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Piston suggestion for 10:1 with Vortec heads.

Stomis

Stomis

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.005 in the hole, .035 headgasket, 64cc vortecs and +18cc d shape dish pistons is like 9.6:1. Not enough.

.005 in the hole, .035 headgasket 64cc vortecs and +12cc d shape dish pistons is like 10.5/10.6:1. Too much because I dont want to bank on finding a sunoco for 93 octane.


Now these are eagle kits I'm looking at with the pistons. Those are the only two offered in a kit. I gather I really need to get a +14cc piston. Is there any reason not to go with the 18cc pistons and mill the heads down to 60cc?

Nothing seems plug and play for 10:1 with vortec heads. I was trying to find a kit since they come with the balanced flywheel and harmonic balancer...
 
If you go with a flat top piston with 7cc valve reliefs and use a .039" gasket you will be at 10.009:1 with the .005" deck height and 64cc heads.
 
4X4HIGH said:
If you go with a flat top piston with 7cc valve reliefs and use a .039" gasket you will be at 10.009:1 with the .005" deck height and 64cc heads.
Click to expand...


Wtf is wrong with this calculator I'm using?!

This: http://www.csgnetwork.com/compcalc.html

gives me 10.77:1 with what you just said. I'm not saying you're wrong just trying to figure out wtf is going on here...



O ps its a 383....
 
So you're building a 383? If so then you're looking at a 4.030" bore and a 3.75" stroke. Let me recheck and see what I can come up with.

EDIT: Ok, a 4.030" bore, 3.75" stroke, 64cc heads, -12cc piston, .039" gasket (4.166" gasket bore diameter) with .005" deck height and you're at 10.14:1 CR
 
Are you guessing at the deck height number or are you having the block machined for that number? The reason I ask is because every block i've seen and measured the pistons are about .025" down the bore at TDC.
 
4X4HIGH said:
So you're building a 383? If so then you're looking at a 4.030" bore and a 3.75" stroke. Let me recheck and see what I can come up with.

EDIT: Ok, a 4.030" bore, 3.75" stroke, 64cc heads, -12cc piston, .039" gasket (4.166" gasket bore diameter) with .005" deck height and you're at 10.14:1 CR
Click to expand...

Whats with the gasket bore diameter? Is it normally that much larger?


4X4HIGH said:
Are you guessing at the deck height number or are you having the block machined for that number? The reason I ask is because every block i've seen and measured the pistons are about .025" down the bore at TDC.
Click to expand...

I was going to have it machined if it was far down in the hole. If not I will match a gasket to give me between .035 -.040.
 
Most performance pistons put the compression height around .010-.020 down in the hole in an undecked block. Most common I see are .017 down in the hole. Find the pistons that give you the dish or valve relief volume you need and then look at the compression height. I use this calculator:

http://www.kb-silvolite.com/calc.php?action=comp

Yes the gasket bore is usually that much bigger. Unless you use a high dollar gasket it will be in the 4.166-4.185 range. You can get gaskets in 4.06 or 4.1 to get the compression right.
 
ryan22re said:
Most performance pistons put the compression height around .010-.020 down in the hole in an undecked block. Most common I see are .017 down in the hole. Find the pistons that give you the dish or valve relief volume you need and then look at the compression height. I use this calculator:

http://www.kb-silvolite.com/calc.php?action=comp

Yes the gasket bore is usually that much bigger. Unless you use a high dollar gasket it will be in the 4.166-4.185 range. You can get gaskets in 4.06 or 4.1 to get the compression right.
Click to expand...


Thanks for the help. I've basically realized that there comes a point where you gotta just order your stuff and mock it up and measure and go from there.
 
For best results you want to achieve as close to .040" quench as possible. Have the block squared and zero decked and then use the 7cc flat top piston with a Fel-Pro .039" gasket and you'll be golden.

You do know that running 10:1 with an iron head is going to detonate unless you have a decent cam that will relieve cylinder pressure or you use premium fuel.
 
4X4HIGH said:
For best results you want to achieve as close to .040" quench as possible. Have the block squared and zero decked and then use the 7cc flat top piston with a Fel-Pro .039" gasket and you'll be golden.

You do know that running 10:1 with an iron head is going to detonate unless you have a decent cam that will relieve cylinder pressure or you use premium fuel.
Click to expand...


Shes gonna be a 91/93 octane pig. Not worried about that. 7cc flat tops dont give 10:1 with a 383. You are right they do in a 350 though.
 
Stomis said:
Shes gonna be a 91/93 octane pig. Not worried about that. 7cc flat tops dont give 10:1 with a 383. You are right they do in a 350 though.
Click to expand...

My mistake, a 383 with a 12cc dish piston will give you 10.25:1 and that will work with 91/93 octane.
 
Have you contacted eagle? my experiance is that most places out there have helpfull tech people. Your spending alot of hard earned money with these guys & its nice to know that they want you to get the right stuff. Happy customers are usually repeat customers. I just built a vortec 383 & should have paid attention better & ended up with a 11+:1 comp ratio and now forced to run a larger chamber alum head that i was saving for a special project. I guess the good thing is that I got a nice set of ported-polished vortec heads sitting on a shelf and will be finally putting my alums to work... LOL woops!
 
order

I ordered the Eagle -12cc dish 377 setup from summit in Nov and have yet to receive it, the hold up on mine was the standard bore piston. Do they have it in stock?
 
correct me if i am wrong. but cant you go a little over and mill the top of the pistions down to get 100% what you want .

example : 10.25:1 cr and mill the top of the pistion off to make it come out to 10.00:1 cr. and then do the balence work after all that is done.

couldnt you also do a ceramic coating on the top of the pistion to help fight extra heat that would cause pre ignition. i think the deisel guys do that stuff.
 
sweetk30 said:
correct me if i am wrong. but cant you go a little over and mill the top of the pistions down to get 100% what you want .

example : 10.25:1 cr and mill the top of the pistion off to make it come out to 10.00:1 cr. and then do the balence work after all that is done.

couldnt you also do a ceramic coating on the top of the pistion to help fight extra heat that would cause pre ignition. i think the deisel guys do that stuff.
Click to expand...


I dont see why not but 10.25 is fine in my book.
 
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