I currently have a built 355 LT1 with a 228/236 .544/.568 hyd roller and ported LT1 heads that flow 268 cfm @ .600 int and 191 cfm @.600 exh. I was wanting to know if I had additional port work done to my current heads, or bought a new set of high flow heads and went with say a 236/242 cam would I see a considerable increase in performance?

Randy

 

i would say your current combo would be good for around 400rwhp, and the combo your thinking of going to might be good for up to 420-430ish depending on how good the heads are.
this is pretty much maxed out for each combo, imo.
jeremy

-edit- my power figures were for a m6 car, so your #s will be a bit lower.

 

You would be very close to my E.T. and mph in the sig. My heads flowed a corrected 295 cfm intake at .600 lift and 222 exhaust at .600 lift and I have a 235 242 .568 .592 112 lsa cam. You car actually might be faster being that my converter is set up for the bottle and is very tight right now...until the 200shot gets put on lol.
Later
Matt

 

Matt, how much did your heads cost? Also, what kind of programming and size injectors are you using? Thanks.

Randy

 

I got the heads in 2001 from GTP so it's been a while. The castings were $700 for the bare castings....you could get the AFR's for a little more so that's what I would do if I did it again. The portwork and parts were $1799 and I think that they charge more for them now so you might find a place that could get similar numbers with less cost. I am using 30lb SVO injectors at about 43 psi fuel pressure and am using LT1 edit with a program from Chris B's car that is close to my combo. I still think my car needs a little tuning to get another tenth or two out of it. If I had a converter that was set up for NA running ad tuned it in I think my car would hit 10.90s @121mph so your should be right at those times. BTW my car weighs 3600lbs with me in it in case you were wondering...I wish I could get it 200 lbs lighter...lol
Later
Matt

 

Well, I'm definitely going to looking in to a setup like yours. I have some money saved up and I'm looking to go fast. My car really hooks well at the track and could handle a significant power increase I believe. Oh btw, my car weighs 3450 with me in it and I'm 225. Thanks for the info.

Randy

 

At the point you are at, I would not do anymore portwork to your exisiting heads. Instead, I would recommend you to start looking into a set of AFRs. My old solid roller 355 was making ~445rw NA.

IF you really want to go fast NA, start looking at solid rollers. That and a set of AFRs is capable of 460rw, and the tradeoff of a solid roller is well worth it. Better driveability, power, and a more linear powerband.

I would go with a set of AFR 195 LT4 either competition ported from AFR (which flow great), or done by a reputable porter.

Jason

 

Jason, What kind of flow #'s should I be looking for, and what cam would you recommend. Also, what would I need to do as far as pcm programming? PCMFORLESS does mine now.

Randy

 

The problem with flow numbers is that people get way to caught up in them. I have seen alot of cars perform really well with peak numbers that were not really that great.

Personally, I really think that AFR's competition CNC program is superior for the money. The 195s are going 282/228 peak at .650" lift. Not only that, but the area under the entire curve is very impressive.

B&B racing in California is another shop that knows AFRs well, and has worked alot with AFR in the past (helping them develop different port configurations). B&B is the shop that does my heads. My AFR 210 headed solid roller 396 was making ~480rw, and would have been closer to 500rw with more tuning. They are now doing my new top end (AFR 215 raised runners).

As for cams, I have had success (as well as others) with Cam Motions grinds. Almost all the fastest NA LT1 cars have CM grinds in their cars.

Jordon had a 246/250 and went 10.8@130 (401ci)
Tim Herrint has a 250/256, 11.0@124 (355ci)
Phil Tobin, not sure on the specs, 10.6@128 (403ci)
Darren Nichols, 254/260 (I think) and went 10.4@128 (396)

and probably some others that I am forgetting.

Solid roller is really the only way to go FAST NA IMO.
Jason