For my engine. Olds called out a piston clearance to the wall of .0007 to =
.0017. To get these GM clearances. Each piston MUST be fitted to EACH cylin=
der. Most engine builders generally say that fitting each piston isn't requ=
ired any more because piston are so good. That is true except for really g=
ood builders.The last Olds engine that I got involved with had on the surf=
ace next to each cylinder. Had letters stamped as to the piston required f=
or that cylinder.. As to bearing clearances. GM called for rod beari=
ng clearance of .0005. (That's 1/2 of one thousandths of one inch ) to .00=
26. For GM. That .0026 was the worn out point. For most builders. Anythi=
ng up to .0026 is OK. Thus doesn't need turned. Main bearings are from .00=
05 to .0021. Thus again any clearances under .0021 is OK. NO it's not for =
a really good builder. I have almost NEVER seen a crank that didn't need tu=
rned. Most builders that except the larger clearances numbers. Recommend hi=
gh volume oil pumps. That covers up a low oil pressure problem. There is =
no engine builder that knows more about GM engines then GM. They built thei=
r engine in ways to protect their reputation. And avoid warranty issues. L=
ook at all the years that these GM built engines have lasted. Our last 78 R=
oyale had 152,000 miles on it. 130 to 135 psi reading on a compression test=
. ( New runs 140, to150 psi. ) And carried 30 psi oil pressure hot at idl=
e. Now look at all the rebuilt engines that aren't lasting with high volum=
e oil pumps. To make them last. It comes down to cleanliness. Craftsmanshi=
p, and building them as GM did. Bob Dunahugh _________________________=
_______ From: Bob Dunahugh Sent: Friday, March 2=
, 2018 5:04 PM To: gmclist Subject: RE: Passcar 455 blo=
ck? The shop here has do 4 GMC engines lately. They tend to go shor=
t of .010 or .020. Then custom size each bore to the size of each piston. E=
ach engine must be balanced. They don't recommend high volume oil pumps. B=
ecause of the details that they put into their machining of parts. They ins=
tall the intake, distributor, oil pan, fuel pump,water pump, and oil in the=
pan with filter. Then it's delivered with a custom steel engine stand, an=
d lifting device mounted by the carb bolts. Then leaves with a case of oil,=
and detailed install/break-in instructions. I dare you to find anything di=
rty, or messy there. The place is spotlessly clean. And that cleanliness sh=
ows up in the quality of their workmanship. Bob Dunahugh ________=
________________________ From: Bob Dunahugh Sent=
: Friday, March 2, 2018 12:13 PM To: gmclist Subject: R=
E: Passcar 455 block? Boring to .060 if fine. It has to have a lot=
of miles on it. So it's well seasoned. I'd go with the block that you have=
the most past history of. Build it now. With a well maintained engine' Yo=
ur good for 200,000 miles. Bob Dunahugh
.0017. To get these GM clearances. Each piston MUST be fitted to EACH cylin=
der. Most engine builders generally say that fitting each piston isn't requ=
ired any more because piston are so good. That is true except for really g=
ood builders.The last Olds engine that I got involved with had on the surf=
ace next to each cylinder. Had letters stamped as to the piston required f=
or that cylinder.. As to bearing clearances. GM called for rod beari=
ng clearance of .0005. (That's 1/2 of one thousandths of one inch ) to .00=
26. For GM. That .0026 was the worn out point. For most builders. Anythi=
ng up to .0026 is OK. Thus doesn't need turned. Main bearings are from .00=
05 to .0021. Thus again any clearances under .0021 is OK. NO it's not for =
a really good builder. I have almost NEVER seen a crank that didn't need tu=
rned. Most builders that except the larger clearances numbers. Recommend hi=
gh volume oil pumps. That covers up a low oil pressure problem. There is =
no engine builder that knows more about GM engines then GM. They built thei=
r engine in ways to protect their reputation. And avoid warranty issues. L=
ook at all the years that these GM built engines have lasted. Our last 78 R=
oyale had 152,000 miles on it. 130 to 135 psi reading on a compression test=
. ( New runs 140, to150 psi. ) And carried 30 psi oil pressure hot at idl=
e. Now look at all the rebuilt engines that aren't lasting with high volum=
e oil pumps. To make them last. It comes down to cleanliness. Craftsmanshi=
p, and building them as GM did. Bob Dunahugh _________________________=
_______ From: Bob Dunahugh Sent: Friday, March 2=
, 2018 5:04 PM To: gmclist Subject: RE: Passcar 455 blo=
ck? The shop here has do 4 GMC engines lately. They tend to go shor=
t of .010 or .020. Then custom size each bore to the size of each piston. E=
ach engine must be balanced. They don't recommend high volume oil pumps. B=
ecause of the details that they put into their machining of parts. They ins=
tall the intake, distributor, oil pan, fuel pump,water pump, and oil in the=
pan with filter. Then it's delivered with a custom steel engine stand, an=
d lifting device mounted by the carb bolts. Then leaves with a case of oil,=
and detailed install/break-in instructions. I dare you to find anything di=
rty, or messy there. The place is spotlessly clean. And that cleanliness sh=
ows up in the quality of their workmanship. Bob Dunahugh ________=
________________________ From: Bob Dunahugh Sent=
: Friday, March 2, 2018 12:13 PM To: gmclist Subject: R=
E: Passcar 455 block? Boring to .060 if fine. It has to have a lot=
of miles on it. So it's well seasoned. I'd go with the block that you have=
the most past history of. Build it now. With a well maintained engine' Yo=
ur good for 200,000 miles. Bob Dunahugh
