jayyyw

Trying to decide on my next step with my motor. Leaning towards keeping the stock rods and crank and adding forged pistons. I was looking at Diamond pistons as it seems a lot of people have good results with them. A buddy mentioned to me that he had 2 motors that lost 30hp going to the Diamond pistons with the supplied steel rings. This is definitely something I am not willing to sacrifice. So, I'm going to be looking at other brands/ring packages.

Basically looking to maximize HP, naturally aspirated. I will be spraying, up to, a 250hp shot of nitrous on top of that every now and then.

Things I will be going to:
LS9 oil pump
Improved Racing crank scraper
Johnson ST2116LSR
New custom cam
PAC 1207x spring kit
Monster LT1-RR clutch

Keeping:
LME stock ported heads
ARH 1-7/8" (willing be upgrading to 2" when I can)
ATI UD balancer
GZ vacuum pump
Holley Hi Ram

Does anyone have any comparisons from stock to just pistons? Any power loss? What brand pistons did you go with?

Unreal

Talk to your engine place about what you want. Almost all the high end shops are using custom pistons for your application. Who actually makes the pistons doesn't matter that much anymore, it is the design/setup of the piston.

jayyyw

Just don't want to go in blind. I plan to talk to a few people.

dmaxx3500

I think ''MAHLE'' makes the pistons for GM

Jwwesttx

Everyone on the forums told me I would lose n/a power going with forged rotating assembly, I went with callies crank, callies rods, wiesco pistons and my car definitely doesn't feel sluggish or slower, I did increase c/I also, but as you know my car made great power, and pulls like crazy!

lamboworld

I bought these CP pistons and they come with rings and pins. https://www.cnc-motorsports.com/bls1...re-11-3-1.html
If I had to buy pistons again, I would probably consider these Mahle pistons because of the smaller ring package. https://www.texas-speed.com/p-6251-m...ength-3cc.aspx

newchevyman

I had diamond forged pistons on otherwise stock rebuild. They were 19 grams lighter than stock per piston IIRC. I specifically chose ones lighter than stock. Car made 611/519 went 169 mph in the half mile from a standing start on 93 full weight. I'd have to look for the PN but they were 4.130" so .005" overbore, 428 cubic inch.

Da Z06

Piston weight is critical and some are lighter than stock.

Look for options like Gas porting, NPR top ring/ss and Napier second. Stick with 1.5mm compression ring package. Gas porting with the right ring package may be worth 10+RWHP over non-gas port.

Bump the CR to >13:1 and you will be fine.

I assume you are going to sleeve the block since you are talking about a 250 shot? If so, I would also go for a 4.155 bore: unsurround the valves (most important exhaust valve), you will gain CFM there and that equals HP.

If you are keeping the stock sleeves then you will be limited at 4.130 bore, and I dont know about a 250 shot then.

jayyyw

Yeah man, your combo is nuts! Hope to, at least, make that much.

Jwwesttx

Thanks man!, it's a pretty basic setup that works! My tuner is willing to do the back to back testing if I throw a hi ram on the car, he's convinced we should see 700whp n/a, he covers the dyno time and tuning but i have to supply intake and cut my cowl lol

jayyyw

Shoot, what are you waiting for then??? I've drive out there and help you do it. Hahahaha. Sounds like a win/win/win. More power, more reliable intake, and free tuning.

Jwwesttx

haha doing it isn't the poblem, buying the intake and getting it setup with my direct port setup and all that, that's the problem, I might eventually give it a shot if I can find a good deal on a hi ram

jayyyw

They are out there for sure.

Bad_AX

I second Lamboworld on the Mahle pistons he linked until I read you want to do a 250 shot. Those pistons are 4032 alloy and most would agree that you want 2618 for boost and/or nitrous. If you go the nitrous route the weakest link now becomes the OEM cylinder liners, and personally, I would not run nitrous on stock liners. In all other respects, the Mahle #LS7181130F03 are perfect for your objectives having a 1mm, 1mm, 2mm ring set. I would have the piston pins DLC coated and call it a day.

rio95

Josh B.

For a piston only rebuild it would be nice to have a Mahle piston as they are excellent quality. That's odd that you heard that Diamond pistons can lose 30hp, I suppose if the wall finish sucks. Because you'll be spraying it you'll want some strength in the design. I can't imagine you losing any hp if you use a premier engine shop like HPR. They'll ensure a correct wall finish I'm sure. Seems that almost all 2618 forgings can be made to be about 440 grams so there isn't alot of advantage to a 4032 forging aside from cold start noise. It's probably best to work with the engine builder on piston selection since they will be the ones fitting it all together.

You could also consider a lower tension ring design because you have a vacuum pump now, but this might be a no no with nitrous engines, don't know.

73DBG

jayyyw

Thanks for all the replies. I made this thread a little pre-maturely. I decided to have a shortblock built instead of going with a rebuild. Got a quote from HPR already. Waiting for a few more. Will likely have my shortblock pulled out this weekend. If any one is looking or knows someone looking for a stock shortblock, LMK. 43K miles, no knock, smoke, and made 646whp just last week.

freddyvette

Never sprayed, right?

jayyyw

Of course