Decent 350?

[Looped]

This could be a decent block (#3970010) for someone down in the FL area to build something nice with. It has a high nickel content that GM made from the late 60’s to late 70’s. This guy probably does not know what he has because it was in a van, but they were installed in a wide range of vehicles. Not many of these blocks are around do to the demand. If were closer it would be mine. http://cgi.ebay.com/ebaymotors/aw-cgi/ebayISAPI.dll?ViewItem&item=569453141&r=0&t=0

Craig

[Forrest]

That a good casting, but not all of those blocks with that casting number were high nickle. You need to peek under the timing cover and look for the numbers 10 and 20, which is the percent nickle and tin (or the other way around). Anyway, the best blocks are the 10/20 blocks, but more importantly you want near zero core-shift an any block you plan to use - especially if you want to take it 0.030" over.

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Forrest

[Looped]

Forrest,
I believe all of the #3970010 had the 10% Nickel in them. The 10/20 (10% tin/20% nickel the same as the Bowtie blocks) were better, the nickel added strength and the tin allowed the block to flex (maybe flex is not the right word) better under high HP without cracking. Most other standard GM blocks have only about 5-7% nickel. Lots of Oval track guys desire these blocks. What is funny is they were mostly made during the worst years for creating HP (after the gas crunch).

Craig

[PaulO]

Forrest,
How do you determine the amount of core shift?
PaulO

[Forrest]

PaulO - just take a look at the cam bore boss and see how close the cam bore is centered on the boss. Since all block machining is in reference to the camshaft/ crankshaft bores, core shift places the one side of the cylinder boars closer to the water jacket that the other. Usually there will be at least some small degree core shift which is usually OK, but you can find blocks that are fairly close to dead-on. On the other hand, I've seen many blocks where the core shift must have been a quarter-of-an-inch that have been bored and run just fine and lasted many miles in a low performance automotive environment.

Craig - I have a pair of 3970010 blocks with an undetectable amount of core shift that I'm using to build my 383s for the Magnum. If that's true about these blocks are composed of 10% nickel, and you're probably right now that I think about it, you just made my day!



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Forrest

[Looped]

Forrest,
I have been going out of my mind trying to track an engine setup for the past 2 months or so. I have heard the same thing from a few people referring to the nickel &tin/nickel blocks. About a month ago I thought I was all set with a 327/375hp block but it turned out to have had a .060 job done to it (now a 187lbs paperweight). I have now found one of these 3970010 blocks to do something with 302, 327, 383….

Craig

[Tim Howland]

Craig,

Way back in '79 I had a 3966921 short block in the plastic back in the crate from the factory. Bought it from Davidson Chevrolet for $675. Was looking to put it into a 1980 Correct Craft Mustang. The boat show salesperson thought I was insane. And then my partner asked about marriage. 350/370horse, four bolt mains, solid lifter, 11 and a quater to one pistons. Sold it to a guy restoring a '69 vette for $975. Two weeks later a guy building modifieds offered me $1200. Wish I had it now, angle plug heads et al. 350's with the 400 crank seem to be the shade tree way to go. Dennis Moore, as much saavy as Grumpy had!

[Looped]

Tim,
That seems to be the best route. The block needs to be bored anyway, so that blows the true 302 & 327 bore size of 4.00". So it really leaves me with the 4.030 bore, 400 crank and say the Vortec #12558062 heads to make a Semi-Vortec 383. Hmmmm

I really need to move on with this engine thing, Sorry.

Craig