Piston to head clearance

V

VicS

Well-known Member

Location

SE Il.

• Apr 21, 2019

• #1

426 Allis Chalmers Diesel. How much clearance between the piston and head. We have .030 piston to top of sleeve and .005 head gasket. For .035 total. Is this enough for 3500 max rpm.

 

M

MikeJM

Member

• Apr 21, 2019

• #1

I always liked to be around.060". I tore one down that had about .057" clearance as measured, but between bore clearance and wear it had about .018" clearance when the piston would rock and it would just touch the head.

It s hard to say, might be enough, it might not. Only trouble is the only way to find out can get expensive.

We could roughly estimate how much the piston will grow with heat.

 

5

535353m

Member

• Apr 22, 2019

• #1

,005 thick head gasket,measure again ?????????????????????????

 

OP

OP

V

VicS

Well-known Member

Location

SE Il.

• Apr 22, 2019

• #1

Stainless o-rings in a groove in the sleeves. Maybe 7 or 8 at most.

 

5

535353m

Member

• Apr 22, 2019

• #1

no water?

 

OP

OP

V

VicS

Well-known Member

Location

SE Il.

• Apr 23, 2019

• #1

O-ring the oil. Then silicone the water. The water can just leak outside.

 

F

forty40

Member

• Apr 24, 2019

• #1

Automotive engines with relatively short strokes and 6-1/8" rods commonly run .030 piston to head. However, tractors with a much longer rod don't seem to always like that small of a clearance. My friend built a 466 converted to gas with .035 and the pistons hit the head after a run. He trimmed the pistons for .040 which solved the problem.

 

5

535353m

Member

• Apr 24, 2019

• #1

many engine (tractors) builders use .050 -- .065 clearance

 

M

molinepuller

Member

• Apr 24, 2019

• #1

If that's not to your liking you can always machine more off pistons.

 

OP

OP

V

VicS

Well-known Member

Location

SE Il.

• Apr 24, 2019

• #1

Thanks guys for the replies. I'm going to go for it. Supposed to be a kinetic boost at .040 or less.

 

5

535353m

Member

• Apr 25, 2019

• #1

let us know how it works

 

OP

OP

V

VicS

Well-known Member

Location

SE Il.

• Apr 30, 2019

• #1

Chickened out gave it .005 more.

 

Destroked 450

Well-known Member

Location

Harned, Ky

• Apr 30, 2019

• #1

Unrelated to pulling but my 5.9 Cummins has around .037 piston to head clearance, mine's governed to 3200 rpm, their min spec is .029

 

5

535353m

Member

• Apr 30, 2019

• #1

how do you add.005 ???????????????? that is not much,

 

F

forty40

Member

• Apr 30, 2019

• #1

(quoted from post at 04:00:53 04/30/19) Chickened out gave it .005 more.

Click to expand...

You won't be sorry.

 

OP

OP

V

VicS

Well-known Member

Location

SE Il.

• Apr 30, 2019

• #1

The pistons were about 3/8 to long to start with. So just have the machine shop take another .005 off.

 

B

buickanddeere

Well-known Member

• Apr 30, 2019

• #1

As close as possible without the piston touching the head .

 

5

535353m

Member

• Apr 30, 2019

• #1

how many rpms?

 

OP

OP

V

VicS

Well-known Member

Location

SE Il.

• May 1, 2019

• #1

Pump set on 3500. Should be optimal for cam. But going to stay at 3000 for a while.

 

5

535353m

Member

• May 1, 2019

• #1

bearings have wear,rods strectch,pistons "grow" with heat and tip,all take away clearances, !!!!!!!!!!!!! Tractors lug down,and cause issues,race cars run optimuim rpms mostly,big difference.For the most part tractors use more clearance,cars not so much in performance situations.Tight causes more heat,propably not much of an issue with short pulls,but back to back classes on a 90 degree,100 % humitity day is a problem.Use extra good fuel.