Pistons and Rings - opinions? Stay calm..

[Sniper]

For what you get?  Not ridiculous at all.  But what most of us don't need, want maybe but need?  no.  A 25% weight reduction in the rod and piston combo along with much stronger rods, much better pistons and much better rings.  You'd be hard pressed to match that with any other engine.

 

A gen II Hemi can be lightened up a lot with aluminum rods, not stronger than stock but lots lighter.  At the cost of $1000+, each.  And those have a finite lifespan. That's the closest weight loss comparison I can think of.

[Bryan]

9 hours ago, thebeebe5 said:

That sounds like ridiculous money... ?

Do you remember what the JE pistons cost you?  I'm guessing about $120-$150 a piston?  Back then Ross was giving me a rough worst case of $900 for 6.

[James_Douglas]

Like I said above, I am only considering this for the big heavy 1947 Desoto that we use as our daily driver. Do remember that we do not own a modern car. Although after 45 years, I am considering buying one...

 

The 1949 Convertible has a basic 251 rebuild and that is just fine for a car that goes to shows and Sunday drives.

 

Since I have documented the pressure drop in the big car over the last 15 years and have confirmed, by talking to a couple of others who experienced the same thing; doing things to slow that pressure drop is warranted in this case.

 

I can tell you that when I had the interior out except for the front seat when I first purchased the Desoto Suburban, with its old and tired engine, there was a marked difference pulling up Waldo Grade to the Golden Gate Bridge. The interior parts added up to about 400 pounds. That was enough to effect the power to weight ratio and made a very big difference.

 

I do not think that many on this forum understand how close these cars are to "edge" power and weight wise. Add 500 to 1000 pounds to your car and see how it goes up a hill. You would be surprised. My convertible with the same engine goes up a hill with ease, albeit at 750 to 1000 pounds lighter.

 

So, is spending $4500 on rods and pistons too much? Perhaps, but the cost of tearing the front end apart, and the steering, to put in a V8 is a lot more costly not to mention the work involved.

 

Food for thought.

 

Merry Christmas all.  James

[Bryan]

12 minutes ago, James_Douglas said:

Like I said above, I am only considering this for the big heavy 1947 Desoto that we use as our daily driver. Do remember that we do not own a modern car. Although after 45 years, I am considering buying one...

 

 

I was considering what to do instead of buying a new car, but my 2015 Toyota Corolla with 113K still has plenty of miles left. Did some research on an off day. Seems like late 60s to about 72 is a good range without computers, emission controls and sensors.  I think around 67 the basic shoulder belts and collapsible steering were required.  Only thing to watch is that early 70s some makes had rust problems.  With research a basic reliable small V8 with proven transmission might be one option.   Or a Ford 240 six or Dodge 225 slant.  Some models of cars have a lot more aftermarket body, floor, fender panels available.

[wayfarer]

$4500 is a pile-o-money. We don't spend that much on a Hemi build.

Forged pistons should be in the $100 each range and aftermarket rods not much more so the remainder would appear to be labour.

I'd like to get that shop rate.....

 

[Sniper]

Hemi stuff is probably "off the shelf"  none of this is, all custom made for a tiny, virtually non-existent market.

 

Just so we all know what we are discussing, here's the stock vs custom assembly in the picture.

[47 dodge 1.5 ton]

1 hour ago, wayfarer said:

$4500 is a pile-o-money. We don't spend that much on a Hemi build.

Forged pistons should be in the $100 each range and aftermarket rods not much more so the remainder would appear to be labour.

I'd like to get that shop rate.....

 

Well— my thought as being a machinist in past years that I couldn’t make a piston in a couple hours with a manual lathe & Mill. There are tight tolerances that must be held. Maybe I’m slow, but without a CNC I would loose my butt on small runs, in addition to sourcing good quality material to start with. 

[thebeebe5]

16 hours ago, Bryan said:

Do you remember what the JE pistons cost you?  I'm guessing about $120-$150 a piston?  Back then Ross was giving me a rough worst case of $900 for 6.

$670 for the six pistons. 

[FarmerJon]

Anyone know about how much the factory style cast Pistons weigh?

[Sniper]

23 minutes ago, FarmerJon said:

Anyone know about how much the factory style cast Pistons weigh?

12 lbs, each

 

Seriously though, my 55 FSM says 462-466 grams (std thru .060 over), each. Which is right at 1 lbs per piston.  Not including pins.

[FarmerJon]

So by my Christmas morning napkin math, roughly accounting for difference in bore size, a 3.25" Piston of same design would be about 5% lighter than stock. With better rings, better squish, and likely higher compression.

[Sniper]

I wonder if the squish would change much.  The stockers are flattops.  I believe the squish would be set by the deck height, the combustion chamber design and the head gasket thickness.

 

Set the deck height to zero by decking the block, assume true flat top piston that doesn't rock and protrude above the deck. 

 

Use a head that has a flat in the cylinder bore area.  Not sure if stockers have this, Edgy does though.

 

Use a head gasket less than .050" and more than .035" thick.  Not sure what the currently available head gasket thicknesses are.  I did find some info from Best on theirs, the 23" head gasket has a nominal thickness of .080" and a compressed thickness  of .052" =/- .002".  A hair too thick, imo.  Wonder how hard it would be to get them to run off one with a .070" nominal thickness?  I guess you could deck the block an additional .005" to 0.010" below zero deck instead making the pistons a very small popup type.

 

 

Edited December 25, 2021 by Sniper

[FarmerJon]

Bee can correct me, but I was under the impression he had the Pistons pop up above deck.

[Bryan]

Wonder what a slight dome in this area would do?  Seen wilder stuff on their site.

[Bryan]

Got to thinking (for a change). Might be great for compression stroke but a dome would take the side force of the combustion force wave.

[47 dodge 1.5 ton]

I believe there would be considerable reduction of force to the piston during combustion if that area was utilized, creating loss. Would make a nice R&D project though. I have seen pistons installed .040” proud to the block face on these. The flow in the head valve area would be the most effective gains aside from the ports.

[Bryan]

31 minutes ago, 47 dodge 1.5 ton said:

I believe there would be considerable reduction of force to the piston during combustion if that area was utilized, creating loss. Would make a nice R&D project though. I have seen pistons installed .040” proud to the block face on these. The flow in the head valve area would be the most effective gains aside from the ports.

If the dome was too radical I think it would have a major effect. Otherwise all these racer experts would have already done it. Maybe a slight dome would be okay. 

[Sniper]

If the pistons stands proud then a partial inverse dome on the valve side of the piston might make sense, IOW it's a ramp not a dome..  The flats to the left of the red dome are all the squish you'll ever need. 

 

 

[FarmerJon]

Lots of parallels to flathead Ford and Harley hotrod tech.

The dome like Bryan illustrated would be of primary interest for increasing compression, but would serve as a wall to incoming fuel/air mixtures, and would likely inhibit flame travel.

Sniper's ramp would likely increase flow, but possibly reduce compression, unless you balanced out the pop up/ ramp with a reduction in the heads transfer slot.