Alf44:
The "Engine Quest"/"Iron Ram" heads, which are improved Magnum heads (both for flow and to mitigate exhaust valve seat cracking) are exactly that. They are Magnum heads in terms of basic design, but can be bought with an LA intake bolt pattern. If you don't want to go to the expense of changing everything (air conditioning compressor, power steering pump. alternator, throttle linkage, etc.), then these are probably the most cost effective way to go. You get some of the best flowing heads ever put on a small block Mopar, and retain all of your accessorites, down to the throttle linkage and transmission kick down cable. Even on the Magnum swaps site, they indicate that the only real issue is ensuring a good port match. The Magnum heads, because they are on essentially an LA short block, must by necessity have the ports in places close to where they were on the LA Blocks. The only hassle is the straight intake bolts on the Magnum heads, and the angled one on the LA heads. But even there, a company called Crosswind makes an intake that fits both bolt angles. I think the Magnum heads are much closer in design to the larger ports on the 4 Barrel LA heads, but did read thatthe throttle body on the earlier Magnum engines could be replaced with a 2 Barrel carb; they were designed to accommodate a 2BBL carb in case Mopar wanted a lower cost alternative. With the flow capabilities of the Magnum heads, though, you would give up a lot of potential power due to the reduced flow from a regular sized 2 BBL carb, or if you used a really large 2BBL carb, would probably have drivability and fuel economy issues.
The Engine Quest heads, besides offering some of the best flow numbers, also increase the CR to about 9.5:1 (58cc combustion chamber volume) if used with a .028" thick head gasket, addressing the low compression issue with the 318s/360s from the mid 1970s-1980s. You do need conversion pushrods and lifters, though.
A hybrid LA/Magnum combo is not only possible, it is a good way to go at minimal cost.
Kostas
P.S. The link for the EngineQuest heads is here:
http://www.aamidwest.com/enginequest/eq-cylinder-heads/
At the bottom of the page is an article about a 318 street engine that makes 402 HP. This was after zero decking the block and using the KB167 pistons. Without the zero decking, I would think that it would easily make the power that you are looking for. They go through the build up logic pretty well, the keys being the flow numbers from the Engine Quest heads, the camshaft used, and the compression increase with the KB167 pistons. If I was not chasing the big numbers that they were, I would think that using the factory 4BBL iron intake (in order to retain all of the factory engine accessories) and not zero decking the block (but using the thin head gaskets) would still give over 300HP easily. I have read that the factory 4BBL intakes for the small block are actually pretty good.
Kostas
ccasion14:
