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High compression pistons...

MonkeyLover
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MonkeyLover Newbie

MonkeyLover

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I've got a mildly-worked over 2.6 that has just murdered a rod bearing. Which means it's apart and now's the time to "upgrade", eh? ;)

 

What I'm looking to do is run around 8.5:1 with lower boost. All of the pistons I'm finding are the stock 8:1. Is anyone aware of a source to get higher compression pistons? I'd really appreciate any info you could provide.

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Indiana Newbie

Indiana

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Stock is 7:1 and you see forged pistons with a compression ratio range and the low number is for a stock height deck and head, the higher is for a stock head but a zero deck meaning you remove a lot of material from the block and that means you need to use an adj. cam gear. If you want to get an even higher CR its possible if you degree your cam to slightly let the piston come up out of the bore. Your CR being higher and even with lower boost you are limited in ways you might not think of. What turbo is going to be efficient at making boost at low pressures for this motor? What pressure are you wanting to use? Leaving the CR low makes your tuning window larger and high boost pressure isn't the devil you may think it is.
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MonkeyLover Newbie

MonkeyLover

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7:1 is stock compression?? Huh...damn, missed that one. Alright then, Wiseco 8:1 would be fine then I suppose.

 

I'll most likely be running a 20g at some point soon but she's sitting with the stock 12a on her now. I'd like to run around 8-10psi on the 20g, if possible.

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Scotty Dont Newbie

Scotty Dont

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10psi for a 20g isn't going to be good for you. A stock turbo at 15-20 would perform better. What has been done to your motor and the rest of the car?

 

To elaborate a 20g at 8-10psi will be a dog but crank that puppy up to +20psi and it will scream you will need flat deck surfaces, heads studs, and a good fuel system at the least. A wideband, maf-t, 3" exhaust and hardpipes will really open it up. :wub:

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Indiana Newbie

Indiana

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First thing you need to do is have your rods reconditioned and not waste money on pistons your STOCK pistons are just fine. Clean the carbon from them and put on new rings if you like. The only time these motors need to be bored again is if coolant pitted the cylinder walls and ruined the ring contact surface to the point the motor would burn oil. All these motors out here with forged pistons aren't half a dozen of them that actually require that piston to be stronger being made from that alloy. Its a big business making forged pistons why else to you get all those free stickers?
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jszucs Newbie

jszucs

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First thing you need to do is have your rods reconditioned and not waste money on pistons your STOCK pistons are just fine. Clean the carbon from them and put on new rings if you like. The only time these motors need to be bored again is if coolant pitted the cylinder walls and ruined the ring contact surface to the point the motor would burn oil. All these motors out here with forged pistons aren't half a dozen of them that actually require that piston to be stronger being made from that alloy. Its a big business making forged pistons why else to you get all those free stickers?

 

Aw man so I wasted my money on wiscos? Would you try a 62-1 @20-25PSI with stock pistons? Want to buy my stock set?

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Richie_Rich Newbie

Richie_Rich

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I've got a mildly-worked over 2.6 that has just murdered a rod bearing. Which means it's apart and now's the time to "upgrade", eh? ;)

 

What I'm looking to do is run around 8.5:1 with lower boost. All of the pistons I'm finding are the stock 8:1. Is anyone aware of a source to get higher compression pistons? I'd really appreciate any info you could provide.

 

I think you need to decide where you want to eventually do with your car.

 

If you plan to run some high boost and push the engine and have the cash to put into the rebuild, go and build the bottom end as bulletproof as you can.

Forged pistons

Full floating wrist pins

Balance

Line hone the mains

polish and balance the crank.

ARP rod bolts

etc.

 

There's a debate of the full floating wrist pins, but my opinion is if you ever have a problem and need to replace a piston or a rod, it's a lot easier to separate them if they are full floating. If you use pressed pins there is always a chance the piston could be damaged if the correct fixture is not used or if a piece of garbage happens to get dragged between the pin and piston.

 

If you ever push an engine beyond stock, you should always be prepared to have to pull it apart later.

 

It's all about piece of mind.

As Indiana indicated, our stock setup is pretty stout already and normally holds up very well to being pushed.

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MonkeyLover Newbie

MonkeyLover

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Wow. A lot of great (and intriguing) info, guys. I really appreciate it *high five*.

 

The engine hasn't been modded all that much yet. It has a Clearwater head on it and has had the balance shaft eliminated. It has a MSD ignition and a wideband installed already. Upgraded MAF, as well. It also has a 3" exhaust.

 

What I want the car to be is a reliable DD that puts out around 275whp. I realize that's a ton of power...but hopefully it's realistic *shrug*. Also, it's not a car that I plan on keeping for 5+ years, either. So longevity isn't a huge issue.

 

I'm still a bit confused as to what pistons I should run. I'd rather keep everything as inexpensive as possible, but new Wisecos obviously aren't cheap. I'll ask my buddy if the stock pistons and cylinder walls are in good enough shape.

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TopDawg_43 Newbie

TopDawg_43

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What I want the car to be is a reliable DD that puts out around 275whp. I realize that's a ton of power...but hopefully it's realistic *shrug*. Also, it's not a car that I plan on keeping for 5+ years, either. So longevity isn't a huge issue.

 

I'm still a bit confused as to what pistons I should run. I'd rather keep everything as inexpensive as possible, but new Wisecos obviously aren't cheap. I'll ask my buddy if the stock pistons and cylinder walls are in good enough shape.

 

If you only plan on keeping the car for around five years, stock pistons will do you just fine. I'd stay from a 20g if you want a DD. If it's running fine now, leave it alone. Bolt on a 14g (or a small 16g), change the oil and plugs. And drive it.

 

You can start getting into this stuff pretty heavy really quick.

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Technology Newbie

Technology

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It needs to be not a starquest. Get a piped and tuned 350z or early evo8 with a 3" exhaust, intercooler, and higher boost. You'll be replacing a lot more than the engine bearings and pistons trying to have a 275whp quest that is reliable.
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creakyjoints Newbie

creakyjoints

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WOW! A local guy had a Conquest (sold it). He rebuilt the engine with JE pistons he bought from TEP. Stock rods, standard crank and a Marnal head with stock size valves. One of Kellys 3inch exhausts,1st gen DSM mass abd super 16g. He did have roller rockers on a 274 cam for awhile until the rollers chewed up the cam. Other than that hey drove it trouble free for 100,000 miles. We went down and ran it on a Dyno which came up with 250 WHP. I guess and extra 25 horsepower is a deal breaker.
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