402 head #'s???

[GMC69mnypit]

Hey, does anybody know the more popular Head casting #'s used on our generation 402's? Or, if not the casting numbers themselves, were ours usually oval/square/peanut port, valve size, runner cc, open/closed chamber etc? Any info would be appreciated.

Thanks,
Brandon

[dave3156]

I have a 1970 402. They are oval port heads. I can get the casting #s for you tomorrow, unless someone else has them handy.

[55454]

www.mortec.com

[GMC69mnypit]

Dave3156, thanks for the info.

Yeah, I've been to Moretec and all of the other casting # sites, but they don't do a very good job of listing the heads used by model, and an even poorer job of listing the head configuration. Sure, there were probably half a dozen different head #'s used on our 402's in '72 alone, but I'm assuming since the HP rating was the same that the configuration of the heads was the same - i.e., 2.19/1.88 or ???/???, open/closed chamber, oval/rectangle/peanut port, runner cc, chamber volume, etc. That's the info I'm looking for. Just trying to get a rough idea what we had factory.

Thanks,
-Brandon

[COBRO]

My 72 402 had 820 heads which is shown to used from 71 thru 84 on 402 and 454. All BBC heads used up thru 72 in trucks were oval port heads and had 2.06 and 1.72 valves,most but not all were open chamber,the 366/427 tall deck used closed chambers. Rectangular port heads were never used on any truck engines and the peanut port heads didnt show up until the late 80s. The best of the bunch for flow are the 049 so I hear. HTH::::::CB

[dave3156]

Here are all the numbers I could find on my 1970 402 heads which came from a 1970 3/4 ton truck: 3975950, GM4T, C28 70 and the words: M TRUCK

Hope this helps.

[drink2mny]

Mine are 820, original to my 402..

Here's a good heads link
http://www.roadsters.com/bbc/#oval

[dave3156]

Mortec lists my stock heads as open chamber. My heads are not listed on the roadster.com site. Are they listed somehwere else as closed? What is the difference in performace between open and closed chamber heads?

[GMC69mnypit]

Thanks for all the info. guys, that gives me a good idea of where I'm at.

Open vs. closed? The casting #sites are usually pretty accurate on this, and I haven't heard/seen an instance where the same casting # was used on both. As far as performance - I think, like everything, its a matter of opinion and a question of "what do you want it to do?" Some people complain that the valves are shrouded with closed chamber heads.

You can SOMETIMES interchange the two to more tailor you compression ratio. If you are running closed chamber pistons, you should be able to use either head. If you are running open chamber pistons with any dome height to speak of and try to swap to closed chamber heads, you're gonna have a big clearance issue - if you can even get the heads bolted on. (pistons are classified open or closed to go with the corresponding head. Running closed chamber pistons with open chamber heads gives you more compression ratio choices, I don't know how/if it affects performance due to combustion chamber efficiency - hot spots/whatever.)

Go to your favorite suppliers website, find some good closeup pictures of open and closed chamber heads AND pistons. Look at the piston dome and head chamber shapes and you'll be able to see what you can mix and what you can't.

[dave3156]

Attached are pictures of the combustion chamber of the heads. Open or closed? I looked at pictures of open and closed heads but really couldn't tell when compared to these.

[55454]

Many 402's came with semi-closed. If you put a set of closed chambered heads on a 454
it will give free horse power (hardened seats). Opinion only not fact.

Tommy

[GMC69mnypit]

Those are open, look at the size and shape of the combustion chamber:

Open:




closed:


gen v and gen vi "vortec" style closed:

[GMC69mnypit]

I agree with what Tommy said, just make sure you're not running this piston with this head

kind of a gross exageration, buy you get the idea.

[dave3156]

Thanks for taking the time to show the pictures. Now I know I have open heads. I still wonder if I should look for better flowing heads. If they increase flow by 20-30% they would be worth it. Anyone know or have an idea how much better the 049 or 781 heads flow? I'm leaning toward having the heads I have rebuilt. Can I improve the heads I have by machine work or using different valves? At a minimium I would have the valves ground, use the comp cam valve springs, and new guides and keepers. Anything else I can do?

[55454]

I dont know the spec's, but over my 25 years of collecting, with the exclusion of rectangle ports, 049's and 781's which pretty much flow the same but the 049 is an older casting are the best for the money on a 454. Unless you want the closed chambered heads and can afford the cost because 40 years later they are desirable to the muscle cars not to mention rebuilding them for todays gas. Like I said before I am not an expert it is only a hobby, but this is the best set-up I can afford, without expensive rect, cc or after market.

Thanks Tommy