LT4 Hot Cam

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LT4 Hot Cam

Postby screamen_seamen » Sun Aug 24, 2008 11:10 pm

Have any of you actually ran this on a tbi truck, if so what did/do you think? Thinking of putting one in my L31 Vortec 350 5spd thats running tbi.
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Re: LT4 Hot Cam

Postby Grappler » Mon Aug 25, 2008 4:09 pm

might be a bit much for a tbi motor to handle. tbi don't breath enough to make the power that cam wants to. hot cam usually comes on around 3g or so i believe. just when normal tbi is dyin. now if you have an aftermarket 4bbl intake with an adapter and the ability to tune your calibration. might do well at supporting it with some work.

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Re: LT4 Hot Cam

Postby superbee » Mon Aug 25, 2008 6:35 pm

that will be a strong running son of a bitch with those vortec heads.

ITs gonna take some tuning to get it to drive right. You will be fine with your throttle body. definalty going to need to jack the fuel pressure way up. Time fo you to bypass the stock regulator and get an after market adjustable one. On egay those cheap ricer regulators for 20-30 bucks actually do the job. Tbi has its drawback, i havent personally built mine up to this point yet but am wanting to this year, but having only 2 injectors, you run into the problem of supplying the needed fuel up high, but possibly having your idle suffer from the pulse width since your gonna be running so high of pressure. They have formulas on thirdgen.org where you can equate your injector lb/hr, with different psi's to get aroung your estimated hp and not have them go static wide open. do a little research, it can be done pretty easy, but not somthing you want to slap together and take it out for a joy ride or you may burn that baby up. Along with that regulator, you will need a fuel pump such as the walboro 255 to have enough volume.

Vortecs and lt4hc are roughtly a 380 ish hp combo with 1:6's.

Btw your vortecs will need to be machined to take the .525 lift from that cam, if you need a set of heads, i have a set of vortecs i was gonna put on mine for this exact combo for sale....
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Re: LT4 Hot Cam

Postby 6SpeedBlazer » Mon Aug 25, 2008 7:43 pm

superbee wrote:
Vortecs and lt4hc are roughtly a 380 ish hp combo with 1:6's.



your not gonna get 170 hp from a H/C/I swap on a tbi motor.

the fullsize L31 guys usually only see about 330ish at the crank
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Re: LT4 Hot Cam

Postby o4SilveradoMykk » Mon Aug 25, 2008 7:51 pm

I put a LT4 Hot Cam & 1.6 RR's in my L31 Vortec Build... But I haven't fired it, swaped it ,or driven it yet.... from everything I've read is that this cam can be a real dog down low on a heavy pickup. Thats why I'm using a 3000 stall locking torque converter for my 4L60E.

Don't qoute me, but I think that cam demands high compression. The L31's stock 9.34-1 might not cut it. I've got 10.2-1 on my Vortec 357ci and the LT4 had 10.5-1.

And as stated earlier, the Vortec heads can't take the lift of the LT4 Hot Cam stock. You can machine the heads. But the easier way is to use Comps beehive springs like I used in mine, no machining to achieve the .525" lift
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Re: LT4 Hot Cam

Postby 6SpeedBlazer » Mon Aug 25, 2008 7:53 pm

o4SilveradoMykk wrote:I put a LT4 Hot Cam & 1.6 RR's in my L31 Vortec Build... But I haven't fired it, swaped it ,or driven it yet.... from everything I've read is that this cam can be a real dog down low on a heavy pickup. Thats why I'm using a 3000 stall locking torque converter for my 4L60E.


ive got it in my L31, but i don't have an auto and my truck is fairly light
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Re: LT4 Hot Cam

Postby screamen_seamen » Mon Aug 25, 2008 9:05 pm

The main thing I am looking for in the lt4hc is the idle I have heard several Fbody cars running this cam and the idle is radical as hell for a fuel injected strret car. I am not expecting it to idle that hard on tbi, but I would think it would be a good noticable rumble. HP i'm not really looking for my truck feels pretty stout and I know what stout is I had a '91 S10 that would run 6.80's in the 1/8. I havn't had it to the track, but there is a guy in town that has a v8 5 spd S10 like mine that has a aluminum headed 350 in it and my truck will destroy it. Also I have been thing of changing to the edelbrock multiport or motorvation 4brl setups what do you all think of that?
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Re: LT4 Hot Cam

Postby superbee » Tue Aug 26, 2008 12:09 pm

ya mark sorry i dotn know why i wrote that, that cam and a good set of cnc aluminum heads would be in that range not the vortecs.

BUt yeah, for a higher lobe separation and faily mild duration it lopes decent. granted you have to lower your idle down in the 550-700 range to hear it.
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89' S10 blazer 4wd: 355, 650 dp, rpm intake, comp 282 roller cam, modified vortecs, T56 Six speed, 8.8 ls rear, headers, x-pipe, spintech pro street mufflers, and......AC

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Re: LT4 Hot Cam

Postby screamen_seamen » Tue Aug 26, 2008 2:02 pm

What do you think the idle would be like on this combination, or do you know of any other cam that would work well and have a slight choppy idle?
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Re: LT4 Hot Cam

Postby 88S10Durango » Tue Aug 26, 2008 2:16 pm

If your baseing your cam choice for your engine on the fact it will sound Cool ,, you`ll have problems , your cam should be chosen on the specs of your engine so all match`s one another , compression , transmision , vehicle weight , exhaust , stall of torque converter , fuel system ,
Anyone can throw a hot cam in a engine ,, I`ve seen people throw one in their engine only to be diapointed later because their vehicle turns into a turtle , with that Lt4 cam you`ll want high compresion , heads that flow good , and a good fuel delivery system , I think the downfall in your engine will be the TBI ,, mayby you could adapt the larger 454 throttle body onto your manifold to help in that department ??
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Re: LT4 Hot Cam

Postby screamen_seamen » Tue Aug 26, 2008 2:36 pm

I know plenty about match ups, I know that more compession and more air would be needed for the HC I plan on pulling the engine and putting flat top pistons, zero decking the block and shaving the heads a touch, and also am looking at other throttle body situations. Has anybody run a holley throttle body? I am looking for a specific idle, but am willing to modify the engine to accomidate what I am looking for.
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Re: LT4 Hot Cam

Postby Easymoney » Tue Aug 26, 2008 2:57 pm

You mentioned tbi and vortec. They have never been together on the same motor from the factory.
1995 was the last year for the tbi and it didnt get the vortecs. 1996 was multiport with vortec heads. Just curious about the heads you are running.

I have had some experience with this and the easiest thing we found was an adjustable map sensor but if you don't add more air/fuel you really wont notice much gain.
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Re: LT4 Hot Cam

Postby screamen_seamen » Tue Aug 26, 2008 3:13 pm

I have a '92 S10 and I took a complete vortec 350 out of a '98 silverado, stripped it down to a long block, put the GMPP TBI to Vortec heads conversion intake on it and put it in the truck with the stock tbi set up for the V6. Again as I stated earlier I am not looking for a big HP add I am looking for the sound.
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Re: LT4 Hot Cam

Postby screamen_seamen » Tue Aug 26, 2008 3:15 pm

Just did a little research and a LT4 came with 10.8 to 1 compression and the hot cam shows to be good from idle to 6000 RPM's
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Re: LT4 Hot Cam

Postby superbee » Tue Aug 26, 2008 5:01 pm

dude don't let these guys scare you, hot cam and vortecs are a proven combo, and as i said, you can flow enough air with your stock throttle body, Fuel is a concern before air on those.... Putting a 454 tb would complicate tuning that thing all that more.

Then later on down the road when you get more money, you can top your engien off with a stealth ram setup and it would be a beast. Theres tons of people that have the hsr, hot cam, and vortecs, with good hp and 1/4 mile numbers.

As far as the cam, that cams been out a while, there are more modern grinds out there. but you wont be dissapointed either way.
ROWING THROUGH THE GEARS! \/
http://www.youtube.com/watch?v=sP7iLypoDI4

89' S10 blazer 4wd: 355, 650 dp, rpm intake, comp 282 roller cam, modified vortecs, T56 Six speed, 8.8 ls rear, headers, x-pipe, spintech pro street mufflers, and......AC

94 sunbird- project turbochicken



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Re: LT4 Hot Cam

Postby 6SpeedBlazer » Tue Aug 26, 2008 7:48 pm

Easymoney wrote:You mentioned tbi and vortec. They have never been together on the same motor from the factory.
1995 was the last year for the tbi and it didnt get the vortecs. 1996 was multiport with vortec heads. Just curious about the heads you are running.

I have had some experience with this and the easiest thing we found was an adjustable map sensor but if you don't add more air/fuel you really wont notice much gain.


thats not true

some 1996 vans got a tbi vortec motor. its an l31 short block with a tbi to vortec adapter intake and it came from the factory like that.

there are some vehicles that got a tbi motor up till 1999ish just because they were so heavy they didnt have to comply to the emission requirements of the smaller vehicels
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Re: LT4 Hot Cam

Postby 6SpeedBlazer » Tue Aug 26, 2008 7:57 pm

screamen_seamen wrote:Just did a little research and a LT4 came with 10.8 to 1 compression and the hot cam shows to be good from idle to 6000 RPM's


the hot cam is rated by gm at 1800-5800 so its a little off idle not from idle.
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Re: LT4 Hot Cam

Postby screamen_seamen » Tue Aug 26, 2008 10:26 pm

I think you said your using one of these cams, so you should know. I am running a 5 speed so it really shouldn't effect me that bad. As I think about it I would like to have a little more top end power out of a cam and tune swap. Bottom end is fine it destroys tires already.
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Re: LT4 Hot Cam

Postby 6SpeedBlazer » Wed Aug 27, 2008 7:36 am

screamen_seamen wrote:I think you said your using one of these cams, so you should know. I am running a 5 speed so it really shouldn't effect me that bad. As I think about it I would like to have a little more top end power out of a cam and tune swap. Bottom end is fine it destroys tires already.


i am running the lt4HC but i havent started my truck yet.

the fullsize truck guys like this cam it seems to be a great combo for the stock vortecs and even the edelbrock e-tec heads

but you are correct, with a 5 speed you don't need to worry about the power bad of the cam as much as you do with an auto. since if you need to you can rev a little higher or just slip the clutch a bit more
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Re: LT4 Hot Cam

Postby o4SilveradoMykk » Wed Aug 27, 2008 7:44 am

As much as I don't want to support the use of a camshaft for just it's idle characteristics. (I'm being sarcastic, afterall. I did use a geardreive in my build) I believe a cam will idle the same way no matter how the engines fed, carb or F.I.

I've heard the LT4 HC in Lt1, L98, L31 & old school carbed rod engines... it pretty much idles the same. Fuel injection just gives you more control.

Here is a Chevelle that came into my shop with a LT4 HC in a LT1... open headers

http://www.youtube.com/watch?v=6CZ0T-ZkA-M
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