BIG BAD BLACKSS

iTrader: (4)

Well i ordered -8.6 cc pistons, even says it on my order sheet. But now im getting around to checking out the shortblock and taking it out of its plastic and the piston sheet reads -14.9cc. Sure enough i look at the bottom of the piston and its indeed diampond piston # 11517

SDPC Part Number: DIA11517
Manufacturer: Diamond Pistons
Bore Diameter : 4.030
Piston Style : Street/Strip Dish
Piston Material : Forged Aluminum
Valve Reliefs : Two
Dish Volume (cc) : -15.0
Wrist Pin Style : Pressed or Floating
Wrist Pin Diameter : 0.927 X 2.950
Ring Package : 1.5mm / 1.5mm / 3.0mm
Compression Ratio : 62cc - 9.7:1, 66cc - 9.4:1
Approx. Weight (grams) : 478
Stroke (inches) : 3.622
Rod Length (inches) : 6.125
Compression Distance (inches) : 1.309
Sold As : Set of 8

I planned on using the 72CC AFR 225s for a compression ratio just off 9:1 (8.9X i beleive it was). Can i use the smaller CC AFR heads and still be close to my target comprssion ratio? The smaller AFRs are a 62cc. What compression ratio will i end up with if i use the GM MLS gaskets? This sux.

98turbls1

iTrader: (17)

Yes you can use them to up the compression...I don't know the exact compression but it'll probably up it .5 to .75...

FormulaFire

iTrader: (20)

WHoever you ordered it from messed up. Somewhere down the line. I'd make them fix it.

eviltwins

-15cc pistons with a 72cc cylinder head will net you around 8.9:1 compression, I don't see what the problem is? The -8.6cc pistons would get you around 9.4:1 compression.

BIG BAD BLACKSS

iTrader: (4)

When i planned this out the -8.6 piston with the big AFR chamber came out to aout 8.9 compression. Im trying to find the post where it was worked out but the search is being ghey again. This is an iron 370 motor with the stock crank and 6.125" rods. I guess the gasket for the bigger bore is a little thicker, forgot the exact spec.

According to the SDPC spec sheet posted above the AFR small chambers will put me at 9.7. Too high for my application. But it does seem like the 72 would put me around 8.9? Somewhere the #s got mixed up? My sheet says -8.6 and when i talked to the shop i bought the motor from they said id be right under 9 to 1 with that piston. If i can get it to work with the head i want im happy. Im just confused why i have something different and when i made another post the math worked out to a -8.6 cc piston and the 72cc head came up to around 8.9? The math is screwed up somewhere.

BIG BAD BLACKSS

iTrader: (4)

This is the breakdown i got on this board from another member when i made a post about this when i first placed my order.

"stock 6.0L MLS gaskets are .071. Not .040. That makes diffrence in the compression ratio.
4.03 bore
3.622 stroke
-8.6 dish
0 deck
.071 gasket
72cc chambers

8.94:1 compression."

https://ls1tech.com/forums/showthrea...&highlight=370

BIG BAD BLACKSS

iTrader: (4)

http://www.race-cars.net/calculators...alculator.html

Just used that calculator to confirm it. 8.94:1 with the -8.6cc pistons with the .071 thick gasket. I can go to a .040 gasket and go up to 9.5:1. Exactly where i wanted to be, between 9 and 9.5 just have to play with gasket thickness. With the -14.9 cc pistons im down to 8.5-9.0 (rounding off here). Less then where i wanted to be.

HAMRHEAD

iTrader: (8)

Tell whoever you bought it from that they need to arrange to have it picked up and shipped to be fixed or just refund your money and you'll get it from somewhere else. Most places should be good about it. It is their mistake not yours. Send digital pics to them if they want. I had to do that once and it was all taken care of. Don't settle for less than what you ordered!

BIG BAD BLACKSS

iTrader: (4)

The shop is local to me so i can work with them on bringing them the motor back, i understand mistakes happen and the shop is known for outstanding customer service. I dont see me having any trouble with them, im just wondering if there is a way i can stay around my target compression and stick with these pistons?

FANTAZ28

iTrader: (2)

fyi... from what i have heard pistons on ls1's are always out of the whole.
so im pretty sure they arent 0 deck.

LS1 SPEED INC.

iTrader: (1)

Those are the correct pistons for your target compression ratio.

Enter Cylinder Bore Size 4.030
Enter Piston Stroke Length 3.622
Enter Head Gasket Bore Diameter 4.030
Enter Compressed Head Gasket Thickness .058
Enter Combustion Chamber Volume In CCs 72
Enter Piston Dome Volume In CCs Negative For Dished Pistons (Use '-') -15
Enter Piston Deck Clearance Negative If ABOVE Deck (Use '-') : 0

Calculated Engine Compression Ratio 9.194284170932075
Total Displacement Volume 92.39288038220492

Go to http://www.csgnetwork.com/compcalc.html if you want to verify for yourself.

This is the exact combo we use in ALL of our 370" Boost motors, including our 995 RWHP shop car turbo combo. WE run this exact spec short block, with AFR 72cc 225's, and the GM 6.0 MLS head gaskets.

If you want a full refund on the short block, bring it back, and we will credit you 100%.

Tom

LS1 SPEED INC.

iTrader: (1)

Dont run a .071" thick gasket, it will hurt quench, and frankly, there is no reason for it. Use the GM MLS, as we have in several 800+ RWHP boost cars, without a single failure.

WIth Gm 6.0 MLS .058" (some say .053") thick gaskets, your compression will be 9.2:1.

LASTLS1

iTrader: (7)

I have the same compression ratio. I made over 900 rwhp through a turbo 400 and it runs mid 8's. I would run it, you'll be happy.

Pro Stock John

iTrader: (34)

Is is a SDPC shortblock? What did it cost? Iron? Ultimately if the order is not right you can look to return it for the right thing.

LS1 SPEED INC.

iTrader: (1)

John, it is one of our shortblocks, with Diamond pistons. On his invoice I mistakenly entered the dish on the 348" pistons (-8.6cc), rather than the correct 370" dish of -15cc. The correct pistons are in the motor, just a mistake by me when creating the invoice.

The correct pistons are in that engine for this application, believe me. But because of my copy/paste error, if it created a problem for him, I will offer him a full refund. We cannot build these fast enough, and it wouldnt be a problem having it back in stock.

ls1psycho

iTrader: (7)

hey tom what do one of these longblocks go for,complete with afr 225 heads?

LS1 SPEED INC.

iTrader: (1)

The 370" short is $3399 including the iron block. Email me tom@ls1speed.com and we can decide on which parts you need, and engine covers, lifter buckets, etc.

slow trap

iTrader: (22)

i think someone told him stock mls gaskets were .071 thick is why there is a confusion,or aparently i am reading it wrong.either way 9:2 with an -15 cc dish seems to be what he is looking for/needs.

FUroundeye

iTrader: (6)

I'm surprised yall are running over 9:1 compression on your turbo motors; I would've expected it to be closer to ~8.5:1

BIG BAD BLACKSS

iTrader: (4)

Yeah i think part of the problem is i was told the GM MLS gaskets were .071 compressed height. It sounds like this combo will work for me after all. I just was confused as to why t he build sheet had one thing and the motor turned up with another. Between that and the wrong compressed thickness on the gasket info i got a lil freaked out. Ive been working too much and trying to get a good combo together and i keep having lil issues pop up that freak me out. Im sure everything will work out in the end and im sure this is just the beginning of the lil stuff that will give me a mini heart attack. Ive heard nopthing but good stuff about speed inc's 370 thats why i chose to go with them. 9.2:1 should work for me im thinking.

Looking to make as much power on 93 octane as i can. With the option of running race fuel for a more agressive tune possibly? Ive heard blowers like 9 to 9.5:1 compression. I was thinking 8.9 would be plenty safe with 93. Not sure about the 9.2 though?