5.3 or 6.0

crawler nut · Jan 27, 2013

Hello everyone, I am running a full body YJ on Rockwells SBC 355 on propane, th-350, 203/205 doubler.
I am thinking of gettin rid of the 355 an pane, an going with a fuel injection 5.3 or 6.0. What would you guys recomend?
I also hear there are better 6.0 than others. What is the best one? An also what can be done to a 5.3 to really wake it up, an still be reliable?
Thanks

patooyee · Jan 27, 2013

I wouldn't bother with it. If you want more power spend some money on your 355. You could probably get 400 hp out of your SBC for what you would spend getting a 300-400 hp LS running properly in your Jeep. And I'm an LS lover.

crawler nut · Jan 27, 2013

patooyee said:
I wouldn't bother with it. If you want more power spend some money on your 355. You could probably get 400 hp out of your SBC for what you would spend getting a 300-400 hp LS running properly in your Jeep. And I'm an LS lover.

It has 305ci heads, Flat top pistons, Comp 280/480 cam. Tell me some secrets. What else can I do to it, to get more out of it?

patooyee · Jan 27, 2013

You didn't say that and I'm no engine builder. But now it really sounds like you have minimal to gain. Your looking at 400 hp max out of a stock 6.0 and less from a 5.3 and spending probably $2000 - $3000 minimum to switch fuel systems, buy the LS, plumb, wire, and tune. Were you planning on doing something to the LS to get some more power?

crawler nut · Jan 27, 2013

patooyee said:
You didn't say that and I'm no engine builder. But now it really sounds like you have minimal to gain. Your looking at 400 hp max out of a stock 6.0 and less from a 5.3 and spending probably $2000 - $3000 minimum to switch fuel systems, buy the LS, plumb, wire, and tune. Were you planning on doing something to the LS to get some more power?

Well, I would. I guess I am just frustrated, I cant seem to get the engine running right. Nobody around here know how to tune propane, an I sure dont. The engine should just come alive, an get with it. But it dont seems to idle radicly an when I hit it hard, for instance hitting a hill an dont make it, when it comes to a stop it will just quite. Fires right back up an repeat. Even yesturday while riding people were saying that it didnt sound right. Almost like it was running on 7 cylinders. Im running an HEI dist. have changed the module, etc. An still cant get it to run right. Dont know the timing numbers as im not running a indicator, beacuse I have herd it dont mean nothing on propane any way. I am just frustrated.

patooyee · Jan 27, 2013

Timing matters with any fuel. On propane you should be around 14 advance at idle without vacuum attached. It should run fine there and you can fine-tune it after that. You can get a cheap timing light at Advance Auto for $40. It sounds like it might be worth the investment for you. Hard to say what is going wrong with your engine but from your description I would agree that it isn't running right. Look around hard for vacuum leaks, propane don't run worth a damn if you have them.

Elliott · Jan 27, 2013

Throw those 305 heads away and get some vortecs, 305 heads will raise compression but they flow like ****.i bet you would gain at least 30-40 horse.And like jj said timing matters on everything.I just had problems with a msd hei, turns out it was advancing wayyyy to much so check your timing at idle and at full advance, should be around 36-40 at full advance.

crawler nut · Jan 27, 2013

Elliott said:
Throw those 305 heads away and get some vortecs, 305 heads will raise compression but they flow like ****.i bet you would gain at least 30-40 horse.And like jj said timing matters on everything.I just had problems with a msd hei, turns out it was advancing wayyyy to much so check your timing at idle and at full advance, should be around 36-40 at full advance.

Which heads would you recommend? Which vortec? Casting numbers? What cc would be the best? I am running 58cc now an would like to keep the compression up, especially with the propane. Would I be better off gettin a good set of aftermarkets? Like AFR, Dart, etc?

Jduck · Jan 27, 2013

crawler nut said:
Which heads would you recommend? Which vortec? Casting numbers? What cc would be the best? I am running 58cc now an would like to keep the compression up, especially with the propane. Would I be better off gettin a good set of aftermarkets? Like AFR, Dart, etc?

http://www.summitracing.com/parts/nal-12529093?seid=google&gclid=CLOahY7DibUCFQf0nAoduV0Adg If you need a little more compression shave em first, but out of the box they'll work great, especially if you have flat top pistons.

InittowiniT · Jan 27, 2013

Buddy @ (205) 591-2267 Precision Sales he will answer most question over the phone. The vortec heads that flow great have three sawtooth's on the front but there going to lower your compression. Sounds like the pane mixer is off there's only a little adjusting you can do before it won't idle at all. So your.close.