340 High Compression Pistons
- Thread starter 70sublime340
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Are these pistons the same compression as the KB
Are these pistons the same compression ratio as the [KB243] units the Professor mentioned ??
Aren't these a little lighter and more compression at 65 cc ??
Keep
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" ] ???
Thank you Cuda Man - I just noticed the pistons you mentioned have 1.812 C/H and the SRP units I mentioned have 1.804 so thank you .
Running stock crank with Scat H beam rods.
Ok thank you
Yes I definitely want forged
Wyrmrider
Well-Known Member
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
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
nm9stheham
Well-Known Member
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).
Thank you Sir for all your info it was lesson the Professor teaching the pupil (Me ) again thanks Chris.
Hey Professor - I know these are Heavy but give me some figures with decking options !!!!
Thanks Chris
yellow rose
Overnight Sensation
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.
nm9stheham
Well-Known Member
Curious..... what head, and what is the mechanism in your case to hurt flow?
yellow rose
Overnight Sensation
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.
nm9stheham
Well-Known Member
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.
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 !!
nm9stheham
Well-Known Member
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?
I've been wanting to ask why a 340 in a Henry J.... just because?
nm9stheham
Well-Known Member
Thanks very much for the detailed explanation. That is good to know. And the last sentence is most amusing LOL
yellow rose
Overnight Sensation
Not to speak for him but he is running a gasser class.
Weight per cubic inch rules and Mainly because Im a Mopar fan and not a Chebby fan !!
Chevy = Boring to me
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