66since71

Any way to tell main bearing size on my L-79 (327/350hp) "CE" replacement short block, without pulling the oil pan?

numbers are:

stamp pad: CEOA 18352
block cast date: L239 (Dec 23, 69?)
Block casting number: 3959512
also stamped (assembly date code?): 106 S3991

Oil pan is the original '66 pan. (I am afraid that alone may be my answer? But I am hoping for large mains.)

Thanks for any help... (Working on engine options again!)

Harry

Vet65te

Harry, you might want to double check that cast date number. If that block casting number is correct, it's unlikely that the last number on the date is a '9'. I had that same CE block in a 66 Coupe and in my 61 Vette now and both of them happened to be dated '63.
Mortec.com has that block cast number listed as follows:
3959512....327...62-67...2...Was also used for some "CE" replacement blocks
I believe the larger main bearing journal smallblocks didn't start till '68 so your CE engine is the small journal variety.
Mike T.

MikeM

AFAIK, there were no CE engines produced to replace '66 model engines. '67 and later with the 5/50 warranty. Also, AFAIK, the replacement CE short blocks were manufactured to original specs so if your engine was to replace a '67 engine, it would have the small mains. If it was to replace the '68 engine, it would have the large ones. Taking a guess, if the block has the rear breather, it's probably a small main '67 replacement.

I don't know anything about those number except the casting, forging dates. They can be several years after the original engine usage but should still be a direct replacement for what was there to start with.

Mike Ward

This presumes that the engine in question was built to replace the original engine in the car- is there paperwork to indicate this?

MikeM

The only SBC with the large mains and the rear breather was the '67 Camero 350 block.

There's actually a number of assumptions that could be made here and the only sure fire way to ID the size of the mains is to LOOK at them.

66since71

Thanks for all the feedback..

Mike T: I'm sure on the casting date. I bought the engine in 1975 from Mustang Chevrolet in San angelo Texas, so a 1969 casting date is not unreasonable. At the time the parts books listed the p/n I ordered as the correct 350 hp short block assembly for my '66. Thanks for the Mortec reference.

Mike M: good point on the intended use. I recall that the engine was to replace all 350 hp 327's. Wasn't the 68 motor a 327? If so, is it possible.......

Mike W: I ordered this engine, and at the time I confirmed that it was the correct listed part number for my car. So I'm fairly sure about its intended application.

My engine builder has a long history at Chevrolet in engine development. He thinks, based on when I bought the motor, there is a fair chance its a large journal motor. We are just trying to figure it out as we plan the next steps in this process.

Finally, you don't need to be named Mike to respond to this post!

Harry

muncieman

I kind of like the small journal motors, less bearing speed, lighter assembly. Is there some reason you want the bigger crank???

66since71

Wally, we are talking about a 383 using the existing block. He likes the larger bearings in that application. We've talked about a 30 over 350 in the same block, and he's OK with the small journal in that application. There may also be some availability issues with 383 cranks for the small journal block.

Harry

Vet65te

Harry, does your CE block have the rear breather hole?

MikeM

The '68 replacement engine will not have the rear breather and will have the large main bearings. The '67 replacement engine will have the rear breather and the small main bearings.

It's that simple.

oldskydog

The 3959512 was areplacement casting for the out of production small journal 327 block beginning in late 68 early 69 when the CE program started. Any replacement engines/blocks before that time would have used current production engines/blocks. After 69, those small journal blocks were no longer in production. GM recast the small journal blocks with new casting numbers to service the small journal requirements.
3959532 283 PASS/TRUCK CE
3959534 283 Chevy II/Nova CE
3959512 327 PASS/TRUCK 327 CE
3959538 327 Chevy II/Nova CE

MikeM

I don't believe this is a true statement if you're implying that a '68 replacement block, for example, was released from parts to replace a '67engine in service.

66since71

Mike, yes it does.

Mike M, I have the rear breather and I was hoping it wasn't (that simple). Apparently the things that make it large or small journal are defined when the block is machined, not necessarily when its cast. My engine was likely assembled in the early 70's, when there would have been a large journal crank for the 68 327, hence the question.

OldSkyDog, thanks for the info on castings. It does make sense, that prior to the CE program, service blocks would be pulled from regular production.

Harry

MikeM

Only if it's a direct fit. The '68 block is not a direct fit for the '67 engine. You could still buy service rear vent engines that were assembled, '62-'67, as normal production up into the late '60's, early '70's. Even complete engines.

I think the intended use for the CE's were to track warranty only and were not intended for general OTC purchase for service. That's not to say that didn't happen because it did. After the 5/50 warranty program expired, the leftover CE engines were put up for retail sale by dealers at big discounts to get rid of them.

I believe there is more meat down around the main webs with the larger main blocks also. It's not just machining.

AZDoug

The new L79 shortblock I purchased direct from a Chev dealer in late 1976 was a 512 CE block, cast March 1970.

It was a bargain at about $350

They are small journals for sure.

Doug

oldskydog

What I'm saying is that when they went to the large journal blocks in 68, they still had some stock of small journal blocks for service but when those ran out, and since they were dropping the 327 for regular production in 69, they came up with the CE program and new casting numbers to service the out-of-production small journal block requirements.

66since71

Doug, somewhere in my memory, I thought maybe you'd already looked at this. Thanks for the feedback.

Harry

JohnZ

The "CE" number says that engine was machined/assembled in 1970.

Marty Mischenko

So I have a large gernal 327 that when I pulled the heads off all 8 pistons where stamped 90? Anyone know what this means?

Robert61

If you familiarize yourself with the crank flanges. On the rear you'll be able to tell if it's a big or small journal. The 327 sj crank is round with 2 notches. The LG crank flange is different.