More 840 head questions...

[moparts]

Does anyone have any old GM tech manuals or parts manuals with this head valve info in it???? 69 dated????

Not having any luck finding the 219/172 combination in any parts books under 427 listing. That combo show up under the 396 listings. Rob and I have been comparing the GM by the numbers book with Gm performance parts catalog and my Sealed Power and Perfect Circle parts catalog and are having lots of problems getting information to match.

Now I am not saying that my parts books are always correct (have a whole shelf full of returns to prove that) but it sure seems funny that out of 3 different catalogs that none of them show the 219/172 combo for the 427 engines.

Now with all that being said, and assuming that the machine shop is telling us right,(assume = ass u me) is it possible that some of the late made 840's would have had 188 ex. in them? and how do you prove it??????

[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).]

[Chevy454]

Well, I got the heads back from the machine shop, and I see what they are saying...they are definitely untouched, and came with the 1.88s.

But, I found something else interesting laying on the shelf in our shop: a 291 head cast just 3 days after (F 10 9) one of the 840 heads that have me stumped! What's interesting is that they also have the 2.19/1.88s, BUT take the peanut style spark plug where as the 840s with the 2.19/1.88s take the N style spark plugs. So, these heads were near the first and last respectively of their type cast...neat, huh!?

Now, more questions: I need to know what the rest of the things cast into the heads mean...like "GM3T", "CONV 4", "NO-5", etc.

Also, anyone know Alan Colvin's phone #?!

[Mr70]

You have mail.

[Rowdy Rat]

That IS pretty interesting...

I saw from your post on the NCRS Discussion Board that Terry McManmon came back with an answer referring to a Corvette with VIN #385## that was equipped with 840 heads. The car I saw in Joplin, MO (actually, Terry saw this one too) was VIN #386## and also had 840 heads. These are both mid-December 1969 cars so it looks as though the 840 heads were used for at least one car line until the end of 1969 production.

Your theory that 1.88" exhaust valves were used in 840 heads (or heads used late in the 1969 calendar year) is going to be harder to prove. You're going to need to find cars with original engines to prove this and the owners of these cars are typically reluctant to start taking them apart so someone can check valve sizes . Add to that the published information from GM that calls for 1.72" exhaust valves and it appears that you have your work cut out for you on this one.

Having said that, I think you may be on to something here. If the 291s were getting 1.88" exhaust valves late in 1969, it makes sense that GM would make it an across the board move and use them in 840s as well... Proving it is going to be the tough part. I'll keep researching this (as well as 840/291 usage) and keep you informed as to what I discover.

Regards,

Stan

[Chevy454]

Stan:

I would GLADLY accept any help I could get on this! Believe me, this is THE LAST thing that I needed right now, as I was just really needing a set of heads to finish our engine for the "Certified Stock", but now I have a set of mint heads that I can't use, as they are possibly peices of a puzzle!

OK, so it seems we all agree that some 1969 cars got 291 heads from the factory? Right?! Terry had saw the 'Vette with 1 291 head and Ed Cunneen told me he had an L-72 (Camaro engine I believe) with 291s that he said came that way. So, now the question is what valves and spark plug seats should these early 291s have? The early (F 10 9) head I have has 2.19/1.88s and takes a peanut plug.

Now for the 840s! I'm kind of at a "cross roads" so to speak with these. I kind of need to run them, but I hate to as they may be something of interest to some people. So, I am going to TRY and hold off as long as possible on using them. But, everyone so far that has seen these heads believes they originally came with the 2.19/1.88s. But, like you said, we have to PROVE it. So, since we live in the "Show-Me" state, that's kind of what I plan to do...to whoever is interested.

So, since I have an 840 head and a 291 head cast just 3 days apart, does this mean these were possibly the days that they quit casting the 840s and started casting the 291s?

[Chevy454]

Well, I talked to Colvin today, and he said it sounded like something he would like to see. So, I'm gonna grab the digital camera and snap some pictures. He said he has been trying to finish up his new book (Corvette by the Numbers) but that he will try and dig through his stuff and see what he can come up with.

As for the 291 heads on '69 cars, he agreed that it happened, albeit on late cars, but he really hadn't had a chance to document any original engine cars with the 291s. So, if you own one, or know of one, you might contact Allen so he can document it.

But, for now, I'm stuck with a set of gorgeous heads I can't use (the 840s), and a set of heads that I am going to have to have re-seated with smaller seats and new and smaller exhaust valves (my early 291s) so i can run at the PSMCDR. Some days it never pays to get out of bed...

[Edited by Chevy454 (06-29-2001 at 04:15 PM).]