After looking into the KB944 pistons and being disappointed after doing the math out. I want to run a zero deck for the tightest quench I can get and a .043 head gasket. After doing the math out Its looking like a piston with a 26cc dish, 1cc valve notches in the block and a 57cc chamber will work out to a static compression ratio of 9.2:1.
I'm thinking about using a compression (pin) height of 1.363, .010 higher than the KB944's so you don't have to deck the block so far. It will cost less at the machine shop. I'll probably also use a metric ring set to reduce the parasitic drag inside the engine.... more power
The next time the boss isn't too busy he will help me fill out the custom piston forms and make the calls to a few piston manufacturers (Diamond, Ross and JE). I plan on buying a set of 7, one extra in case I make a boo boo sometime down the road.
I'll try to get the price as soon as possible, but I can't make any promises on when I will have them.
~Alex
The enemy of good thing is wanting something better.
Not yet, I'm going to deck the block to see where it cleans up at and give it a rough hone to make sure there are no supprises in the bores. Also I'm going to stress relieve, shot peen, install ARP rod bolts, resize, maybe nitride the rods and give them all and make them all have the same center to center distance. Once I do that then we will put the calls into the piston manufacturers. The boss said that Diamond has been very fast on the turn-around for custom pistons (delivered in 2 weeks) but as I said, We'll get prices from Ross and JE.
~Alex
The enemy of good thing is wanting something better.
Alex22 wrote:After looking into the KB944 pistons and being disappointed after doing the math out. I want to run a zero deck for the tightest quench I can get and a .043 head gasket. After doing the math out Its looking like a piston with a 26cc dish, 1cc valve notches in the block and a 57cc chamber will work out to a static compression ratio of 9.2:1.
I'm thinking about using a compression (pin) height of 1.363, .010 higher than the KB944's so you don't have to deck the block so far. It will cost less at the machine shop. I'll probably also use a metric ring set to reduce the parasitic drag inside the engine.... more power
The next time the boss isn't too busy he will help me fill out the custom piston forms and make the calls to a few piston manufacturers (Diamond, Ross and JE). I plan on buying a set of 7, one extra in case I make a boo boo sometime down the road.
I'll try to get the price as soon as possible, but I can't make any promises on when I will have them.
~Alex
Don't write off the KB944's just yet. Here's a stroker recipe (modified version of the 4.7L medium buck recipe on my site http://jeep4.0performance.4mg.com/stroker.html ) that could work for you:
This assumes 57cc chambers in the head. If you grind them smooth you might gain a couple of cc's and lower the static CR a bit. Even the above combo should run on 89 octane with that nice, tight quench.
9.5 would be pushing it with 89 octane gas. since this is a daily driver I'm going to build it on the safe side, looking at 9.2:1 with a quench of .043 and run it on 89. I'm going to be decking the block on Monday and resizing the 4.0 rods sometime next week. I'd rather order a custom piston to fit an engine than build an engine around a piston.
~Alex
The enemy of good thing is wanting something better.
Alex22 wrote:9.5 would be pushing it with 89 octane gas. since this is a daily driver I'm going to build it on the safe side, looking at 9.2:1 with a quench of .043 and run it on 89. I'm going to be decking the block on Monday and resizing the 4.0 rods sometime next week. I'd rather order a custom piston to fit an engine than build an engine around a piston.
~Alex
You could work the heads and see how many cc you might gain. Stock heads are around 57cc but I've seen heads with combustion chambers increased beyond 60cc. Even 60cc would lower the CR to 9.2:1 and get you where you want to be.
