I'm currently rebuilding one of my 429 SCJ's and decided to go with a 460 crank in my .030 block with a set of Probe dished pistons at zero deck which puts me right around 10.8:1. I really want to maintain the original appearance of the engine with the stock intake and cast iron manifolds however the machinest porting and setting up my heads doesn't like the factory SCJ exhaust manifolds. He claims the intake is a pretty good piece, weight excepted, but that I really need to run headers. The heads are being set up with the 2.25 int's. and 1.76 ext's. with port work to the ext. He has ten years experience working exclusively on 429/460 heads but I have also been told that there are guys running these factory manifolds on some much bigger inch engines than mine and also making good HP figures. Are these manifolds as bad as he says or could they maybe benifit from an extrude hone? He is also telling me that I really should run about a 850 to 950 Dbl. pump Holley since I'm running a Toploader w/ 4.30:1 gears. Does anyone have a flat tappet solid cam profile that they would suggest to run with the stock manifolds? Any suggestions would be greatly appreciated. Thanks, Mark
Would headers be better than OEM cast iron exhaust manifolds? Of course.
Headers will almost always offer more power than the OEM iron manifolds. Also, the OEM SCJ iron can
support horsepower, but headers should offer up more ponies...specifically with bigger cube engines and/or higher rpm engines.
I'm a marine guy so I had to do some searching, with the help of a friend, in order to find some info that can provide you with some insight. Here's what I saw (the bold
lettering is mine):
Originally Posted by Grumpy
I'm the guy with the 1970 Cobra in FAST. 557 12.2 compression, stock scj intake and exhaust manifolds, 2 1/2 daul exhaust. Made 710 hp at flywheel with SCJ exhaust, 815 with headers. The car is 4150 lbs and has run 11.02 at Cecil county on Bias plys.
Originally Posted by Grumpy
DOOE-r heads, intakes have been filled then reported and raised.
SCJ iron exhaust manifolds extrude honed then hand ported, outlet opened to 2 5/8., SCJ iron intake, extrude honed first, plenum milled out to increase area. .
I deleted a lot of engine build info from that second quote. This was a wild 557 cubic inch engine into which a tremendous
amount of detail was performed. The reference for you, though, is in the power difference between the headers and the exhaust manifolds.
So by using SCJ exhaust manifolds, I think you will give up some power in that solid lifter cammed, SCJ-headed 466. The above engine suffered a 100 hp loss, but
it is a bigger, higher rpm engine. Your HP loss should be less....but it's obvious that you'd definitely feel the difference in the upper rpm range.
For a solid lifter cam with those heads, I would look for an intake/exhaust split of at least email@example.com, more split if possible but you'll probably need a custom ground cam to get a profle with more than 10-12*.