need help

[i_pooped]

i had a head milled and i used a erling head gasket and when i started the car it has making a loud tap noise so i tore the engine back down to find this..





could i get a thicker head gasket or should i get a new head????
its only on cylinder 6 and a lil on the head on cylinder 5

[e30davie]

Did you rotate the engine by hand before you started it?

And when you pulled it down did you check if you had the cam timing correct?

[i_pooped]

i double check timing before i started and before i tore it down and it was in time

[digger]

that's not a cam timing issue, so how much was milled off the head? im wondering what kind of damage it could have done to bearings/rod or something depends how hard of a kiss it was.

you could use a 1mm thicker MLS gasket atleast that would give you 1mm clearance which is about what you want on a static measurement

[i_pooped]

i dont know, is there a way to tell

[digger]

whats the head thickness at each corner?

[i_pooped]

its 4 15/16 inches at all 4...... sound right?

[digger]

4.9375" sounds wrong to me. did you measure the parallel distance with a suitable tool?



i measured a head ive got here with a set of vernier calipers and it was 125.04 mm smack where it should be

what crank is in the bottom end?

[i_pooped]

the tool i used wasnt very accurate so i will get a different tool today to remeasure. its the 2.5 bottom

[Kershaw]

Just so I understand what I'm looking at, the piston hit the actual cylinder head?

[i_pooped]

yea its heating the head but only on cylinder 6 and a lil on 5

[i_pooped]

123.8mm

[i_pooped]

so is it trash or will a .3mm thicker head gasket work????

[digger]

123.8mm

That makes sense, its 1.3mm thinner than the original spec of 125.1mm
i.e. 125.1 - 123.8 = 1.3mm

Nominal piston to head clearance is 1.25mm for a 1.75mm gasket
i.e. 75/2 + 135 + 34.2 = 206.7mm (stack height = crank throw + rod length + piston compression height) )

Piston sits 206.7-206.2 = 0.5mm above deck (block deck height ive measured is 206.2)

Gasket 1.75mm less amount piston sits above block (0.5mm) = 1.25mm

So you have machined all the clearance away

So you need an extra 1.00-1.10mm thicker gasket (2.8mm / 0.110” total) which means you need a custom MLS as the replacement thicker OEM is 2.05mm thick (+0.3)

assuming there are no other issues that resulted

[i_pooped]

ok thanks