what happens if you use too thin a head gasket?

**Michael2** · 12th September 2022, 08:50 PM

I spun a big end bearing the other week, and have rebuilt a 300Tdi engine with new STD crank and pistons. I had to use a couple of the old oil rings though after snapping them.

There was piston protrusion on this engine, which there wasn't on my previous, but I didn't measure it properly. I went for a 3 hole gasket and now that it's assembled it has a harsh noise on acceleration (haven't driven it yet, just revving it in the driveway). I suspect I might have had to use a 0-hole gasket.

Can someone confirm that this would be a symptom of using a thinner head gasket? Or should I look elsewhere?

Thanks in advance, Michael

**johnp38** · 13th September 2022, 09:50 AM

on my Td5 the 3 hole is the thicker gasket, so just a quick google and it seems tdi are the same.

so 3 hole good choice with piston protrusion. with thinner gasket pistons may bump into head/valves so you don't want to go thinner unless you measured the piston protrusion and want every miniscule bit of compression gain.

I don't know jack about tdi but is the crank, cam and fuel pump all 'timed' to how they should be? maybe fuel not injecting at right point or valve train not in sync with crank?

double check the basics

**loanrangie** · 13th September 2022, 09:51 AM

Pistons would come in contact with the valves, was it a new head or did you have yours skimmed ?

**Michael2** · 13th September 2022, 01:45 PM

Originally Posted by johnp38

on my Td5 the 3 hole is the thicker gasket, so just a quick google and it seems tdi are the same.

so 3 hole good choice with piston protrusion. with thinner gasket pistons may bump into head/valves so you don't want to go thinner unless you measured the piston protrusion and want every miniscule bit of compression gain.

I don't know jack about tdi but is the crank, cam and fuel pump all 'timed' to how they should be? maybe fuel not injecting at right point or valve train not in sync with crank?

double check the basics

0-hole is the thickest head gasket for a 300Tdi Suited to 0.81-0.9mm protrusion. I took the head off and it was 0.8 witha feeler gauge, so I went for the thicker gasket.

The timing was done with the motor out of the car, so visualisation was good. I double checked the pin timing with a DTI and it was 1.55mm lift.

The noise still seemed to be there, but did quieten once the car warmed. I wonder how much is my imagination.

**Michael2** · 13th September 2022, 01:47 PM

Originally Posted by loanrangie

Pistons would come in contact with the valves, was it a new head or did you have yours skimmed ?

Turners head, 2 years old.

**loanrangie** · 13th September 2022, 03:00 PM

Originally Posted by Michael2

Turners head, 2 years old.

so not machined at all ? you'll need the thickest gasket then.

**350RRC** · 13th September 2022, 09:05 PM

Originally Posted by loanrangie

so not machined at all ? you'll need the thickest gasket then.

Or two thin ones?

That'd be a legendary bodge.

DL

**scarry** · 14th September 2022, 07:54 AM

Originally Posted by 350RRC

Or two thin ones?

That'd be a legendary bodge.

DL

Done that a few times on large open drive refrigeration compressors,no issues

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