68 L71 3919840 vs 3964291 cylinder head

[Erik S.]

I own a 68 L71 - the left cylinder head is all correct dated and numbered (#3919840), but the right head is a June 17 1970 # 3964291. This is what I found from a previous thread (as per Joe L)

"3964291 cylinder heads are rectangular port, hi performance cylinder heads originally used on all 1969 Chevrolet cars equipped with special hi performance, solid lifter 396 and 427 engines. They were also used in 1970 for 402 and 454(LS-6) engines with special high performance and solid lifters installed in Chevelles, Novas and Camaros."

My question is - apparently the head is functionally interchangeable with the 840 as it came off a properly running engine, but are there configuration differences? Should I swap the 291 for a 840 as numbers are not judged here?

Thanks again, from the lovely Amsterdam,
erik

[Joe L.]

Re: 68 L71 3919840 vs 3964291 cylinder head

I own a 68 L71 - the left cylinder head is all correct dated and numbered (#3919840), but the right head is a June 17 1970 # 3964291. This is what I found from a previous thread (as per Joe L)

"3964291 cylinder heads are rectangular port, hi performance cylinder heads originally used on all 1969 Chevrolet cars equipped with special hi performance, solid lifter 396 and 427 engines. They were also used in 1970 for 402 and 454(LS-6) engines with special high performance and solid lifters installed in Chevelles, Novas and Camaros."

My question is - apparently the head is functionally interchangeable with the 840 as it came off a properly running engine, but are there configuration differences? Should I swap the 291 for a 840 as numbers are not judged here?

Thanks again, from the lovely Amsterdam,
erik

Erik------

The GM #3964291 is a completely acceptable replacement for the GM #3919840. There should not be any significant external configuration differences PROVIDING that the 3964291 head uses gasketed type spark plugs and not the tapered seat spark plugs. The 3964291 heads were manufactured both ways.

One other difference between the two heads that won't show and shouldn't cause any real functional problem: the 3919840 uses 1.72" exhaust valves whereas the 3964291 uses 1.88" exhaust valves.

[Erik S.]

Re: 68 L71 3919840 vs 3964291 cylinder head

Thanks Joe - saves me a trip to Ebay