[Chevy454]

Well, here is what we have come up with so far. Let us know what you guys think.

The set of 840 heads we found are untouched, and original, and came with 1.88 exhuast valves...absolutely positive of that. They are also machined for BOTH plug types: N and peanut. This was common on early 291 heads, so I am thinking that the heads I have are kind of "in-betweens", or a combination 840/291.

Now, some food for thought. It took me a while of reading to figure out what Colvin meant in his descriptions of the 840 and 291 heads. He states that the production of 840 heads ceased around May of 1969. So, that means they switched over to the 291 heads, which had the 1.88 exhuast valves. He lists the 291 heads as available on the Chevelle, Camaro, Corvette, Chevy II, and Chev/Pass with the L-78/L-72/L-71 in 1969. That makes sense, as both the Corvette and Camaro production ran into early '70(?), and the 1970 L-78/LS-6 Chevelles and the L-78 Novas got the 291 heads. So, why would GM still be making the 840 head in late '69? They didn't...they switched to the 291 head across the entire car line around may of '69. The L-78 Chevelles were made before the LS-6 Chevelles were made, and L-78 Chevelle production ceased when the LS-6 debuted. But, they were still producing '69 Corvette and Camaros! So, you could essentially have a '69 Camaro/Corvette built AFTER a '70 Chevelle/Nova! Right?!

This explains why a lot of parts books and machine shop books only show the 2.19/1.88 combo for '69 cars...GM switched to the 291 heads around May '69, thus "updating" to the 1.88 valve, which would mean the latest combo is the one that the books will show. Another intersting note is that the NHRA shows the 291 head as being legal for 1969, along with the 840 heads. BUT, they only show the 2.19/1.72 combo on the '69 L-72s...why? Probably because the manufacturers had to have thier info submitted and approved PRIOR to the racing season, and GM didn't know about the "update" to the larger 1.88 valve until later in the season.

So, what is my point? Well, it looks like 1.88 exhuast valves were available in 1969 production cars, whether it be on some 840 heads or on the 291 heads. Now, how do I prove that my 840s originally had 1.88s, and who do I prove it to?

[Edited by Chevy454 (06-21-2001 at 01:21 PM).]