which cc are they 180, 195, 210, 220, 227?
Dont bash this guy, hes not asking dumb questions or anything.
If you dont want to pull the heads and cam out i would start with making your pacesetter lt's into a true dual setup. Throw on a 52 or 58mm tb, 1.6 rockers, and a dyno tune. That should do the trick.
Depending on which afr's you have i would send them to le or ai and have them port them. Than let them cut a a custom cam.
This will net you way more than just the 400rwhp your looking for.
As for your buddy, theres thousands of 400rwhp lt1's around here. He prolly hasnt ever looked.

 

Look for a longer number under the valvecover area. It should end in 561, 643, or 371. The 643 or 371's are the best for porting, but the 561's can be decent too.

 

I believe there are 561. The AFR's are the 180cc street heads. The reason I used 1.56 rocker arms is with 1.6's it would have made over 600 lift the springs in the AFR's are only rated to 600 lift and I was out of money and just wanted to car to run. I forgot to add this on my sig the car has been tuned by TPIS the tune seems to be very good A/F is perfect all the way to redline.

 

If you want 400 rwhp with your current combo then get a ported manifold and electric w/p and you should be really close. If you want to use this as an excuse to do a little more work to the car then send the heads to Lloyd to open them up along with what I mentioned above. If you want to do a cam swap then buy my used LE1 cam that meets your goals with a mid 220 duration instead of your 240.

 

What catback exhaust do you have?

I ask because if you have the Flowmaster, switching to Magnaflow (or better yet, Corsa) could put you over 400 all by itself.

 

^^^ that's true, if you have a crapmaster, take that thing off or at least put a cut out in.

 

Myth....from LS1tech.com

 

I've seen it with my own eyes, not a myth.

 

And I've seen it with my own eyes here locally that says it is a myth. I guess it just depends on the set-up

 

There are details in a setup that can have a significant impact on exhaust sensitivity.

For a muffler I do think an outright flow test is fairly meaningful and flow wise the Flowmasters suck. Heads flow numbers don't mean as much but the flow they have to cope with is a bit different.

 

I'm not saying that flowmaster has the best performing mufflers out there, I'm just saying I don't think they're as bad as alot of people think. I've personally seen a car gain a measly 7 rwhp from an single open cut-out vs a flowmaster catback...but then again I can think of another car locally (one I help build actually) with a 402 ci LQ9 that had twin cut-outs in the y-pipe and a flowmaster catback...it made 489rwhp with the cutouts closed and 513 with them open. I don't think you can blame the muffler as much as the single 3" pipe in that case though.

I've never really agreed with using cfm as a good indicator of how well a muffler is capable of performing, because exhaust comes in pulses which means scavenging can be beneficial...something a strait-through muffler can't do....

But at the end of the day, run whatever muffler makes you happy I personally have a single out flowmaster 3.5" race series two chamber on my car and I love it

 

I saw the 4" Flowmaster that Mufflex uses in their 4" catback removed (along with the rest of the catback) from an LT1 blown 383, making 1,125HP, and there was no change in HP. When I pulled my 4" Mufflex system off, and substituted XR1's and 3" pipes back to the axle, there was no HP change.

The flow data I've seen referenced that shows low #'s for Flowmaster compared to others is at least 20 years old, and probably for mufflers most of the manufacturers no longer make. And, there are several different designs for Flowmaster mufflers, so generallizing with comments like "crapmaster" is sort of pointless.

 

The mufflex system doesn't use a crossflow muffler like the catback does so this data is irrelevant. The 80 series crossflow muffler is the restrictive one.

 

As Fred said there are lots of different Flowmaster options but in a street car with in all likelyhood a fairly restrictive system with the muffler a long ways away from the engine I feel the "importance" or potential of scavanging is grossly overstated. Talk a race car with collector mounted mufflers and that would change things.

People wear blinders and fail to see the big picture.

For instance I had a dual 2.5" system on my car with mufflers and resonators and gained almost noting disconnecting the catback, for a long time I thought that meant that the 2.5" was all I would ever need, but I have since done some learning and a few guys made some good points and I am looking to do 3" before I do an engine build. There was still a cork in the system I had not considered.

 

I agree, thats why when I hear people bashing flowmaster I tend to step in and give my $.02 worth.

I'd doubt that my flowmaster muffler is costing me anything at all horsepower wise with my 3.5" mufflex system on my ~400ish rwhp motor.
Agreed. If any of them are overly restrictive, the 80 series would be the ones. But then again, the car I mentioned in a previous post that only gained 7rwhp with the cutout open had an 80 series on it....