LT4 Performance Cam for the '96 LT4 engine

[Hondo]

Does anyone know which Cam will be the best choice for my Vette? I'm looking for more horsepower(of course) and mid-range punch. I already installed the K&N filter and bracket, and added less restrictive mufflers and also removed the resonator. I would like to up my horsepower to around 400 HP, but I'm not sure if this is possible without doing some major work on the engine. If somebody has info on the best way to accomplish this please let me know.
Thanks in advance for your help.

 

[Rob]

Hondo,

I'll copy this into the LT4 Forum for greater exposure...

 

[twiget]

GM has a "Hot Cam" for the LT4 engine. A few GS guys use Crane Cam's in their LT4s too. I dont have the spec's or part numbers for them, but the GM "Hot Cam" and the Crane Cam seem to be pretty good.

Hope this helps,

Jason

 

[Hib Halverson]

You're going to have a tough time getting to 400hp with a 350 and stay emissions legal and free of OBD2 codes.

The GM "hot cam" for LT4 is good for 20hp but only if you pull off the cats and have a low-restriction exhaust system. My guess is, with the typical LT4 that puts out more power than rated, with the hot cam, no cats and low back-pressure, you're looking at 360-375hp.

To get another 25 is going to take more camshaft and more airflow. Problem with more cam is it plays havoc with the OBD2 engine controls.

In fact, just the hot cam alone sometimes does that unless you recalibrate for a 800 rpm idle.

The best way to a legit 400 hp is a 383.

 

[Hutch]

If you are referring to Rear Wheel Horsepower (RWHP), then I'm afraid I pretty much have to agree with Hib on this one. Gee... ya got any idea how much I hate doing that?!!!

My original goal with my GS LT4 was 400 RWHP yet still remain perfectly streetable. I've since decided that is a pretty lofty goal for a n/a engine with stock displacement. My current RWHP is 364 (see http://www.hashmarks.com/gs633.htm for details). I'm pretty certain that with the addition of long tube headers and a few well chosen tweaks I could manage 375-380, but that's probably the real world limit as a streetable 350. Like Hib sez, for that kind of power and reliability you really need to consider a 383 or 396 stroker.

On the other hand, if you are talking about flywheel HP, then 400 is a much more readily attainable goal. For example, my 364RWHP roughly translates to 428HP at the flywheel using a conservative 15% correction factor. If my math serves me correctly, you only need about 340RWHP to equate to 400 at the flywheel. And honestly, that's quite a lot of fun on the street.

A lot of folks go with the GM hot cam because its cheap and it works, but you do have a LOT more choices. I originally went with a Comp 210-224 unit because I wanted a lot of torque and a stock idle and that cam delivered. Still hungry, I recently swapped to a Crane 222-230. It has a bit choppier idle (which I like, actually) and winds a lot higher, but I'm still tweaking this combo. Like Hib sez, more cam gives you more (potential) tuning problems, too.

I think the Comp 305 cam would be a nice grind for a street machine. Add to that a set of CNC heads, 52mm throttle body, Corsa or Power Effects cat-back exhaust, adjustable fuel pressure regulator, and a professional dyno tune and ECM reprogram and you should be real close to your goal.

GOOD LUCK and most importantly, HAVE FUN!!!

 

[brooks]

415HP...$9100.00 at http://www.lingenfelter.com/ as they say "speed costs money, how fast do you want to go"

 

[Hutch]

415HP? Heck, Brooks, I make more than that now. Keep in mind those are not RWHP numbers. But for $9100 you get the Lingenfelter name on the throttle body plate, not to mention a 2 year warranty. No question, LPE makes fast, bullet-proof motors... for a price.

A friend of mine had them "do" his LT5 on his ZR-1. He showed me his receipt... $27K and that's for the engine work alone. Yowza! :eek Sure is a lot of fun to drive, though. I hated to give him back his keys.

-Hutch-
hutch@hashmarks.com

 

[Mez]

cam

I agree with the others regarding getting 400 rwhp from the LT4. Difficult without power adders such as NO2, supercharging, 383/396, etc.

I had heard from other the Hot Cam was only worth 30 hp, but I suppose it also depends on other modifications.

I read about lots of people swapping the cam first thing. I was concerned about a lumpy idle and OBDII issues, so I took a different route and had the heads pocket ported and 3 angle valve job. It picked up 22 rwhp to 322 rwhp. The engine runs exactly like before with a dead smooth 750 rpm idle.

For details, see: http://temp.corvetteforum.net/c4/tmezger/

Although this may not seem like much compared with other modified LT4's, but it cost less than $600 and I was able to have a smooth idle and quiet interior by keeping the stock cam and exhaust system. The only negative was pulling the heads, no trivial job. But I am happy with my choice.

 

[Hutch]

Mez, my only question is why would you want it smooth and quiet???

Nyah, seriously, 22HP for $600 total outlay was a great investment. And when you DO opt for a cam swap, they'll combine to add even more.

My previous cam was a Comp Cams 210/224 unit that was a *great* street cam. Perfectly smooth idle and a wide, flat torque curve. You don't always have to sacrifice driveability for more power.

 

[Mez]

cam

Yeah, everybody asks the same question why do I want a nice smooth and quiet car. I like the fact my car looks and sounds completely stock but is very quick so I guess I am a little different.

When I had the heads off, I did consider replacing the cam but all you read about is the Hot Cam which is too main stream to me. I considered other cams including the Lingenfelter 211/219 but never saw the cam you mentioned. I will have to check up on it. I am very happy with my engine's torque curve but if I could move it up 30 ft lbs without any negative effect, that would be fabulous.

As a side note, a friend just dyno'ed his stock 1990 ZR1 a few hours after mine at the same shop and got 325 rwhp and 315 rw tq. But he was just doing a base line before engaging his new NO2 kit. He then got 460 rwhp and 556 ftlbs torque. Shucks.

 

[Mez]

Comp Cam

I looked up the spec's of the Comp Cam you suggested. It looks very good for my application.

Here it is:
-----------
Comp Cam Xtreme RPM Hydraulic Roller Camshaft
"Best for original LT1 with stock computer"

Part number: 07-304-8
Grind #: 266HR-14
Adv. Duration (w/1.5 rocker) 266 Int. & 276 Exh.
Duration @ .050 lift 210 Int. & 220 Exh.
Lift (1.5 ratio rockers) .500 int. & .510 Exh.
Lift w/1.6 ratio rockers .533 int. & .544 Exh.
Lobe Separation Angle 114 degrees

The duration is exactly what I looking for as it is half way between the stock and Hot Cam in duration. The lobe separation angle is exactly what I looking for.

I am a little concerned about the lift being more than the Hot Cam's .525 and valve spring binding and life with the stock LT4 1.6 ratio rocker arms. But it is not that much more.

The lobe separation angle has to be the reason for the smooth idle as it keeps overlap short. I recall the Hot Cam is 112 degrees and the stock is 117 degrees.

This is about the closest cam to what I am looking for. Thanks for the recommendation. I will give it serious consideration.

 

[Hutch]

It's a really nice street cam, Mez. You should be very happy with its smooth idle, driveabililty, and overall performance gain.

 

[Mez]

Cam

For my car, what would you guess it would pick up with this cam? Perhaps another 20 rwhp?

I am debating if a lower restriction exhaust system may be the next step instead of a cam. However, a new cat-back system are much more expensive than a cam.

I definitly do not want any resonance like I have heard on some systems and will keep the stock exhaust manifolds and cat's.

 

[Hutch]

Mez -- I think 20 RWHP is reasonable but with stock exhaust your max possible gains are limited.

Personally, I'd do the exhaust first and cam later. Unless you are doing all the work yourself, a cat back system will be cheaper than a cam R&R. Besides, a nice exhaust note is hard to beat.

For zero resonance, a nice sound without being too loud, and decent power gains, I usually recommend a Corsa cat back. I love my PowerEffects, but they are a good deal more expensive and quite a bit louder than the Corsa system. Its your choice, of course.

 

[brooks]

There isn't a quite 20+hp exhaust system. The way to generate more HP is to decrease restriction. Decreasing restriction always increases noise.

 

[Hutch]

Hey Brooks!

You might want to read back through this thread. The discussion wasn't really about exhaust systems, but rather camshafts!

Now pay attention, or we'll have to send you to your room.

 

[brooks]

I'll try harder. I get home and have 101 emails so I try to get thru them as fast as possible, obviously too fast..by the wqay do you know what the asking price on eBay was for the GS with the goofy hood. It was from Fl.

 

[Hutch]

No worries, Brooks. I get at least that many legit emails every day plus as many Spam messages!

I didn't recall the price on that GS but using eBay's search utility I found it, Item # 598110210 topped out at $12,900 with 8 bids but reserve not yet met. The car was from the Ft. Myers area. Hope it stays there until someone changes that gawd-awful hood!

 

[sleepyhead]

I saw that Grand Sport with the messed up (to put it politely) hood. That thing had around 120,000 miles on it! I suppose that it's a fine testiment to GM quality, but I don't know who in their right mind would be looking to buy a '96 with that many miles on it.

-J.

 

[Hutch]

Actually 90193 miles according to the eBay ad. Ignoring that ugly hood for the moment, you do need to keep in mind that it IS a Grand S port, after all.

For the right price, even one with that many miles could be a good deal if it was in good shape otherwise. Clean ones will always be in demand no matter how many miles on them, but I'd want $2K right off the top to get rid of that hood! Yech!!!