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

 

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

 

Sounds like something he would do.

 

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

 

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.