View Full Version : 305 heads? for a 307 in a CJ

06-08-2009, 10:26 PM
My buddy got a 76 CJ with Chevy V-8 conversion.

Seller said it was a 350 but turns out to be a 307 with bad valves in #1 and #2.

So we pulled the engine and heads and are considering a valve job (might be too far gone) or have heard about putting 305 heads on this engine.

Anyone have 305 heads or a 305 engine?

Anyone knowledgeable about 305 heads on a 307?



Agent Orange
06-08-2009, 10:36 PM
You can but will give you around 10.5 to 1 comp ratio. 307's arent the best of motors.If possible put a
350 in there

06-08-2009, 10:46 PM
As said, it will raise your compression ratio...

run it...

Agent Orange
06-08-2009, 11:07 PM
And if it is to much comp you can always put thicker head gaskets on or enlarge the bowls. Also you should be able to get those 305 heads almost free, if you dont have them allready

06-08-2009, 11:22 PM
if its a cast iron 307 my old 76 silverado had one with 305 heads and would smoke all 4 36:1350 swampers it had a sm 420 with a 205 case.man i miss thay truck

06-08-2009, 11:27 PM
drop in a 400 crank and its bad arrssss.

06-09-2009, 04:09 PM
You can but will give you around 10.5 to 1 comp ratio. 307's arent the best of motors.If possible put a
350 in there

This is what we are learning. Getting max performance out of a 307 vs a stock 350, the 350 is cheaper and more reliable.

We were thinking about the 305 heads because as said can be picked up cheap and we don't think our 307 heads are salvagable.

With the higher compression we would need to run high octane gas I am guessing.

Our thoughts were to be simple and cheap. As with most Jeep stuff may not end up that way.

Even stock the 307 with 200 hp and 300 torque would in my opinion make a good Jeep motor.

The plan for it is hunting, for the most part unmaintained dirt roads.

That is what my friend who owns it says for now. I think after getting him out on some tougher trails he will catch the Jeep bug.

Jeep bug: Usual symptoms; broken AMC 20 axle due to hard trails and too big a tires, long hours in junk yard looking for flat top Dana 44's or 60's, pondering lower gears in the stock transfer or go for the Atlas, increasing chance of roll over after installing roll cage, and so on.

Agent Orange
06-09-2009, 04:47 PM
So true if that thing just needs heads put on the 305's. Plenty of power for that jeep, Very easy to do, Like I said you can get those heads almost free(I would call local machine shops first they always have a ton of parts laying around from customers performance upgrades), Then search junk yards.

And run that motor till it breaks, if it needs other work done though i wouldnt throw money in it.