the engine. Once this is done, that filter setup is removed, and the running filter is installed. After break-in, I cut both open to see what I've got.

Works for me.. never had 1 go flat.

Good tech here. Verifying lifter rotation is a must these days.

 

[QUIP'6']

'87 GN 3.8L

I've wiped the #3 exhaust cam lobe three times. I read somewhere that GM put out a number of 3.8L turbo Buick blocks with a misaligned tappet bore(s). I read that Buick solved the problem by using specially built cams that had lobes positioned to deal with the offset(s) from spec.

Of course, all aftermarket cams are built to factory spec., so they fail pretty regularly.

Comp Cams (at least the tech. I spoke with) has never heard of this issue.

Question: Is this real? Or just some mechanic's excuse for another wiped cam lobe?

I have a set of roller cams to install, but wonder if a bad block (if I have one) will destroy them, too.

make sure you use stp oil treatment at break in and every oil change lots of zinc in there to protect the cam. never lost one