Has anyone on here built up a high compression engine as far as the 4.0? I was thinking if you were to maybe bore out the engine .030" over or so, maybe use stronger rods and pistons (forged or soemthing). Now to make it a high compression i could use a thinner headgasket and perhaps mill a bit of the head. However, when you overbore the engine, do you have to match the "bore" of the head (basically the part of the bowl on the bottom of the head that matches the block). If so, if it was milled a certain amount and also widened, would it make it inefficient in any way because it is more flat than rounded? Is it possible to make the compression ratio go from 8.8:1 to something more like 11:1+ I wouldnt care to run higher octane then. I hear you can put liners in the cylinders to help strengthen it. I was just curious as to if it was possible and if not any other ways, maybe a stroker with the same setup.
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- Thread starter BBeach
- Start date
j99xj
NAXJA Forum User
- Location
- Colorado Springs, CO, USA
The gains from an 8.8:1 cr to an 11:1 cr wouldn't be worth the amount of money and time spent on preparing the motor for it, or the extra money spent on high octane gas. Plus the stock cam is too "low" for a high compression ratio and would probably knock and ping like crazy at low rpm because the cylinder pressures are too high.
If your willing to tear the motor apart you might as well build a stroker engine and get far better overall driveability.
High compression ratio engines are also harder to turn over so you might have to upgrade the starter.
Just some thoughts.
If your willing to tear the motor apart you might as well build a stroker engine and get far better overall driveability.
High compression ratio engines are also harder to turn over so you might have to upgrade the starter.
Just some thoughts.
Maybe keep the iron linings or whatever and then overbore a little with upgraded rods and pistons. Then be able to set it up for a turbo or something. I figured if i was to lower the NA compression ratio, would it allow for more boost from the turbo? Ive been following the awd turbo thread but was thinking of one of my own one of these days. And also, with any situation i would upgrade the cam and exhaust, etc.
Is the added compression similar to adding a small turbo? I tried working out the pressures and volumes and all that of the air and such. It would bea boost, but most likely not what could be compared to a stroker which addes compression and at the same time adds displacement as well. Would it be more feasible to maek a higher compression stroker?
MogifiedXJ
NAXJA Forum User
- Location
- Tellico, TN
BBeach said:
Go here and read replies 40, 43, 44, and 45. I think they pretty much have nailed that subject.
http://www.naxja.org/forum/showthread.php?t=93852&page=3
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