Opel GT Forum banner

1 - 10 of 10 Posts

·
Member
Joined
·
335 Posts
Discussion Starter · #1 ·
I have my GT head ready to go back together and started to install the cam bearings when I found that the replacements I got from OGTS ( Perfect Circle SH-796S) are smaller than the ones I took out of the head. Thinking maybe some one had line bored the head I checked another head that was also on the bench, same story. The Originals measure .082 in thickness and the new ones measure .076 and the new ones can be pushed though the mounting area with finger pressure. Has anyone else seen this and what can be done? (Measurements were with a dial caliper, so they may not be exact)
 

·
Registered
Joined
·
200 Posts
If it is a 71-up 4 bearing head they need to be line honed. If it is a 3 bearing they should just get press in and the cam will slide in.
 

·
Member
Joined
·
335 Posts
Discussion Starter · #3 · (Edited)
I should have said, it is a 1970 three bearing head and according to Dennis these were "finished" bearings that only needed to be pressed in. The bearings do fit correctly on the camshaft, they just seem too small in outer diameter. I'm still waiting for the Left Coast to wake up and then I'll give those guys a call.

Update: I spoke to Gil and it seems that there are two early style heads one is marked with a * and the other with a Triangle or Delta, these use a different size bearing............. sucks another weekend out of luck.
 

·
Super Moderator
Joined
·
5,298 Posts
Washout said:
I have my GT head ready to go back together and started to install the cam bearings when I found that the replacements I got from OGTS ( Perfect Circle SH-796S) are smaller than the ones I took out of the head. Thinking maybe some one had line bored the head I checked another head that was also on the bench, same story. The Originals measure .082 in thickness and the new ones measure .076 and the new ones can be pushed though the mounting area with finger pressure. Has anyone else seen this and what can be done? (Measurements were with a dial caliper, so they may not be exact)
They ARE different sizes, largest in front, next largest, next largest, next largest . . . whether 3- or 4-bearing head!!!!

They are finished bearings and only need to be pressed in, but in the matching bearing hole. It's in the FSM.

:mad:
 

·
Member
Joined
·
335 Posts
Discussion Starter · #5 · (Edited)
tekenaar,
Do you honestly think I would be changing the cam bearings myself if I wasn't smart enough to know that each bearing had a different inside diameter? But to answer the question, yes I was putting the #1 bearing in the #1 position and so on.
 

·
Super Moderator
Joined
·
13,812 Posts
Yes, there are oddball Opel heads that use oversized OD bearings. I've run into this problem many times over the years, it used to drive my machinist nuts!

My belief is it was a way to 'save' assembly-line screwups by oversizing the bearings....this was cheaper for Opel than tossing new heads away. The triangle marking on the head was supposed to indicate this, but I've seen a lot of them that were oversized and hadno markings to indicate this.
 

·
Member
Joined
·
335 Posts
Discussion Starter · #7 ·
Thanks Bob,
Just my luck to end up with two of these oddball heads, one off of a 69, and the other off of a 70. I was able to locate some of the "correct?" bearings in Utah, along with some overnight shipping I should have them tomorrow. This head has been fighting me all the way.:rolleyes:
 

·
Opel Rallier since 1977
Joined
·
2,278 Posts
Just to add to this cam bearing discussion from the 'way-back machine':

I just measured the front cam bearing bore in 4 heads and while I need to make my measurements again to get down to the last .001", these bores are all over the map. Here is what I have now:
  • '75 head: 2.111"
  • '75 head: 2.107"
  • Early 3 bearing head with triangle: 2.105"
  • Early 3 bearing head with triangle: 2.097"
Now the '77 dealer parts manual lists 2 different OD bearings for the front cam bearing position: 2.11" and 2.07". And every other bearing position in both 3 and 4 bearing head also has 2 different OD bearings listed, with one that is .04" smaller than the other.

So these 4 heads would all use the larger of the 2 different bearing OD's from the Opel parts catalog. Durabond lists their front bearing OD as being 2.1069" So the 1st head in the list above looks like the Durabond front bearing would have too small of an OD, and that bearing would 'fall through' the front bearing bore if nothing else was done. I need to check that particular head again, but it sounds like the problem that the OP ran into... he needed an original Opel front cam bearing with the larger OD.

BTW, I will make a suggestion on what to do about any bearing bores that are slightly too big for the Durabond bearings: Use Permatex High Temp Sleeve Retainer compound. (PN 64000). It is rated by Permatex to be used with diametrical gaps of up to .007" and stand temps up to 400F. One of its explicit uses is for bearings in loose bores. Also, it can be used on valve guides so it can take all the heat that the cam bearings will ever see.

One thought about assembly with this compound: apply it and then insert the cam (with a thin coat of light grease on the cam journal) to make sure all is lined up. Just make sure that it does not get on the cam journal: The mfr's instruction for diassembly reads something like 'heat the parts to 500F and apply pulling force to disassemble'! LOL

For the others, it looks like there will be a variation in the front bearing interference fit with the Durabond cam bearing set. No wonder some folks report that their cam bearings needed some shaving for the cam to fit in. That by itself is not unusual in many other applications.
 

·
Detritus Maximus
Joined
·
2,787 Posts
I wonder if we couldn't put this info in sticky of some sort. I'm not sure how anyone would find it without a lucky search.
 

·
Super Moderator
Joined
·
5,883 Posts
I wonder if we couldn't put this info in sticky of some sort. I'm not sure how anyone would find it without a lucky search.
Thread moved to the "Engine Rebuilding" Forum and "stuck"
 
  • Like
Reactions: opelbits
1 - 10 of 10 Posts
Top