Thread: New kid on the block / with a block

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Hi folks, I am knew to the page, so forgive me if this has been covered before.

I just bought what apparently is a GM crate motor, out of a 69 Chevrolet truck.
The block is a 3970010, the seller knows it has 4 bolt mains, and the heads read 3998993, which from all my sources should be 75cc Mexico Goodwrench heads. The entire engine was corporate blue/green, with a Q jet and not much smog stuff and plumbing. The water pump must be a "long" pump, because it does not look like the pump that was on my 58 283, 64 327, etc.

Somebody tell me what I have. I bought it for the block, so really the rest is icing on the cake, but I sure wish it had 69 era heads on it.

Originally Posted by Bobaloo

Hi folks, I am knew to the page, so forgive me if this has been covered before.

I just bought what apparently is a GM crate motor, out of a 69 Chevrolet truck.
The block is a 3970010, the seller knows it has 4 bolt mains, and the heads read 3998993, which from all my sources should be 75cc Mexico Goodwrench heads. The entire engine was corporate blue/green, with a Q jet and not much smog stuff and plumbing. The water pump must be a "long" pump, because it does not look like the pump that was on my 58 283, 64 327, etc.

Somebody tell me what I have. I bought it for the block, so really the rest is icing on the cake, but I sure wish it had 69 era heads on it.

Welcome,
Your 993 heads are a good street open chamber head.
If you want to go faster you have come to the right place.

Mortec shows it as either a 302 from 69, or a 327 from 69, or a 350 from 69-80, you have the same casting numbers my 350 has

My short range plans are to gather speed equipment, as in a 2178 "Duntov" solid cam (okay so I am old - this is what I like), lifters, roller rockers, get the squish up to about 9.5 or 10 to 1, and later place it neatly into a 70 to 73 Camaro or 68-74 Nova. Sure wish there had been some humps on those heads.

The way to tell if it is the early, block is that the distributor hole goes right up to the top of the intake manifold sealing rail.
If yoy want to tell the difference between a Mex block and a USA block the easy wak is to look at the rear where the bellhousing bolts on... On a USA block the bolt bosses are blind the casting extends right back to the water jacket wall. On a Mex block the holes are open, you can see light out the other end.

Also do you know how to read casting dates ? And where they are located ?

The only casting date I could find is A 05 79

where was it ?

That translates to January 5th 1979

I can't remember if it was on the head, or at the rear of the block. I was trying to remember so much stuff, I wrote down the date, but I can't remember where it was. The good news (I guess) is, there was no sludge in the rocker area, I could read the casting number, and probably the casting date without much trouble.

That would probably be for the heads, as you said they are the Mex heads, if the whole engine is corp blue green then the chances are that it is a Mex block, but you never really can be sure untill you check the block casting date.

Okay, now let me ask this in the nicest way...Should I care if it's a Mexican block? Are they better worse, or no different than a Tonowanda?

WEll............

The Mex blocks are about 20 lbs lighter than the tonawandas, they shaved metal off for weight savings. On the bellhousing bosses like I mentioned, but also in the crankcase webs, and very importantly also in the cylinder bore thickness.
So as a consequence the Mex blocks are not as rigid or strong as the Tonawandas. Also you can only rebore them .030 Max in the majority of cases.
Also another factor is the metalurgy, there is no tin or nickel, they just use cast iron as a consequence they wear fast and can be porous.

In my opinion you are better off with a Tonawanda 2 bolter. they take up to 500 Hp as a conservative figure with 2 bolt mains. If you want 4 bolts get an eagle 4 bolt main conversion kit for $69.00 on Ebay, they are the angled caps, but if you do this also know that the block must be align bored. Then you have strong horsepower foundation for your next project motor

Originally Posted by Bobaloo

Okay, now let me ask this in the nicest way...Should I care if it's a Mexican block? Are they better worse, or no different than a Tonowanda?

If you are looking at more than 400 HP I.M.O. then I would look for a different block.
Also I would look at newer cam grinds.
Cams have come a long way in 30 years.
I have a customer that likes the older cam grinds.
We did the old "switch aroo" on him.
He thinks he is running a 350 hp 327 cam what he does not know is it is a Lunati Voodoo cam which makes about 25 hp over his old cam.
What he does'nt know won't hurt him.

Well he went and dissapeared, I hope we hear from him again

Hi folks,
I didn't go away, the page would not let me log in. I tried for hours last night and again this morning, even sent the webmaster an email. Finally I got it to take my log-in. It kept saying "the page was not found"!

Last night while reading the Chevrolet Small Block Interchange Manual by David Lewis, he seems to be a fan of Mexico 350's. At least he was in 1989.
Pointing out that they have the 1.94 valves, a strong head casting, and so forth. Has the quality gone down the hill in the last 20 years? Since mine apparently was manufactured in 1979, is that something to be considered.

Bottom line, I have paid the man his $200, and got my fairly clean engine (the whole thing from air cleaner down, except the exaust manifolds), for better or worse.
It's a shame I have to pick it up in a F*** F100.

get the stamped #'s off the front pad and take them to a chevy dealer. they'll tell you exactly what it is. did it for years