Looking at possibly changing to aftermarket heads on my 96 LT4. Car is used on street and some track/autocross. Car now has LT headers, decatted, and plan to put and LT4 hot cam with change. Bottom end is stock so I would need to stay close to stock CC.Recommendations appreciated.

 

I'd send them to Lloyd Elliot if you can afford to have the car down for any amount of time

 

The stock LT4 head flows like 240cfm where the LT1 head only flow 212cfm according to the Grand Sport Registry. 13% more flow is gonna be tough to improve on. You may gain some power with expensive top brand heads over the stock LT4's but the bang for the buck will be small. IMHO I would just install the Hot Cam and get the engine/computer tuned.

 

LTX platform is pretty limited on cyl heads.

You could send your LT4 heads to someone like Llyod or TEA for porting.

You could also buy a set of AFR's. I'd go with the 195 Street Port PN 1032.... I've made 540HP with that head so it will do a great job with a Hot Cam on the stock bottom end. You should contact CF member Jim Barth (421 TPI Vette) if you decide to buy the AFR's. He will give you the best price you will find anywhere.

https://www.corvetteforum.com/forums...421-vette.html

Will

 

Like the others, I'd suggest pricing and comparing both a good aftermarket head like the AFR rklessdriver recommends vs porting your stock heads. I'll recommend another option for porting, which is Greg Good in Houston. Many moons ago he ported my LT4 heads, and they flow shockingly well: 308/223 cfm at 0.600". I don't know if he'd recommend the same ports for a shorter-lift cam like the Hot Cam, so it would be important to have that discussion with him (or any porter). Anyway, it's one other option.

 

Totally agree here. I run AFR 195 Comp Ports on my 406 sbc. Great Flowing heads.

 

x1 on afrs...to make the LT4 heads breathes too many guys overport them turning the car into a soggy dog (even with a hotcam and 4.10s)

 

My plan if I get there. 100%

Plab B is AFR195's.

 

I have also heard good things about Greg's work from other sources. No first hand experience, but would be another good person to get a quote from.

 

I'm sure that's true. Going for the highest flow number only is a good way to get that (undesirable) result. I will say that my heads have very good low-lift flow, too. They match up well with AFR 195 Comps, actually outflowing AFR's published numbers on the intake at lifts between 0.1"-0.5" and matching them a 0.6", and slightly lower flow at all lifts on exhaust. In my 396 with a cam that most people would consider teeny (XFI 3014 and 3015 with 108 LSA) it pulls hard from 2k-6k and slightly outruns a stock C6Z, all while still being able to run at 60mph in 6th gear with the stock 3.45 rear gear (~1500rpm) and knocking down 26mpg on a long drive. It's mid-rangey enough that people tend to think it has more power than it really does.

So it can be done right with good flow numbers, but probably not be very many people. I have no idea if it's a cost-effective alternative in today's world compared to aftermarket heads. But I know Greg is still going strong in the industry, working with some of the leading engine builders in the country. I'd have him do any work I wanted done.

 

Would be interested to hear about your 396 build.

Thanks

 

Wouldn't the larger combustion chamber on the 195's lower his compression ratio to much ? I went with the 180's

 

You can probably have them cut to whatever chamber you want

 

The PN 1032 I recommended has a 54cc chamber. Same as the factory LT4.
Will

 

Sorry for the delay, it's been a busy week. MSR, the previous owner, is still on this forum. He's a very good friend of mine, with real professional experience modifying cars. He is responsible for this build, with some input and work done by another friend that now is the guru at HP Research, as well as the aforementioned porting done by Greg Good. This engine was spec'd and assembled roughly 10-12 years ago. I think it's pretty straightforward these days, although back then a 396 was less common. It's a stock block with the heads and cam I've already mentioned. The emphasis on cam selection was to get fast ramp rates with lots of lift for the duration. It has a ported LT4 intake, and the short-runner intake seems to like the overlap provided by the 108 LSA. For a while it had a custom that made more power, but MSR was street-driving it and that cam was a little too much for that use - for example, he couldn't use 6th gear on the highway at anything close to legal speeds. MSR wanted a stable valvetrain with aggressive-ramp cams, so it has Jesel shaft rockers with 3/8" pushrods. With the current cam, it is as flexible as the stock LT4 was. the block was well prepped with drilled oil mains and billet 4-bolt caps. The crank is a forged version with large counterweights (I don't know what brand), and the pistons are very light custom JE designs. It is internally balanced without any heavy metal added to the crank. It runs a Kevko road race oil pan, Hooker long-tube headers, and a custom 3" exhaust with X-pipe, metal-substrate cats, and Corsa mufflers that MSR built himself. Oh yeah, and a 13lb Fidanza flywheel with a lightened GM racing pressure plate lets it rev pretty quickly.

It's been anvil reliable, and as I said it is a very streetable engine that is also perfect for autocross use and breathes well enough for track use. It was definitely not spec'd to chase peak horsepower numbers, but with the more radical cam it made 460rwhp. I'd guess that it's around 420rwhp now. People who ride in it tend to think it has more power than it does, which tells you that it concentrates its power in a curve that's accessible on the street and autocross courses.

I'd be happy to tell you any details that I know of, so feel free to ask.