Is there enough piston to handle a 300 shot of nitrous using a direct port setup using a 396 (3.875 stroke) and a 6 inch rod? It just seems to work out to a very small piston.

Michael

 

I don't run NO2 but I do run up to 19 psi of boost...no problems yet (custom Diamond pistons w/zero deck)

 

The compression height would be just over 1", I'd call the piston manufacurer you plan to use and ask them. Sounds kind of skimpy to me.

Rich

 

To be exact, my compression height is: 1.072" However, I have more ring land material and skirt lenght on the 396/6" rod -12cc Diamond pistons than I did with my JE -28cc 383/6" rod pistons (I went to a 76cc head which allowed for a smaller dish). Rich is right, it's a pretty tight ring pack for a 300 shot...a shorter rod would makes more sence. Personally, I've not had any problems and I'm making +700rwhp and I drive my car like I stolen it everytime I get in it.

 

Well, you can't argue with success! But I do think calling Ross or JE or whoever might be a good idea.

Rich

 

What ring widths are these pistons using? are they using 2 different size comp rings?

 

I used SpeedPro rings in 1/16th top, 1/16th second, & 3/16th oil. I gapped the first and second rings at 0.028"....

 

You are crazy to run that much NO2 without at least .150 compression height pistons. .180 down would be preferable. Just my .02.

 

5.85" rod is what i use, and it sees heavy dosage.

g'luck Mike

 

I just ordered a set of custom nitrous pistons from Diamond and was curious about this very same issue. A search of the N20 forum brought up a post from Rich saying to call the manufacturer.

I did just that, and Diamond has nitrous pistons just for a 6 inch rod. Mine is a 3.48 stroke (obviously different) with 6 inch rods. I believe I talked with Dave or David at Diamond and he told me that it didn't really matter. I asked if it was preferable to move to a 5.7 rod while I still can, and told him that my builder recommended a 6.0 rod. I asked specificly about a 300 shot with my setup and he told me it would be fine. He set me up with some custom compression pistons (for pump gas/daily driving). He told me a couple of times that the 6.0 rod nitrous pistons would not have any problem with a 300 shot or more.

Here is their website where they show the domed nitrous piston for 6.0 rods in a 3.48 stroke. http://www.diamondracing.net/pis_sbc_8.asp

Sorry if this doesn't apply to you...just what I found out from calling the manufacturer. Call Diamond or whoever...they are very helpful.

-Sean

 

I've been surprised over the years at the compression heights people are running with good success.

Quite a number of guys running ~1.1 CH with fogger setups. I'd trade the lightweight piston for a bit more durability on the street.

-Mindgame

 

Okay, maybe I have lost my mind completely, but here goes. I am toying with the idea of running a 3.80 stroke with a 5.850 rod on a 9.00 deck height. From my calculations, this will give me a 1.250 compression height. Can someone verify my poor math skills. Also, what do you think of this setup. If my calculations are right this puts alot of off the shelf pistons into play.

Michael

 

Yep, the math is right. GM picked a 3.80" crank for the crate stroker because it allowed them to use existing pistons.

Rich

 

How much is that crank?

 

The shop that built my engine tends to be extremely conservative, favoring reliability over squeezing the last ounce of HP out of an engine. Knowing I was going to spray a 300-shot, they recommended a 5.85" rod, even on a 3.75" stroke. They also followed that approach with George Baxter's LT1 engine, which ultimately survived and proved extremely reliable at the 1,100+HP level, running 20# of boost. His 383 engine actually started out life with 5.7" rods, but they were replaced with the 5.85" Oliver Billets, when the previous Oliver forged rods started to shown signs of stress.