I had been using SRP piston in my supercharged and turbocharged engines for quite a while. They seem to be the only company that makes a large dish off-the-shelf 383 piston. I've broken many of them and always assumed that I detonated (though they did seem to be not very tolerant of detonation). However, on my newest build, I found out that SRP doesn't make a .060, 5.7 rod, 3.75 stroke, 30 cc dish piston. After a little research, I found that no one makes such an animal. However, Ross does custom pistons at a decent price, so I ordered a set.

The Ross pistons came in Friday and I was impressed when I inspected them. The dish is round instead of SRP's D-shaped dish. Since the dish covers more area of the piston top, it doesn't have to come as close to the edge of the piston, or be as deep. This leaves me with alot more meat between the bottom of the top ring groove and the dish (where the SRP's keep breaking). Also, they moved the oil ring as low as they could get it without disturbing the pin hole, giving it thicker ring lands.

They only unknown is the combustion chamber shape. Since the dish is round, there isn't as much quench area. I'm not sure what effect this will have on power or ignition timing required, but I'm hoping for the best.

Mike

 

Mike, did you just break another piston?

 

It's been about a month ago. The engine had a slight knock that I was trying to diagnose. One day, the head gasket started leaking coolant, so I pulled it and found the #1 piston had broken above the top ring (usual location). A lip of metal pulled up and was lightly tapping the head. I was going to replace it with the motor still in the car, but I decided to put the 3.75 crank back in it and go through the trans, plus have the converter re-stalled (tightened). Since I destroked to 3.5", it just doesn't seem to run as good or produce dyno numbers like the old 383.

Short block is done, going to finish up the engine today. I should have it running next weekend.

Mike

 

I believe the srp pistons are 4032 material. High output usually prefers 2618.

 

i've heard that srp uses softer metals for quieter start ups

 

Mike, you think the pistons would have lasted longer at 15psi versus the 18-20 that you run? I have a forged 383ci with those pistons and are worrying a little now...I plan on only 14-15psi though.

 

The JE and SRP line are different materials (2618 v. 4032 aluminum). The JE 2618 material is stronger but requires more bore clearance and therefore is noisier, may scuff at startup, etc., and is more $$$. The 4032 used in the SRP line is high silicon aluminum which is less tolerant of detonation than the low silicon 2618 alloy used in most of the JE pistons.

Ross makes a good piston as well, but most engine builders prefer the "D" shaped dish. I bet JE/SRP would not recommend the SRP line for high boost.

Rich

 

More than likely. My plan, actually, is to increase displacement and lower boost to ~15 - 17 psi, hoping for the same power as smaller cid and higher boost, shooting for better reliability.

Mike

 

Ran across this:

http://para.noid.org/~lj/1000hp/images/o-rings.jpg

That's what my new Ross pistons look like.

 

They worked for LJ

 

Mike,

I am also curious about the quench effect. the full dish seems to work very well on 4 valve applications but as you mentioned, our head design is different with the flat section towards the centerline of the motor. speculating that it is still going to have some quench at the perimeter I think it will be alright and I also am wondering if aving the compressed gases more evenly distributed across the top of the piston when ignition occurs may actually benefit or help.

for what its worth, I have ross pistons in our solid roller 355 high compression engine and they have performed flawlessly, very nice pieces. different design then what you are using but I think If I were to build another low compression hsortblock.. this is the route I would take.

on another note.. I also hope my current setup lasts under the higher boost pressures.. I am running straight 110 leaded race fuel and do not plan to ever run anything else as it is only 4.59/gallon compared to 3.20/gallon for 93.. no brainer in my opion. I am currently using the TRW/Speed Pro heavy slugs.. hope these can handle the boost.. so far they are doing agreat job at 20psi... knock on wood!

Chris

 

Mike- I am running the ROSS piston similar to yours except my pistons are -35 cc. I have talked to the guys at AI that are doing a custom full port job on my heads and they dont think the quench will be an issue at my boost level(up to 25psi). I have also looked into having them coated but I have heard mixed things about heat tampering when coating and how they are tempered by ROSS ( in short it might not hold any benefit and may actually shorten the pistons life in a turbo application). Thats just what I have heard thus far. All I know is that I feel good about my choice to go with ROSS. They are indeed very nice pistons. How is your car coming?

 

Got it running Saturday night. I took the wastegate spring out to see how low I could get the boost with "only" a 40 mm wastegate. Seems like 12 psi is the number. Time to put the spring back in and see how it does at 16 psi

 

I'd like to throw another name in the hat here, Diamond Pistons. We use them almost exclusively in our builds. Having seen and used pistons from just about every manufacturer our there I feel that Diamond has a superior product in both design and durability. I have some pistons that we have beat to hell and back with huge boost and also nitrous and seen them hold up to the flame perfectly.

I'll admit they are a lesser known company than JE or Wiseco, but I think that mostly has to do with marketing and level of advertisment. Diamond is more racer oriented and can identify with the customer and build a piston that fits their needs and handles the abuse.

A good portion of NHRA Pro Stock and NMRA Renegade run Diamonds and have had great results and keep coming back season after season. If nothing else, I'd give them a call or I can spec a piston for you as well.

Just my .02

www.diamondracing.net

 

Nick and Eric at Victory built my Forged 383 9:1 CR with Diamond Pistons. From what I have witnessed a lot of Turbo and Blower guys on LS1tech run Diamond pistons. At the time VRE was using JE/SRP pistons and for around a $200 upgrade You could get the Diamonds. Eric recommended me the Diamonds for my needs of a D1SC with Ported LE AFR heads.

Heres a Pic
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