Need help identifying pistons

[peakandscoot]

I have a 383 that my uncle changed the pistons on in the early 80s. They identify as 30 over but i am trying to find out what my compression ratio is. When i google the numbers all that come up are some Wiseco motorcycle pistons. They are marked 2309PA on the top and on the inside 29o-99 its just like that with the little o. There is also a T with a triangle around it. Can anyone help identify these.

 

[33 IMP]

Trw makes a L2309F piston for a four inch bore, but it says it's for a Continental engine [aircraft?]. more physical desc. would be helpful. can you tell if they are cast or forged,valve reliefs or complete flattops, how far down in the hole. Your best bet will be to measure and calculate it yourself, published compression ratios are frequently bullship. I got a 100cc syringe used from a veterinarian, a piece of clear Plexiglas and do my own. All you have to do is get a good measurement of how far down the piston is,and look up a calculator on line. A zero to one dial indicator can be had for as little as ten bucks to measure deck height[down in the hole].

 

[NOSTRT980]

a few pics might help

 

[BSB67]

I have a 383 that my uncle changed the pistons on in the early 80s. They identify as 30 over but i am trying to find out what my compression ratio is. When i google the numbers all that come up are some Wiseco motorcycle pistons. They are marked 2309PA on the top and on the inside 29o-99 its just like that with the little o. There is also a T with a triangle around it. Can anyone help identify these.

A pic would help. Is it a flat top? Does it have valve reliefs? If you measure the deck to piston top at tdc we'll probably be able to determine what the CR is

 

[wyrmrider]

measure the compression height center of pin to top of piston
measure the deck clearance at all four corner holes if possible
do cc your heads
post up the casting number on your heads
I'll see if I can find my 80's TRW catalog but dimensions work equally as well
tell us if pistons have valve relief "eyebrows"
measure the head on the exhaust side by a head bolt with some calipers - should be 1 inch unless heads milled a bunch

 

[peakandscoot]

OK i finally put the crank and a single piston back in. Its a flat top piston and as you can see in the picture the cylinders have relief cuts. At TDC i was able to get 12.2 cc in it before overflow. 30 over pistons.

Who is the math person who can tell me my compression ratio now. Also yes i know when i took the picture i was not yet level

 

[33 IMP]

You won' like what I came up with. First, a LOT of assumptions. I'm going to assume your measurement is correct for volume above piston to deck. Next I'm assuming something like a standard felpro gasket and UNcut 906 heads. 915s or aftermarket heads, steel shim or thick cosetic gaskets substantially change the numbers.
Swept volume of 030 over 383 is796.9cc
Volume above piston to deck (your measurement) 12.2cc
ASSUMED measurement of gasket, 4.4"bore, 035 compressed is 8.72cc
ASSUMED 906 head UNcut is in reality around 88cc.
Calculation is 796.9+12.2+8.72+88=817.82÷12.2+8.72+88= 7.508cr.
Now remember, this is ALL a guess. Actual measurement of head cc.s ,actual head gasket, actual deck hight ( feeler gauges under your level might be close enough) will give much more accurate results.