340 High Compression Pistons

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nm9stheham said:
Yeah I looked at the SRP's and the CH is .036" lower than a standard 340 piston so that is not promising. Same goes for the Ross pistons. I'll keep looking. BTW, do you have to use stock rods and crank?

Some lighter flattops that would work are the KB 243's; usable off-the-shelf. The 1.840" CH is the same as the stock 340 pistons. Mill the block's deck to a deck height of 9.565"; IIRC that is quite safe but check that out. Then the KB243 pistons will stick up .053" above the deck and with the .027" head gasket, you will be at the 11.8-11.9 SCR range. The KB243 weight of 720 grams piston + pin weight is a lot lighter than the stock which is around 873 grams piston + pin. You'll take weight off the crank to balance these.
These KB's are hypereutectics, not forged, so keep that in mind.

And Hughes lists some Icon FHR's that would work and are forged, but they list a piston weight of 724 grams. I cannot say if they are listing piston only or piston + pin weight. These are not in the online catalog so that weight number that bears checking. (I think 70aarcuda knows but a quick call would do it.) The eyebrows are 7 cc's so the CR will be a few tenths lower.

BTW, I recall another piston MFR being mentioned that does custom variations for a lot less than $1000. Dang, wish I could remember the name.[/QUO

Thank you for the info - I need to PM you and lets chat , thank you Chris
Click to expand...
 
70aarcuda said:
Jegs has those FHR pistons for the small blocks...

United Engine Machine IC9975.040: Chrysler 340ci FHR Forged Pistons Flat Top 2V | JEGS
I believe you are looking for 4.080

https://www.uempistons.com/catalogs/icon_catalog.pdf

on page 68 of catalog......piston weight 606 pin weight 118 grams
Click to expand...

Are these pistons the same compression as the KB
70aarcuda said:
Jegs has those FHR pistons for the small blocks...

United Engine Machine IC9975.040: Chrysler 340ci FHR Forged Pistons Flat Top 2V | JEGS

I believe you are looking for 4.080

https://www.uempistons.com/catalogs/icon_catalog.pdf

on page 68 of catalog......piston weight 606 pin weight 118 grams
Click to expand...

Are these pistons the same compression ratio as the [KB243] units the Professor mentioned ??
 
nm9stheham said:
The man heard his name called LOL... A ton cheaper, and I bet even with the block decked, still a bunch cheaper.
Click to expand...
Aren't these a little lighter and more compression at 65 cc ??


Keep
70aarcuda said:
Jegs has those FHR pistons for the small blocks...

United Engine Machine IC9975.040: Chrysler 340ci FHR Forged Pistons Flat Top 2V | JEGS

I believe you are looking for 4.080

https://www.uempistons.com/catalogs/icon_catalog.pdf

on page 68 of catalog......piston weight 606 pin weight 118 grams
Click to expand...

Screenshot_2018-07-08-22-15-14.png
 
nm9stheham said:
The man heard his name called LOL... A ton cheaper, and I bet even with the block decked, still a bunch cheaper.
Click to expand...

Keep
nm9stheham said:
Yeah I looked at the SRP's and the CH is .036" lower than a standard 340 piston so that is not promising. Same goes for the Ross pistons. I'll keep looking. BTW, do you have to use stock rods and crank?

Some lighter flattops that would work are the KB 243's; usable off-the-shelf. The 1.840" CH is the same as the stock 340 pistons. Mill the block's deck to a deck height of 9.565"; IIRC that is quite safe but check that out. Then the KB243 pistons will stick up .053" above the deck and with the .027" head gasket, you will be at the 11.8-11.9 SCR range. The KB243 weight of 720 grams piston + pin weight is a lot lighter than the stock which is around 873 grams piston + pin. You'll take weight off the crank to balance these.
These KB's are hypereutectics, not forged, so keep that in mind.

And Hughes lists some Icon FHR's that would work and are forged, but they list a piston weight of 724 grams. I cannot say if they are listing piston only or piston + pin weight. These are not in the online catalog so that weight number that bears checking. (I think 70aarcuda knows but a quick call would do it.) The eyebrows are 7 cc's so the CR will be a few tenths lower.

BTW, I recall another piston MFR being mentioned that does custom variations for a lot less than $1000. Dang, wish I could remember the name.
Click to expand...

Sorry just noticed your statement , the SRP have 1.804 C/H and the Icons Cuda man mentioned have 1.812 C/H !!!!! What would these be with [ 0.27 MLS gaskets & block decked to 9.565" ] ???
 
1Badcolt said:
Keep


Sorry just noticed your statement , the SRP have 1.804 C/H and the Icons Cuda man mentioned have 1.812 C/H !!!!! What would these be with [ 0.27 MLS gaskets & block decked to 9.565" ] ???
Click to expand...


Im running the stock steel crank
I sold the factory rods and pistons .
 
nm9stheham said:
Yeah I looked at the SRP's and the CH is .036" lower than a standard 340 piston so that is not promising. Same goes for the Ross pistons. I'll keep looking. BTW, do you have to use stock rods and crank?

Some lighter flattops that would work are the KB 243's; usable off-the-shelf. The 1.840" CH is the same as the stock 340 pistons. Mill the block's deck to a deck height of 9.565"; IIRC that is quite safe but check that out. Then the KB243 pistons will stick up .053" above the deck and with the .027" head gasket, you will be at the 11.8-11.9 SCR range. The KB243 weight of 720 grams piston + pin weight is a lot lighter than the stock which is around 873 grams piston + pin. You'll take weight off the crank to balance these.
These KB's are hypereutectics, not forged, so keep that in mind.

And Hughes lists some Icon FHR's that would work and are forged, but they list a piston weight of 724 grams. I cannot say if they are listing piston only or piston + pin weight. These are not in the online catalog so that weight number that bears checking. (I think 70aarcuda knows but a quick call would do it.) The eyebrows are 7 cc's so the CR will be a few tenths lower.

BTW, I recall another piston MFR being mentioned that does custom variations for a lot less than $1000. Dang, wish I could remember the name.
Click to expand...
Running stock crank with Scat H beam rods.
 
forged are you thinking spray? boat, motorhome, truck, sprint car, blower
for most everythhing hypers work fine
whatever
find a combo with tight quench that gives the cr you are looking for for the fuel you have available
was it this thread that showed a circular dish?
and I said send them back
a circular dish can work with a wedge head with good fuel and higher rpm-higher compression they can make the same HP
for a usual street build a D-Dish or a Dish that matches the combustion chamber works better, more fuel tolerant and will show more torque , less advance and work better with lower compression
On our high boost engine we had too much squish area and cut it back to a larger shallower dish but that is not usually the case
 
Wyrmrider said:
forged are you thinking spray? boat, motorhome, truck, sprint car, blower
for most everythhing hypers work fine
whatever
find a combo with tight quench that gives the cr you are looking for for the fuel you have available
was it this thread that showed a circular dish?
and I said send them back
a circular dish can work with a wedge head with good fuel and higher rpm-higher compression they can make the same HP
for a usual street build a D-Dish or a Dish that matches the combustion chamber works better, more fuel tolerant and will show more torque , less advance and work better with lower compression
On our high boost engine we had too much squish area and cut it back to a larger shallower dish but that is not usually the case
Click to expand...

No spray
Drag motor
Henry J Gasser.
 
1Badcolt said:
Sorry just noticed your statement , the SRP have 1.804 C/H and the Icons Cuda man mentioned have 1.812 C/H !!!!! What would these be with [ 0.27 MLS gaskets & block decked to 9.565" ] ???
Click to expand...
Ooops, DANG, I missed the 1.812 CH on the FHR's; very sorry about that; it looked like a great choice. If you did the .027 gasket and the 9.565" deck height, then these FHR's would pop up only .025" above deck. In that case, there would not be much quench with the piston-to-head gap up at .062". Static CR would be down to 10.6. S

If you could mill the deck to 9.535" (and I DON"T know if that is good or safe so check on that) then SCR would rise to 11.6. You would get your tight quench gap back too. (At a gap of .032" you gotta make sure EVERY dimension on every hole is right!)

I tend to agree on the forged being good for your application. But FWIW, I rallied a Mitsubishi 2.6L with 14 lbs boost for a long time; that was around 65-70 HP per hole. I used both hypers and forged and never had a problem either way, I only had detonation once and corrected it immediately. (I tired to push to 17 lbs boost.... no dice.) If you keep the dimensions right and the engine out of detonation, then the hypers may work for you. Your HP is not going to be super-duper high; I assume you can use race gas.

Other than that, its back to some custom piston, the KB's, or a traditional pop-up. I personally would strive to keep a tight quench gap, which probably nixes the pop-ups and says to use flat-tops; it is a good aid to fighting detonation plus helps combustion efficiency (the 'swirl' concept before 'swirl heads' came out LOL).
 
nm9stheham said:
Ooops, DANG, I missed the 1.812 CH on the FHR's; very sorry about that; it looked like a great choice. If you did the .027 gasket and the 9.565" deck height, then these FHR's would pop up only .025" above deck. In that case, there would not be much quench with the piston-to-head gap up at .062". Static CR would be down to 10.6. S

If you could mill the deck to 9.535" (and I DON"T know if that is good or safe so check on that) then SCR would rise to 11.6. You would get your tight quench gap back too. (At a gap of .032" you gotta make sure EVERY dimension on every hole is right!)

I tend to agree on the forged being good for your application. But FWIW, I rallied a Mitsubishi 2.6L with 14 lbs boost for a long time; that was around 65-70 HP per hole. I used both hypers and forged and never had a problem either way, I only had detonation once and corrected it immediately. (I tired to push to 17 lbs boost.... no dice.) If you keep the dimensions right and the engine out of detonation, then the hypers may work for you. Your HP is not going to be super-duper high; I assume you can use race gas.

Other than that, its back to some custom piston, the KB's, or a traditional pop-up. I personally would strive to keep a tight quench gap, which probably nixes the pop-ups and says to use flat-tops; it is a good aid to fighting detonation plus helps combustion efficiency (the 'swirl' concept before 'swirl heads' came out LOL).
Click to expand...
Thank you Sir for all your info it was lesson the Professor teaching the pupil (Me ) again thanks Chris.
 
nm9stheham said:
Ooops, DANG, I missed the 1.812 CH on the FHR's; very sorry about that; it looked like a great choice. If you did the .027 gasket and the 9.565" deck height, then these FHR's would pop up only .025" above deck. In that case, there would not be much quench with the piston-to-head gap up at .062". Static CR would be down to 10.6. S

If you could mill the deck to 9.535" (and I DON"T know if that is good or safe so check on that) then SCR would rise to 11.6. You would get your tight quench gap back too. (At a gap of .032" you gotta make sure EVERY dimension on every hole is right!)

I tend to agree on the forged being good for your application. But FWIW, I rallied a Mitsubishi 2.6L with 14 lbs boost for a long time; that was around 65-70 HP per hole. I used both hypers and forged and never had a problem either way, I only had detonation once and corrected it immediately. (I tired to push to 17 lbs boost.... no dice.) If you keep the dimensions right and the engine out of detonation, then the hypers may work for you. Your HP is not going to be super-duper high; I assume you can use race gas.

Other than that, its back to some custom piston, the KB's, or a traditional pop-up. I personally would strive to keep a tight quench gap, which probably nixes the pop-ups and says to use flat-tops; it is a good aid to fighting detonation plus helps combustion efficiency (the 'swirl' concept before 'swirl heads' came out LOL).
Click to expand...

Hey Professor - I know these are Heavy but give me some figures with decking options !!!!
Thanks Chris
 
nm9stheham said:
Ooops, DANG, I missed the 1.812 CH on the FHR's; very sorry about that; it looked like a great choice. If you did the .027 gasket and the 9.565" deck height, then these FHR's would pop up only .025" above deck. In that case, there would not be much quench with the piston-to-head gap up at .062". Static CR would be down to 10.6. S

If you could mill the deck to 9.535" (and I DON"T know if that is good or safe so check on that) then SCR would rise to 11.6. You would get your tight quench gap back too. (At a gap of .032" you gotta make sure EVERY dimension on every hole is right!)

I tend to agree on the forged being good for your application. But FWIW, I rallied a Mitsubishi 2.6L with 14 lbs boost for a long time; that was around 65-70 HP per hole. I used both hypers and forged and never had a problem either way, I only had detonation once and corrected it immediately. (I tired to push to 17 lbs boost.... no dice.) If you keep the dimensions right and the engine out of detonation, then the hypers may work for you. Your HP is not going to be super-duper high; I assume you can use race gas.

Other than that, its back to some custom piston, the KB's, or a traditional pop-up. I personally would strive to keep a tight quench gap, which probably nixes the pop-ups and says to use flat-tops; it is a good aid to fighting detonation plus helps combustion efficiency (the 'swirl' concept before 'swirl heads' came out LOL).
Click to expand...

Sorry forgot photo here it is ####

Screenshot_2018-07-09-08-17-33.png
 
yellow rose said:
Even that piston calls out to be out of the deck .018 and that probably isn't enough. I'm at a skosh over 11:1 with a small dome and I'm .045 out of the hole. I did leave my heads at 68cc's because if I took much more off I'd start hurting flow.
Click to expand...
Curious..... what head, and what is the mechanism in your case to hurt flow?
 
nm9stheham said:
Curious..... what head, and what is the mechanism in your case to hurt flow?
Click to expand...

Any OE style chamber. Even the chamber used in the W-5 head is very sensitive to cutting the decks. In a perfect world, you would have a nice, clean .125 wide top cut all round the valve. As you start removing the material you start encroaching on the top cut. The closed chamber W-5 hated that and it's a ***** to correct once you do it. As your intake valve gets bigger, the effect is more noticeable.

That's why I don't like milling the open chamber head down to remove the open side. I've found once you get the quench pad below .060 deep (which is about .040 off depending on the castings) you start getting issues.

I was working with a guy who just thought getting rid of that side of the chamber was all that. So I went home an pd brought back two matching heads. One with the chamber milled the other not.

We didn't even measure flow. We just watched the manometer and listened to the flow. A deaf, dumb and blind kid could hear the difference.

After that, he gave up on that and found other ways to irritate me to no end.
 
1Badcolt said:
Sorry forgot photo here it is ####
Click to expand...
These L2316F's have the same CH as the KB's and are only 0.5 cc larger on the eyebrow volume. So if you set them up the same as the KB's (like in post #87), they SCR would be < 0.1 point less.

And just one thing to point out that goes along with post #68, just 3 cc's variation will change CR by a full half point when you are up in the 11-12:1 SCR range. So the measurements and everything become pretty critical, and the paper computations can be off by 0.2 pretty easily. Things like truly flat and even decks, a true crank, and so forth become critical to consitent cylinder-to-cylinder parameters. The one good thing is that the aftermarket performance pistons/rods/rings/etc. are pretty consistent to their spec's, with decent tolerances.
 
yellow rose said:
Any OE style chamber. Even the chamber used in the W-5 head is very sensitive to cutting the decks. In a perfect world, you would have a nice, clean .125 wide top cut all round the valve. As you start removing the material you start encroaching on the top cut. The closed chamber W-5 hated that and it's a ***** to correct once you do it. As your intake valve gets bigger, the effect is more noticeable.

That's why I don't like milling the open chamber head down to remove the open side. I've found once you get the quench pad below .060 deep (which is about .040 off depending on the castings) you start getting issues.

I was working with a guy who just thought getting rid of that side of the chamber was all that. So I went home an pd brought back two matching heads. One with the chamber milled the other not.

We didn't even measure flow. We just watched the manometer and listened to the flow. A deaf, dumb and blind kid could hear the difference.

After that, he gave up on that and found other ways to irritate me to no end.
Click to expand...
Cambell Enterprises
Is going to get a custom set done for me ordering next I just cant spend $400 + for those Heavy traditional slugs when a custom lite weight set is only $1000 so here we go !!
 
Good deal! I'd like to see what you end up with... something new to learn.

I've been wanting to ask why a 340 in a Henry J.... just because?
 
yellow rose said:
Any OE style chamber. Even the chamber used in the W-5 head is very sensitive to cutting the decks. In a perfect world, you would have a nice, clean .125 wide top cut all round the valve. As you start removing the material you start encroaching on the top cut. The closed chamber W-5 hated that and it's a ***** to correct once you do it. As your intake valve gets bigger, the effect is more noticeable.

That's why I don't like milling the open chamber head down to remove the open side. I've found once you get the quench pad below .060 deep (which is about .040 off depending on the castings) you start getting issues.

I was working with a guy who just thought getting rid of that side of the chamber was all that. So I went home an pd brought back two matching heads. One with the chamber milled the other not.

We didn't even measure flow. We just watched the manometer and listened to the flow. A deaf, dumb and blind kid could hear the difference.

After that, he gave up on that and found other ways to irritate me to no end.
Click to expand...
yellow rose said:
Any OE style chamber. Even the chamber used in the W-5 head is very sensitive to cutting the decks. In a perfect world, you would have a nice, clean .125 wide top cut all round the valve. As you start removing the material you start encroaching on the top cut. The closed chamber W-5 hated that and it's a ***** to correct once you do it. As your intake valve gets bigger, the effect is more noticeable.

That's why I don't like milling the open chamber head down to remove the open side. I've found once you get the quench pad below .060 deep (which is about .040 off depending on the castings) you start getting issues.

I was working with a guy who just thought getting rid of that side of the chamber was all that. So I went home an pd brought back two matching heads. One with the chamber milled the other not.

We didn't even measure flow. We just watched the manometer and listened to the flow. A deaf, dumb and blind kid could hear the difference.

After that, he gave up on that and found other ways to irritate me to no end.
Click to expand...
Thanks very much for the detailed explanation. That is good to know. And the last sentence is most amusing LOL
 
nm9stheham said:
Good deal! I'd like to see what you end up with... something new to learn.

I've been wanting to ask why a 340 in a Henry J.... just because?
Click to expand...
Weight per cubic inch rules and Mainly because Im a Mopar fan and not a Chebby fan !!
 
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