Wow, this is taking me back ... If my memory is to be believed, closed or small chamber heads were from 1967 ... from 68-71 (and possibly later) the heads had larger combustion chambers (the casting number 906 comes to mind).
I could be WAY off on this though ... take the valve covers off and get some casting numbers, then hit google and see what comes up.
If they are the small chamber heads, I'd be looking at the possibility of a head swap ... high compression on the street with the gas we have now can't be too much fun.
Who knows, you might even have some of the earlier Max Wedge heads on that thing (413,426) ... casting numbers will tell you what you have.
-- Edited by Pint and a Pound on Tuesday 27th of November 2012 09:52:16 PM
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I have been looking into finding more information on the 440 in my Plymouth and can't find all whats inside but have found out that it was rebuilt and done .30 over and was told it has a mild cam and also has closed chamber heads, just wondering if someone can tell me about them, fairly sure it has pretty high compression, guessing at least 11:1 or maybe a little more and have had the problem with knocking once the engine gets lots of heat under the hood and has been driven for anymore then about 20 miles, coolant temp is fine but just a lot of internal heat and with todays crappy gas have to use premium and octane boost to help out so decided to get a Snow water methanol injection kit for it, will post more once i find out how well this works. So if anyone can tell me what exactly closed chamber heads are and what other heads there are out there and are these heads giving me a higher compression also, thanks for any help.
The only closed chamber heads for the 440 were in 1967, and if I recall the last 3 digits are 915. All other big block heads from the non-smog era were the 2843906 heads. I can't remember what I had for supper last night, but I still remember a friggin casting number for a cylinder head !! Geez..
All heads previous to 1968 were closed chamber with a nominal 78.5cc chamber. The most common heads are the 516 casting which were available on all big blocks 64-67. This included low performance 440's. They have 2.08/1.60 valves and smaller ports than the later castings, with a poor short turn. Sometime in the 67' model year they stopped using these heads on low performance 440's and went to the much better 915 casting. The low performance 440's did keep the 1.60 exhaust valve, even with the 915 heads.
My guess is that they were using up existing stock of 516 casting heads on the low performance 440's, and when they were gone, they went to the 915's. The 516 was the only head available on the 440 in 1966, the first year for the 440.
All high performance 440 in 1967 got the 915 casting head with 2.08/1.74 valves. In 1968, they went to the open chamber 906 casting head on all big block motors, making the 915 a one year only head with closed chambers and the better ports. The open chamber heads have a nominal chamber size of 88cc's.
I have taken apart about five 67' 440's, and 3 of them had 915 heads. The other two had 516's.
452's are good street heads - did you know there are two different heads with the exact same head casting number? The heavy duty heads use a smaller plug to help keep them from cracking.
452's were made from 76 to the end of the big blocks. They have induction hardend valve seats, and a large open chamber - usually just over 90cc. The exhaust port is identical to the ports used from 67 onward, but the intake port is a bit flatter with short turn that is not as tall as the 906 or 915 heads. They are easy to port heads to get decent flow increased from, but for ultimate flow, the 906 or 915 are better heads.
The main reason I used the 452s was because of unleaded fuel, so I wanted the hardened seats. It was only a street car, so giving up a bit of power(at high RPM) for longevity was worth it. This was a daily driven car that got lots of miles put on it. I only had a Holley 650 on it because I wanted bottom end snap and wasn't too concerned about buzzing it to 6000. It was a fun car !!
