I have some freshened #5 heads that I would like to swap onto my '74 350. I am wondering if changing will be a noticeable upgrade. I already have dual exhaust and an Edelbrock intake and carb. I know it should bump up compression but I don,t know how much. I have #8 heads now. I also wonder if the stock cam will run OK with higher compression. It is in a '42 Chevy with a T400 and Nova rear with 2:73? gears. It runs good now and doesn't burn oil or anything. I will replace timing chain at same time and am trying to gain power for cheap, will this make a difference? I am trying to make it better until I can rebuild the 455 for it and don't want to spend much. This is a pic of what it is in.

 

To make it really worth your while you may want to make sure it has 2.00 intakes in it. That along with a bump in compression should make a noticeable difference.

Good luck.

 

Gain power for cheap...
Stock camshaft?
Have the heads been milled?
Have the valves been cut more than once?
1.88/1.56?
I did a quick check on the KB piston calculator, and with best case scenario, I get a boost of nearly 1 point. Most likely you will gain another 30 or so hp with that point of compression, and around15 lb/ft of torque.
There is still more you can do to the heads for low dollars, while they are off the engine. Purchase thin head gaskets (factory .017, you can sometimes find on e-bay). Back-cut the intakes with a 30 degree cut, will help midrange and part throttle. Filling the crossover in the heads will gain power too.
Optimize timing, and carburetion will gain just as much power. The AFB (old term for your carburetor) is not as good as a good rebuilt q-jet. There are kits available to help, but I would rather see you go back to the q-jet.

Changing rear gears will do a bunch also. How many highway miles do you drive? Even a move to 3.08, or 3.23 will help get this massive Panzer of an automobile marching down the road quicker.

Sure looks cold in that picture.
JMO
Jim

 

Hey, if you already have them why not go for it? Ain't gonna' hurt, that's for sure.

+1 on lower rear gear. Obviously won't make more horsepower, but the car should feel enough quicker to be decently satisfying until you can do your 455. Whether this is what you consider cheap kind of depends on what it will cost to get it set up. If you can DIY, it's a bargain considering how much more fun the car will be.

 

I know the heads have not been milled and the valves are not sunk in the seats. I am planning a gear change, that will help as much as anything else. I can do all the mechanical stuff myself. Believe it ir not the '42 only weighs 3200 pounds so it isn't a slug now, just want more. I also have the Q-jet and am going to use it, I love them. The fastest car I ever owned ran a Q-jet ,it ran 115 in the quarter so I know they are a great carb. Thanks for the help. I am also planning an overdrive trans, so upping the gears won,t hurt mileage much.

 

That is a cool car.

sb

 

Thank you. I have owned several old cars and this one is my favorite hands down.