(Slightly)Used Forged Pistons-Thoughts And Opinions

[Al K]

As I've often stated,I'm trying to do things on a tight budget. I know cheap isn't always good,but once on a while...

A couple of years ago,I picked up a set of used Venolia +.030 slugs at a very good price-with pins and Spirolox. Supposedly only used for a short time on a dyno,until something went amiss and the engine was disassembled. I checked them out at the swap,didn't see any major issues(cracks,etc.),shelled out a buck-fifty and walked. Now,I'd like the opinions of those more well-versed than myself. If you cats tell me I've got eight new ashtrays,I can live with that-but please tell me why.

The suspects:

There are some slight "scratches" on the sides-on some,but not all. Will they clean up?

Also;a couple of them had valves make contact. Nothing serious,but there are marks there. I had a magnifying glass with me,checked the pin area and underside for any cracks due to this and saw none.

Like I said;if you guys think they aren't worth the potential problems,I can accept that. Just means I'll have to come up with the $$$ for new stuff. Donations can be sent to... Since I've got the heavy 908 rods,I was hoping to cut the swinging weight with these pieces. I plan on polishing and rounding off the sharp edges to cut down on any potential hot spots,and enlarging the fire slot. The Mopar Performance book also has a diagram showing how to remove some of the dome(rounding it off),again for eliminating a possible detonation-causing area. Might consider that. I'll also be using Fel-Pro head gaskets(.039"),so that should keep the compression to a reasonable(10.5 or so) level. I will be mixing racing gas with pump Premium as well.

Gentlemen;I value your opinions, You haven't steered me wrong yet in matters of advice. As always,THANK YOU!

 

[nothingbutdarts]

Can you feel an endentation where the valves hit the pistons?
It looks to me like you saved yourself a few hundred dollars! Go enjoy the build. My .02

 

[Al K]

Can you feel an endentation where the valves hit the pistons?
It looks to me like you saved yourself a few hundred dollars! Go enjoy the build. My .02

Yeah;but they're REALLY slight. I should be able to remove them with a bit of sandpaper. Is that OK?

 

[nothingbutdarts]

I would just check the few that got hit close in the pin area for cracks (most likely there will be none) and run them if they look good!

 

[RustyRatRod]

Run hell out of um. Good score.

 

[fanucme]

Back when I first got into it building cars I had an Olds motor built with forged pistons and the machine shop set the block up with cast piston clearances (way too tight) it ran real hot , after disassembly the pistons came out scored up, but a local racer sanded them up and I re ran them , it worked , a little noisy but it worked.

Knowing much more now , Use a micrometer to check them for taper from top to bottom at 90 deg to the pin boss and if good, I'd say up to .002.003" max , I'd wet sand them on the skirts ( not to remove the scratches but to knock the edges down ) and don't look back. I agree with the others about inspecting for cracks but those pistons should be tough as nails. I've been to a few NMCA events , once as a guest in Pat Musi's pit and saw some stuff I wouldn't believe worked if i didn't see it myself.

 

[RustyRatRod]

When shoppin for used pistons, I've always thought people made too much fuss about scratches on the skirts. Remember it's the rings that do the sealin. The WEAR on the skirts really isn't critical, especially if you're going to bore to the used pistons.

 

[Wedgeamacallit]

I would not be afraid to run them. I had a set of used stock 69 340 standard bore pistons that I put in a 1973 block. Clearance checked out so I ran them. Engine ran great

 

[Meep-Meep]

Crap, those look new compared to some of the stuff I ran. I was king of the rering jobs back in the 80's. A couple of things you want to make sure are good and that would be the ring lands and the skirt dimension top to bottom. A new set of rings should have very little up and down clearance (there is a spec for this) and the skits should not taper drastically smaller as they go away from the pin. Scuffs and such are not usually a problem but if they are deep and look like a lot of material has been removed, then they got really hot. The dimples from the valves are probably fine as long as no cracks (of course). Smoothing the tops out like you said is a great idea too and be sure the engine is rebalanced after all that work. Don't do anything to the skirts other than remove high spots and the pin bores can be lightly honed if needed.

 

[tallhair]

Glad you asked this question.

 

[goose69]

Looks like you are getting good advice, as usual from this site.
I also am one to piece things together with used parts when I can. I am sticking in a 440 into my Belvedere that I bought a used set of forged pistons for. There was light scrapes on the skirts like yours and a small imperfections here or there I was concerned with but I bought them cause it was a great deal. I took them to my machinist who is very respected and he said they looked just fine to use. He bored the block for them and he said everything looked fine! So I also would say.....no problems if everything checks out with them.
So go build that motor!!!

 

[Al K]

Goose;I am SO glad to have found this bunch of characters and haven't been steered wrong. Thanks to all!

 

[wannadrag]

When shoppin for used pistons, I've always thought people made too much fuss about scratches on the skirts. Remember it's the rings that do the sealin. The WEAR on the skirts really isn't critical, especially if you're going to bore to the used pistons.

X2

 

[Cranky]

Like mentioned, make sure the ring grooves are good and the skirts mic out. Ever see a set of 'knurled' pistons before?