snowmaker2000

I have a stock 1996 C4 with the LT1 engine. From looking at most of the forum topics on streetable cam options, it seems that the best chioce is the LT4 Hot cam.... and anything over this cam means torque at a higher rpm.

Question #1, Can I leave the stock converter in with this cam? Idle quality etc?
Question # 2 Would porting the heads give me more overall power with the cam?
Question #3 Is the stock TPI ok with this cam?

I'm ultimately looking for a street car with about 375-400hp and 375 torque numbers Tired of getting whupped by a neighbor's almost stock WRX!!!. That car launches HARD and then I can't catch the b*tch.

NEVERL8

I put an LT4 hot cam, 1.6 ratio roller rockers with 110# springs (LT4 spec), an LT4 knock sensor and a tune into my totally stock 95 LT1 6 speed. Here is my take on it. Others may have different opinions.

The engine had a slight lope at idle. The idle speed was increased to 750 RPM with the tune so that it would not set a misfire code. Some tuners do not increase idle speed. Can't say if this sets codes or not.

The car ran essentially stock up to about 3000 rpm (meaning no noticeable loss of hp or torque) then came on strong up to 6000 RPM (I did have the fuel cutoff increased to 6500 RPM with the tune). I never dynoed the car after the cam install so I have no data to show the exactly hp increase. Some claim 30 to 50 hp.

I can say that unless you are willing to go through the complete intake and exhaust system to maximize airflow you will not get the most out of the cam and tune. My car ran good after the install but I could definitely tell that the intakes, heads and exhaust were now limiting the benefits of the cam, rockers, springs and tune. I do not think the stock 48mm throttle body was the limiting factor. If I were to do it again I would definitely do some head work (as you are considering) and then pay attention to freeing up the exhaust. Port the heads, put in some LT4 valves and springs, use the 1.6 roller rockers, headers, high flow cats, low back pressure exhaust and you might pick up 40-50 hp at the rear wheels.

You are talking some significant money and time to do this. Does you car have the performance axle? A better rear end gear would go a long way to getting the performance you need without a lot of engine work. If you already have the performance axle then you are stuck unless you want to put in a 3:45 dana 44 pumpkin.

I would not go through the LT4 hot cam conversion again unless I was willing to do the complete intake and exhaust system as well. Just my opinion.

snowmaker2000

That was very informative. It makes a lot of sense. Thanks a bunch!!

bobmic93

Dont worry about those terribly ugly WRX STI's. Those things get out of the hole quicker then most every car due to all wheel drive. Those cars stock run 13.3 which is around most LT4 and C5s do. Head work with a hotcam and headers and your Lt1 should see 350 to 375 rwhp. That kinda of power and you should see mid 12s or better. Go see Ron at www.advancedinduction.com these guys live off the LT1.

LT4BUD

A higher stall torque converter might be enough to give you the harder launch you need to spank that WRX........

Also as suggested above if you have 2.59 rear gears, a change out there would further improve your launch.....

IMHO a cam change without the heads, etc. really leaves a lot on the table......

Good luck...go get that WRX...

Lichen

The stock TPI part I don't get.
It is very streetable, but have it speced before installation. Their quality control isn't that great. And yes, have the heads ported. Actually, you can probably find better flowing heads than porting for less money. And don't forget the 1.6 rr.

96GS#007

If you change the idle speed to smooth the idle, you'll probably want to change the torque converter. The guys I know change it anyway.

On a '96, you'll need to have the parameters for the misfire rpm changed (or the idle raised to ~850rpm) to avoid setting a misfire code (P0300). I bumped the misfire tables in mine such that the min rpm it looks for misfire is 1500 rpm. Btw, '96 is the *only* C4 that has this issue because it's the *only* C4 that has OBDII. Another poster mentioned "misfire code" in conjunction with his '95. '95s do not have the capability to set this code (not OBD II, no crankshaft position sensor, etc).

The cam is very streetable. I had one for years.

On my LT4, my rear wheel hp was 342 after my own tuning. Other mods were the exhaust and an electric water pump. With a mild pocket-porting of my cylinder heads, my rwhp jumped to 363 at ~6300rpm.

As another poster mentioned, 1.6 rockers are a nice to have (they're stock on LT4s) and are worth 10-15hp by themselves.

snowmaker2000

Thanks for the OBD info. Why would it register a misfire? Is that caused by the idle loping or spitback at low rpms?

96GS#007

Technically either could cause it....a cam with a lope or a poorly running engine. To detect misfire, the PCM looks at the acceleration and deceleration of the crankshaft via the crankshaft position sensor. Every time a cylinder fires, the crank accelerates and between cylinder firing, there's a small deceleration of the crank. When the boundries programmed into the software are exceeded, the PCM cries misfire.

By raising the rpm, you get away from the "lope". Conversely, if you like the lope then change the misfire detection rpm so the PCM doesn't look at the info until the engine is at a higher rpm

rocco16

I don't think the C4's issue is lack of power, it's more like lack of traction...in which case a high stall TC will just exacerbate the problem.

Snowmaker; try some drag radials if you want to stay close to the WRX at launch.........cheaper and easier to install than the engine work you are thinking about.

Larry
code5coupe

torchred96

My 96 has the hot cam, automatic and lt4 engine. It has a mail order tune and is at the limit where the stock converter wants to move the car forward...any more rpms and it would be unpleasant. As others have advised me, a slightly higher stall would allow me to raise and smooth out the idle a bit more and not have the creep where I have to stay on the brake at traffic lights.


But as far as a daily driver, the hot cam is perfect for me. I also agree, that the car is traction limited already and the above reason (for me) would be the only reason to go to a higher stall. But I'm no racer..

jsavoy

w/ you all. I've got a 96 w/ the hot cam and some other bells & whistles.

Most modification are interdependent on other components to obtain the maximum benefit as you've probably gathered from the previous post. It sounds like you've got a goal (375-400hp and 375 torque numbers--RWHP?). Really look at what you want to spend and plan the project out. Lots of options on how to obtain your goal [forced induction is one] but again I refer back to my original statement about interdependency. Your $$$ will run out [figuratively speaking] before your ideas do. Plan and you'll start a project that you'll be happy with at the end. Start bolting on parts without one and you'll feel like you're chasing your tail. Luckily you in the right place [CF]. Now, where to start. Good Luck...JS

BTW, we're never "happy" at the end. Just temporarily satisfied until you look at what toy someone else has installed.

jsavoy

I almost forgot. "street racing" stories = bad on the CF

But we know you meant, "While testing the performance of my car at the track, I'm tired of getting whupped by a neighbor's almost stock WRX!!!"

bobmic93

A 3200 stall and a 3.73 will get you out of the hole as fast as a WRX with no engine mods at all.

Warp8

You ASSUMED it was on the street!

snowmaker2000

We actually raced on private property, and each every time he whupped me good. He told me he was able to tweak his turbo and get a few more psi.
I raced one of those new Nissan Z cars and barely beat him.

Out here in PA plenty of spots to drag without breaking the law.

snowmaker2000

Today I was at a traffic light and I held the brake while raising the rpms to 850. GEEZ, that is downright up-pleasant. . . not to mention dangerous. I also think I would eat up brakes if I had to raise the idle that high with the stock converter.

Is the hot cam lope that bad that I would have to raise the idle on a (stock 350)?
What is wrong with leaving the idle near stock RPM with the sweet lope? Vacuum problems perhaps???? (hot cam).

d48mclain

Two votes..... but I would also add headers and dyno tuning. Actually made 360 rwhp using the stock cam but with ported intake, ported LT4 heads, long tube headers and very good dual 3" exhaust. Pick your poison.....just depends upon what ya want but the headers n exhaust got me to 330 rwhp with a fair amout of tuning.

jsavoy

After I installed the hot cam, my idle RPM dropped to @ 500 RPM. Although it had a really nice lope to it, when I placed the car in gear it would slowly stall the engine. If I sat at a traffic light, I had to put it in neutral or raise the RPMs while it was in gear--essentially driving w/2 feet. I changed the torque converter, it still idles a little low @ 500 - 600 RPM but no longer stalls when its in gear. I've had no vacuum problems since the install.

I believe you'll be able to keep the idle down, just add tuning to your list when you do the cam swap. You should be able to do it via mail since you'll be close to stock. Maybe those that have used PCMFORLESS will chime in.


Great to hear @ the legal racing, my apologies for the assumption...

Lichen

You will need to raise your idle RPM to around 900 rpm. There are plenty or WRX's out there that will kick you butt, but so what? You have a Corvette which will remain a classic forever. The point of owning a Corvette is not to be the fastest car on the road.