NHRA rulebooks: '69 or earlier

[Verne_Frantz]

Rob,
I'll go back and check again. Computer at work - - - books at home.........

Belair,
The Z-11 did get delivered with the full stock exhaust, just as any other hi-perf 409 would have had. The cast iron manifolds were the std. 925-926 units. Nothing wild like Pontiac did!

Verne.

[Chevy454]

The Chevys were definitely lacking in the exhaust manifold department. Here's a couple of "cast headers" the competitors offered:

426 Hemi:
http://www.v8buick.com/attachment.ph...p;postid=56021

427 FoMoCo:
http://www.v8buick.com/attachment.ph...;postid=217637

Wouldn't it be nice... [img]/ubbthreads/images/graemlins/tongue.gif[/img]

[Verne_Frantz]

You know Rob, going back over these old rule books is bringing back memories and making me feel like an old drag racer again. Could be dangerous!

Anyway, I couldn't find any specific reference or rule regarding compression ratio. The only mention of it is under "pistons". Any aftermarket piston was allowed as long as it was based on the OEM design and no piston could be used that would increase compression ratio.
That rule is present from '65 - '69. There's another way it could be raised though.
'67-'69 rules permit up to a .030" overbore (on '63 and later engines) but with a maximum cubic inch size of 430ci in SS/A & SS/AA. (A .060" overbore was allowed on '62 and earlier engines with no maximum size specified). It also notes that the bore size would be measured above the ring travel, to allow for cylinder wear. So, we know that for Chevy V8s (except for the 348-409 W design) boring increases compression ratio. (swept volume increases, but combustion chamber volume remains the same).
One other possibility to raise the C.R. might be if the parts system listed thinner head gaskets. In general, the rule says all engine components must be of the type originally offered to the public (unless noted otherwise, as with the pistons).
For '65 & '66 the overbore rule was slightly different. Same as above, except the maximum size was 427.2ci. (!!) in S/S, S/SA, A/S, A/SA and FX classes.
So, there you go.........
Are we planning on getting serious with the 1320 here????

As for those cast iron manifolds, the '63 & '64 409 design actually did flow much better than the earlier ones, but not as well as those radical F--d or Pontiac units. I have a set of those on my '62, and can squeak by the critics since that design was offered as part of a service package in April '62. (it's a late April car).
I know your MKIV big blocks were choked pretty hard with the factory manifolds, and really wake up with a set of headers.

Regards,
Verne.

[Chevy454]

[ QUOTE ]
Are we planning on getting serious with the 1320 here????

[/ QUOTE ]

I wish! I would love to have a A/SA car to play with, but too many other projects, and too little time. There's not a chance in Hades I could be competitive, but yanking the wheels like they do has GOT to be good for something!

Mainly I'm just curious about how NHRA "used" to be. NHRA seems to be trying to phase out the sportsman guys as of late, so pretty soon all this "class" stuff is gonna be history...

[Belair62]

Here is the ugly end of an aluminum Pontiac SD exhaust manifold...cast collectors.

[Chevy454]

Are those dumps?! Way cool! Did they come from the factory with those on the ends of the manifolds?

[Belair62]

Yes those are factory dumps....manifolds came from factory either aluminum or cast iron..pretty exotic stuff....

[JoeG]

Very nice--- [img]/ubbthreads/images/graemlins/beers.gif[/img]

[Belair62]

Probably should have kept that one.

[JoeG]

[img]/ubbthreads/images/graemlins/shocked.gif[/img]----Gone????