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Old 06-12-2006, 06:12 PM
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Cam selection for Vortec Chevy 383

Hello to the group,

I have a 94 Chevy SW4x4 1/2 ton with none of the stock drive train in it. I'm 24 years old and Iíve been wrenching on this thing since I was 18. The engine I built for it 2 years ago goes as follows.

76 Chevy 4 bolt block
Probe 5140 crank
Probe 5140 6 inch rods
Probe Forged SRS pistons 9.6 : 1
Vortec heads modified for clearance
Performer RPM
Comp XE274
Holly 4150 650CFM Double Pumper

4L80e trans with 2400 stall
4.56 gears
and a heavy 4600 pounds



I'm going to rebuild this motor using the late model block that came in the truck with a 2 to 1 piece seal adaptor and reusing the SRS pistons. The motor now has about 40,000 miles on it and is pretty tired. When I first built it I used moly rings thinking I was going to put NO2 on it but never did. Not good for cylinder pressures after 40,000 hard miles. Quench on it right now is a little thick, about .065 which I will fix using the stock vortec head gaskets that are .025.

I'm trying to figure out what cam I want to use. I've ran a XE268*(for fuel injected engines) and currently a XE274 that seems to like to make valve train noise. I was not impressed with the XE274 (even with a 4150HP 750)compared to the XE268*. I wondering if my vehicle weight is hurting me here even with 2400 stall 32 inch tires and 4.56 gears. This truck used to run 14.05 @ 98 MPH with the XE268* on the trucks computer with a 670 CFM TBI. The best I've got out of it lately is 14.5's with the XE274 and Holly 4150HP 750. OK this is not a fair comparison. When it ran 14.0's it still had the 4L60e but I fragged it one last time and had to upgrade to the 4L80e which weighs about 120lbs more including the transfer case.

Has anyone out there had a combo like this. I'm thinking about one of those Comp Extreme 4x4 cams 1800-6000 cam 226 234 @ .050 but I'm not sure how much the vortecs will like it. I've also thought about going to a roller since the new block is set up for a lifter tray but I don't know if it's worth the money.

[URL=http://store.summitracing.com/partdetail.asp?part=CCA%2DCL12%2D243%2D3&N=115&aut oview=sku]

Thanks for readin any input would be appreciated,

Ross

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Old 06-12-2006, 09:43 PM
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I have that cam in my Nova. It's also a Vortec head on a 383. My compression is 10.5:1 and it dynoed 463 HP and 461 HP with a real flat torque curve.

I couldn't agree more with the valve train noise. Actually sounds like a sewing machine. I am told this is from the steep ramps and the valves slamming shut. Whatever, I understand your aversion to the noise this cam makes. How would you know if you have a lifter noise or exhaust leak with this cam?
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Old 06-13-2006, 05:05 AM
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For sure... Seems to make all the noise (at least what you can hear) at cruising speed and idle where your manifold vacuum is at it's highest. I was hoping someone here had used a Comp 4x4 cam but it's looking like not. My springs (comp 961's) probably should be a little stiffer to get rid of some of that noise.
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Old 06-13-2006, 07:41 AM
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My understanding is that the lifters actually fly off of the cam then make that noise when the valves slam shut. If that's true then wouldn't stiffer springs actually force the valves to slam shut even harder causing more noise? I'm not sure, just thinking aloud here.
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Old 06-13-2006, 05:49 PM
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72 Orange, I was just curious if you knew what the dish (or dome) of your pistons are. Also, does your car run on pump gas (91 octane)?

Mytruck, I have a couple of ideas why your truck may be running slower. First off, as you stated, the tranny is 120 lbs heavier, also the tranny may take more hp to use which means that you are also getting fewer hp to the wheels. Also, a 750 carb is probably a little large for that motor. You need low end torque to get that big thing moving. The larger cam and carb probably ate up some low end torque. My guess is that your 60' probably decreased and your MPH increased or stayed the same, but overall, the truck got slower. That is just a guess, but I would be interesed if that was the case or not.

Adam

Last edited by firestone; 06-13-2006 at 05:56 PM.
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Old 06-13-2006, 05:50 PM
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I've heard the stiffer springs hold the lifters downs better not letting them fly off. But you end up eating your cam and lifters faster... Always a trade off.
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Old 06-13-2006, 08:30 PM
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I have the comp 4x4 cam in my 454 It has 270/278* With .544/564 lift
It idles like a sewing machine and I couldn't notice any valvetrain noise.
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Old 06-14-2006, 07:16 AM
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Quote:
Originally Posted by firestone
72 Orange, I was just curious if you knew what the dish (or dome) of your pistons are. Also, does your car run on pump gas (91 octane)?
Yes, it runs great on 91 octane, no signs of detonation.

I'm not sure what pistons were used. I didn't spec the motor, basically told my builder the power I was looking for and let him use whatever he thought was best. He told me it was 10:5 to 1 compression.
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