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Vortec 383 horsepower guesses?


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These are the ideas in my head for my engine build, just curious if someone a bit more experienced would give me a hp guesstimate.

 

'97 vortec block and heads

Gm lt4 hot cam (and springs to make it work)

Full roller rockers

11 to 1 compression

Msd

Performer rpm air gap intake

3 angle valve job

Holley 750

 

I have searched and found many comparable but they're all from big magazine companies and may be inflated numbers.

See any problems with this combo?

Thanks in advance

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I would guess at 350 -400 hp but with good low end torque.but it is more fun to drive a car with torque than an over-cammed engine that falls on its face when you stab the throttle.I think either Car Craft or Hot rod uses a place called westech in socal.I have spent a day there with a friend while he was getting a boat engine dynoed.they run alot of engines there and the operator knows his stuff.my buddy had a 555" short deck big block chevy built for a jet boat that made 802 hp on 91 chevron pump gas.that wasnt a cheap motor.

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That's why I'm not machining down the valve guides for a bigger cam. I've heard these can be torque monsters if built right :)

This will be my first bottom up engine build so it probably won't be right, but I have to do it on the cheap. So no aluminum heads, no extensive machine work. But still ok hopefully.

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Yeah I guess there's some things I won't /can't do that would help

As is:

Not zero decking

Not align honing

Not running a monster cam

Not buying $2000 heads

 

However I think this is a pretty good package, I guess I'll find out :-). I don't have a ton of money and I still need just about everything for the car...brakes, coilovers, LSD, interior, paint, bodywork etc... So no 555 for me

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Jason, I think your combo, with a decent exhaust, would make 400chp pretty easily. Torque would probably be more, and the hp peak probably in the low 5k rpm range. Looks like the cam is 218/228 @ 50, and with 11:1 and iron (?) heads, it may have some detonation problems, or at least require careful attention to fuel and tuning. Of course, 11:1 advertised doesn't mean you will wind up with a true 11:1, so it may not be a problem. Otherwise it looks like a fun combo to me.

 

jt

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You need a bigger cam to run 11:1 cr with pump gas.

 

I run a 292H compcam with 11:1cr with no issues. 292/292 advertised, 244/244 at 0.050".

 

A 383 with vortec heads and a "big"cam can still have good low rpm power due to the small ports in the vortec heads. But I would still recommend a 3000 stall with a cam in the 290 degree range.

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Price out the machine work to the heads first before its done. The valves, valve guides and seats all have to be in somewhat good shape. May be cost effective to purchase procomp 200cc intake cylinder heads from KMJ. Use flat top pistons and get the squish as good as it can be. Smooth out the Vortec head chambers before assembling the engine to reduce detonation.

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I have already smoothed the combustion chambers, polished the exhaust chambers, and ground a bit off the spark plug boss. Just some basic stuff I saw in an article about those heads. Nothin fancy as I didn't want to ruin them. Anyway, if I can get 400hp or a bit more, I'll be happy. The entire motor was free so I'd like to use it

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I just read a write up that made 401 hp, it had 9:1 compression, stock vortec heads, a hollley 750, the hot cam, hei, and the air gap manifold. It was a 350. So I'll go ahead and keep my hopes up. I'll have more displacement, and a better ignition system, plus the little head work done. From the sounds of it I'll probably stick with 10:1 or so compression. All the torque is made early so it should a fun street car

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Well I was bored and owned a dremel, I did a couple things on my coffee table to 'port' the heads. Honestly I probably did more harm than good, so in my boredom I may have nicked the valve seats. I don't really know but figured I'd err on the side of caution and get a valve job done. I wish Id of had more experience and known better, but it is what it is. Should I get the valve job done now or just cross my fingers?

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You can mark the seats with a magic marker, put the valves in and spin them (with a drill or with a stick and rubber hose) and see if the nicks are actually on the contact area of the valve and seat. If not, they're probably OK. If you know someone with some engine building experience, you could get them to take a quick look.

 

jt

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  • 3 weeks later...

You need a bigger cam to run 11:1 cr with pump gas.

 

I run a 292H compcam with 11:1cr with no issues. 292/292 advertised, 244/244 at 0.050".

 

A 383 with vortec heads and a "big"cam can still have good low rpm power due to the small ports in the vortec heads. But I would still recommend a 3000 stall with a cam in the 290 degree range.

 

 

i would like more info on your combination.

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