Any truth to this 396/402 update?
 

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Well I know this to be somewhat true from experience. Buddy of mine had a 375hp 396 and he blew the motor. Most of his parts dealings were through the dealer. When he opened up the motor he found that it was .030 over. He went to the dealer thinking he could get some warrenty relief. The dealer showed him a GM letter that explained why the motor was a &quot;402&quot; and that there was a series of blocks that were inadvertantly bored .030. also interesting is the fact that the pistons were TRW. This was in late 69. He bought the car off the lot in 68 after getting home from Viet Nam. </div></div>

Re: Any truth to this 396/402 update?
 

I don't think this was that unusual accross manufacturer's. I have had some Mopar motors which were the same way.

Re: Any truth to this 396/402 update?
 

He's claiming there was a mistake.

Re: Any truth to this 396/402 update?
 

I remember at some point that seemed to have happened. I had a 69 dusk blue 350 hp 396 with ac that when I went to have it rebuilt the machine shop guy told me it was already 30 over and thought it had never been rebuilt. Ten the 70 SS 396 Chevelle was actually a 402&quot;.

Re: Any truth to this 396/402 update?
 

What model year was the car in question?

Re: Any truth to this 396/402 update?
 

I think you're missing the point.

He's claiming that the bored-out 396 was initially a mistake and suggesting that &quot;The dealer showed him a GM letter that explained why the motor was a &quot;402&quot; and that there was a series of blocks that were inadvertantly bored .030. also interesting is the fact that the pistons were TRW.&quot;

I've never heard this and believe it to be wrong. The only thing I've heard ever was that all 396s in 1970 were 402s and that was a running change, most likely for emissions reasons.

I was hoping someone here would know for sure.

Re: Any truth to this 396/402 update?
 

If the 69 Camaro was a late production car (Fall of 69) the engine would have been a 402.

Didn't the 1970 modelyear 396 engines became 402, and for Tonawanda all production was for 1970 even if the Camaro was called a 69.

That they still were labeled 396, that's a different story.


Jan

Re: Any truth to this 396/402 update?
 

There's a technical bulletin that talks about the late `69 396's as being .030 oversize.

http://i36.photobucket.com/albums/e4...ulletin009.jpg

Re: Any truth to this 396/402 update?
 

i thought i remembered that they were green blocks that were machined too soon and had to be rebored .30 over.

Re: Any truth to this 396/402 update?
 

What I was told in order to meet the new emmsion problems the cubes would have to increase in order to have the same HP.

The 283=307 the 327 = 350 the 396= 402 and the 427= 454

All motors were increased in size.

Re: Any truth to this 396/402 update?
 

But, Kim, using your logic, then the 265-283 would have been for emissions too.

I think, in most cases, there was a natural progression to meet the demands of more power for cars that were gradually getting heavier. However, the 396-402 nudge was so negligible that it must've been done for other reasons, such as emissions.

Re: Any truth to this 396/402 update?
 

Just tryin' to thing back a bit........pretty sure it's in a magazine I have somewhere..??
Maybe some emission cave-in in design..??.But part of the chatter back then was some sort of hood clearance problem with the L78 highrise manifold in the 1970 Chevelle or Camaro....??

Re: Any truth to this 396/402 update?
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 442w30</div><div class="ubbcode-body"> He bought the car off the lot in 68 after getting home from Viet Nam.</div></div>

The statement above is the reason I inquired as to what model year car was in question. If this person bought the car in 68, then it was either a 68 (or older) or a early production 69 model. In either case, there was no wholesale .030&quot; overbore of 396 engines from the factory in that time frame, hence such an example could indeed have been some sort of 'mistake' from the factory.

Re: Any truth to this 396/402 update?
 

Do you think the factory would have sold a car with an overbore like that?

It was a Mopar board, so for all I know he could have been getting the year wrong. It was a sub-topic/tangent in a debate about 400 SBC and BBC. Getting 3 pages worth of Brand X there without the haters coming out was interesting. :-)

Re: Any truth to this 396/402 update?
 

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 442w30</div><div class="ubbcode-body">It was a Mopar board.....Getting 3 pages worth of Brand X there without the haters coming out was interesting. :-) </div></div>

Wow, that had to be a rarity, indeed!

Hard to say if the factory would have produced an engine like that or not prior to late in the 69 model year [img]<<GRAEMLIN_URL>>/dunno.gif[/img] If it was a very late production 69 model car, then there's little doubt that it came that way.

Re: Any truth to this 396/402 update?
 

If a 396 built for the 1969 model year has a 3 letter suffix, it is the 402. I has an 08E of 69, 69 Camaro, 3 letter suffix, 402 inch....Joe

Re: Any truth to this 396/402 update?
 

The 265 was changed to a 283 in 1957 had nothing to do with what was happening in 1970 and up. The HP was lowered each year after that. Hey that is what I was tolded back then.

Re: Any truth to this 396/402 update?
 

No 396 motor would be repaired with an overbore by the factory. It's not worth the time, they would just scrap it and do it again.

The 396 to 402 was changed effective the (regular) 1970 model year, which means it went into the late 69 Camaros.

From http://www.camaros.org/drivetrain.shtml#PadStamps
In 1970, engine application codes changed from a 2 digit to a 3 digit code by adding a prefix letter to the code. The prefix letter for passenger cars was C and the prefix letter for trucks was T. For example, the 1969 JF engine code became CJF in 1970. This change did affect late 1969 SS396 Camaros (but no other 69 Camaro model). Per the Sep-Oct 1969 Chevrolet Service News, these big-blocks with the 1970-style engine codes actually are 402 cubic inch engines. This was simply a .030 overbore of the 396 block. All advertising and sales literature still referred to the 402 engine as the 396.

Re: Any truth to this 396/402 update?
 

Haven't we discussed this here in the past and the extra bore was an economical way to intentionally total more than 400 actual cubes thus resulting in these engines being classed under a different and less stringent (and cost) emissions class?.
Being the 1970 production year was when GM dropped their no more than 400 cubes in an A-Body rule, is this perhaps the actual reason?.

[img]<<GRAEMLIN_URL>>/hmmm.gif[/img]
~ Pete

Re: Any truth to this 396/402 update?
 

I thought the overbore was to improve emissions.

Re: Any truth to this 396/402 update?
 

To go back to this, I suspected it was related to emissions too. But I've never found any 1970 rule change that being over 400 cu in would help. And .030 wouldn't affect emissions enough either.

But for some reason, they made the change. And it got really confusing cause they called it a 396, but it was a 402. But all the service docs called it a 400 - and there was also the SB 400. Reading service docs can be like a replay of 'who's on first...'

Re: Any truth to this 396/402 update?
 

This might be what the dealer was talking about. Here is some 1970 Model Year Info. It does mention the 1969 Camaro 396 as it relates to the 402 introduced in 1970. See page 7.

1970 New Model Summary

And information on the 402 Mark IV Block

400 Cu. In. Engine Released

However would not apply to an earlier 1969. That would have probably be a green block issue.

Greg