Has anybody else done this?

I took my pistons down to the machine shop, and had 'em remove 20 thousandths off the top, and I'm going to run a 20 thousandths thicker headgasket.

Any thoughts or idea's on this?

This will be for my daily driver. About ~400RWHP.

Merrick

That might reduce compression. Granted the dome will be smaller and tighter but the head will be raised. Wouldn't that affect the flame travel?

Are you planning to have them recoated? I believe there's a stock hardening somewhere there that you'd need to resolve.

brnadon.

i would think for a 400 hp street truck you will miss the bottom end power. that will be a pretty good loss of compression. but in laredo i don't think winter starting will be a problem. mike

Mach 4.8's
Mad ECM
PDR Cam
PDR Head
Haisley's Head Studs
J.R. Twins (35-3B)
.020 Head Gasket
.020 Shaved Pistons
SBC FE Conv. Clutch
FASS w/-10 fuel line

We will be grossing up to 40,000Lbs.

What HP do you think this will put out?

With my COMP it did 546 on a 248c Dynojet, but I will be running w/o a COMP now.

Merrick

EDIT: No recoating, just some trick polishing, and dimpling. ;)

Ive heard of it done to a powerstroke. A local just has a drag truck thats got a powerstroke in it. Boosted up the power alot at least thats what he told me :rolleyes:

Merrick didn't take 20 thousandths off the top, he stuck put them in a vice and ran a handheld beltsander for 2 seconds on each piston [eyecrazy]

Sounds like something he would do.[laugh]

I heard he over torqued the bottom end to shorten the stroke???[laugh]

Would yall recommend .040 longer piston return springs to compensate?

Merrick

Merrick, just curious, how low are you figuring the compression? The commercial engines have pistons down to 15 to 1. They would keep the bowl shaped right instead of the deck lower.

Just wondering and learning... would stock pistons be surface hardened at all?

How much is off the head surface? How deep are the valves from the deck?

With a 20 thou over gasket, the low end suffers a bit. Removing 20 thou off the outside ring of the piston is no big deal, but adding the thicker gasket wil lower compression enough to feel it in the lower rpm range.

The stock pistons are cast. They are not hardened on the top.

Don~

Hey Don,

I'm glad you chimed in here.

I had .010 shaved off my head to get it back in shape.

The valves are factory depth.

HID,
I'm not sure of the C/R. Maybe somebody can help me out here.
I just really wanted to lower the C/R and space the valves farther from the piston, as the pistons were allready makin' love to the intake valves. (.020 or more, since after a .020 shave, there were still some indentions...)

I did not want to buy new pistons, that is why I shaved 'em.


I do not mind feeling less power in lower RPM, as long as this truck pulls good at 2,000-2,800.


Merrick

I misunderstood Merrick, I though you were trying to lower the compression. A slight drop will not make much difference. Like Don said, a little less torque till it gets boost.

Originally posted by Haulin_in_Dixie
I misunderstood Merrick, I though you were trying to lower the compression. A slight drop will not make much difference. Like Don said, a little less torque till it gets boost.

I'm not specificly trying to drop compression, although it is a welcomed side effect. I'm trying to male clearance for the valves.

I know with the turbo'd gassers, you wanna drop compression, and how this truck will be used, (street/strip), I wanted to relieve as much stress as I could. I don't mind loosing 20HP, if the motor will last me 10,000 more miles.

Merrick

Don't you mean, 10,000 miles, period?

Nope,

10,000 more miles...

I'm trying to build this motor to last at 400rwhp.

Merrick

So a total of 11,000 miles?[laugh]

Honestly, I'll be happy with 50,000, but if it went more, I'd be tickled to death.

Bottom line is, as long as *I* Break it, it's ok, but if something just wears out, I'll be upset. hehe.

Tyler,

Going to make it to IRP next month?

Merrick

http://www.dieseltruckresource.com/pics/data/500/21483shaved_and_sanded.jpg

Here's the piston after getting shaved, and some work with a piece of sandpaper.

Merrick

What's IRP? Depending on work (my boss is gonna be grateful enough to give us a week off) and when one of my friends is coming into town I might be able to make it.

Indianapolis Raceway Park...home of the Indy 500.

Coming up in June, and I can't make it. Already scheduled my vacation for that week, but I'm boing to Michigan!!

If it wasn't so far away, I'd drive down, but it's about 600 miles to Indy from where I'm going (but only 135 from home:confused: )

Chris

Merrick, about the 20 thou you are taking off. I am curious what results you will have. I'm not shure how much affect squinch clearance has on these motors. It is very important on gassers because it helps prevent detonation. Its one of the reasons most gassers have valve clearances machined into the top of the pistons. I don't think that it is going to cause you any piston bowl problems. Let us know how it runs.

Horace

Ahh. There's no way I can make that. I've only got a week off of work and that's already booked solid.

Horace,

I'm very excited as well.

Detonation isn't that bad on a diesel, compared to a gasser, but it is hard on parts... (My 12v with over 35* had some detonation under 2,000RPM,, :) )


I read in alldata that my motor has a 16.5:1 compression. If I have -.010 on the head, +.020 on the gasket, and -.020 on the pistons, what would the C/R be now?

I'm hoping with the Mach 4.8's, and Mad ECM, I'll be able to keep the boost low enough to not blow out a headgasket with head studs only, and no o-rings... Think I could do that? (35/14-3B/26)


Merrick

Are you guys shooting from the hip??your static C/R not much to do with running dynamic C/R......20 th will hardly do nothing,and if valve clearance is what you want ( I cant imagine you need that much kift with boosted eng.) I suggest a diff turbo set up rather then that high lift.
Gassers need that much lift and duration to get the flow going at high rpm,,,much much high then you CTD will ever see.

It's a PDR cam, but I think my valve springs couldn't handle as much boost as I was running.

My main goal was to not have to tear the motor down again anytime within the next couple of years.

Dropped C/R, lower EGT's, valve clearances. I don't really care that much, just as long as I don't crack the block, and don't bend a valve.


Merrick

At least you know how to tighten P-Pump Governor Springs down now, right Merrick?[laugh] [laugh] by the way..there's a dyno day on the 18th up here ..are you going to make it ?

Yup.

No problem.

Shut down solenoid diagnostics, and custom "keys",, no problem.
Idle issues? Not there yet, LOL.

I don't THINK that I will make it, but I'll give it a shot.

Merrick

Merrick....................Nothing has been said yet, but the head has been O ringed? Right!

The 400 HP thing is a shoein. That's really not much power in todays trucks. It will last as long as a stocker, you know that. I know my truck is a 96, but with 325K on the meter I still tow 15K all over the place. I'm at 306 on the dyno and have been there for 4 years. I took out the 370's, I was at 406, cause of to much smoke on the fiver.
Still, 400 is easy and will last from now on.

We shave the pistons .050 for the race engines and make 750 HP. Still they last.

Good luck.

..Preston..

Well,, the head was o-ringed, but because of the "lack of ability" here locally, and my need to get the head straight again, it is no longer o-ring'd, but still has the head studs.

What boost should I be good to? I'm running 40 exactly, with only the MAD ECM, and the Superchip tuner somehow squeezed in there. I do have A-1 Head studs (12mm) trqd to 125lbs.

The truck feels real nice, EGT's peak pretty high (1400-1600) but cool right back down to 1200-1300 once the turbo's light.

Merrick

I would say you will be good to 50 lbs of boost with the 12mm bolts at 125 lbs. Maybe ever a little more. Thats a good clamp on the gasket, If you know the head is flat, and the sequense was correct on the studs, you will be in good shape. I would feel a lot better if the head was O ringed.

Preston..