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Old 03-01-2011, 04:26 PM
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350 more horsepower

Hey guy's, I have a 76 corvette 350 california smog motor and by all the information it has 180 horse power. Im putting it in a 30 model A coupe and would like to up the horse power up to 300 HP. I believe it is pretty much stock right now and I will be runing a 350 trans and a 9" rear with 300 gears. I would love to do a stroker 383 but I really need to keep the price way down. I have a need for speed but need to keep the bucks down to a minimum. Any help or advice would be greatly appreciated. Bill
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Old 03-01-2011, 04:57 PM
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Best path is to remove and discard the incredibly crappy stock heads, they are what holds these 70's engines back the most. Then cam change, headers and 4 barrel intake and carb.

The '96-2000 Vortec 350 head is one of the best low cost alternatives, and some of the aftermarket versions of this design.
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Old 03-01-2011, 05:54 PM
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Quote:
Originally Posted by ericnova72
Best path is to remove and discard the incredibly crappy stock heads, they are what holds these 70's engines back the most. Then cam change, headers and 4 barrel intake and carb.

The '96-2000 Vortec 350 head is one of the best low cost alternatives, and some of the aftermarket versions of this design.
X2 On this been there done that, You have to lose the heads and be very careful in intake choices but either way you will need to keep the stock drop base air filter housing on it, or it will hit when you close the hood you don't have to ask me how i know. And if it's in your budget go with a set of coated headers also.


Cole
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Old 03-01-2011, 06:26 PM
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Will I be able to pick up 120 HP with the new heads, cam, carb and manifold and not have to go into the block? Is there any modification to the block with these 96 or later heads? I know the intake side requires a different manifold from what I've read here. bill
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Old 03-01-2011, 06:54 PM
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You will be able to pick up that much easily, the heads alone probably 70 hp of that.

No mods to the block required for the Vortec head. Just the intake manifold change and self aligning rocker arms are the only specifc pieces, and of course the valvecovers as they are centerbolt style.

Aftermarket Vortec type heads (from RHS, EngineQuest, World Products)are usually drilled for both valvecover patterns, and often both intake manifold bolt patterns.
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Old 03-01-2011, 07:25 PM
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Quote:
Originally Posted by bill plise
Hey guy's, I have a 76 corvette 350 california smog motor and by all the information it has 180 horse power. Im putting it in a 30 model A coupe and would like to up the horse power up to 300 HP. I believe it is pretty much stock right now and I will be runing a 350 trans and a 9" rear with 300 gears. I would love to do a stroker 383 but I really need to keep the price way down. I have a need for speed but need to keep the bucks down to a minimum. Any help or advice would be greatly appreciated. Bill
SMOG engines suffer from no compression, very limited cam timing, and poor combustion characteristics.

It's easy to get 300 horses out of a 350, you don't need to strain too hard for that.

First off if you're going into the block, it's a help to change the piston configuration. The piston forms half the combustion chamber shape and the circular dish the factory uses is opposed to the efficient manufacture of power. You can over come this if your not changing pistons but if you do; you want to match a D dish piston to a small chamber head to optimize squish and quench which are ways to build not only efficiency into the engine but detonation resistance as well. But a small chamber head alone is a huge help to the engine.

These days the first off reaction to heads is to lay your hands on a set of Vortecs. Chamber design between what's really good and what's really bad is very subtle. The heads you have are designed to minimize NOx emissions which in 1976 were a big problem so the factories just reduced compression to where the combustion temps and pressures didn't make NOx. The advent of the 3 way cat has changed that and restored higher compression levels. The L31 Vortec head needs to be your design guidance if not your selection. There are many versions of this sold these days by GMPP as well as the aftermarket in iron and aluminum. The major features to look for is a small heart, or some people call them kidney, shaped chamber 64 ccs or less, with the spark plug canted toward the exhaust valve and centered as much as practical, with a squish/quench deck that has a beak penetrating the chamber to about the distance to the valve guide center line. The Vortec is a proven 20-40 horse gain just bolting them on with no other changes.

To get 300 horses will also take some camshaft, the Comp Extreme Energy 262 or an equivalent will be plenty when this is teamed with 1-5/8 headers and a 650 cfm Holley on something like an Edlebrock Performer RPM intake to take this to about 330 to 350 horses. A cam with the timing of the old 300 horse 327, 929 cam which is even more mild and will top a 350 at about 300 -310 horse with a lot of torque on the bottom end. This is with modern compression limited to about 9.5 in the Vortec head, D dish piston configuration using premium unleaded. In the 300 horse 327 days of 100 plus leaded fuel, the factory pumped up the compression to 11 to 1. So this cam in a 350 with 9 and fraction to 1 delivers about the same power curves as the old 327 by trading less compression for more inches.

Bogie
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Old 03-01-2011, 07:42 PM
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Quote:
Originally Posted by ericnova72
Best path is to remove and discard the incredibly crappy stock heads, they are what holds these 70's engines back the most. Then cam change, headers and 4 barrel intake and carb.

The '96-2000 Vortec 350 head is one of the best low cost alternatives, and some of the aftermarket versions of this design.
Best advice.Totaly.
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Old 03-01-2011, 10:42 PM
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There's no need to go nuts w/the cam specs- you'll see 300-plus HP using the Vortec heads a cam w/no more than 220 @ 0.050" lifter rise.

The stock Vortec heads will require a new set of springs. Many guys run the inexpensive (~$35/set) Z-28/LT-1 springs sold by most suppliers, w/o the inner damper. You can reuse the original retainers. CLICK for some more info on Vortec heads and mods to them, etc.

Keep the lift around 0.450". This keeps the likelihood of having to reduce the valve guide boss height for more retainer-to-seal clearance (or resorting to other means) to a minimum. You will still need to check to be sure there's enough clearance at full lift, but in all likelihood there will be adaquate clearance- just be sure the seals are fully down in position on the guide boss. Sometimes it will look like there's not enough clearance, but it's only because the seals aren't fully pressed into position.

A cam like that will have good idle vacuum so power brakes will work and even the mileage won't be that bad- possibly better than stock for that matter- depending on how you drive it.

So you're going to use a 9" rear end?
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Old 03-02-2011, 04:57 AM
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How about an Edelbrock package...heads, cam/lifters, intake and carb? And will it fit under the Vette hood? I'm thinking of doing the same thing to a '77...
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Old 03-02-2011, 05:13 AM
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Everyone missed, this Engines going in a 1930 Model A. Not a Vette.
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Old 03-02-2011, 07:20 PM
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350 300hp

I did something similar for my camaro years ago, had a bone stock 350 2barrel motor from a '73 caprice. I cleaned it up, put in all new gaskets, a Comp Cams 268H 218@.050 .454 lift. (I used the K-kit with matching springs) I used 4 barrel heads from the 79 camaro with a little pocket porting, a valve job, and 1.6 rockers on the exhaust. Performer Intake with a stock Q-jet. No doubt there are better combos available, but that's what I used and it really ran good for what it was, cheap!
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