Question about 4-bolt main BB engines

[Steve Antonucci]

Hi all !

I have a fast one for those of you knowledgeable with big blocks.

I am trying to determine if Tonawanda could have / would have made 4-bolt main
big blocks without the external oil cooling provisions being machined-in.

It has been reported that some applications got 4-bolt main blocks ( where
2-bolt mains were std. ) due to availability issues. In these cases, the
blocks may not have been drilled for the external oil cooling provision that
is std. with all 4-bolt main SHP blocks. I myself do not agree with this as
I believe that at the time of manufacture, there was no way to know if the
block would have been used for non-SHP applications. Furthermore, I suspect
that any block machined for 4-bolt main provisions would also have been
machined for external oil cooling. Can anyone here tell me if there were
exceptions to this "rule". Also, would truck or fleet BBC engines ( not tall
deck blocks ) fitted with 4-bolt mains also have the external oil cooling
provision? I know many of you have been around mark IV engines for decades
and I was hoping one or more of you have some first hand knowledge.

Thanks,
Steve

[Clem Z.]

Re: Question about 4-bolt main BB engines

never saw a 4 bolt w/o the oil cooler connections and never saw a 2 bolt with the oil cooler connections.

[Joe L.]

Re: Question about 4-bolt main BB engines

Steve------

In general, if not exclusively, I believe that the machining operations for 4 bolt main installations included not just the extra block machining for the main caps, but also the extra machining for the external oil cooler provisions. Could Tonawanda have done one without the other? Of course they could have; no problem, at all. Did they actually machine some for 4 bolt caps without also doing the machining for the oil cooler? That I don't know. It would be difficult to say, at this point, since 2 bolt big blocks can easily be converted to 4 bolt configuration. For many years, all 5 main caps were available in SERVICE to use for such conversions.

I don't know the answer for the truck-only big blocks. However, keep in mind that heavy duty trucks (especially the kind requiring 4 bolt main blocks) also often use oil coolers. It's not just a "racing thing" when it comes to truck engines.

[Dick W.]

Re: Question about 4-bolt main BB engines

And remember that the truck engines, 366 cid and 427 cid, were of the tall block variety.

[Steve Antonucci]

Re: Question about 4-bolt main BB engines

Clem, Joe & Dick - All good points !

Joe, I agree with your position on the 4-bolt main & external oil cooling being
done as a standard operation for this provision. That would make perfect sense.

Regarding the "conversion" from 2-bolt to 4-bolt mains - I know that this is
fairly easy. However, I have never found a shop that wanted to tackle the external
oil cooling gun drilling that was required to look & function as original.

If any of you know of a shop that has done this, please let me know.

[Phil P.]

performance machine pomona ca

if you need this done you need to haul a$$ as the shop has been sold and the "block" man (phil) is moving back to new zealand (sp) after the first of 07---he has youngsters and does'nt want them to grow up in gangbanger land---has done lots of motors for me zero failures---good luck,phil

[Mark #28455]

1980's blocks are not drilled

All vintage 4 bolt main blocks are also drilled for the oil cooler holes, in addition, all 4 bolt 427 and 454 blocks had valve reliefs cut in the top of the bores - 2 bolt blocks did not. All 396 blocks had valve relief cuts.
Good luck,
Mark