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High comp 420A pistons

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BlackRaptor

15+ Year Contributor
203
1
Apr 18, 2005
Owatonna, Minnesota
Can someone point me in the direction of a good brand of high comp pistons for my 420A cars in storage time to start building it up. I am planning on using eagle rods but I can't decide on a piston brand. I want to go 11.1 comp.
Thanks guys.

What i'm thinking of doing is running 11.1 comp pistons then 5lb of boost on a turbo. is this a good or bad idea.
or with turbos should you always go with lower comp pistons?

I'm VERY new and trying to learn as i go.
Thanks.
 
BlackRaptor said:
Can someone point me in the direction of a good brand of high comp pistons for my 420A cars in storage time to start building it up. I am planning on using eagle rods but I can't decide on a piston brand. I want to go 11.1 comp.
Thanks guys.

What i'm thinking of doing is running 11.1 comp pistons then 5lb of boost on a turbo. is this a good or bad idea.
or with turbos should you always go with lower comp pistons?

I'm VERY new and trying to learn as i go.
Thanks.

High compression and boost make engines go pop.

First, you'll be hard-pressed to find a turbo that will actually hold 5psi and not creep higher. Second, you'll make more power on 8:1 and more boost.

Unless you're a diesel, this is a bad idea.
 
I'll have to disagree with the fact that its a bad idea, High comp. pistions definately make more power, at the same boost level, but you definately have less room for error when it comes to tuning and keeping your car in tune. If you plan on doing a complete rebuild it might be worth it. I'd be looking into building your valve train as well. With such high compression you can't go off the same boost numbers as everyone else, For example people with a stock bottom end have 9:6:1 compression and on avg. don't run past 8psi of boost intercooled. You on the other hand might not want to run past 5psi.

I understand your new at this so you might want to consider going the safe route with lower compression pistions that way you can have more room for error.

These Items I'm about to list are recommended for our turbo applications, I'm going to state that its probably a must for you.

1. Wideband air/fuel gauge and data logger. (don't even attempt what your doing w/out it)
2. Exhaust Gas Temp gauge (EGT)
3. Oil Pressure gauge
4. Fuel pressure gauge
5. Stand alone ECU or high quality piggy back
6. hopes prayer's and a lot of luck

I probably wouldn't go higher than 10:5:1 compression with a turbo either.
www.howellautomotive.com and www.modernperformance.com will point you in the right direction.
 
Thanks for all the info guys.
I feel like i'm on the road to a much faster car.
Wednesday i'm picking up an extra 420A motor from the junk yard with 80K on it i'm going to build this motor and leave my stock motor alone as a backup.
 
One last question with stock internals if i stay under 7lb of boost can OEM parts on a 420A hold up to that?

just playing with different options.
I also have to do the auto to manual swap this winter. only have so much monoy to play with. trying to decide after the manual whats step two.
 
You shouldn't run higher then 5 psi on stock internals. Any higher and you risk detonation, not just because of stock internals, but also because of a stock fuel system.
 
id say just get the turbo and the tranny and wait on the lower comp pistons until you get more money

high comp pistons will only break a dsm with turbo

get the turbo, intercooler, a walbro 190 (or 255 if you want), a fmu, bigger injectors, turbo ecu, and the countless other things you need when going turbo, theres hundreds of thread on it
 
Thanks guys.

I've heard i can see pretty good performance jump with high comp pistons but i think the real performance jump will be with turbo so I think i'll just slowly go that direction.


Thanks for all the help.
From this point i'm sure i can find everything else from searching the forums. :thumb:
 
Pistons:
Venolia - available at Exile Racing Technologies in Chicagoland.
JE - available damn near everywhere, more expensive thank Venolias
CP - another brand people consider, not sure where you get them, not as common imo
Wiseco - I will never suggest them to anyone, but you can find them everywhere

Nothing wrong with turbocharging a higher CR motor, but it will make things a LOT riskier. If you know what you're doing and have the means to properly tune it, 10.5/1 should be just fine. If you don't know what you're doing (which is apparent in this case), your best bet is to buy the turbo system and install it on your currently stock engine. Run an intercooled 7lbs through it while you rebuild the spare engine with forged internals. When/if the stocker pops (all in the tuning), you will have another engine ready to go.

Just do your homework and study hard.
 
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