To make a long story short I have to replace a set if custom Wiseco pistons that Fedex destroyed. I have spent the last two months trying to get compensation from them. Worst shipping experience I have ever had. Anyways, since I wasn't compensated enough to buy the same pistons I started looking at piston/ring kits for my 383SR motor. As with most guys I want the pistons to be able to handle a shot a nitrous incase I have to lay my manhood on the cutting block

Here are some options I dug up on Summit: http://www.summitracing.com/search/P...eyword=pistons

Basically comes down the SRP, Mahle, and Wiseco piston/ring kits. All three are 4032 alloy. Only big difference between the three other than brand are the ring thickness. The Mahles of course are coated.

SRP- 1.2mm/1.5mm/3.0mm
Mahle - 1.5m/1.5mm/3.0mm
Wiseco - 1/16" - 1/16" - 3/16"

What is everyones opinion on these ring thicknesses for a 150-200 shot of nitrous?

I can get a pretty good deal [$590 out the door] on the Mahles at the local performance shop. I like dealing with local shops when I can. The machine shop recommended the Mahle Piston Pack, but said he would use any "good" piston I wanted. This is primarily a N/A car, but as I mentioned I would like to be able to toss a shot on the car if I want down the road.

-Dustin-

 

The Mahle is a better piston for the money.

 

If you are considering a shot of nitrous in the future, I'd also compare the thickness of the ring land above the top piston ring. As the thickness of the top ring land increases, the direct heat you expose the rings to decreases.

 

Thanks Machinist and MatLT1. As is turns out is was doing some calculations wrong and I'll need a small D dish piston. Wiseco makes a 13cc dish piston pack which brings me to 8.5 at 4000ft and 9.1 at 1000ft [Right on the edge for pump gas at 1000ft and 8.5 DCR for the Southwest heat and 91 octane]. Mahle has a 16cc one, but that will bring my DCR down too much. SRP makes a 16cc also, although I did see that Probe makes a 2618-t6 piston with a 12.8cc dish. Now that would work, and supposedly the 2618 is stronger but causes more engine noise till the heat up.

So with that introduced to the equation what do you folks think about 4032 vs 2618 pistons?

EDIT: Here is some compression ratio data I have compiled about my motor. The combustion chambers and camshaft IVC are estimates for right now, since I have not CC's the heads personally, and the camshaft will be one of the variables to bleed more or less compression as necessary. I am doing everything I can to keep optimum quench [.035 to .040, compression [8.5-9.1], and not waste compression [high SCR and bleed a bunch off]. I'm also trying to run pump gas in New Mexico [4000-4500ft above sea level w/91 octane]. Problem is, the LT1 shootout and other events back east are going to bring the DCR up .5-.6 so I must build it anticipating 0-1500ft altitudes in the Eastern part of the country. I know I'll be sacrificing here in the rare air, but it's not like I'm going to be breaking records at 5000ft.

Ignore the KB DCR since I was using the wrong values.

__________________________________________________ ____________

Compression – Control Numbers 4.030 bore, 50-51cc Combustion Chambes and 3.750 stroke
Variables – Deck Height, Head Gasket, Gasket Bore, Piston Volume.

KB Website: http://www.kb-silvolite.com/calc.php?action=comp
WALLACE: http://www.wallaceracing.com/dynamic-cr.php

STATIC Compression: Zero Decked with Felpro .039 Gasket
5cc
Wallace - 13.41
KB - 13.34
5.4cc
Wallace - 13.33
KB
7cc
Wallace - 13.03
KB – 12.96
9cc
Wallace – 12.67
KB – 12.61
13cc
Wallace - 12.02
KB – 11.96
15cc
Wallace - 11.72
KB

DYNAMIC Compression: With Zero Decked with Felpro .039 Gasket, 68 degrees IVC


5cc = 13.41 @ 4000ft – 9.57
@1000ft - 10.17

5.4cc = 13.33 @ 4000ft – 9.51
@1000ft - Static compression ratio of 13.33:1.
Effective stroke is 2.83 inches.
Your dynamic compression ratio is 10.11:1 .
Your dynamic cranking pressure is 214.63 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 10.11 :1.
V/P (Volume to Pressure Index) is 186
KB Website 13.34 SCR – 8.89 DCR

7cc = @ 4000ft Static compression ratio of 13.03:1.
Effective stroke is 2.83 inches.
Your dynamic compression ratio is 9.28:1 .
Your dynamic cranking pressure is 192.45 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 9.28 :1.
V/P (Volume to Pressure Index) is 167
KB Website 12.96 SCR – 8.65 DCR

9cc = @ 4000ft - Static compression ratio of 12.67:1.
Effective stroke is 2.83 inches.
Your dynamic compression ratio is 9.01:1 .
Your dynamic cranking pressure is 185.31 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 9.01 :1.
V/P (Volume to Pressure Index) is 161
@1000ft - Static compression ratio of 12.67:1.
Effective stroke is 2.83 inches.
Your dynamic compression ratio is 9.61:1 .
Your dynamic cranking pressure is 201.22 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 9.61 :1.
V/P (Volume to Pressure Index) is 174
KB Website 12.61 SCR – 8.63 DCR

13cc = @ 4000ft - Static compression ratio of 12.02:1.
Effective stroke is 2.83 inches.
Your dynamic compression ratio is 8.52:1 .
Your dynamic cranking pressure is 172.46 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 8.52 :1.
V/P (Volume to Pressure Index) is 149
@1000ft - Static compression ratio of 12.02:1.
Effective stroke is 2.83 inches.
Your dynamic compression ratio is 9.12:1 .
Your dynamic cranking pressure is 188.21 PSI.
Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of 0 PSI is 9.12 :1.
V/P (Volume to Pressure Index) is 163
KB Website 11.96 SCR – 8.012 DCR


-Dustin-

 

You are overthinking this. Any of those pistons will work fine.

Rich

 

I'd go with either Mahle or the new SRP Professional pistons..flip a coin and go with it.. I'm going with the SRP professionals on my next 355 build..good luck with the build...

 

I definitely over think details, I'm not as worried about piston brand as I am the DCR, pump fuel, and detonation. So Rich, which CC piston do you think will work best? If 9.0 is basically the limit for pump gas then it looks like 13cc is my only option.

I was also playing around with the idea of running E85 and using the higher compression pistons. It's cheaper than 91 octane and I wouldn't have to bite my nails worrying about the motor detonating on warm days. I'm only wondering how high I could go on 105 octane [e85].

-Dustin-

 

Just my .02: The E85 will allow you to worry less about detonation, but the alcohol has a much, much lower energy density than gasoline meaning less HP. I could feel the difference in my car when they started putting up to 10% ethanol in gasoline, 15% would make it even worse.

Then again, being at sea level in FL is a lot different than being at a 4000/1000 altitude. I don't know much about how the altitude affects things.

 

Altitude brings the DCR down so you can run lower octane, but it's also hot here, and oxygen is limited.

If I did e85 I would pump more into the motor to make up for the BTU's and use 100% E85

-Dustin-

 

What are your cam specs?

Rich

 

E85 is up to 75% more ethanol. The "85" means (nominally) 85% ethanol. You have to increase the E85 mass flow to compensate for the reduced specific energy content, and tune for a different A/F ratio.