1970 3963512 Block Strange One

[Kim_Howie]

I heard that alot of big wagons had 4-bolt blocks in them???

[3macs1]

Just thought I should share this info. Had a call last night from a good friend who has been working in an engine shop rebuilding motors for over 40 years. BBC his speciality.I told him what happpened with my 512 block.
He indicated that he has seen that many times over the years in the 70-454 and in 66- 396 and 427's . Most of the oval port 4 bolt's did and some didnot not have the oil filter bosses drilled for external oil cooling and dropping the pan was the only sure way to know what you have. He said if you don't beleive me colvin ????mentions it also in his book. They would fit the caps due to potential warranty issues but machining for an oil cooler was not necessary to complete the vehicle.
Sure enough I checked today and on page 57 a note is listed
In many cases, due to scheduling and parts availability, a 4 bolt block was used in a 2 bolt application.
Also stated many times during a block production run, a 2 bolt block might have been drilled for a 4 bolt application with no factory documentation of the change"
To sum it up best to drop the pan before we sell a BBC especially if it is a 66 or 70.

[nuch_ss396]

Joe,

First time I ever heard this. I will have to do some
research of my own to confirm this.

My understanding was that any block machined for 4-bolt
mains got the external oil cooling modifications as well.

Colvin certainly did a hell of a lot more research than any
of us did in this area. BTW, I did find the passage in his
books regarding this, but he didn't mention anyhthing about
the oil plumbing being different. I'd still have to contend
that 4-bolt enabled blocks would have been drilled for the
external oil cooling provision. Keep in mind that when the
machining process was being performed, there was no tie-in
to the application ( SHP vs. non-SHP ). All 4-bolt blocks
would have to be assumed to be SHP, so I expect they all got
the external oil cooling modifications. If, as you contend,
some 4-bolt main blocks were used in place of 2-bolt main blocks,
I still think they would have external oil cooling provisions.
Anybody else have an opinion on this?

Lastly, do any of you know if 4-bolt main truck or fleet
BBC engines did not have the external oil cooling provision?

Steve

Steve

[3macs1]

Steve:
I always thought so also but there seems to be a gray area when they took a finished 2 bolt and converted it on the fly to 4 bolt. Those I could see them not bothering with the oil mods.
Another thing that makes me believe this is true is I had that engine for years and would have noticed the plugs especially when I was racing l-72's.
Let us know what you discover
Joe

[nuch_ss396]

Joe,

I brought this topic up on the NCRS technical forum and heard
from some very knowledgeable, long-time big block owners
and racers ( past & present ). I rely on these guys heavily
as many of them have been around big blocks from almost the
start of the Mark IV program.

The general consensus is that all 4-bolt main BBC engines
would also have received the external oil cooling provision
as part of this SHP feature. No members reported seeing a
4-bolt main block without the external oil cooling provision
and this jives with what we have been discussing here.

Not conclusive proof, but I have learned to trust the input
of the NCRS on all topics of an historical nature.

Steve

[3macs1]

Interesting Steve. I can see my friend in the engine shop possibly running into this since who knows who could have fitted the 4 bolt caps by the time he got the engine. It may not have been GM , but he was so specific and hit the years in question right on. At the same time I am not disputing the knowledge of the NCRS.
One thing that sticks in my mind is the fact these engines came out of cars that were put together in Canada. Would they do any engine machining I wonder. In the meantime I am watching the 512's.
Thanks for doing the research
Joe