454 bbc main bearing clearance HELP

[sawracer]

I have a new motor for my elco. It's a .030 454, kb domes, 647 lift solid roller, worked 990 heads. I bought the remains of July 07 Popular Hot rodding's "Ironman 454" from a local engine builder. I got the cam, lifters, pistons, rings, and rods. I sacrificed a good running dually for the rest. (God rest her soul). It is all freshly machined and ready to party. Here's the question. I plastigauged the mains and got .0030, NOT the .0025 max for all but the rear main which is .0030 spec. , the rear main is OK at .0030 according to my manual. Should I let it ride or can I order .0005 over main bearings? The crank is standard. I read bbcs's like it tight, not loose. ??? THANKS

[72_Ventura]

Re: 454 bbc main bearing clearance HELP

I don't know if you're willing to pay the money, but you could get it fixed at the machine shop. Either bore it out to something over that you know you can find the bearings for or have them cut the caps and re-bore it to stock. Smallest I've seen is .001 over.

[sawracer]

Re: 454 bbc main bearing clearance HELP

OK that solves it for me then, I am gonna run it. I paid $900 for them to handle the blueprint and quite possibly the size between it properly read with mics and me with the plastigauge could just be that half a thou. After bruce fulper of pontiac shame screwed me royally I check everything and ASSUME NOTHING. At least when it fails I know who to blame.

[biginch]

Re: 454 bbc main bearing clearance HELP

that 0025 number is for stock, never to be revved to the moon engines. slightly loose isnt gonna kill it.too tight will kill it in a hurry. depending on how loose the lifter bores are you could have a little lower oil pressure, use a good pump. the higher the hp of the engine, the more clearance it will like, things tend to move around more.

[sawracer]

Re: 454 bbc main bearing clearance HELP

Hi psi or hi volume pump?? Which oil pump is preferred?

[BlackoutSteve]

Re: 454 bbc main bearing clearance HELP

The 0.003" is OK in my book too, but when you plastigaged it, was there oil still present in the upper shell?
If so, that will take up about 0.001" meaning you might have 0.004" on the mains.
If the bearings were dry, I would be reasonably confident you have 0.003".

IF it were me, I'd probably pull the crank and measure properly to be sure.
0.001" and 0.002" undersized main bearings are available for cranks that are "loose" with standard grind, so you can tighten up if you need.
Plastigage is handy, but can be a little misleading at times.

Regarding the pump. If you're going to spin this engine over 6000, I'd go the HV pump WITH a bigger pan, otherwise the stock volume will do.
GM only fit HV pumps in all their BBC crates now, so the HV is still good.
Standard pressure pumps (that bypass at 55-60psi) are just fine regardless of volume.
Remember, a high pressure pump will do nothing for low oil pressure. It's only the bypass pressure that is higher. ;)

[Robert1320]

Re: 454 bbc main bearing clearance HELP

That platsic stuff is guess. You need to measure the bore/brg and the crank.

[biginch]

Re: 454 bbc main bearing clearance HELP

the looser the clearances the more VOLUME you need, high pressure is good, but if the pump isnt moving enough volume, you will never be able to build any pressure.

[min301]

Re: 454 bbc main bearing clearance HELP

That platsic stuff is guess. You need to measure the bore/brg and the crank.

Agreed.

[hiway]

Re: 454 bbc main bearing clearance HELP

If .003 is accurate then I'd run it.