On Center Build questions

[turbo89]

Well it is .125 . So a order the right pistons . The piston from that I bought from this board he swar that theses would be perfect with my entire rotating assemble . Any way we shall see how to work this out . I'll tell u one thing it will be worked out one way or another

I'm sorry I didn't read through this entire post ...

you have a 3.625 crank with a 6.500 rod .. what is your finished deck height at ? .... What is the Bore size ?

 

[rag231]

Maybe the piston was made for a 3.750 stroke odd fire crank, 8:1 motor. Do you have any info scribed on the bottom of the piston? I am sure the crank had 3.625 stamped on it correct? There is some number that came up short somewhere.

 

[750H.P.V6]

You can't say u didn't say something lol you commented on my my post when I got the Pistons saying that dish looks shallow .View attachment 294838

Chris,

The pin height in those pistons doesn't seem that far off. Are you sure the crank isn't a 3.400" stroke rather than a 3.625"? If so the piston would be .112" further down in the hole that it should be.

Neal

 

[dank GN]

Chris,

The pin height in those pistons doesn't seem that far off. Are you sure the crank isn't a 3.400" stroke rather than a 3.625"? If so the piston would be .112" further down in the hole that it should be.

Neal

I was told the crank is a 3.625 stroke . I will use my calipers to measure the stroke . There is no markings on it with stroke info . Just the company name . Thanks guys and sorry for all the stupid?? I reall appreciate the help

I'm sorry I didn't read through this entire post ...

you have a 3.625 crank with a 6.500 rod .. what is your finished deck height at ? .... What is the Bore size ?

I know I have put the info up more then once on this thread but it's a 4.060 bore , 3.625 wide journal billet crank, 6.500 on center wide journal rods . Block is the latest 153 block that is virgin. Deck heigh needs to be double checked as well as stroke but it should be very close to standard

 

[rag231]

I was thinking that the crank may have been a 3.50, but I don't remember LA Billet making anything but a 3.625. There are no stupid questions, kudos to you putting forth the effort building your own motor. Just looking at the motor as it sits, it appears that you would have very low static compression. Tomorrow I will call every engine guy that I know and see if they can set me straight on some info.

 

[dank GN]

It is a 3.625 crank I just measured the stroke . Also the guy I got the Pistons from stated he had them made for a low 8.0 :1 compression ratio . So would that explain why it's that far in the hole ? So I would just have to run a lot of boost like 40psi ??

 

[dank GN]

I was bored of looking at it as a shortblock so I slapped on the heads and intake just so I can see it in all its glory and to fit these headers I'm working on .

 

[dank GN]

 

[ek02]

The only way to know for sure what the compression ratio is would be to cc the cylinder at TDC, add the head gasket and cylinder head CC's, and use the formula. I would not guess. A piston that far from the deck does not seem right. My employer back in the 70's ordered 11-1 pistons for a Keith Black Hemi Blown Alky engine and Venolia sent him 8-1 pistons for a Nitro engine. It was down on power and cc'ing it showed why. Your engine really looks great.

 

[Reggie West]

You are making a killer motor but why go with a 3 bolt turbo ? A 4 bolt will be much better considering the power you are after with this. Not trying to rain on the parade I swear..

 

[rag231]

Maybe TSM?

 

[turbobitt]

OK so here is my opinion, If the piston is in the hole .125" than that's about 26.5 cc's worth of dead volume compared to 0 deck regardless of piston or head volume. I'm not saying you should run 0 deck but just to give you a feel for the numbers. Now if we assume about 45 cc's for the head volume and about 44 cc's for the piston dish than we could be running in the neighborhood of 7:1 range. Obviously I just guessed on these numbers and made some assumptions but again just to get a feel for what the compression may actually be.

I wouldn't target anything less than 9:1 and preferably closer to 10:1 and especially if your running a 3 bolt. There is no making up for it with boost so just erase that thought since its much more complicated than that. The compression will effect cylinder fill and VE so higher is better to a point.
AG.

 

[bison]

It is a 3.625 crank I just measured the stroke . Also the guy I got the Pistons from stated he had them made for a low 8.0 :1 compression ratio . So would that explain why it's that far in the hole ? So I would just have to run a lot of boost like 40psi ??

Yikes


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[750H.P.V6]

Chris,

I hate to tell you this but I think you're in the market for another set of pistons. What you've got won't work. I'm sorry you had it all balanced and assembled but I'd tell you to bite the bullet and buy the right pistons. You'll never be happy otherwise.

Neal

 

[dank GN]

Yes well so much for a deal . How
Much am I looking at for a set of
Custom Pistons pins and rings? I just talked to my machinest and he said to re balance it shouldn't be bad as we are in the ball park already . He did have to add 100 grams to the crank already .

 

[Reggie West]

Figure $800 for set of pistons.

Give Kenny a call he can get them and the rings for you.

 

[chris kirk]

Yes well so much for a deal . How
Much am I looking at for a set of
Custom Pistons pins and rings? I just talked to my machinest and he said to re balance it shouldn't be bad as we are in the ball park already . He did have to add 100 grams to the crank already .

Chris Hogeland did a set of diamonds for me for $1200. Sorry to hear about your troubles. Also, gotta agree with Reggie West, ditch the T3 and go with a 4 bolt. Will be much happier....

 

[dank GN]

Just a updated I am ordering new Pistons from earl . He is getting me a set that he had designed to my specs for 1/2 what the other ppl are charging. The piston would have worked if I wanted to run 50psi and have it be a complete turd at anything under 20psi lol 7:1 compression ratio isn't going to cut it . Now that I have all my specs I am going to be in the ball park of 9.5:1 which I'm sure will work a just Alil bit more then 7:1 . And I am also coming up on a bunch of Indy car stuff later today I will post pictures in a different thread of that . But here are acouple pics of the old pistons .

 

[dank GN]

I can't remember if I posted on here about flowing my TA heads . Anyway I just finished porting on the heads and will go back to the bench to make sure they are all within acouple CFM from eachother

 

[750H.P.V6]

Chris,

Pull off the oil control ring and take a measurement from the pin bore to the top of the piston I'd be interested to know what the compression height is.

THX

Neal