I have a set of 3964291's. They have 2.19" Intake, and 1.72" exhaust. They are completety stock (no porting, polishing, etc.) except they have after market springs and minor surfacing before they were put on the shelf. Date codes 61269/D1370 (both 4291's, 2.19/1.72) Can anyone help verify if these are "Yenko"/COPO heads for the 427 L78z. Also, where would one post them for sale.

Thanks,
Jerrid
legend@itol.com

Why would you think that they are COPO heads? All that I have come across were service replacement heads sold over the counter in the early 70s. There is no way of telling a COPO head from any other. They are an excellent closed chamber head with a real good intake port.

4291's were used on 1970 Camaro, Nova, and Chevelle L-78's, and 1970 Chevelle LS-6 454's; also available over-the-counter as service replacements.

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JohnZ
'69 Z28 Fathom Green

For those of you here who also visit the Supercar Registry Bulletin Board (http://www.yenko.net/cgi-bin/Ultimate.cgi), you all know that I have lately been researching the use of the 840/291 heads, and the valve sizes available with them. But, for those of you who don't, here is a recap...

The 291 heads were indeed used on late '69 model cars, in place of the 840 heads, which are identical except for different spark plug seats and valve sizes (sometimes). Sometime in May '69, 840 head production ceased, and the 291 heads were started. Now, that leaves some time after the allotment of 840 heads ran out, that the 291 heads would need to be used, as the normal run of most of the Chevrolet car lines had a couple more months of production left. BUT, the Camaro and Corvette production ran into 1970. Near the end of the calendar year 1969, you had both '69 and '70 model cars being built, using virtually the same head, so why would you ened 2 different sets? I have talked with individuals who have found 291 heads on '69 Corvettes and on COPO Camaros, so it did happen. And, if I researched long enough, I could probably find people who have found them on the other models as well. It also states that they were used across the model line in Alan Colvins Chevrolet by the Numbers, so you don't have to just take my word for it!

As for the valve sizes in these heads, have the heads ever had seats put in them? If so, you won't be able to tell if they came originally with the 1.72 or the 1.88 exhuast valve. The reason I ask is, that I recently acquired a set of 840 heads that are essentially "untouched", and have never been seated, yet they are machined for the 1.88 valves. [Note: I am working with Colvin on documenting them.]

As for documenting them as Yenko heads, that will be an impossible task, as Yenko bought his cars through Chevrolet, the same as any customer, and the 291 heads were used across the board in late '69 (L-71/L-72/L-78), and as someone stated above, on the 1970 L-78/LS-6 cars.

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Rob Clary
'69 Yenko Chevelle
Numerous Yenkos
Interested in COPOs, Yenkos or other dealer built muscle cars then go here: The Supercar Registry (http://www.yenko.net)