Turbo... Dished pistons... yes? or no?

[slayer61]

Alright motor guys, the time has finally come to actually start on my turbo project. Keep in mind that this motor was originally assembled by a shop. This is the first time I've been into it.

I pulled it down to short block status to do the maths for the compression ratio. My deck height is only .020-.020". The combustion chamber is 55ccs and there was a. 060 copper head gasket in place, netting me a compression ratio of 9.2-1. A little high for a turbo street car.

As I can't put the cylinder out any further, do dished pistons make any sense?

Be well
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[BFB]

( assuming were talking about the 2276 in your signature) youve got .080 deck then, the guys are going to tell you to fix that for sure.
You could dish the pistons, or open up the combustion chambers, or both. Depends on what CR your after but if your going to tighten up the deck and want the CR below 9:1 your going to have to find a fair amount of cc’s somewhere.
To run .050 deck and 8.5:1 CR youll need 67cc chambers.
Or keeping your .080 deck you could run 62cc chambers to get 8.5:1.
All depends on what you want, what you want to spend or how scared you arent to go hogging out some heads and dishing pistons, and how much boost you plan to run.
Most i ever pulled out of a set of heads was right around 10cc, possibly a little over, (i dont remember the exact number now). But they are a completely dished chamber like you see on some boosted LS’s.
If your only going to run 7 - 8lbs of boost then id say to just run your 9+ CR.
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"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[slayer61]

Check. I understand that I have to set the deck height closer to 40-45 thou. I REALLY don't want to hog out my heads or semi-hemi them either. Ultimately it comes to dished pistons for me. Are they suitable for a street car and less than 15 pounds of boost?
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[BFB]

You don’t HAVE to set deck at 40 - 45, obviously, youve been running at .080 and plenty of ppl have run with more than that.

And you’re not going to get 12cc out of dished pistons.
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"how am i supposed to torque the rear wheel nut to 250 ft lbs??? " - clonebug
An interesting thing happens in forums where everyone starts parroting the same thing and "common knowledge" takes over.
Most experts aren't.

[jim martin]

Here is a 4cc dished piston . Gonna have to be a bigger cut
If you want more

_________________
B.C's fastest street legal vw , June 2006 Hot VW's feature car 9.81 sec at 145.26mph.
Sponsored by :
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KROC head porting services
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Airspeedparts.com topic http://airspeedparts.com/forums/index.php?topic=914.0

[slayer61]

[jim martin]

Call Dan Lawson at cevw
Available in 040", .060", .090" and .125" thicknesses.
Done
_________________
B.C's fastest street legal vw , June 2006 Hot VW's feature car 9.81 sec at 145.26mph.
Sponsored by :
LUCAS OIL PRODUCTS http://www.lucasoil.com
KROC head porting services
Dialedinperformance.com
Airspeedparts.com topic http://airspeedparts.com/forums/index.php?topic=914.0

[rayjay]

Do you really want to be making the piston crown thinner on a turbo build? How about a shorter stroke crank? Suddenly everything is happier. Run some numbers on CB's calculators and see what stroke allows your current pistons to be suitable.

[b-man]

It’s not like piston manufacturers don’t have piston blanks available that are forged with enough material for a reverse dome or dish. Contact Icon or whoever and get whatever dish volume you need, done.

I have custom Ross forgings in my Pontiac V8 with a 27cc dish, what’s the big deal? Of course you don’t take a lightweight flat top forging and cut a big dish in it, you start with the right forging blank designed for a dish.
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1956 Dove Blue Panel
1966 Velvet Green Single Cab
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[jim martin]

This is the calculator I use . Really great and can enter any value even with a decimal point .

https://www.rbracing-rsr.com/compstaticcalc.html
Turbo motor won’t care if it’s .040 or .100 deck in my experience
_________________
B.C's fastest street legal vw , June 2006 Hot VW's feature car 9.81 sec at 145.26mph.
Sponsored by :
LUCAS OIL PRODUCTS http://www.lucasoil.com
KROC head porting services
Dialedinperformance.com
Airspeedparts.com topic http://airspeedparts.com/forums/index.php?topic=914.0

[VdanielW]

How much boost are you planning on running? Is this for the 2276 with a w125 cam? I am building a turbocharged 2332 with a w125 for my daily driver and will be setting compression at 9.2:1. Mine will be a blow through system with intercooler, water/meth injection, and a J&S Safeguard knock sensor system. The plan is pump gas, 20psi boost. I was doing it with a much smaller cam at 20psi and 8.4:1 (242 duration @ 50) and it ran great.
Don't forget- that cam has alot of top end and the turbo will just push that up.
When I ran a w120 in my old 2276 it would want to pull past 7800rpm with 16psi boost.

[slayer61]

Hi Daniel,
Yes. It's going on my 2276. I have a forged rotating assembly and will be sucking through a DCOE 45. I hope to see 15 pounds of boost on occasion. Nothing more high tech than the MSD to control timing and an electronic boost controller.

Wish me luck!
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[oprn]

[slayer61]

[BFB]

[esde]

The path of least resistance would be heads with the correct cc for what you want to do..
Seeing how much you can lower the compression and then building the turbo system to suit it, is sorta bass ackwards. Usually you just get what you get, not what you wanted.. not to say I haven’t done the same thing. But I usually wish I had just done the obvious thing to start
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modok wrote:
Bent cranks are silent but gather no moss. I mean, ah, something like that.

[slayer61]

[Chip]

[Michaellatini]

What about going to thick wall 92 P&C?

[slayer61]