how to tell if pistons are bad

[dlampe]

I am working on the parts list for my new 427. How do you know if you should replace the pistons? I have LeMans rods, are those likely to need replaced?

[KrAzEcJ]

Not to sure of your question without a little background info. You wrote new 427, what machine work has been done to the block? Anyway need a little more info to try and help. If the block has been machined and you have the old pistons that came with the motor most likely they are now to small. If you havent had any machine work done at all you need to have the block checked out by a reputable machine shop and once its checked out you will know how each cylinder bore is and wether it has to be bored 20, 30, 40 etc.... to get the bores in good shape and alligned. Then you will know about piston size. As far as rods have them tested and sized. When you get a chance post some more information.

[Big-Foot]

Rods - You can probably get by with magnafluxing them, installing new bolts and re-sizing the big ends.

Pistons - It all depends on what you are going to do with the bores. If you are boring the engine to the next oversize, the pistons you have are now better ashtrays and paper-weights. If you are not boring the block, you need to have each piston mic'ed to determine if the skirts are worn too far to be re-used, cleaned and check the tolerances of the ring grooves and wrist-pin holes and then finally have them Zyglo inspected (looks for cracks).
New pistons will cost about 25-50% more than the work you need to do to re-qualify used pistons.

Hope this helps!

[FFR428]

Besides new cap screws for the rods get some fresh dowels for them also. DSC sells them www.dscmotorsport.com They have the cap screws also. They are ARP's I beleive. Hey Randy nice to see you here. Hope all is well, Glenn.

[dlampe]

I have spoken to my builder and he has his doubts about being able to rebuild the motor and reusing the pistons. He would like to go with new custom pistons and clean up the bores. Even if it is only .015 or .010 over just to be sure. That is the path I think I will take. I want a great dependable motor that is going to hold up to road race conditions and I want to take out the weaknesses.

[SCOBRAC]

How old are the piston you have, are they forged? Cast? Are they scuffed or scratched? Are the pin holes standard size? Can you reuse them at all, did the engine stay at the bore the piston was made for. Sometimes the answer is yes, sometimes no.

These are all questions you must ask. When in doubt replace them all. The piston is literally where the pedal meets the metal. You can never afford to spend too much on good quality pistons.

[Excaliber]

FFR428 thanks for that link to DSCMOTORSPORT. I had an interesting chat with owner.

I'm having my ROSS pistons milled to remove the "pop up" portion in order to reduce the compression ratio. That will remove about 10-15 cc of material, the pistons will still have enough thickness on top. That and a thicker head gasket might get me down to 10 to1 (from 12.5 to 1).

I wouldn't buy new pistons unless my machinist indicated there WAS something wrong with my old ones. Mine checked out fine. I think the key to a good reasonably priced engine build is to measure everything and do what needs to be done to bring the parts within specs.

Some just go in and replace and machine and buy and do everything to the max. Thats fine, if you got the money. Me? I'll measure twice and think about what I REALLY need to do.

I've heard some say those "old" FE con rods HAVE to be replaced. Maybe, maybe not. I'm not throwin' MINE out before I measure them carefully and consider my options! I don't buy into the idea that just because there "old" there "weak". Hey, maybe there "seasoned" and stronger than ever (like me)!

I like the idea that MOST of my engine will in fact be "original" Ford spec OEM parts from the mid 60's. Yeah I know those Edelbrock heads are great, but mine are the "real deal". High Rise with a Ford aluminium 2X4 intake sitting on them! I'm going to run a flat tappet camshaft too, just like "back in the day"!

Oh, I have the Super Cobra Jet rods,,,,, cool.

[dlampe]

Well, I pulled the heads to look at the bores and the pistons. The bores are in fact standard. The tops of most of the pistons look pretty beat up. It looks like the valves have nicked them up pretty bad. I think it is a real low milage motor but the pistons do not look good on top. I think these babies are going to get replaced. Thanks for the input.