How much is too much PTW?

cityredneck

cityredneck

Diesel Mechanic
So there was a mishap at the machine shop with a block for a drag truck build. It is a 12 valve and will stay around 1000-1200hp. +.020 mahle motorsport cast pistons .150" fly cuts, 13mm pump w 5x.025s. Single 80mm charger.. wet motor. Will see the dragstrip and the occasional 10 mile drive to a car show

PTW was to be set at .010"... in the end it wound up at .0135". My question is, go ahead and run it, or will we run into issues. w To much rocking, blowby even with rings set correctly? can this prematurely wear the rings?

Time is a factor here. Cam tunnel is already done. Would rather not start over or sleeve unless absolutely necessary.

Thoughts?

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That’s a lot, I think I’m running .005 PTW stock is around .003” my Motor had nitrous in mind when I built it.




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I’m almost in the same exact spot, I ordered D&J pistons for a STD bore 6.7 and they were .013 PTW right out of the box. Drew claims .012-.014 is what he likes to see and has ran them as loose as .015-.016 without seeing any issues. Not sure if that’s just for his pistons or if that’s all of them in general. I’m sure they all grow differently. So if it makes you feel any better, after my torque plate hone is done mine will be ran about .0145. Lol
 
24vppump59 said:
I’m almost in the same exact spot, I ordered D&J pistons for a STD bore 6.7 and they were .013 PTW right out of the box. Drew claims .012-.014 is what he likes to see and has ran them as loose as .015-.016 without seeing any issues. Not sure if that’s just for his pistons or if that’s all of them in general. I’m sure they all grow differently. So if it makes you feel any better, after my torque plate hone is done mine will be ran about .0145. Lol
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“Loose” just how you like your woman
 
Cflanery88 said:
“Loose” just how you like your woman
Click to expand...

Ewww


Sean,
.015" is relativity normal in the performance world, but break in becomes an important issue. An engine dyno would be ideal.

FWIW, I wouldn't expect a "street" driven engine to run that kind of PTW. Not for very long anyway.
 
0.0135" sounds like a solid block forged piston type engine setup. We just threw an engine together for the Junker with Mahle Cast Performance Pistons on a standard bore and ended up around 0.011" piston to wall on #5 and #6 and closer to 0.01025" for #1 thru #4 bores. I was surprised how long it took for the rings to seat in and slow down the blow by, like several dyno pulls on a hot engine after 2 complete quarter mile passes on the fresh setup.

If you're going to run it really hot all the time, it'll probably be fine but it's bigger than we've ever experimented with on a wet block with cast pistons.
 
I decided to just bore it to .040 over and start fresh. Pistons will be here tomorrow and then we can finish hone and reassemble tomorrow night, how fun. I dont feel comfortable with it for this guys application. 2nd ring was total seal but just going to use standard ring since it's going to be getting bored again. If it were a dedicated puller or higher hp drag ONLY I would probably just run it. But he will take it on the street at times. I dont feel like worrying about the walls being beat up a year from now and being in the same predicament

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