2618 Piston Street Use Longevity

[A853]

Lots of good info here and I appreciate the experts chiming in! I went with the JE Asymmetric Pistons. Not sure if anybody has had any success with them of if the reduced skirt area on the non thrust side is of any hinderance of longevity, but I guess we'll just see! I really enjoy every response and appreciate the time taken to give your input.

[Bradley67]

in your unbiased opinion if you can (dont know where you currently work) which are the main aftermarket companies that do ovality and barrel shape best? in that they really tailor the shape to the application of a custom piston? for example a short skirt design that pulls the piston quite far down the bore at BDC so you want to stop rocking and skirt wear.

I currently still work for me, since I determined long ago that I'm the only one that will put up with me.

I actually have never kept up with what other were doing as far as custom skirt designs go. Were used to do a bit of Nascar stuff, but that was all to their specifications, we didn't keep the data, nor did they give us the
I used a skirt design that was designed by Ford, and it was incredible, as far a wear goes. But it wasn't designed to do what you're talking about, but nothing else really is either. Pulling a piston out of the bottom until the oil ring falls out will never with the "best engineered" prize.

I'd probably go with CP and Racetec. And yes, I know how weird that sounds. Frankly I've never see a skirt design that looks as good as mine did after a lot of use.

We just tore down a 427 Windsor with 100K on it and the skirts don't look a lot different.

Just for the record " Digger" asked about ovality not me Bradley67

[digger]

I used a skirt design that was designed by Ford, and it was incredible, as far a wear goes. But it wasn't designed to do what you're talking about, but nothing else really is either. Pulling a piston out of the bottom until the oil ring falls out will never with the "best engineered" prize.

i didn't mean anything as extreme as that of course....
there were a few threads recently with guys getting wear on the skirt on configurations where the pin was pulled quite far down at BDC (i think it was a Windsor engine). on that thread the barrel shape was discussed and having the checking height being a position that does not go below the bottom of the bore at BDC but the ovality would seem to go hand in hand.

[Mark O'Neal]

I used to have pictures of a 347 Ford in a Boss block, scared me half to death.

Then I saw a Cleveland with a 4.000 stroke and a six inch rod and felt better about the 347.

The gauge point is a half inch up and that is a long way from the bottom of the cylinder. We used to chamfer the heck out of the bottom of the cylinders.....and pray.

[DaveMcLain]

I used to have pictures of a 347 Ford in a Boss block, scared me half to death.

Then I saw a Cleveland with a 4.000 stroke and a six inch rod and felt better about the 347.

The gauge point is a half inch up and that is a long way from the bottom of the cylinder. We used to chamfer the heck out of the bottom of the cylinders.....and pray.

In a 408 Cleveland build with a 6 inch rod isn't the pin centerline higher in the bore than a stock 351C at BDC?

[piston guy]

.030 lower. 6-5.78=.220 . 4-3.5 divided by 2= .250. Difference .030.

[piston guy]

Mark ,
I do not know how Mahle gets the pistons to live in the "new" Boss block but Ford says "no problem". 632 BB Chevy is another ugly one for coming way out of the bottom and chafing skirts especially with rod bolt clearance added.

[DaveMcLain]

.030 lower. 6-5.78=.220 . 4-3.5 divided by 2= .250. Difference .030.

That's right, I was thinking that the stock 351C rod was 5.720

[digger]

Mark ,
I do not know how Mahle gets the pistons to live in the "new" Boss block but Ford says "no problem". 632 BB Chevy is another ugly one for coming way out of the bottom and chafing skirts especially with rod bolt clearance added.

so what is the worst people have seen?

one way for comparison is the dimension from the bottom of the cylinder liner/bore to the the pin C/L how close have you seen?

[Mark O'Neal]

Mark ,
I do not know how Mahle gets the pistons to live in the "new" Boss block but Ford says "no problem". 632 BB Chevy is another ugly one for coming way out of the bottom and chafing skirts especially with rod bolt clearance added.

They use a very short skirt, compared to Probe, anyhow and reduce the taper. because the skirt is about a half inch shorter.

Seems to work fine, I've just never messed around with Mahle pistons. Furriners...you know..

[Mark O'Neal]

so what is the worst people have seen?

That part is not much of an issue. The longer the skirt is the more taper you have in there and that area right under the land stack is quite a bit smaller than the gauge point. Then the diameter at the ring stack is .030 to .040 smaller than the max diameter. That's a lot of rattling around in there at BDC, even with thermal expansion. (a highly technical term there)

So, make the skirt as short as you can, and chamfer the bottom of the cylinders and you've done everything you can do.

[MadBill]

Line2line's 'wear to fit' abradable coatings should help with piston rattle: https://www.line2linecoatings.com/

[digger]

does the style of forging/skirt come into it e.g. CP have X vs round forging and JE have the FSR and round etc.

[Mark O'Neal]

does the style of forging/skirt come into it e.g. CP have X vs round forging and JE have the FSR and round etc.

Absolutely.

I have never paid much attention to any of them, but you can see what the result is when you pull them out.

[A853]

Line2line's 'wear to fit' abradable coatings should help with piston rattle: https://www.line2linecoatings.com/

Wow I appreciate that link! I'm probably gonna send the pistons off to them