427 head questions...

[COPO]

The exhaust valve is larger on the #291 heads. 1.72" vs 1.88". There were a number of COPO's built after May of '69 consequently they would likely have had #291 heads. Can't help you on the part #'s.

[Chevy454]

COPO:

Thanks for the help. I knew of the valve size difference, but was wondering about the other stuff...combustion chamber, ports, etc. Any idea?

[Mis B]

I'm not sure if I understand your question about the part number on 840 and 291 heads. The only numbers for the heads that I have seen is the casting numbers: 3919840 and 3964291. 840 heads are square ports while 291 heads are oval ports. Jerry MacNeish states that 291 heads may have been installed on late model 69 Camaros but none have been found to substantial that. Our 69 Berger is a late May car and has original 840 heads. The original engine block has a Feb casting date.
Hope that helps.

[COPO]

The #291 are most definitely square port heads. They are on the '70 LS-6 and the '70 L-78. I believe you may be thinking of the #290 which are oval ports. I have not seen a '69 w/#291 heads, but the info in CBTN says they ceased production in May of '69 on the 840's, so any solid lifter BB built after the existing stock was gone would have had the #291 heads. I can tell you the #840's are much easier to find.

[Mis B]

291 heads ARE square port. I need to proof read my posts closer. Thanks for catching the mistake.
We do not see either 840 or 291 heads at swap meets in this part of the country anymore. All the 840s I remember seeing were early 69 cast dates. I do have any extra set of good 291s.

[Chevy454]

I was just curious to see if the older 291 heads carried the same part # as the ones that are available in the GM Performance Parts catalog.

Does anyone have a set of the newer 291 heads? If so, are they the same as the old heads?

[bkhpah]

We currently have a 69 375 Chevelle that we are doing some minor touchup work on. It is a June car with F-23-9 840's on it...BKH