Piston help for a wounded 304

Well got the motor back from the machine shop. Crank was trashed, as I knew it would be, and needs a minimum of .030" bore to fix cylinders. So I ask, who here runs the 304 pistons and what compression ratio do you use? This is going into a CJ5 jeep that is 90% street, and 10% off road. So it is getting a nice comp EX262 cam for good mid range, and long tube headers, along with a performer intake manifold. Would I could get the cheaper Sealed Power 30 over pistons for $244 from summit racing, I wonder what the power bump would be by getting say 1 full point of comrpession added to make a 9.5:1 compression ratio in this jeep. Looking to make it a fun driver.

Don't bother asking about a 360. The price of a used motor around here, then the parts it might need are far more expensive then fixing up my 304. Plus its a jeep not a race car. I found one used motor minus flywheel (that's another $197) for $600 and its got 130k on it and is about $100 away in fuel. So it's just not worth it to us to get a 360.

If it's just going to be a driver, the cast pistons will serve you well. Don't worry about forged pistons unless you're going "hot street" or competition. 9.5 should give you a good HP boost and run well on mid or premium grade gas. Factory compression is only 8.25:1. Spend a little more on the rebuild and have the rods resized, and have the engine balanced. The cam, along with intake and headers should give you a nice combo. Don't over carb. A 500-600 CFM carb with vacuum secondaries will be plenty.

I had a 304 in my Jeep that I used to mud bog. It had 10.5 compression, shot peened rods, balanced, a lot of head work with 1.94 and 1.50 valves (stock are 1.78 and 1.40), a .488 lift, 282 duration cam, Edelbrock Performer with Holley 600, and long tube headers. I was pushing a little over 300HP. It revved easily to 6000. A lot of guys thought I was running a small block Chevy. I broke it in a hill climb competition when I had a little too much timing, and some bad gas. Detonation broke a piston and scored the cylinder. Swapped in a 360 and never looked back.


Bob
tufcj

Thanks for the reply. I figured if we are paying for pistons, I would rather get some more compression and tougher forged unit so I could possibly boost or most likely hit it with a 100shot of nitrous for purely fun. Of course I can do it on cast, but I can't even get Bulltear to respond to my price question on pistons. I sent them an Email about 12 days ago...

Matt's a pretty busy guy. He seems to have problems with mail going into his spam folder, so the best bet is to make a phone call.

I built the 390 in my AMX with Ross forged pistons and stainless valves so I could hit it with a 100 shot of N2O. Once I got it on the road, I'm very happy with the performance the way it is. Never added Nitrous.

Bob
tufcj

I pretty much end up with a kit on everything I own lol. I'm calling the shop now. Thanks again!

To answer your question if I heard it right...their aren't really most folks running any certain compression but only what has been commercially available. Because we are offering a custom piston for cheap the compression are all over the map. I would run a 9.3-1 with a performer camshaft not a comp cam if its a jeep motor. For the last year or so I have been unsuccessfully trying to divert tech questions to the forum.

This is also Matt and I try to get to everyone that calls in with a tech questions. I handle 90 percent of them on the AMC side but I am one of many here. If your not getting a return phone call its because I (Matt) am swamped. If you want to call in and bullshit with one of the guys you can do that any day of the week but you may not get the proper answer. (All due respect to the employees of Bulltear you know-it-alls...lol)

Thanks for taking the time to answer. Turned out the price for pistons was to much for my buddy to spend. This is his Jeep I am just the mechanical brains and brawn behind the rebuild. I did get some oil parts and cam bearings from you guys. I'm sure I will end up with some other parts too as time goes on.

Can anyone help me find overbore head gaskets for this 304? Ours is getting 0.040" bore to fix the cylinder walls. I am having a hard time finding head gaskets that aren't $150 to fit this need. I'm sure Felpro has some I just can't find the correct numbers.

Quote:

---

Originally Posted by spike_africa

Thanks for taking the time to answer. Turned out the price for pistons was to much for my buddy to spend. This is his Jeep I am just the mechanical brains and brawn behind the rebuild. I did get some oil parts and cam bearings from you guys. I'm sure I will end up with some other parts too as time goes on.

Can anyone help me find overbore head gaskets for this 304? Ours is getting 0.040" bore to fix the cylinder walls. I am having a hard time finding head gaskets that aren't $150 to fit this need. I'm sure Felpro has some I just can't find the correct numbers.

---

Felpro makes a 304 head gasket. You don't need an overbore head gasket just a stock replacement.