piston questions
Thread Starter
On The Tree
Joined: Apr 2009
Posts: 123
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From: Livingston, LA
piston questions Alright i found some pistons while looking around on ebay. I was wondering if i would be able to use them in an lt1. http://cgi.ebay.com/ebaymotors/Small...item4a9efdfd33 Isn't there a formula to figure out if they will fit the deck height?
Also is there a certain compression distance have to use or is it based on it the deck needs work?
I will be building a .030 over 355 with a 6.0" rod looking for about 11.5 cr. going to probably end up with le2 setup so it will use 54cc heads. Also if the deck doesn't have to be messed with and using the setup mentioned, with a stock style thickness headgasket what cc piston would i need for that cr?
Also is there a certain compression distance have to use or is it based on it the deck needs work?
I will be building a .030 over 355 with a 6.0" rod looking for about 11.5 cr. going to probably end up with le2 setup so it will use 54cc heads. Also if the deck doesn't have to be messed with and using the setup mentioned, with a stock style thickness headgasket what cc piston would i need for that cr?
If you're looking to go with a zero deck clearance then you want a compression height of 1.285 (based on a stock deck height of 9.025...SBC/LT1). Based on that you could do a flat top piston with valve reliefs (typically 4-5cc) and that would give you 11.8:1 (5cc reliefs with a .040 compressed thickness gasket). That would be a solid foundation for any 355 project IMO. The biggest thing then is to check the PV clearance when assembling the top half to make sure you don't have some issues, but if you're not going with a crazy cam you won't have to many worries. If you go to eaglerod.com you can play with numbers and get you're compression ration and even piston speed for a specific RPM. It all depends on where you go with the block.
Thread Starter
On The Tree
Joined: Apr 2009
Posts: 123
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From: Livingston, LA
Alright found a ross racing piston on summit, part number 90003. When plugged into the calculator on eaglerod.com I get
Deck height- 9.025
Bore - 4.03
Stroke- 3.48
Rod length- 6.0
Chamber volume- 54cc
Gasket Thickness- .04 (used this as just a general size)
Piston Dome- +4.0cc
Pin Height- 1.245 (this would be compression distance right?)
Which gave me:
Deck Clearance- 0.04
Compression Ratio- 11.91:1
Engine size- 355.1
Rod Ratio- 1.72:
Max Rod angle- 16.86deg
So this wouldn't be a problem unless the deck had to be milled down for some reason right? If i wanted a little less cr i could use a thicker gasket?
Deck height- 9.025
Bore - 4.03
Stroke- 3.48
Rod length- 6.0
Chamber volume- 54cc
Gasket Thickness- .04 (used this as just a general size)
Piston Dome- +4.0cc
Pin Height- 1.245 (this would be compression distance right?)
Which gave me:
Deck Clearance- 0.04
Compression Ratio- 11.91:1
Engine size- 355.1
Rod Ratio- 1.72:
Max Rod angle- 16.86deg
So this wouldn't be a problem unless the deck had to be milled down for some reason right? If i wanted a little less cr i could use a thicker gasket?
Even if the deck has been milled down it shouldn't be too much, usually it's just done to flatten the deck so they take very little material away. It'll bump the compression a little...very little if the deck is taken down. And if it has, just go with a thicker gasket and it'll bring the compression down. If nothing else consider a set of flat tops as opposed to the domes and that alone will drop the compression ratio even more. I would figure out what your deck height is and then determine what you need to get it where you want it.
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Thread Starter
On The Tree
Joined: Apr 2009
Posts: 123
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From: Livingston, LA
Even if the deck has been milled down it shouldn't be too much, usually it's just done to flatten the deck so they take very little material away. It'll bump the compression a little...very little if the deck is taken down. And if it has, just go with a thicker gasket and it'll bring the compression down. If nothing else consider a set of flat tops as opposed to the domes and that alone will drop the compression ratio even more. I would figure out what your deck height is and then determine what you need to get it where you want it.
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Thread Starter
On The Tree
Joined: Apr 2009
Posts: 123
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From: Livingston, LA
To be honest i have no idea about quench. I just looked up the terms used for quench in the combustion chamber. What would be good and how would i go about finding it? Like i said i've never dealt with it before when building an engine, just bought parts and put an engine together.
in the research I have done which I confirmed with my machinist ~.040 quench is about right on a street motor. Usually this is achieved by zero decking the block and using a .040 or in our case .039 compressed thickness head gasket. If you do some searching around there is a ton of info involving quench and squish and I am sure any number of those articles could explain a lot better than I can. How it applies in your situation though with what I have found is that you can not get a pump gas compression ratio with flat tops and a small head cc if you zero deck the block and have the appropriate quench. I am using 54cc heads and with my quench a .044 I had to use an inverted dome piston to keep my compression around 11:1 static....
