compession with after market pistons

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alsdemon

alsdemon

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my shop guy said i have a 340 bore on my 360 block said it had a 4.04 must be 40 over ? how do i fine compession? i only see numbers on the pistons. als
 
If you don't have the piston part # and specs you could cc the bore with the piston at TDC if they're flat tops but pop ups would be far more difficult to figure out. You would have to make some kind of plexiglass tube with a known volume, grease the bottom for a seal and cc it again while placed over the bore and piston. Then put your numbers into a calculator like this one: http://kb-silvolite.com/calc.php?action=comp
 
you have a .040 over 360...which is 4.040...

compression is based on the alot of things....head gaskets...head cc...compression height on the pistons...

need alot more info to figure out compression...

what pistons do you have....what heads....what head gaskets...???
 
70aarcuda said:
you have a .040 over 360...which is 4.040...

compression is based on the alot of things....head gaskets...head cc...compression height on the pistons...

need alot more info to figure out compression...

what pistons do you have....what heads....what head gaskets...???
Click to expand...

That's why I gave the link to KB so he could fill in the blanks. :)
 
no it,s a 77 360, it has been overhauled before i got it it has stander 360 4v heads. i will look for part#. it had set for 6 years and freeze plugs needed change so i went throught it. thanks for replays. i wound like to put a lumpy cam in it cause it,s a four speed with manual brakes so idol is not that inportant. als back from the shop will post a pic. later of piston flat tops looks like. arent the rods all the same just differant piston for compression. als
 
ok pistons have 40 stamped on top the #405p are on the side/ press pins. but the rods all have3418645 on one side of the rod.But differant # on the other side/ differant type or stamping on more that one or two. one rod has on it big type WDF . now it,s a fact finding goal. need batterys will post pic,s soon. als
 
How did you get those pistons?......did YOU buy them? You should find the brand and part number, then go online and to the manufacturer's website. You've really got to find out.....mfgr and piston part #.
 
they were in the motor . Which was given to me by my borther out of a plow truck that my stepdad had worked on and got to rusty but had been reman by dealer not meny mile only run two or there mouth a year. so it sat four 6 years and ipulled it out to start on the motor.als
 
here are soom pic,s of parts

P1011063.jpg


P1011065.jpg


P1011064.jpg
 
Scrap those pistons if you are looking to make power. Those are just some stock .040 replacements. As far as compression with those things.......I would guess maybe 8-1 if your lucky and have good heads.
 
no power just want a street car. like always moneys tight, bye pistons or pay gas bill. thanks for the replyes.i will check with my freind who works a summit see if there anything cheap. als
 
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