Piston Experts need help
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From: Lake Lure NC
Piston Experts need help
Ok I am going to run in the BSP class SCCA in a 1992 LT1. I have had the heads milled .010 and I am going to run the Impala SS head gasket. My current head CCs is 54.5 and with the impala head gasket at .028 compressed my new ccs would be 52.5. Now for the hard part. I can run OE style (same or greater weight and same valve relief as stock) cast or forged. I need my compression to stay at 11.0:1. Does anyone have a piston recommendation to get me there without paying 100 bucks a piston custom made? Additionally a part number would be great.
Last edited by mothersworry; Dec 21, 2004 at 03:06 PM.
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From: The Top of Utah
Originally Posted by mothersworry
My current head CCs is 54.5 and with the impala head gasket at .028 compressed my new ccs would be 52.5.
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Go here. http://kb-silvolite.com/index2.php They have a nearly unlimited selection of pistons and even if you don't use theirs, you can figure out the specs you need. They also have several different types of CR calculators and lots of other useful info.
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From: The Top of Utah
Originally Posted by mothersworry
The engine is an LT1 and the compression ratio with just the milled heads is 54.5. The head gasket will reduce the ccs by 2. The combined total will be the 52.5.
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Safety Car
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From: Charleston SC
Originally Posted by mothersworry
Ok I am going to run in the BSP class SCCA in a 1992 LT1. I have had the heads milled .010 and I am going to run the Impala SS head gasket. My current head CCs is 54.5
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From: The Top of Utah
Originally Posted by FD2BLK
Did you cc the head with the spark plug in? Because a normal Lt1 head will cc right at 54.5 with the plug in place before it is milled
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From: Texas
Originally Posted by mothersworry
Ok I am going to run in the BSP class SCCA in a 1992 LT1. I have had the heads milled .010 and I am going to run the Impala SS head gasket. My current head CCs is 54.5 and with the impala head gasket at .028 compressed my new ccs would be 52.5. Now for the hard part. I can run OE style (same or greater weight and same valve relief as stock) cast or forged. I need my compression to stay at 11.0:1. Does anyone have a piston recommendation to get me there without paying 100 bucks a piston custom made? Additionally a part number would be great.
Bore Diameter: 4.000
Stroke: 3.480
Gasket Bore: 4.100
Compressed Gasket Thickness (in): 0.029
Head Volume (cc): 54.500
Deck Clearance: 0.028
Piston Valve Relief Volume (cc): 5.00
...your Compression Ratio would work out to 11.019:1
You don't say if you're retaining the stock bore. If you have to bore the engine, that'll affect CR as well.
An excellent piston to consider without breaking the bank is SRP. I didn't see a standard size p/n listed, but I would think one is available. I bought my rods and pistons from CNC Motorsports. Excellent and VERY fast service. Here's a link to their website:
http://www.cnc-motorsports.com
I'd call them and ask about a standard size SRP piston.
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From: Lake Lure NC
To answer the questions. The heads we angled milled by CNC Cylinder heads .010. Pete told me that the heads CCed at 54.5. Because I am using the impala head gasket I will lower the cc's by 2. Hence the 52.5. Just the nature of the impala shimmed gasket. I will be having the block cleaned and bored 30 over. I must use the stock style piston which I believe is a flat top piston with two reliefs correct?
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by mothersworry
I must use the stock style piston which I believe is a flat top piston with two reliefs correct?
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by mothersworry
Thanks Corvette Kid I just looked at them and you are correct they are flat to 4 relief. So with that said, does that hurt or help me finding a piston that works that is not custom?
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From: Texas
Originally Posted by mothersworry
Thanks Corvette Kid I just looked at them and you are correct they are flat to 4 relief. So with that said, does that hurt or help me finding a piston that works that is not custom?
New Four Valve Relief Pistons
Engine Displacement: 355
Engine Bore: 4.030 (.030 oversize pistons)
Stroke: 3.480
Rod Length: 5.700
Compression Height: 1.560
Valve Relief volume: -5cc
Weight (grams): 460
Piston Part Number: 156505
Piston Ring Part Number: J100F8-4030-5
Application: Claimer Applications Requiring 4-Valve Relief Piston
Engine Displacement: 355
Engine Bore: 4.030 (.030 oversize pistons)
Stroke: 3.480
Rod Length: 5.700
Compression Height: 1.560
Valve Relief volume: -5cc
Weight (grams): 460
Piston Part Number: 156505
Piston Ring Part Number: J100F8-4030-5
Application: Claimer Applications Requiring 4-Valve Relief Piston
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From: The Top of Utah
Originally Posted by mothersworry
To answer the questions. The heads we angled milled by CNC Cylinder heads .010. Pete told me that the heads CCed at 54.5. Because I am using the impala head gasket I will lower the cc's by 2. Hence the 52.5.
RACE ON!!!
Last edited by CFI-EFI; Dec 22, 2004 at 11:07 AM.
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From: Lake Lure NC
Thanks for all the help guys. I have finally figured it out. Here we go.
Cylinder Head Volume: 54.5
Piston Head Volume: -7
Gasket Thickness: .039
Gasket Bore: 4.125
Cylinder Bore Diameter: 4.030
Deck Clearance: -.010
Stroke (in.)- 3.48
Puts me at 11.086 compression.
Will this compression be ok on pump gas?
Cylinder Head Volume: 54.5
Piston Head Volume: -7
Gasket Thickness: .039
Gasket Bore: 4.125
Cylinder Bore Diameter: 4.030
Deck Clearance: -.010
Stroke (in.)- 3.48
Puts me at 11.086 compression.
Will this compression be ok on pump gas?
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From: The Top of Utah
It should be. A lot depends on the cam you use. You will want to record knock counts during competition. That .010 deck height looks rather optimistic, if you haven't decked the block. Of course you won't know for sure until the trial assembly with the new pistons. Even with the .010 deck, you don't have the quench working very strongly in your favor.
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