Thread: tall deck pistons

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Originally posted by pat mccarthy
the numbers i a gave you are the ones that will work. from the top of the pistons .not the dome. it needs to be 1.395 .the dome are not part of it this. it is the center line of the pin to the the top of the nondome part of the pistons.

the dome pistons will add to the cr and so will more cid but the dome will move it faster and buy that i mean the cr . the way i seen it was if it would change the cid any way if you run the pistons with a dome they will be 10.9 to ?? this has a lot ot do with your head and cc this 10.9 is off a 112 cc head and the flat top is 9.0 base off 112 cc head or less if the cc are less the cr is more

Thanks for the clear up. So thoughs two numbers are the ones I should pick from. Now I dont know if this is possible but I wanted to run the merlin heads with 80cc chambers. Is there a piston I could use to still run pump gas.

your off 80 c c big block head ?? the pistons SRP ARE THE CHEAP WAY TO GO work with them or pay $1000 or more for customs

Pat knows way more about BB Chevys than I do, but I was just doing a little research. KB makes a piston KB380 for a 4.320" bore, 6.535" rod and 4.500" crank. The stack adds up to 10.215" with a piston compression height of 1.430", so a shave off the piston crown for zero deck with an 0.040" gasket or a little thinner gasket (0.025") with a 0.015" pop-up could achieve a 0.040" squish. This piston has a 20cc dish and I'm figuring 10 cc's for the gasket/pop-up.

112 cc head 8.61:1
95 cc head 9.64:1
80 cc head 10.82:1

http://kb-silvolite.com/performance....tails&P_id=130

i look at this piston and for a 4.375 crank and a 6.535 and a 10.200 block it is in the hole over 0.40 ?? but for what he needs the 1.395 may work better if you tru -deck it with b.h.j.and deck the block down. but so wound the KB i guess it has alot to do with money and the head cc are and if he want to deck it or cut the tops down JE makes D s a drop in pistons but they are$1000 and the srp are$550 and he knows what the CH is he can start looking

I know in KB's info, it says the piston is for a 4.375" crank, but if you do the math, you'll find that they have made an error and that the stack is 10.215" with a 4.500" crank, 6.535" rod and 1.430" piston, so it's obviously for a 4.500" crank. Same piston and rod on a 4.375" crank would have the piston in the hole 0.0475" and you'd never get squish in the motor without surgery on the deck.

not to get in a pissing contest with you richard but the block is 10.200. the 1.395 is the best pistons and it just happens to be the rigth sizes and that kb is just not right for the 4.375 or 4.500 ??i think some thing is off i think i would call them if he want to run them .i have used the 1.395 and they work.if you want to look at it look at je pistons on the web and you will find i am right on this one. did not what to sound like a smart ass but ? beside i not a big fan of the kb. on that the srp may not cost much more and are much better. remeber if you tru-deck it with the b.h.j like i have it will take 0.010 or a bit more to get the deck right so at that point the 1.395 looks good .

Originally posted by 76GMC1500
When building custom engines, you can't just buy parts because they say they fit a tall deck block or something. What you need to do is calculate the proper compression height for the piston using your deck height, rod length, and stroke. Then make a piston selection.

Just for kicks, here are some big pistons. 17" bore by 21" stroke.

them are some big rods on the tv they had a big ship yard making big cranks and ship engines that stuff is cool

What do you mean I am off!!! They are a the merline-X cylinder head and ocording to world they flow over 400 cfm out of the box, I want these heads but like I said they have 80cc combustion chambers. I dont want that high of a compression so I was hopeing there was a deep dish piston I could use. But I am afraid Its not going to happen.

Originally posted by joe bogger
What do you mean I am off!!! They are a the merline-X cylinder head and ocording to world they flow over 400 cfm out of the box, I want these heads but like I said they have 80cc combustion chambers. I dont want that high of a compression so I was hopeing there was a deep dish piston I could use. But I am afraid Its not going to happen.

that head is way to muchCFM when a set big O ports will do and to make them heads work you need more than pump fuel and big roller cam if you run them heads and a small cam with no CR it will be a pig

joe if you tell me what you want i can try to help or not that is up to you but .them heads can not be to cheap and if you want them heads then build some thing bigger thay can be made to work but this will be a verry $$ engine . the pistons will not be any thing to stop you for $1000+ they will make you a set but this would be a pro built engine. i can type and spell so much. if you go this way you will need help. this will be a hi rpm engine you need to find some one that hase done this stuff before to do it or to be rigth there to make shure every thing is rigth and has done it. if you spend this kind of money. spend more and get a block that you can get out to 632 all parts at this point will be the same prices wou may have $3000 more in this build and over100 cid

Ok so the heads are out then. Can I positively use those pistons from srp. And are those the same ones in the catalog. The one part number you gave me (142973) is in the catalog but I dont see the other one. I will go to SRP's websight (if they have one) right now and wait for your reply. Thanks.

I found that JE has a new piston made just for tall deck engines and they have a piston for a 525 that has the same rods,stroke,bore and such as the combination I am going to use.The web site is http://www.jepistons.com/pdf/2005-je3.pdf. Part #131670 Take a look and see what you think. I couldnt figure out how to make the web address a button sorry.

look at the numers of the pistons i gave you they will work 1.395 the new one are low on cr 8to1?? is this what you want ????

It may not work but just to know what would the compression be with the 80cc heads. Probobly to high but just to know. Your right I dont want that low of compression but is there anything that I could do to get it higher with those pistons.