Help with deciding which piston cc to go with for new build.

Kburf79

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Hey guys, not a new member but first time poster here so forgive me if I've posted in the wrong section.. I am in the process of freshening up my stock motor.
I will be adding COMP stage 3 blower cams as well as pistons and I'm having trouble figuring out which pistons to go with for my desired setup. Stock bore and stock heads, It will mainly see 93 pump gas and I would like to keep my boost around 20psi as it is now.
My question is, what is the absolute highest static compression ratio I can have at this boost level? Also, how much will these cams affect dynamic compression and will this allow me to go higher than 8.5:1 static while staying on 93?
 

SVT_Troy

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OP

Look no further than Joe's link above..... It has all the correct info you need....prepare your wallet though! If your not ready i would just find a used short block and call it a day until your ready.
 

Kburf79

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Good info on the pistons but let me ask my question without the background info.
I would like to know: What is an ideal Static Compression ratio to use with the specs on the COMP stage 3 blower cams in order to achieve a dynamic compression ratio close to stock? Assuming that dynamic is the actual compression that will matter when using pump 93 and 20psi on a PD blower.
 

Quick Strike

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You would need about 10.2:1 static compression to make 7.75:1 dynamic compression with those cams on a 116 LS advanced 2*. This was calculated with a .020" overbore, 0 deck, .035" compressed gasket, 52.5 cc heads and 4.5 cc valve reliefs.


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Kburf79

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You would need about 10.2:1 static compression to make 7.75:1 dynamic compression with those cams on a 116 LS advanced 2*. This was calculated with a .020" overbore, 0 deck, .035" compressed gasket, 52.5 cc heads and 4.5 cc valve reliefs.


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Thank you very much. And at 7.75 dynamic, it will be safe to run 93 pump and 18-20psi correct?
 

Quick Strike

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Thank you very much. And at 7.75 dynamic, it will be safe to run 93 pump and 18-20psi correct?

That is about what the stock engines have for dynamic compression, and they can do alright there with 93 octane and 18-20 pounds of boost. You know a good tune is also a must.

I run custom cams that are between Comp stage I and II specs with 9.8:1 static compression and 7.75:1 dynamic compression. My street tune has about 20 pounds of boost with 16 oz of Torco per tank. The Torco is not necessary with that tune, but is a protection against bad gas. I also have the Vampire knock sensor/ignition retard system. I have never triggered that system on the street tune.


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Kburf79

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That is about what the stock engines have for dynamic compression, and they can do alright there with 93 octane and 18-20 pounds of boost. You know a good tune is also a must.

I run custom cams that are between Comp stage I and II specs with 9.8:1 static compression and 7.75:1 dynamic compression. My street tune has about 20 pounds of boost with 16 oz of Torco per tank. The Torco is not necessary with that tune, but is a protection against bad gas. I also have the Vampire knock sensor/ignition retard system. I have never triggered that system on the street tune.


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Ahh, thanks for the info. I've been researching this non stop the past couple days. It seems that most who install big cams don't take DCR into account when they choose which ones. I will just need to determine which cc pistons to choose. Any brand recommendations? Not trying to go most expensive but I've had JE or Diamond in mind.
 

Nightmare302

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For a 10.2 static with a large valve relief you would need to go flat top. 0cc. I would suggest lowering the static compression a touch from 10.2 on a PD blower car. The on and off can be violent. I'd look into the Wiseco 6cc pistons for an off the shelf piston. 10.2:1 on 20psi on 93 would need a dead nuts tune, very little timing and would leave zero room for bad gas/random issue.
 

Kburf79

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For a 10.2 static with a large valve relief you would need to go flat top. 0cc. I would suggest lowering the static compression a touch from 10.2 on a PD blower car. The on and off can be violent. I'd look into the Wiseco 6cc pistons for an off the shelf piston. 10.2:1 on 20psi on 93 would need a dead nuts tune, very little timing and would leave zero room for bad gas/random issue.
Rick Kaknes suggested those same ones, I believe he still runs them in his car. I will definitely look into them. Not saying the car will stay on pump as I do have an e85 station 20 minutes from me but I'm just looking at it for practicality, especially since I tend to go on long cruises and 300+miles to Myrtle beach every year. My ideal setup is to keep the boost level the same while having the ability to switch between corn and 93. With e85 being the first choice.
 

Quick Strike

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You have to watch the overlap and power range with the bigger cams. They tend to have more overlap and duration. This pushes the power band higher and excessive overlap can cause reversion/ heat issues out of boost and at idle.

The Gibtec pistons are a good deal and have some package deals with rings as I recall reading. I have CPs, but would have done the Gibtecs if they were available when I built it.


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MalcolmV8

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4.5 cc valve reliefs.

How big are those valve reliefs? I have 0.150" intake valve reliefs on my flat tops and they're - 1.67 CC pistons because of that.

OP I wouldn't be so dead set on running 20 PSI. More compression and less boost is more efficient. Within the confines of your pump gas of course.
 

Kburf79

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How big are those valve reliefs? I have 0.150" intake valve reliefs on my flat tops and they're - 1.67 CC pistons because of that.

OP I wouldn't be so dead set on running 20 PSI. More compression and less boost is more efficient. Within the confines of your pump gas of course.
Not completely dead set, right now I'm just learning as much as I can before I select the pistons. What boost level/CR would you recommend for this setup? I was under the impression that more boost, less compression on 93 will make more power. However, I do have the ability to change out my pulley for more or less boost. Just in case I do go the e85 route.
 

Nightmare302

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How big are those valve reliefs? I have 0.150" intake valve reliefs on my flat tops and they're - 1.67 CC pistons because of that.

OP I wouldn't be so dead set on running 20 PSI. More compression and less boost is more efficient. Within the confines of your pump gas of course.
I would assume he meant intake and exhaust. Even then those would be very large reliefs.
 

MalcolmV8

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I would assume he meant intake and exhaust. Even then those would be very large reliefs.

Could be. You don't need exhaust reliefs on our 4 valves. Even with flat top pistons and big cams I still have miles of clearance on the exhaust side. It's the intake side that gets tricky.
 

Kburf79

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Could be. You don't need exhaust reliefs on our 4 valves. Even with flat top pistons and big cams I still have miles of clearance on the exhaust side. It's the intake side that gets tricky.
Malcolm, is that high compression TVS build still your current setup and What numbers did it make?
 

MalcolmV8

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Malcolm, is that high compression TVS build still your current setup and What numbers did it make?

Yeah 10.5 SCR with TVS and E85 put down 800 whp and 720 something ft/lb. That was just a quick pull from a street tune on base timing to see where its at. I haven't had a chance to tune it on the dyno and play with timing etc.
 

Kburf79

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Yeah 10.5 SCR with TVS and E85 put down 800 whp and 720 something ft/lb. That was just a quick pull from a street tune on base timing to see where its at. I haven't had a chance to tune it on the dyno and play with timing etc.
Wow..those are awesome numbers for a TVS. How much boost?
 

MalcolmV8

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Wow..those are awesome numbers for a TVS. How much boost?

It's a built motor though. High compression, ported heads, cams etc.
Boost was between 22 ~ 24 PSI. This is from the dyno pull. You can see boost tapper off a little on the top end.

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