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Wake up the 350 challenge!!!

Jeff427

Jeff427

1/2 ton status
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May 22, 2000
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Gladwin, MI
I have an interesting challenge for you guys. My Dad has a 1980 Corvette with a 350 and a 4 speed. He wants more power out of it, but there are two catches that make it a challenge; he does not want the compression ratio bumped at all (currently has 8.5 to 1, and runs on cheap gas). And he does not want the stock external appearance changed at all, so no headers, or aftermarket intakes. Any suggestions on how we can wake this motor up with those restrictions? Roller cam and lifters? Roller rockers?
 
Since the cam is the brain of the motor. A cam that is set up for the weight, gearing, and RPM range desired would be the best investment along with massaging the current heads and stock intake to take full advantage of that cam. Without changing the appearance the only other thing that might be able to be tweaked is the fuel delivery system and make sure the ignition is operating at peak performance.
 
You could get some head work done or maybe even switch to heads with bigger valves and do the port work, still look factory. Then go to roller tip rockers and a slight bump in cam size. All that is a good start but won't help didley if the exhaust don't flow.
 
A roller cam is unnessary with those parameters.
What heads are on it now? Are they the ones to be used?
Along with the cam that will make the difference.
Cast exhaust manifolds.. /forums/images/graemlins/thinking.gif look into the earlier vette manifolds, for the day they were better than most.
Same for the intake, look for an early Z28 one.
The cam and heads will dictate what size carb if you are using a square bore one.
An 80's SBC spread bore (Q-jet) leaves alot to be desired.
As for a cam.. I bought a Rhoads hydra solid cam and lifters that are going into the plant in the K5.
www.rhoadslifters.com
If this cam works as they say it does it would be a good choice for a sleeper.
Compatible with 180 - 200 cc runners and works best with a compression ratio of 8.5 - 9.0:1.
They claim an RPM range of idle to 7K.
80 Vette.. I like that year.
 
Aluminum heads, aluminum intake (both painted Chevy orange) Port the exhaust manifolds heavily, add a moderate roller cam with roller tipped rockers...then top it off with a stealth routed NOS system. I've seen them routed through the back of the intake valley with all the plumbing on the underside the intake manifold.

Rene
 
I can spot a painted manifold from a mile away.
One dude I know that has a 69 camaro that has a basicly stock lookin plant outruns rice rockets with it.
All stock early GM stuff except cam and manifolds which are cast.
Not Rice mobiles.. he outruns bikes with it down hwy 30 and the hills. Although he has had it for 20 some odd years and has done all kinds of cool stuff to it. Convertable too. Scary fast ride.
The only other ride that had me thumpin was one dudes Cobra clone with a nasty 460 in it.
Paying the $$ and painting aluminum heads is a crime IMHO.
To the eye getting a stock set of early LT1 heads, massaging them a bit and installing 2.05 valves would be the way to go.
Yes aftermarket heads cost about as much as gettng a set of those rebuilt but if originality is the key then the cost is justified.
When ya pop the hood and see a cast intake and headers and a set of GM heads pumpin life to the critter then it makes it all the more better.
Anyone that has a credit card can buy all the goodies.
A clean lookin azzkickin plant is something else entirely.
 
[ QUOTE ]
Aluminum heads

[/ QUOTE ]

Useing 8.5 comp, aluminum heads will cost H/P.

Heat is horsepower !
Less heat wasted into the cyl head, is more heat in the combustion chamber, where it's used to force the piston down the bore. Aluminum heads will disipate heat quickly. With only 8.5 compresion, aluminum heads are not needed.
Only run aluminum heads when the compression ratio demands it.

With a four-speed trans, you can go a step higher with the cam. It doesn't need the "low-end" power, that it would with an Auto.
I think that is the key to this combination.

Furthermore, I'd bet;
If he has closed chamber cast heads now, cleaning them up would allow enough flow to make them preform. If he doesn't - then get some. Closed chamber heads (v.s. open) will increase the compression ratio - but probably not enough to require higher than stock octane requirements.
Keep the oil out of the chamber, the air/fuel ratio rich-ish. I'd bet you could run as high as 9.0/1 compression with stock/cast heads and mid-grade octane. (we can, "up" here, in our altitude)
 
Well, if you are looking for maximum performance, then I suggest a stroker kit to get some displacement. Maybe stroke it out with a 400 crank, and bore it .030" over and you'll have yourself a 383. Then just get upgraded valves on the heads, better valve springs, and a port job on the heads and intake plenum. (port heads, then match the intake to the heads) And also the throttle body, and upgrade the injectors, or if he has a carb, get bigger jets. And get a catback system, they sound awesome and still give you a small boost in hp. And yes, with a nice stroker like that, you would want a nice roller cam to reap the benefits of that stroker. But be sure that the cam is just big enough to keep the heads from making it fall on its face. Good luck

Remington
 
How about the distributor curve? Start with the simple stuff!

What are the rules for the rest of the exhaust? Does it have to look stock or just sound stock?
 
The exhaust is brand new, and larger than stock diameter, but laid out the same as stock (y's together just before the converter, y's apart just after the convertor, and has a high flow convertor with dual mufflers out the back). Since it is new, he doesn't want to replace it. I really don't think it is too much of a restriction though. The exhaust manifolds are the "center dump" or "ram horn" style manifolds, and we will probably gasket match them to the heads, along with gasket matching the intake to the heads. I guess it boils down to primarily help with cam choice to get the most out of what he has. Seat of the pants feel, and torque are of more concern than horse power, which is why I thought this would be a good question to ask here, since that is more along the lines of what K5'ers are looking for /forums/images/graemlins/grin.gif. He is considering a mild roller cam, with these specs,
Specifications:
* Advertised duration: 276 intake/284 exhaust
* Duration at .050 in.: 214 intake/222 exhaust
* Gross Valve Lift: .488 in. intake/.509 in. exhaust
* Lobe separation: 112 degrees
* RPM range: 2,000 to 5,500
* Good idle, daily performance usage with supercharger
* 2,600-3,400 rpm cruise range
* 8.5:1 max compression ratio recommended
* 8 lbs. max boost with
Which is the Crane Powermax 119821

Or would the Cran Powermax flat tappet hydraulic 113492 be just as good a choice?
Specifications:
* Advertised duration: 272 intake/284 exhaust
* Duration at .050 in.: .216 intake/228 exhaust
* Gross valve lift: .454 in. intake/.480 in. exhaust
* Lobe separation: 112 degrees
* RPM range: 2,000-5,000

He kind of likes the idea of freeing up some power with the roller lifters and roller rockers (advertised at about 15 hp each, they don't tell the important number, which is torque).

Hmmm...found this post on another forum:
[ QUOTE ]
I would probably swap the camshaft for something along the lines of a Crower 00915, or some other similar "RV" type of camshaft. Keep the lift below about .440" to avoid problems with the valve springs.

[/ QUOTE ]
What has to be done to have the springs clear higher than .440 lift? Machine the heads, or just different springs? Or is this a load of bull? Any more info would be greatly appreciated /forums/images/graemlins/thumb.gif.
 
Has anyone had any experience with either of these cams I mentioned in my previous message?
 
[ QUOTE ]
He kind of likes the idea of freeing up some power with the roller lifters and roller rockers (advertised at about 15 hp each, they don't tell the important number, which is torque).


[/ QUOTE ]
Roller cams are nice and all but the primary purpose of a roller cam is to be able to use a cam with a radical profile.
With that profile I would stick to a flat tappet cam.
Roller cams are spendy and for just a few ponies it is not worth it IMO. So it will rev a bit higher, the engine will be out of it's powerband and it will be a moot point.
With stock heads, manifold and exhaust you are kinda limited as to what can be gained.
Both those grinds are not matched to the rest of the plant.
To big IMO.
To take full advantage you would want to run headers, a good set of heads and a performance manifold.
What is the overall goal of the plant? Vettes are a performance type car.
What's the budget?
If you are having to use what is there then a smaller cam would be a better choice.
Something like the Ebrock performer or Cranes 113902.
204*/216* both are similar grinds.
cam selections these days can be kinda confusing with so many types out there. But one thing has never changed.
The more duration and lift added in then you will need to be able to move the air in and out to make it all come together.
If I had an 80 Vette and wanted a stock appearing plant I would use a set of World Products Sportsman II's, headers and an aluminum dual plane high rise. But with a Vette that is a problem with the hood. And there is nothing sneaky about a hood with a bulge in it. But then again it is a Vette and is not exactly a sneaky rig to begin with.
I mean it isn't grandmas old car.
 
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