396 vs 427

[Jim D.]

I recently looked at a 65 396 roadster. The owner has passed away but his wife and my brother have been friends for decades. In the late 60's, the 396 froze (no anti-freeze) and cracked the block. My brother remembers towing him to a Chevy dealer and the owner told them to put in a 425HP 427. I didn't have much time to examine the car so I didn't get a casting number but it has the original intake, carb, TI ignition, exhaust manifolds etc. My question is, would they have replaced the short block or put in a long block? The pad is stamped "CE" and "OA". Nothing else. My brother said the car was noticeably faster with the new motor. Comments???

[Patrick B.]

Re: 396 vs 427

CE designates either a fitted block (block and pistons with rings) or a whole short block. Either one would be sufficient for a dealer to replace a freeze cracked 396 block while turning it into a 427. There would have been no reason to change heads unless a head was also frozen. Remove a valve cover and look for the 3856208 casting number for the 396. I don't think they sold long blocks, only complete engines which would have had the 427-425 assembly stamp.

[Jim D.]

Re: 396 vs 427

Thanks for the info. Pat. I thought I remembered reading that bare & short blocks didn't get the CE stamp. I guess I'm wrong. I was hoping the additional OA stamp may signify something. If the widow decides to sell the car, I'll get a better chance to check numbers when I pick it up.

[Joe L.]

Re: 396 vs 427

I recently looked at a 65 396 roadster. The owner has passed away but his wife and my brother have been friends for decades. In the late 60's, the 396 froze (no anti-freeze) and cracked the block. My brother remembers towing him to a Chevy dealer and the owner told them to put in a 425HP 427. I didn't have much time to examine the car so I didn't get a casting number but it has the original intake, carb, TI ignition, exhaust manifolds etc. My question is, would they have replaced the short block or put in a long block? The pad is stamped "CE" and "OA". Nothing else. My brother said the car was noticeably faster with the new motor. Comments???

Jim------

Essentially and for all practical purposes, the L-78 and L-72 are identical engines except for bore size.

[Duke W.]

Re: 396 vs 427

Duntov made a famous statement when the press asked him why the bore size was increased. His answer: It reduced weight.

I believe the 427 blocks have different internal coring to allow the larger bore size, and I don't think you can bore 396 blocks out to 4.25" without ending up with too thin cylinder walls.

Like Joe said the L-78 and L-72 are essentially identical other than bore size, and if a 396 block cracked six months after production started and the repair was customer paid rather than warranty, it would be a no-brainer to order a 427 fitted block for the repair.

Duke

[Joe L.]

Re: 396 vs 427

I believe the 427 blocks have different internal coring to allow the larger bore size, and I don't think you can bore 396 blocks out to 4.25" without ending up with too thin cylinder walls.



Duke

Duke-----


Yes, 396 blocks were a unique casting designed for the 4.094" bore of the 396. For the most part, a 396 block cannot be bored safely to the 4.25" bore of a 427. 0.060" is about the maximum safe overbore which only gets one to 4.154". I would never feel comfortable going beyond 0.060" even if sonic testing showed it could be done for a particular block.

[John H.]

Re: 396 vs 427

The pad is stamped "CE" and "OA". Nothing else. My brother said the car was noticeably faster with the new motor. Comments???

Jim -

The "CE" says warranty replacement, and the following "0A" says 1970 date of manufacture; a Tonawanda "CE" short block pad stamp would normally be followed by a five-digit sequential number between 50,000 and 79,999. There should also be a crude date stamp on the starter pad, visible after removing the starter.

[Jim D.]

Re: 396 vs 427

Jim -

The "CE" says warranty replacement, and the following "0A" says 1970 date of manufacture; a Tonawanda "CE" short block pad stamp would normally be followed by a five-digit sequential number between 50,000 and 79,999. There should also be a crude date stamp on the starter pad, visible after removing the starter.

Wouldn't 1970 be out of the warranty period for a 1965 car? There was nothing on the pad other than the CE & OA. I can only hope that the widow sells me the car and I can post more info. It's a Glen Green, blk interior, 2 top car.

[Michael H.]

Re: 396 vs 427

Wouldn't 1970 be out of the warranty period for a 1965 car? There was nothing on the pad other than the CE & OA. I can only hope that the widow sells me the car and I can post more info. It's a Glen Green, blk interior, 2 top car.

Jim

Yes, the car would have been out of warranty. All partial engine assemblies were stamped with the CE after some time in late 1968 or 69 even if they were not warranty.

[Patrick B.]

Re: 396 vs 427

1965 396 4-bolt blocks made until August 65 were unique from other 396's. They had the same water jackets around the bores as a 427. If you compare the distance between the cylinder walls looking thru the freeze plug holes these blocks are the same as a 427. They can be bored to at least to 4.310". They are perceptably heavier than a 427 block; Zora was right about that.

[Jim T.]

Re: 396 vs 427

Did the dealership paint the block before it was installed?

[Stuart F.]

Re: 396 vs 427

I lost the 305CI from my 87 caprice due to a porasity crack down through the valley - front to back. This was a well published foundry fault that happened to a series of engines (the car was still under warranty). I knew the dealer well enough to have them cooperate and get me a replacement 350CI (I worked for GM then and made a few calls as well). So, it could be done, but I believe you had to push a few buttons.

Stu Fox

[Kenneth B.]

Re: 396 vs 427

Jim

Yes, the car would have been out of warranty. All partial engine assemblies were stamped with the CE after some time in late 1968 or 69 even if they were not warranty.

No matter when it happened I don't think GM would replace a engine under warranty because someone didn't put antifreeze in the block in the winter.

[Joe L.]

Re: 396 vs 427

1965 396 4-bolt blocks made until August 65 were unique from other 396's. They had the same water jackets around the bores as a 427. If you compare the distance between the cylinder walls looking thru the freeze plug holes these blocks are the same as a 427. They can be bored to at least to 4.310". They are perceptably heavier than a 427 block; Zora was right about that.

Patrick------


I've hear this before regarding the 3855962 blocks. However, here's what I don't understand. The block as you describe it would be, essentially, a 427 block although underbored for the 396 application. As such, why wouldn't GM have used this exact same block casting for the 1966 L-72?

[Michael H.]

Re: 396 vs 427

Patrick------


I've hear this before regarding the 3855962 blocks. However, here's what I don't understand. The block as you describe it would be, essentially, a 427 block although underbored for the 396 application. As such, why wouldn't GM have used this exact same block casting for the 1966 L-72?

Patrick, Joe

I vaguely remember hearing that the original 396 was actually supposed to be a 427. Before introduction of the new 427, there was an AMA (?) ban on engines over 400 cubic inches for cars weighing less than some minimum weight. The original/early blocks were then bored to 4.094" (?) instead of the 4.250" of the 427.
Then, supposedly, the later 65 castings were changed slightly and now had somewhat thinner wall.

That story was floating around way back in the 60's. Who knows if it's true but it does sound somewhat reasonable.