1968 427 390hp block

[Patrick B.]

Re: 1968 427 390hp block

Yes, on a 2 bolt block, there is boss that it not drilled and tapped as on a 4 bolt. The boss that is drilled and tapped on both versions is a larger thread on the 4 bolt. I have seen several JC stamped blocks and none were 4 bolts. I have never seen a document saying that 400 hp engines should have 4 bolt blocks.

[Jimmy D.]

Re: 1968 427 390hp block

Ok good to know. So was the process that GM required 435 hp 427 to receive the 4bolt? If there we shortages then the engine plant would make changes. I guess the dealership could also make changes under warranty.

[Joe L.]

Re: 1968 427 390hp block

I have seen several JC stamped blocks and none were 4 bolts. I have never seen a document saying that 400 hp engines should have 4 bolt blocks.

Patrick------

Here's one reference that I could easily lay my hands on (I've seen others but they are not handy). This is from Alan Colvin's book "Chevrolet By The Numbers". Keep in mind that Colvin used Chevrolet records to research the information presented in his books.

DSCN3991 (2).jpg

[Patrick B.]

Re: 1968 427 390hp block

Patrick------

Here's one reference that I could easily lay my hands on (I've seen others but they are not handy). This is from Alan Colvin's book "Chevrolet By The Numbers". Keep in mind that Colvin used Chevrolet records to research the information presented in his books.

[ATTACH=CONFIG]110568[/ATTACH]

[Patrick B.]

Re: 1968 427 390hp block

Ok good to know. So was the process that GM required 435 hp 427 to receive the 4bolt? If there we shortages then the engine plant would make changes. I guess the dealership could also make changes under warranty.

[Michael B.]

Re: 1968 427 390hp block

I have an Oct 4, 1968 build date with an original L68. It has 2-bolt mains. I have overhauled one other 69 L68 and it was also a 2-bolt main. Also note that on the build sheets these are listed as 390HP 427 options and on a separate line the "390HP to 400HP equipment" is added. TankStickerc.jpg

[Jimmy D.]

Re: 1968 427 390hp block

Mike
That's interesting they listed it as a L36 and below a L68. Was that normal practice to list them both? Thanks Jimmy

[Leif A.]

Re: 1968 427 390hp block

Mike
That's interesting they listed it as a L36 and below a L68. Was that normal practice to list them both? Thanks Jimmy

Yes, it was...

[Tim G.]

Re: 1968 427 390hp block

The 400 horse motor was always an addon to a 390 horse motor. Here's an original window sticker from a car I owned, they called it out this way on the window sticker, also.

[Jimmy D.]

Re: 1968 427 390hp block

Tim that's cool. First time I saw that.
Thank you