Quench could have been adjusted by compression height when they were cut. Most guys just order compression ratios and do not spec a compression height for the pistons to be done for the build.
Info wanted: how many miles on your ovals, what do you think?
- Thread starter Hot COCOAL
- Start date
If you change the height won't that change that ratio
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Yes it does. But only because it changes the Quench. If you decked the block 0.005" and shave the pistons 0.005" you've not changed a thing. Change from an "A" gasket to a "C" and you lose 1/2-3/4 point in compression and vise-versa.
I spec the pistons by chamber volumes. I then use that volume to ball-park the CR for a typical build. However, it is up to the builder to realize that mucking with the quench will change the CR.
In rough terms, each 0.005" change in the quench is worth about 1/4 point in compression.
I spec the pistons by chamber volumes. I then use that volume to ball-park the CR for a typical build. However, it is up to the builder to realize that mucking with the quench will change the CR.
In rough terms, each 0.005" change in the quench is worth about 1/4 point in compression.
new ones have same Compression height as the ones I pulled out...
the LBZ I did the finger pistons I got from fingers where ~.015" shorter ended up flush with a virgin deck block... ended up running grade A head gaskets with it..
the LMM pistons where flush on tear down with the deck. Bs came factory on this.. Cs went in back in November on a head gasket job..
IIRC As are ~.035" thick and Bs are ~.040" thick
nothing noticeable was wrong with the deck surface of the LMM on tear down... so far my machine job has turned into a bore, balance, polish crank, and main bore/hone job(with arp main studs) kind a pointless putting TTY main bolts back in when it needed machine work..
I still got my old split LBZ piston I could do a side by side with my LMM ones
7,000miles on new build so far. Mpg seams bout same as before.... Plan on getting to Firepunks dyno getting some runs on it.. Truck seams to Down shift more than before.. Engine hazes can only really see it at night.. In the headlights
Copied this from another thread, but I though the discussion would go better in here.
I've personally dealt with two engines with these pistons, and I've seen the same thing. For whatever reason, they tend to be dirtier and more difficult to get to clean up. They also seem to have a slightly rougher idle than normal pistons. I would be interested to hear if any others that run them have noticed the same thing.
I've personally dealt with two engines with these pistons, and I've seen the same thing. For whatever reason, they tend to be dirtier and more difficult to get to clean up. They also seem to have a slightly rougher idle than normal pistons. I would be interested to hear if any others that run them have noticed the same thing.
I've got an lmm we r trying to work all of the bugs out of and its the same way. It's pretty smokey epically off idle. Not black out the road but definately more then stock. Stock injectors and 68stg2r
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Is it possible these have a less efficient burn due to losing some of the swirl/mixing action with oval bowl shape?
You really shouldn't have a problem to get that setup to run clean. Is it a single truck or compounds?
Single turbo. I've been battling a boost leak but should have that remedied with a new egr tube. Egts seem to run warm too.
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That a good possibility..
I re mapped part throttle area on both MM3 dearie tq tables and timing tables... And it.. has cleaned up since miles have been put on it as well..
The stock pistons didn't soot anything up.. These do
about 180 miles total so far, with a base tune from mark. Slight haze at idle, and pretty smokey. 6480 af cam 100% injectors ported heads s366 t-4
Reduce the fuel pressure at idle and they seem to smooth out.
The key is to get on top of the turbo as soon as possible. This means reducing fuel pressure and taking out some timing in the transition areas of the map.
I've put 22,750 miles on mine since about mid January of this year. .040 over, 15.75:1 cast oval bowls. They have cleaned up after a few miles for sure. DP 72mm 4094, 75% over injectors, SoCal 6460 cam. Still a slight haze at idle though. They do seem a little rougher at idle than stock pistons, but then again I didn't build this engine to blend in with stock trucks. Can't really compare mileage due to so much else being changed during the build. If I had to do it again, I'd still go with these pistons without a doubt.
Update:
Said lmm in earlier post seems to be doing better all around. He had put about 7k on the truck already. Has picked up 2mpg since truck was put together. Just got the new egr tube in today and should be installed tomorrow. Overall very happy with piston choice.
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Said lmm in earlier post seems to be doing better all around. He had put about 7k on the truck already. Has picked up 2mpg since truck was put together. Just got the new egr tube in today and should be installed tomorrow. Overall very happy with piston choice.
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Mine seemed smokey at first too. Seemed like after a couple thousand miles it started to clean up and not bad at all now. I am happy with them and would buy them again.
Mine have always been smokey. Have around 14k miles one them. Switched from a Danville 72mm to a s475 and it went from being smokey on top end, but clean spool up, to smokey on low end but clean after spool up. Figured that would happen though which can be a easy fix. Running 80 overs.