Head Gasket (upgrade?)

[cspatter]

I have a small oil leak from the front of my head. I'm going to assume it is head gasket as this is an original no-mod engine. My question is will my engine benefit from a thicker head gasket with the stock components? I plan on also purchasing arp head studs with this project. I have seen TOMEI gaskets from 1 to 1.5mm, Nissmo at .6 and Kameari from 1 to 2mm. Please chime in with your thoughts.

[datzenmike]

Check the 4 10mm bolts around the front of the head/timing cover for tightness. Take care they are small and don't need much.

 

I would spray it clean with brake cleaner and watch to see if it is the head or valve cover (which is more likely)

[cspatter]

Check the 4 10mm bolts around the front of the head/timing cover for tightness. Take care they are small and don't need much.

 

I would spray it clean with brake cleaner and watch to see if it is the head or valve cover (which is more likely)

 

Thanks,

I cleaned it a couple days ago with purple power and the leak looks like it is directly under the timing cover but low enough to be the head gasket. You think it might be the timing cover? Does that cover have a gasket? I'll check the torque in my manual and tighten them up to factory specs.

 

Any ideas on the sizing/performance of the head gasket if it goes in that direction?

[datzenmike]

If you mean the oval plate on the front of the head... could be that and easy to replace it.

 

The timing cover is directly below the front of the head and there are 4 small bolts from the head down into it with the front of the head gasket between.

 

The head gasket in the timing chain area does not seal in any oil under pressure, mostly fumes and oil mist or spray from the chain. But it can leak and that's annoying.

[DanielC]

to answer the question about head gasket thickness, a thicker head gasket will lower the compression. This will make your engine less efficient. It will have less power, and get poorer gas mileage.

 

However, if you have to run premium gas to avoid the engine knocking, you may end up being able to run a lower grade of gas, and even though you are getting fewer miles per gallon. you might come out ahead with lower operating costs due to cheaper gas. But the difference in cost would take a long time to pay back the price of the new headgasket, even if you do all the work yourself.

There is also a possibility that putting in a thicker headgasket would cause the engine to knock worse, because the "quench" areas in the combustion chamber are now too large to "quench" as the engine was designed.

 

Quench is the narrow gap that separates the top of the piston from the bottom of the cylinder head at TDC, or Top Dead Center. The narrow gap draws heat out of the fuel and air mixture in the quench area, and prevents it from burning too fast. As the piston moves down, this area is opened up, and the fuel air mixture then burns, in a controlled manner, without knocking. The close gap quenches the flame, thus its name.

 

If the engine is stock, use a stock head gasket, from Nissan. They know what is best for the engine they designed.

[blue72]

The head gasket in the timing chain area does not seal in any oil under pressure, mostly fumes and oil mist or spray from the chain. But it can leak and that's annoying.

 

Yep, quite annoying indeed. It first happened to me when I bought my 240Z. The previous wanna-be mechanic/owner had badly botched a timing chain replacement job and at the same time had horribly mangled the front of the head gasket when they put the timing cover back on. I later did the same thing to myself after the timing tensioner slipped and I tried to put the front cover on with the head and oil pan in place. The front cover caught on the head gasket and bunched it up (I also managed to tear the oil pan gasket, fun times). Now I've got the same exact thing happening on my 510 in the exact same area between the head and the front cover. I've just got to wrap my head around to doing this for the third time, bah. At least I've got lots of practice at replacing head gaskets.

[Skib]

your head gaskets fine.

 

its just the corner where the timing cover, head, and block all meet.

 

it all needs to be perfectly clean an tight when assembled or even add a tiny touch of grey sealant right there and its fine.

 

 

 

You think it might be the timing cover? Does that cover have a gasket?

 

 

if your talking about the timing chain inspection cover than yes, it has a gasket.

[datzenmike]

There is also a possibility that putting in a thicker headgasket would cause the engine to knock worse, because the "quench" areas in the combustion chamber are now too large to "quench" as the engine was designed.

 

Quench is the narrow gap that separates the top of the piston from the bottom of the cylinder head at TDC, or Top Dead Center. The narrow gap draws heat out of the fuel and air mixture in the quench area, and prevents it from burning too fast. As the piston moves down, this area is opened up, and the fuel air mixture then burns, in a controlled manner, without knocking. The close gap quenches the flame, thus its name.

 

 

The quench or pinch area would only apply to closed chamber heads and works best with flattop pistons. Although there is a small strip around the outside of all dished pistons, it has no effect on an open chamber head.

 

 

On open chamber heads there are rich and lean mixture areas in the combustion chamber. Rich areas will be cooler and not burn completely , leaving carbon deposits. Lean areas run hotter because they don't have the cooling effect of evaporated fuel.

As I see it on a head with a quench/pinch area, the fuel air mixture caught between the rising flat piston top and the flat head surface (separated only by the head gasket thickness, about 1.2mm) is violently pinched out into the remaining combustion chamber. This causes beneficial swirl and turbulence which does two related things. It promotes more complete mixing of the fuel and air which in turn burns more completely and there is reduced hot spots and carbon deposits that can be an ignition source when hot.

[dvboth]

your oil leak could be comimg from the fuel pump. check closely if it's getting on the underside of the hood and all over the passenger side of the engine compartment it may be from the fuel pump!