'75 Chevy Silverado

[AkGary]

I have a '75 c-10 shortbed and I'm currently in the process of doing the body work but will be looking at doing some engine mod's soon. I'm trying to tweek all the speed out of her without throwing in a supercharger. Its got a 350 with a turbo 350 behind it. Any suggestions??
 

[WA-Hal]

It depends somewhat on what you plan to do with the truck when you are done. If you plan to drive it much, I would suggest not getting to radical with the engine mods, since real hot engines usually get lousy gas mileage, won't idle decent and often don't last very long.

The 350 Chevy is one of the cheapest engines to rebuild and get pretty good power for a reasonable price. If your engine is the one that came in the truck and has not been rebuilt, it probably has a pretty low compression ratio, a terrible cam and not the greatest heads. If I were building a nice street engine I would go for a compression ratio of about 9 to 1 with flat top pistons, a hydraulic cam that was recommended by one of the cam companies for the combination I specified to them when I called for advice, a 4 barrel carb on an aftermarket aluminum intake, fairly small tube headers with true dual exhaust about 2.5 or 3 inches in diameter, a hotrodded
HEI ignition and whatever brightwork that suited my mood and budget at that moment.

There are lots better heads available than what came on 1975 pickup 350's. Depending on your budget, you might consider some later Vortek iron heads (which I think require a dedicated intake manifold) or some of the aftermarket iron heads. Or there are lots of aluminum heads for sale, and they would allow a bit higher static compression ratio.

The turbo 350 is a good transmission and if yours is in good shape, use it. It is tempting to mess with a "high stall" converter, but if you plan to put very many miles on the truck, such a converter will be hard on the gas mileage. And you should add a big transmission cooler with a high stall converter, since they produce more heat to the ATF.

If your current transmission isn't too good, you might consider using a later overdrive automatic. The Turbohydro700-R4 uses a very low first gear that really gives strong acceleration taking off, almost like having much deeper rear gears, yet with the overdrive ratio, freeway speeds allow low RPM's for less noise and better gas mileage. The overdrive automatics have been around long enough that the transmission builders have figured out what modifications are needed to keep them working with lots more horsepower than they were originally designed for.

Good luck with your pickup. Watch for rust,as the Chevys of the early and mid 70's really rusted badly in a number of areas. Otherwise, they were pretty good pickups, and are supported by the aftermarket about as well as anything is.
 

[AkGary]

Once the truck is done I only plan on driving it 4 maybe 5 months out of the year and Im willing to sacrifice gas mileage for power.
 

[ericlb]

gary are you wanting speed or horsepower? if you just want a higher top end, swap in a taller rear end ratio, a set of 2'73's should get you aproaching 140mph, not recomended in a open bed pickup truck due to arodynamics , if its horsepower you want ie; quicker from a standing start to 100 or so how much power you get basicly depends on how much money you want to spend for a driver that is both quick and reliable swap in a crate engine 383 stroker there cheaper than rebuilding yours once you pay for all the nessassery machine shop work for a good rebuild, that will put you in the 400 hp neighborhood with a little tweeking and manifold and carb set for around 3 grand [ stock '75hp is around 185] and still be a reliable street drivable truck, beyond that the money goes fast as the hp climbs as well as you'll be spending every weekend tweeking your engine also keep in mind this is a pickup with a relitivly light weight rear end, you can only stick just so much hp to the road then you'll just be smokin the tires , the stroker will burn the tires right down to the rims if thats what you want