Hi all!
I've been following the forum for performance advice for a few weeks now and have consistently seen praise for the hotcam. Needless to say I was surprised to see this in the tpis faq section. I'm a bit of a performance newb, anybody have thoughts or clarification about the following?...
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Q: I have a 95 LT1, it has LT4 heads and intake, LT4 fuel injectors, 1.6 roller rockers, 52mm throttle body, 1 3/4'' SLP headers, GM Performance Parts Hot Cam, ACCEL 300+ Ignition and K&N fuel injection performance kit. Idles good, but when I hit the throttle it is slow to respond, and when it does, it isn't very impressive. Do I need a re-programmed computer? A larger fuel pump or an adjustable fuel pressure regulator? Any help you can give me would be greatly appreciated.

A: The Cam is too big for a 350 motor. I get this question all the time with the LT4 Hot Cam. If you look at the duration @ .050 it doesn't look bad , but it must be huge everywhere else in it's lift range. It would be fine in a 383 or bigger motor with a lot of compression, and a deep gear. Also the intake port volume of the heads are big for a 350 street motor. In order to use these pieces you would want to stroke the motor and or raise the c/r, or add a supercharger. When you go with big cams and 1.6 rocker ratio, and add big heads you will lose a lot of your bottom end power and most of your mid-range power. What happens is the velocity of the air slows down that's why you go slower. The whole set up is still on the big side for a 383 ci motor. You will make more power but it will be all up top.
TPiS
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Jeez.....I wonder what that guy at TPIS has been smoking The GM HOT cam is a very good all around mild performance cam. It is NOT too large for you application at all. Especially when you have installed what is basically the GM LT4 conversion kit with the HOT cam as well. GM claims 425+ Hp with this conversion kit, and a few years ago Chevrolet HP magazine did a test on a LT4 when the HOT cam was released in I think 1997 or late 96, there tests show gains in excess of 425Hp! A lot of people here on the forum has installed and with great sucess the venerable HOT cam. I too have installed it in two cars, one is a very mild 383 that will run 11.99 and he doesn't have the LT4 heads!

I also disagree with their comment about the LT4 heads being too big for a 350 engine. If that is so then why did GM even build the LT4 engine?? There is more to heads than just the sheer size of the runners. Sure the LT4 heads are larger in runner volume but the runner is also raised over .100" making it a more of a straight path to the intake valve. This makes up for the lost velocity from the larger volume, not to mention other factors such as swirl and substaintially increased flow. Also if that was the case then why are they selling their own modified AFR LT1 CNC ported heads with even larger runner volumes and promoting them for stock displacments?? Sometimes I wonder about them guys

If you have not reprogrammed the PCM, it maybe wise to do so. Even though the enging is running OK, there maybe a lot more in it with a good calibration. The last one I installed was in a 95 F body, and the throttle reponse was by no means slow. Who installed the cam into your engine? It is a possibility that the cam is a tooth off on its timing gears? And I have seen where people have indexed the opti spark wrong as well, and this can cuase retarded timing which can cause the problem that you are describing. One client of mine in Hawaii that I reprogrammed his PCM for, has a very low vacuum. He installed a double roller timing set into his LT1 and after speaking with him I am 99.9% sure that his cam timing is off.

 

What they are saying is that you must maintain intake air flow velocity to maintain good low end torque.

If you have too much valve event overlap for the engine displacement air flow will suffer at low RPM so low end torque will drop off, as it will with too much port volume.

Usually lift isn't the issue but rather the combo of duration and LSA, as this is what creates overlap. On a NA 350 cid engine try to stay below 25-30deg of overlap for good low end torque.

 

I agree with that, but the HOT cam is by no means a large cam with a lot of overlap. The HOT cam is like the 219 cam to the L98 boys

 

So how is the Hot Cam in an L98 with a better intake and headers?

 

the hotcam is rather mild. the lobes are very peaky and personally i dont like it. i have a hot cam in a zz385 crate motor and it is definatly not enough cam. there are much better cams out there that you can choose. i know a guy that did a hot cam swap in a ls1 camaro, dont get me wrong it sounds nice, but he only picked up .1 in the quarter. only 10 hp?? something doesnt sound right. granted he didnt do any head work but he was rather disapointed with the results. for a l98 i like the zz409 cam from tpis or comp cams 276.

 

Anyone have any good cam recommendations for a 400 small block? Picked up a good block and just starting to plan. Want a good street/strip car, but it will not be a daily driver. I am willing to sacrifice some driveability for strip performance.

 

HotCam may not be the best cam out there, but since you already have it in your car, I suggest you make the best of it by getting the car tuned. Take the car to a dyno, and see how the Air/fuel ratio is. A dyno is a great tuning tool, and if you have spent that much money on a car to improve its performance, you have to get the computer reprogrammed to see the full benefits. I have the HotCam in my '97 Z28, I love it (and my torque curve is as flat as Florida )
I would only replace the stock pump if it goes bad, and an adjustable fuel pressure regulator will do nothing for you since the computer will simply decrease the time the injectors stay open when you increase the pressure, therefore not letting the car get any additional fuel. Good luck.

 

TPIS is slamming the gm parts because they didn't build them. PERIOD.
Their whole reply is BS. LT4 heads too big for a 350? Hmmm, then I guess the LT4 must not really be a 350. A hotcam too big for a 350, then I guess the 219 lingenfelter is too big along WITH their zz409.

 

i dont know why tpis said that about the hotcam. i think the hotcam is rather mild for a 350. maybe tpis meant that is was too big for a stock lt4 head, which it may be. i think the lt4 heads flow like 240 max. the 219 cam is a little more mild than the hot cam, but the zz409 is quite a bit more aggressive than the hotcam and they recommend it for for a 350ci, so it doesnt make any sense for then to say that.

 

I really don't know about some of the advice they give. I called them before I was going to do my head cam swap and got conflicting advice. I like thier headers though!

Maybe they slam the hot cam because GM supposedly stole thier miniram design for the LT1 intake.

LT4 heads being to big for a 350 is silly, I have Stage3 heads and a bigger cam than the hot cam, sure my car doesn't come off idle like a stocker but thats why they make GEARS!!! I have no problems with driveabilty especially now with the LTCC really the car is great to drive around town plus I can rip it to 7000 rpms if so desired!!!

 

I agree with most of the above posts.

I looked at the hot cam kit for my LT4, and opted for a bigger cam.

I love it. Picked up 60rwhp with the cam and cat back. That was with a great tune!

 

I have talked with TPIS before. Basically, everything they have is golden and their competitor's stuff is junk that won't perform as well as their own. The attitude I got with them is "Give me your credit card and stand back while I do my thing and no one can do better than I." I have a 383 with the Holley Stealthram and AFR 190 heads and a custom camshaft that made 411 HP at the wheels after going thru an A4. My new cam specs are 230/236 - 110 lobe sep, 108 intake centerline (2 deg. advanced). Lift with 1.6/1.5 rockers is .622 / .570. This is a custom grind by Comp Cams.

 

TPIS is very proud of everything they develop and exaggerates a little when it comes to the peformance of those parts.

A few guys in my old corvette club used to run their ZZ9 cam with the TPI setup back in 94 and it was a very good all around cam, and still is.

As far as products they develop, ZZ9 & the miniram is what put them on the map but they seem to be stuck in the early 90s in R&D because I don't see any good products they made since. Nothing really spectacular for LT motors and nothing at all for LS motors.

Overall I think they have a good company but just don't believe everything they say.