cometic bore size ???? need help

Posted By: earthmover

cometic bore size ???? need help - 07/11/12 01:18 AM

ok guys i ordered my new cometic head gaskets for my 451 build..the bore size i ordered was 4.380 the block is 4.375...they sent me 4.410 should i send these back or will they be fine???? new to this big block stuff and this type of build....thanks mike

Posted By: Deepockets

Re: cometic bore size ???? need help - 07/11/12 02:08 AM

i'm not sure on there reasoning. when i ordered my 4.500 bore they said to run the 4.530 gasket. so i did. everything's fine.

Posted By: Jeepmon

Re: cometic bore size ???? need help - 07/11/12 02:16 AM

Quote:

i'm not sure on there reasoning. when i ordered my 4.500 bore they said to run the 4.530 gasket. so i did. everything's fine.

Thats funny.. Just today I got my Cometics.. 4.500 bore and they sent me 4.540...

Posted By: jamesc

Re: cometic bore size ???? need help - 07/11/12 02:18 AM

Quote:

ok guys i ordered my new cometic head gaskets for my 451 build..the bore size i ordered was 4.380 the block is 4.375...they sent me 4.410 should i send these back or will they be fine???? new to this big block stuff and this type of build....thanks mike

they probably saved you the hassle of finding out the 4.38 gaskets wouldn't fit because they overhang the bore or combustion chamber. 4.38 only leaves .0025" per side for tolerances and normally chrysler blocks have a pretty heavy chamfer at the top of the bore. even with the 4.41 that's only .018 per side, put them on and go on your way

Posted By: jamesc

Re: cometic bore size ???? need help - 07/11/12 02:21 AM

we'd all like to have gaskets that perfectly fit the bore but that's not the reality of tolerances. bore chamfer, dowel pin location, bore location, combustion chamber location and size, think about it. you need a margin with this stuff unless you're going to precisely locate and machine all of these dimensions.

Posted By: Performance Only

Re: cometic bore size ???? need help - 07/11/12 02:28 AM

run them. that's what i would've sent you also. they did you a favor by giving you a little room. you don't want the gasket the same as the bore size.

Posted By: MR_P_BODY

Re: cometic bore size ???? need help - 07/11/12 02:32 AM

With the chamfer on top of the bore its much bigger

Posted By: earthmover

Re: cometic bore size ???? need help - 07/11/12 02:44 AM

thanks guys. also would like to add not a bash just asking as i am new to this..mike

Posted By: 440Jim

Re: cometic bore size ???? need help - 07/11/12 03:04 AM

Quote:

ok guys i ordered my new cometic head gaskets for my 451 build..the bore size i ordered was 4.380 the block is 4.375...they sent me 4.410 should i send these back or will they be fine???? new to this big block stuff and this type of build....thanks mike

For the bore size you ordered, that is a reasonable size gasket. I have a 4.375" bore and I run 4.440" Cometics because the 1978 Chrysler factory put a chamfer on the top of the bore the size of the rings of Saturn...

Don't send them back for smaller gaskets!

Posted By: CompWedgeEngines

Re: cometic bore size ???? need help - 07/11/12 04:08 AM

You NEED an extra .030-.060 extra above and beyond the actusl bore size. Run em.

Posted By: mopar dave

Re: cometic bore size ???? need help - 07/11/12 04:30 AM

i'v been told to run .030 bigger on gasket bore than the cylinder bore.