Questions on 304 Mods

Hello everyone,

I've just joined the forum, but I've been monitoring for quite a while now. I just purchased a 1972 Commando with a 304 V8, although I haven't received it yet; it's being shipped from Tucson (I'm in Baton Rouge).

34,000 original miles
believed to be stock
no significant oil leaks
runs well
compression test shows 115 #'s on all cylinders except one which shows 20
no smoke from the exhaust
recently passed Arizona emissions
sounds like it may have a minor exhaust leak

Because of the lack of smoke from the tail pipe, I'm thinking that either a valve is bad or the head gasket is leaking.

I'd like to run my plans by some of the more experienced folks here and get some feedback. My intended use for this vehicle is 90% street and 10% mud riding. I'm not into "low end grunt" and ultra high torque. I have a CJ-8 with the 4.2 that I put a fuel injection system from a '94 cherokee. That's for low end grunt. Fuel efficiency is not the most important thing, but I'm hoping to get AT LEAST in the low teens. I also don't want to spend a massive amount of money chasing ponies. I'm hoping I can do all of the following for under $1500 and have a nice reliable engine.

Edelbrock performer intake
Cam upgade - don't know which one yet
Remove heads and get a valve job - should I port/polish change anything?
GM Throttle body injection from chevy 5.0
As part of the TBI upgrade, I'll need to swap the distributor to a Ford Duraspark

Please don't tell me to swap in a 360 or 401. I don't want to swap engines, and I don't want to change anything in the lower end of this one.

What kind of horsepower could I expect? Any pitfalls or suggestions? Any other mods that are good "bang for the buck"?

Why did the the 304 get lower power ratings through the years? I understand it had something to do with trying to meet emissions, but what physically changed?

I'm in the same boat. Buddy got a 79 CJ5 we are making into a rusty rat jeep. Its keeping the stock drivetrain for now including a mild 304 build. Long tube headers from flowtech, edelbrock performer intake, Comp Cams 262 Extreme Energy cam for solid mid range power, e fan conversion, all new bearings and rings, stock crank is beat up and is getting looked over by machine shop. Already has a 4 barrel carb and true dual exhaust. So without good pistons or ported heads, I hope I can be close to 200hp. Which in a light jeep will be a fun street driver like you are looking for.

Low compression could be either a burnt valve or bad rings. Once you get it, squirt some oil in the cylinder (maybe a tablespoon full) and re-test the compression. If it's bad rings, the oil will improve the reading, burnt valve, it won't.

I ran an Edelbrock Performer cam/manifold and Howell TBI fuel injection on the 360 in my CJ (stock bottom end). Got about 11 MPG on the highway, remember you're pushing a brick through the air. I ran mine with a Mallory distributor. The Howell system was about $1250 to my door, was bolt on, and aside from a couple of bad O2 sensors (my fault), it was flawless for the 12 years I had the Jeep.

In the 70s, the HP ratings went down because they changed the way they measured it, not because they changed the engines. Early measurements were made at the crank with no accessories attached (water pump, PS, alt). Later measurements were made with all accessories and emissions equipment attached, which really yielded a truer number. I'd say with EFI and a quality valve job (if that's the problem), you're looking at around 250 HP.

I had a 304 that was built .030 over, 10:1 compression, balanced, heads ported and polished with 1.94 intake and 1.50 exhaust valves (stock is 1.78 and 1.40), cam with about .480 lift and 282 duration. Torker intake, long tube headers, Holley 600. It did just shy of 350 HP on a dyno. Rods were shot peened, and I regularly spun it to 6500 RPM. Finally broke it when I put in a little too much timing, had some detonation under load, broke a piston around the lands and scored the cylinder. Went to a 360 and never looked back.

Bob
tufcj