Bad main caps ???

Ty 1885

Ty 1885

Member
Yesterday i found out that the pro gram 4 bolt main caps is the reason that it spun bearings! Accoding to machinist.
The caps move about .10 in the block (side to side) contacting the crank and spun bearings!



I just love the quilety of some peoples work:tdown:
 
Last edited:
bezerk

bezerk

New member
Re: Bad main caps !!!

Re: Bad main caps !!!

i think it's more the fault of the builder than the cap itselve.
been there done that
 
Foot Performance

Foot Performance

Donating Member
Re: Bad main caps !!!

Re: Bad main caps !!!

I would think if the line bore was done correctly and the bottom end was tightend correctly the main cap shouldnt move at all I cant really see that being the caps fault:dunno:
 
JSM

JSM

Active member
Re: Bad main caps !!!

Re: Bad main caps !!!

So who installed these caps if they didn't fit tight? Or did .1" just disapear during the engine running?

90% chance not the caps fault at all, but whoever installed, machined for them.
 
8

89shortbox

Member
Re: Bad main caps !!!

Re: Bad main caps !!!

What they said.

The cap registers should have been checked for fit and reset or caps ground to fit. Then align hone without question.
 
Ty 1885

Ty 1885

Member
Re: Bad main caps !!!

Re: Bad main caps !!!

I unfortunaly did not put the short block together. The caps stick out abit on the block (in the crank area). The machinist told me that due to heat, the caps ends closed up making the bearing spin.
Heres the funny thing, looking at the block, you cannot see any sigh of the spun bearings, but there are sighs on the caps. Also there is no sigh of exess heat.
 
REVEREND HARMON

REVEREND HARMON

Party in a box!
Re: Bad main caps ???

Ty 1885 said:
If the caps did not move in, then it must be the shops fault ?
Click to expand...

Id say it was deff a clearance issue from the initial install and alignment.

I really dont see main caps/ especially programs getting got enough to expand causing a bearing to spin.

IF the bearing got that hot then there was a clearance issue or wrong bearing installed in the first place. With the oil going through there it should not heat up enough to cause it to expand that much.

I can see the cap cracking before that much expansion though.
 
Ty 1885

Ty 1885

Member
Re: Bad main caps ???

HARMON said:
Id say it was deff a clearance issue from the initial install and alignment.

I really dont see main caps/ especially programs getting got enough to expand causing a bearing to spin.

IF the bearing got that hot then there was a clearance issue or wrong bearing installed in the first place. With the oil going through there it should not heat up enough to cause it to expand that much.

I can see the cap cracking before that much expansion though.
Click to expand...


I agree 100% My friend years ago cracked a main cap in his 390 AMC, did NOT spin the bearing.

Was reading something on Turbobuick site about a warning from Sunnen co. (they make line boring and other machines) that because Buick blocks being shorter than SBC, that the bar being used for line booring may bend slitely causing the center caps to be tight.
They recommend that EVERY cap MUST be checked for clearences. (Most shops only check the outer ones.)
 
JSM

JSM

Active member
Re: Bad main caps ???

Splayed caps? Very difficult for splayed caps to move, thats the benefit of the splayed.
 
ghettosled

ghettosled

SYTY SUPERSTORE
Re: Bad main caps ???

Your machine work was crap. Plain and simple. Has nothing to due with the caps. There isn't even .100" slop in the bolt holes, yet alone the register.
 
S

Syclone #1721

I LOVE 4UM SUPERSTARS
Re: Bad main caps ???

I gotta laugh at this and be offended as an engine machinist all at the same time..:rotf:...If anything grew .100 in your engine due to heat, it would be a miracle....hell, the bearing shell is in the neighborhood of .100.....bad machine work.....nothing else.
 
Ty 1885

Ty 1885

Member
Re: Bad main caps ???

Syclone #1721 said:
I gotta laugh at this and be offended as an engine machinist all at the same time..:rotf:...If anything grew .100 in your engine due to heat, it would be a miracle....hell, the bearing shell is in the neighborhood of .100.....bad machine work.....nothing else.
Click to expand...


I agree, the billet splay caps are much stronger than the block, but the block shows no sighs of problems (Heat, spun bearings, ext..) That shop f**cked up!!!

I wonder if they even line boored the black at all ?


Thanks guys for your inputs:tup:
 
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