Heads Up! Pondering Info?

[dartjack]

I just reread an article in Mopar Muscle/July 06 about Mopar heads. It rated the various heads as to power output. It said that the swirl port head(302-308 casting) would make more power than the X or J heads!? Following that would be the 92 and up Magnun head. Of course the aftermarket heads would follow from there. The reasoning was the quench chamber design would outperform(out power) the larger port and valve heads? I can see their point at lower rpm levels or smaller displacements. I guess what I'm seeing is better burn is better than more flow. My question is how much difference would it make on a moderate 360 streeter? In the planning stages now but I am one of the old school guys who would rather build good torque than peaky HP. It doesn't make to much sense to me to have 500HP when 99.9% of my driving will be under 2500rpm. Feel free to knock this one around. To "stroke or not" was a good thread(a little heated) but I don't want to open another my opinion is better than yours feud.

Thanks guys.

 

[BJR Racing]

dartjack,
The small quench heads are very good for street as this is what they were built for, to help emissions and make more power in the low rpm range and more torque. Just stay with the stock size valves and do some work to the heads and it should be way more than what you will need on the street. A small cam will help alot with the torque and low rpm HP and it should be good to 5000 rpm's, open the bowl area up and gasket match the heads and you should be set.

 

[dartjack]

Are you refering to the 302/308 heads or the magnum heads? This will be a project over time. Would a 360 magnum be a good choice to build? BTW the car will be a 75 Swinger with an 833 4spd or od. I have both. Car is now a /6 904. By the time the body work is done several deals on core engines will have come and gone.
Thanks

 

[BJR Racing]

Yes any of the quench heads 302/308 or magnums. The 360 magnum will work but it's a thin wall casting so the over bore should be kept to a minimum, they also use different rods and pistons so the older engines won't interchange with parts, the cranks have different rod journals also so you'll be limited on selection. But should be good for what your trying to achieve.

 

[moper]

There are all kinds of schools of thought on that. This is how I understand it. The high swirl stuff is the first attempt for higher velocity vs. more volume in ports, combined with trying to use tumble in the chambers to help emisions and mileage. Courtesy of Larry Widmer.
The 302 castings are a quench design, which uses a high swirl port and bowl, and a quench pad (the "closed) part of the chamber to get the benfits, and is found only on 318 cubic inch, because of the smaller (properly sized for the displacement) port and valve design.
The 308 uses a physically bigger port for the intake and exh, and swirl inducing design, but has no quench pad (open chamber), and is designed with the larger port and valve design for 360s.
The down side was both these heads were used on existing shortblocks, that rendered the better design only partially successful. You must consider the combustion chamber as the dome of the piston, the gasket cross section, and the head's chamber as "the chamber". Having no quench pads or quench rings on the pistons, or not getting the parts close enough together at the right time, and you lose a bit of the swirl's affect, and all the tumble/quench affect.
The Magnum head took the idea further. A smaller chamber, with a dished piston, but the piston coming further up in the bore, coupled with a physically smaller port and valve that was a much better shape than past designs, let the full benefits of both concepts really come thru. The down side to the magnums is, there is a point where the design cant really move any more air, even with porting, because of the design. Some say you can make big naturally aspirated numbers with the Magnums. I've never witnessed a set making over a true 480hp on a 360, but I'm sure a good builder could get a little more from them, albeit not from port flo, but overall engine design and assembly. A set of well done "308" castings can move enough air to make more, but you loose the quench. The 308s are IMO the best factory head for a 4" stroke tho. The 302s work very well on 273-360s, but the bigger the engine, the more limited they are. I run them in ported form on a mild 360 I have, and on several 318 street engines. The 318s will rev better, the 360 will pull a house at 1500rpm in over drive, but is pretty well done at 5300. The 318s have bigger cams too, so it may be just my cam choice. For what it's worth...lol.