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Old 10-06-2011, 09:04 PM   #1
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Vortec 5.7 with lt1 cam? Hp rating?combo questions

Well my motor is eating itself up right now and im already looking into another engine build.

I picked up a 5.7 vortec with all accessories for 300 bucks. I plan on having it rebuilt and fix mistakes made on my last build.

Last time around i had too big of a cam for the vortec heads (.560 lift) so im considering just using an lt1 cam this time.

Im not looking to make the car into an all out drag car i just want to be able to defend myself against foxbodies and a few v6 imports around my area. What kind of horsepower should i expect from the following combo?

5.7 vortec headed engine..bored over .30, forged internals, 650 holley carb, edelbrock performer rpm, lt1 cam, shorty headers with 2.73s (for now)

I really just want a solid combo guys,with the peace of mind of having a safe cam..im looking for feedback as to what i could do to give me a few extra horses (good intake choice?) before i start buying the parts.

Has anyone had experience with an lt1 cam in a vortec carbed motor? Should i expect more low end or top end? I know lt1s have better top ends and truck motors usually have the low end.. So how good would it work out? ( want to focus on top end)

Thanks for reading, inputs appreciated.
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Old 10-07-2011, 10:14 AM   #2
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Re: Vortec 5.7 with lt1 cam? Hp rating?combo questions

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Old 10-07-2011, 11:16 AM   #3
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Re: Vortec 5.7 with lt1 cam? Hp rating?combo questions

I read once that a vortec with a LT1 cam will make around 275 hp. Im sure the other mods would free up quite a bit more, tho the 2.73s is gonna hold you back bad. Look into getting a torque converter. Factory stall is only like 1300 orr something close.
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Old 10-07-2011, 12:57 PM   #4
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Re: Vortec 5.7 with lt1 cam? Hp rating?combo questions

The stock cam in an L31 (Vortec 5.7) is identical to the B-body LT1 cam. The L31 is rated 255 SAE net hp with that cam. The F or Y -body version of the LT1 cam would make an additional 10 hp at most. The reason that the LT1 in the Vettes and F bodies were rated higher was more because of better intake and exhaust flow than cam profile.
Just to demonstrate the huge effect other parts of the engine package contribute:
The tuned stock L31 in my pickup made 254 rwhp with only longtube headers and single 3" exhaust, so that's a solid 300 at the crank. The tuned stock LT1 in my ImpalaSS (same cam) made 309 rwhp with uncapped exhaust; that's about 370 at the crank. I expect your carb and Perfomer RPM would be about midway between those two, if it's tuned well.

If you're changing cams, make it worthwhile and go slightly bigger than any of the LT1 cams. Look for something with at least 206 intake duration at .050".
You'll need upgraded valvesprings for anything more than the stock L31 cam, so at the same time install matching retainers that will give you clearance to run whatever lift you choose.
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Old 10-07-2011, 03:23 PM   #5
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Re: Vortec 5.7 with lt1 cam? Hp rating?combo questions

No reason for forged internals on a 300+ hp motor. Save that money and do the machine work to the heads for the LT4 cam.
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Old 10-07-2011, 05:19 PM   #6
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Re: Vortec 5.7 with lt1 cam? Hp rating?combo questions

thanks for the info guys, ive been reading and basically whats recommended for the lt4 cam is for the heads to be machined to support .49 lift, screw in studs, and ls6 springs?

Is there anything else im missing?

What hp rating would come from the lt4 cam?
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Old 10-07-2011, 07:43 PM   #7
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Re: Vortec 5.7 with lt1 cam? Hp rating?combo questions

The alternative way of accomodating extra lift on stock Vortec heads is to install beehive type valve springs. Comp Cams makes a drop-in system that requires no machining. They can accomodate an LT4 Hotcam (.525" lift with 1.6 rockers, .490" with stock 1.5 rockers, if memory serves). Plus they get a good bit of weight out of the valvetrain which helps keep things under control better at higher RPMs.

They're not cheap, but when you add up the cost of maching the guides down plus the cost of a set of traditional non-beehive springs, the two ways of accomplishing the same result are roughly comparable.

Screw in studs you will probably want in either case.
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Old 10-08-2011, 12:27 AM   #8
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Re: Vortec 5.7 with lt1 cam? Hp rating?combo questions

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Originally Posted by J0hn_J0hn08 View Post
thanks for the info guys, ive been reading and basically whats recommended for the lt4 cam is for the heads to be machined to support .49 lift, screw in studs, and ls6 springs?

Is there anything else im missing?

What hp rating would come from the lt4 cam?
Not completely true. It can be done.

I would suggest going ahead and doing the work to them. Do it right the first time.

I had to keep the 1.5 rockers. 1.6s would have put the retainer very close to the seal. Too close for comfort.

here was my install. Mine is alittle different, I already had the motor in and didnt want to go through the pain of pulling the heads.

http://www.thirdgen.org/techboard/te...ortec-lt4.html (5.7 Vortec LT4 Hotcam Install Pics and Information)

Whenever the motor does come out, it will be fixed.

Last edited by 3rdgenmaro; 10-08-2011 at 12:39 AM.
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Old 10-08-2011, 12:27 AM
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