Essentially want something that flows comparable to the Stage 2 LS6 Style Heads from Patriot Performance. Any custom porters have heads that flow this good? I'm going to shoot some e-mails out but i figured i'd post and ask first.

 

to get 300 cfm you will probably have to get an aftermarket head and get that ported. I havent seen any factory heads flow that good

 

Most definately, you'll need at least a pro ported set of AFR 210s at the very minimum.
I've only seen LT4 factory castings ported extensively reach close to 300 cfm. (and they didnt reach it)

 

I have seen a set of stock cast LT1 heads reach 293 before. But that is the best I have seen. I would recommend the AFR 210s or 220s.

 

Guys flow numbers are great, but they arent every thing. The heads have to work well. Also 300 cfm out of an LT1/4 head is going to be at some nasty lift. If you want 300cfm go for a ported AFR 210.

 

Why do you want that much cfm? What do you want to run in the 1/4?

You could run low 11s on the motor alone with Lloyd Elliott heads and a decent size Joe O. cam with the right suspension and tires.

 

Good question. Just to get maximum potential out of my motor. I'm 99% sure i'm going with a Forged 383 and throwing a Procharger on it but until then i'll be N/A. I'd like 450 Horsepower N/A before i even up the cubes and throw the blower on.

 

That won't be hard to do with stock LT1 castings. My friend made 432RWHP N/A with a 383 LT1, through a 4L60E, stock driveshaft and rear. This was with ported stock LT1 castings flowing around 270cfm, ported stock intake manifold, and a solid roller.

-Matt

 

450rwhp is doable but blower freindly cam and compression are not going to work well here. 300+cfm heads are not needed for 450rwhp on a stock cube motor. I have two customers now who will probably hit the 450rwhp mark with cam, ported intake, ported heads and bolt ons, the motors should twist to 6800rpm. I know the BS flag will come up but 450rwhp with a head cam package has been done. You might just want to do that and then sell the top end off the motor and then build the 383 all up as a blower engine.

Bret

 

PM'ed you on a cam...

 

max flow numbers look nice just as max hp number look nice but the fastest cars are more concerned with average flow numbers and average hp... aka area under the curve.

 

AKA Area under the curve in the RPM band that you are going to use the motor in anger.

I've done some work on area under the curve motors (which they all are) like the Engine Masters motor we did, 2500-6500 area under the curve. Does that make sense for fast street car you use for drag racing, nope works much better if it's 4000-6500. Two different motors. Different tricks for different parts of the RPM range. Heads are the same way, area under the curve is exactly right, but too much here or there can hurt power just as much as too much here or there in the right spots can help power.

Bret

 

Not directing this at anyone in particular, Brad just brought it up and made a good point with it. Bottom line is, you can preach what Bret just posted to people all day long and they still won't get it. Like I said in another post.... area-under-the-curve, while important, has to be one of the most misunderstood terms in hotrodland right now.

Good post Bret.

-Mindgame

 

I have seen a set of LT1 heads go slightly over 300 CFM@.650 with a 2.00/1.56 valve....BUT the intake port was moved over , welded and required offset lifters and shaft rockers. SO thats a little extreme, but it has been done.


David