high and low compression pistons.

[99eclipse420]

I am going to be rebuilding my motor again... and I would like performance pistons and rods I'm getting JE rods. However I am confused on the compression ratios. I want a all motor build I don't plan to boost any time soon, or at all. I will get a gsx or gst for that but I want a bit more power out of my 420a As followed, I plan on getting new cams not sure what size yet, I already have new valves 15 degree shave with a 3 angle, port and polished head, What my question is what piston compression ratio should I go with? I want more kick and I no idea which low or high compression will give me that. Also mpgs are a factor I would like not to lose gas mileage if that factor comes into play at all. Thank you all and have a good day.

 

[Kalub]

High compression.

You're going to see a decrease in mileage too depending on how you drive it, and you may actually need a fuel/tuning solution.

 

[bryanwheat]

What are you going to be using to tune this? With high compression pistons you are going to need to pull timing.

 

[swiftdeathtsi1]

You will want high compression. Low is for boost. You will need to tune this some how though.

 

[99eclipse420]

What would be best to tune, when it comes to cars I know how to take them apart and fix them but my knowledge is limited when it comes to performance. I would like a cheap piggy back system, I don't plan on building this motor up more than an all motor build, no 255 fuel pump and all that. Simple works for me. So be sides re building the motor what after market items are needed to tune/ fuel items, I am Broke As a Joke right now and I really just wanna get the car back on the road. T

Thank you all for your comments.

 

[bryanwheat]

IF you want to adjust the timing than you are pretty much limited to running a standalone type of ecu.

 

[99eclipse420]

I would like to leave timing alone if that's possible? I plan on dropping close to 2 grand on everything cams pistons, rods, a new crank, and a new block plus machining, so my funds are limited and so is time I need this car back on the road by the end of april.

 

[jimbob_843]

Just do a stock rebuild and throw it in. Drive it until you save for a turbo dsm. Not trying to pull you away from the 420a but to even compete with a stock 4g63t you will need to drop some bread. Enough bread to buy a decent used 63 dsm. Check craigslist in your area, i always see alot of 1g shells going for cheap. Like 400-600 bucks.

 

[99eclipse420]

The only low compression pistons I can find the ratio is 8.8:1 and the high compression ratio I can find is 10.5:1 and the stock compression ratio is 9.6:1 will I really need to tune due to being such a slight difference, with the 4g63 there are ratios going from 8.1:1 and 11.1:1 that I know of but with the 420a there are only 2 options to choose from. You guys are the experts on this subject not me.

I plan on getting a turbo awd spyder, they are rare and hard to find but, I would rather have that than blow money on a 420a turbo build I would just like my dd to be a bit quicker. But stock rebuild sounds good to me, plus with bigger cams and the ported head and all I should get a few more hp out of all that. Thanx guys.

 

[whiteboyz]

The only low compression pistons I can find the ratio is 8.8:1 and the high compression ratio I can find is 10.5:1 and the stock compression ratio is 9.6:1 will I really need to tune due to being such a slight difference, with the 4g63 there are ratios going from 8.1:1 and 11.1:1 that I know of but with the 420a there are only 2 options to choose from. You guys are the experts on this subject not me.

I plan on getting a turbo awd spyder, they are rare and hard to find but, I would rather have that than blow money on a 420a turbo build I would just like my dd to be a bit quicker. But stock rebuild sounds good to me, plus with bigger cams and the ported head and all I should get a few more hp out of all that. Thanx guys.

As Stated above, You do NOT want low compression pistons. Low comp is for Forced Induction and not N/A (natuarly aspirated)

As you already know stock comp in a 420A is 9:6:1 so going with a 10:1 is not going to be much of a difference at all. If I am correct you gain anywhere from 3/6% hp for each comp you jump.

JE and Wiesco both make high comp pistons. I would go with 12:1 especially if you are going to run only pump gas, I would not recomend goign with a higher comp then that. Or you could have some custom pistons made up. Bolt on's would help out aswell. There are other things that could help you out.

Why are you going to buy a new block ? If you old block is still good I would just rebuild that one and save some cash, that could go towards other parts etc etc.

 

[99eclipse420]

My old block has a hole the size of a half dollar in it. So yeah I wouldn't have to do a rebuild again if I didn't throw a rod through the block, the crank journals were warped and kept blowing rod bearings, as I was coming back from a shop to figure out what was going on I threw a rod so I need a new bottom end.

 

[Spyder Sean]

Curious I have a 2.4l 4g64 all motorbuild in progress where can I find 12:1 pistons I can't find those or anything else for this motori need help to.