Bore scope ??

[Highbanked Hauler]

 Can you tell if there is a ridge on a cylinder with a bore scope ?

[c00nhunterjoe]

Should be able to. What is the concern?

[Highbanked Hauler]

Should be able to. What is the concern?

   About 4 years ago I bought that less than a hundred mile 12:1 comp 440 and can read the numbers on top of the pistons so I want to see if there is any cylinder damage  that would prevent a set of lower comp pistons  being put in. If there is no damage or ridge this idea would be closer to working.

[Challenger340]

Should be able to. What is the concern?

   About 4 years ago I bought that less than a hundred mile 12:1 comp 440 and can read the numbers on top of the pistons so I want to see if there is any cylinder damage  that would prevent a set of lower comp pistons  being put in. If there is no damage or ridge this idea would be closer to working.

Forgive me for asking here, but if you can read the numbers on the top of the Pistons ? What are they ?

Lots of "so-called" 12:1 Pistons, are actually no where even close to 12:1, meaning there may be alot cheaper ways to skin a cat if running pump gas is the problem ?

[Highbanked Hauler]

OK the number I got is 7025 with a P or F or maybe a 1..  By the 0.30 they must be 30 over..

[Bronzedodge]

I believe TRW had a 7025P piston for 440's.

[c00nhunterjoe]

7025s are not 12:1 pistons unless you have a milled set of closed chamber heads on it and .020 gaskets if i recall that number. More like 10.5:1 on a 906 and 041 gaskets. I will have to do some digging to find the compression height of them to be conclusive. Is there an issue with the engine? How big a cam is in it? What heads? Might run fine on 93 depending on what else is in it.

[Challenger340]

OK the number I got is 7025 with a P or F or maybe a 1..  By the 0.30 they must be 30 over..

That's kinda what I thought ? Probably nowhere even close to 12:1 
The 7025P were identical forging to the current L2295F Pistons, built with a 12 cc Dome, but at a Compression Distance of 2.029" or about .050" down on an unmilled Block.
They were designed to be about .050" "Down" Hole from deck @ TDC and have the Dome compensate for C.R. purposes, so they would "act" like a Flat Top Piston at ZERO Deck ? (But with diddly for quench)
Meaning, (and like Joe already stated)
low 10's:1 using a 906 or any open chamber iron head and Composition style Head Gasket.

Lots of questions:
What Cam ?
What Heads ?

EDDY RPM Heads come in an 88cc Version, depending on Camshaft.... should be fine.

[Highbanked Hauler]

      NOT being an engine person I was taking the prior owners word for it but that actually turns out in my favor now as the car will be  street driven and not raced .  The heads are 906, it has stainless steel valves,mild porting, Crane 1.6 roller rockers. I don't have numbers on the cam but has a little more lope than the stock cam in my 500 if that tells you anything.. I do not know if the block was planed or not..

[c00nhunterjoe]

Do a compression test on it and report back the numbers. Will give a better idea. What is the elevation where you live?

[Challenger340]

Do a compression test on it and report back the numbers. Will give a better idea. What is the elevation where you live?

And don't forget when doing the Comp Test:
* All 8 spark Plugs OUT
* Disable the ignition (Crank it off the starter relay)
* Wire the Carb Throttle Plates wide open
then,
* watch the gauge while Cranking, 4 "bumps" only per cylinder on the Compression Tester needle, record the 4th and final reading.

[c00nhunterjoe]

And note the 1st bump too. 100 psi on the 1st bump is indication of healthy bottom end.

[Highbanked Hauler]

   Houston we have a problem, the engine is sitting on a dolly.. I have a video of it in the car running on  E-85 which it did fine but I can't post on here also the car is on the rotisserie now. My idea was address the compression situation figuring I would have to change pistons before the engine goes in the car but since it seems to be a 10:1 that improves things considerably.

[c00nhunterjoe]

Could always pull a head, measure the piston, cc a head, and get the grind number off the cam. That would make it exact.

[Highbanked Hauler]

Could always pull a head, measure the piston, cc a head, and get the grind number off the cam. That would make it exact.

When you say measure the piston do you mean the depth in the hole or diameter ? The literature on the cam must be in the front ?

[375instroke]

Just engine, or is it bolted to a trans?

[Highbanked Hauler]

Just engine, or is it bolted to a trans?

    It has a flywheel,clutch and bell housing on it..

[Challenger340]

Could always pull a head, measure the piston, cc a head, and get the grind number off the cam. That would make it exact.

When you say measure the piston do you mean the depth in the hole or diameter ? The literature on the cam must be in the front ?

Pull a head, rotate a Piston to TDC, measure the distance from the Flat portion of the Piston, up to the deck of the Block. The 7025P will be about .050" to .060" down from the Block deck @ TDC.

[375instroke]

Just engine, or is it bolted to a trans?

    It has a flywheel,clutch and bell housing on it..

I would imagine you can put a starter on it, then, and do a compression test.

[Highbanked Hauler]

 Wouldn't you have oil in it and prime it like a fresh start up ?

[375instroke]

Are you asking for a checklist of how to do a compression test out of the car?

[Highbanked Hauler]

Are you asking for a checklist of how to do a compression test out of the car?

  No I just wasn't thinking about priming it.