Identifying pistons
Thread Starter
Racer
Joined: May 2007
Posts: 334
Likes: 17
Identifying pistons
Can someone please help me to identify these pistons:
http://www.vtr-racing.de/Corvette/Piston.jpg
They are in a 73er BB (# 3999289) but with 66er heads (# 3872702 with 98 cc closed chambers).
I assume they are not stock...
Thanks!
http://www.vtr-racing.de/Corvette/Piston.jpg
They are in a 73er BB (# 3999289) but with 66er heads (# 3872702 with 98 cc closed chambers).
I assume they are not stock...
Thanks!
Burning Brakes
Joined: Feb 2005
Posts: 894
Likes: 91
Can someone please help me to identify these pistons:
http://www.vtr-racing.de/Corvette/Piston.jpg
They are in a 73er BB (# 3999289) but with 66er heads (# 3872702 with 98 cc closed chambers).
I assume they are not stock...
Thanks!
http://www.vtr-racing.de/Corvette/Piston.jpg
They are in a 73er BB (# 3999289) but with 66er heads (# 3872702 with 98 cc closed chambers).
I assume they are not stock...
Thanks!
The photo is definitely a "cast" piston and appears to have a "short" dome.
This is the first item you need, the height of that dome, can't tell accurately from the photo. The second item you need is the "stroke" on the crank. You can measure that by using a ruler and record the distance from the "deck" of the piston, the "flat" section, not the dome, at BBDC to the deck surface of the block. It will be either 3.750" (average) or 4.000". If it turns out to be the 3.750" number you have a 427", if it's the 4.000" number it's a 454".
The year on the block doesn't tell you anything but the fact you have a 4.250" bore "as-cast". This is the block numbers used on the LS-5's in the '72 era!
My own personal "guess" strictly from the photo would be a "cast-piston" 427, as there weren't many vendors making that type cast piston for the 454's.
I'm using the 3.750" as opposed to the actual 3.766" number for the 427 stroke to make it easier to measure using a std. ruler!
Thanks, Gary in N.Y.
P.S. If the stroke is a 427" (3.750") and the dome is about .300", you have a 12.5:1 unit with a 98cc head. If the dome is about .140" (this is what I believe the photo shows), you have about 10.5:1.
Now if the stroke is the 454" (4.000") and about a .270" dome you have a 12:1 unit, if the dome is nearer .100", you have a 10.75:1 unit.
(These numbers are based on a 9.800" deck and an .028" gasket and are ALL averages!)
Thread Starter
Racer
Joined: May 2007
Posts: 334
Likes: 17
You need to determine 2 items to make a "guess" at the piston and C.R.
The photo is definitely a "cast" piston and appears to have a "short" dome.
This is the first item you need, the height of that dome, can't tell accurately from the photo. The second item you need is the "stroke" on the crank. You can measure that by using a ruler and record the distance from the "deck" of the piston, the "flat" section, not the dome, at BBDC to the deck surface of the block. It will be either 3.750" (average) or 4.000". If it turns out to be the 3.750" number you have a 427", if it's the 4.000" number it's a 454".
The year on the block doesn't tell you anything but the fact you have a 4.250" bore "as-cast". This is the block numbers used on the LS-5's in the '72 era!
My own personal "guess" strictly from the photo would be a "cast-piston" 427, as there weren't many vendors making that type cast piston for the 454's.
I'm using the 3.750" as opposed to the actual 3.766" number for the 427 stroke to make it easier to measure using a std. ruler!
Thanks, Gary in N.Y.
P.S. If the stroke is a 427" (3.750") and the dome is about .300", you have a 12.5:1 unit with a 98cc head. If the dome is about .140" (this is what I believe the photo shows), you have about 10.5:1.
Now if the stroke is the 454" (4.000") and about a .270" dome you have a 12:1 unit, if the dome is nearer .100", you have a 10.75:1 unit.
(These numbers are based on a 9.800" deck and an .028" gasket and are ALL averages!)
The photo is definitely a "cast" piston and appears to have a "short" dome.
This is the first item you need, the height of that dome, can't tell accurately from the photo. The second item you need is the "stroke" on the crank. You can measure that by using a ruler and record the distance from the "deck" of the piston, the "flat" section, not the dome, at BBDC to the deck surface of the block. It will be either 3.750" (average) or 4.000". If it turns out to be the 3.750" number you have a 427", if it's the 4.000" number it's a 454".
The year on the block doesn't tell you anything but the fact you have a 4.250" bore "as-cast". This is the block numbers used on the LS-5's in the '72 era!
My own personal "guess" strictly from the photo would be a "cast-piston" 427, as there weren't many vendors making that type cast piston for the 454's.
I'm using the 3.750" as opposed to the actual 3.766" number for the 427 stroke to make it easier to measure using a std. ruler!
Thanks, Gary in N.Y.
P.S. If the stroke is a 427" (3.750") and the dome is about .300", you have a 12.5:1 unit with a 98cc head. If the dome is about .140" (this is what I believe the photo shows), you have about 10.5:1.
Now if the stroke is the 454" (4.000") and about a .270" dome you have a 12:1 unit, if the dome is nearer .100", you have a 10.75:1 unit.
(These numbers are based on a 9.800" deck and an .028" gasket and are ALL averages!)
(the profound knowledge in this forum is always amazing!).I just measured the parameters you suggested:
Stroke is (approx) 3,77"
Dome height is (approx) 0,140"
Clearance to deck is (approx) 0,027"
So it is really a 427. CR must be then about 10.5:1 (I had a shim metal head gasket installed with about 0,021")?
Do you also have a guess regarding the HP?
Thanks!
Dirk
