Advice to get the engine HP to agree with the sticker

[6shark9]

I want to restore at least the 300 gross (or more) HP back to a '69 base 350.
#s matching

Looking at the paperwork that came with the car, 25K miles ago the engine was re-built.

Negatives:
TRW Turbocharger pistons 8.6:1 comp.

Neutrals:
Added forged steel crank
Crane Blueprint Camshaft Stock 350ci 300HP grind

Positives:
Bored .030
Heads rebuilt, ported, 2.02/1.60 valves,Z28 dbl valve springs. combustion chamber bowl work??
Recent:
Holley Street Avenger 670 cfm carb
Pertronics electronic ignition with High energy coil

I would think the low compression and its age have me well below 300 gross HP.
Seeking advice on adding a little "BAM!" to really kick it up a notch.
Without radical changes.
My thoughts were to get the compression up to a managable 9.25 or 9.5 to 1
and throw in a Comp cam 268 or 270.
Your thoughts???

 

[Mako]

I wouldn't be surprised that with the better flowing heads that the engine is still making nice power inspite of the smog friendly CR.

Before throwing any parts on the engine I would do a basic tune up then put the car on a chassis dyno and dial in the carb with the dyno's wide band O2 sensor and tweak the timing to maximize the current setup.

Once you have a good baseline setup, then start looking at parts.

Remember that a 355 engine is a rev happy combination. I'd look at a better intake to support higher revs, although with the stock small block hood you're really cramped for vertical growing room.

An Eldlebrock Performer combined with an LT-1 drop base air cleaner would gain you some real power.

As far as more cam goes, due to intake manifold restrictions, you don't want to over cam the engine to where it needs more air than the manifold can deliver.

Try installing 1.6:1 roller rockers on your existing setup. That's like adding more cam, costs about the same $ but you don't have to rip the front of the car apart to do it.

These suggestions are do-able in your garage in one day and won't cost you a sick amount of cash.

Take the car back to the dyno once this work is done and dial the carb and timing in for the new combination. I figure you'll see at least +20HP at the wheels, possibly more. Your biggest gains should be in torque, maybe +30#/Ft at the wheels with the new intake and everything dialed in well.

I'd drive it long and hard at this point. Don't sweat the compression ratio until it's time to rebuild the engine. With Mobil 1 or Redline oil, you should get at least 50K more miles out of the engine.

Installing headers on a Shark is a BIG win. If you don't have them yet and don't mind the extra noise and non-stock appearance, consider installing them. You will need to tweak the carb to add more fuel to avoid going lean when you do that.

Good luck!
Mako

 

[JohnZ]

Good advice from Mako. BTW, Z/28's never used double valve springs - they used exactly the same "grocery-getter" springs every other Chevy V-8 used (85# closed, 190-200# open).

 

[6shark9]

Good advice from Mako. BTW, Z/28's never used double valve springs - they used exactly the same "grocery-getter" springs every other Chevy V-8 used (85# closed, 190-200# open).

John,
Thats understandable as this is a type written account by a former owner. There are dbl valve springs on the heads though, so I don't know what he meant by Z28.
He repeatedly refered to various "palancing", I assume that he meant balancing, unless he had Jack Palance do the rebuild

Thanks for the tips, I think I will go with the 1.6 rockers first. I have no more vert clearance so I can't slap the Edelbrock Perf, taking up my garage space, on there.