And Momentum, thanks for the cheap shot about head gaskets. As was adequately pointed out they went as a result of bad tuning that would have killed any headgasket, even the indestructible OEM. So not a really good example on your part.

 

I think we can settle this with a non-biased experiment.

Go to a mechanic and ask for two quotes: one for a 3mm headgasket, and another for decompressed pistons. This will tell you a real opinion on what the comparison is.

 

[QUOTE=drewmob,Jan 22 2010, 11:36 AM] Such weak sauce...

 

Your not the only one that's been through a head gasket so it's not a cheap shot, search blown 3mm gasket the results are endless.

As for asking a mechanic to quote if you ask them to do it without a hone the way i described I bet the difference won't be as far off as you think. I would guess 600 for the head gasket vs 1500 for the pistons. I know when I used to work at a performance shop I would have done it for a customer for the difference in parts costs plus 2 hours labor.

I have personally put stock used pistons and rings out of a donor motor into my motor with no hone (I also mix and matched used bearings but that's another story). Obviously this is not the right way to do it but I had 24 hours or would have missed a race. Not only did it last the race weekend it makes more power than the original motor (100% oem and untouched) has the same compression numbers and is STILL running at over 600whp.

FYI right from Honda:


All S2000 and 1990 and later VTEC and SI Preludes have Fiber-Reinforced Metal (FRM) cylinder liners. FRM honing is not required unless the cylinder has deep vertical scratches that run the length of the bore. Cylinders with light colored spots or flaking cannot be corrected by honing and must be replaced.

To hone FRM liners, perform the following:
· Use a rigid hone (not a ball hone) with GC-600-J or finer stones for nonferrous
metals. The honing pressure should be 200-300 kPa (2-3 kg-cm2, 29-43 psi).
· Use an oil type honing oil.
· Hone at 45-50 rpm to a 60 degree-crosshatch pattern.
· Do not stroke the hone more than 20 cycles.
· After honing, thoroughly clean the engine block of all metal particles by
washing with hot soapy water, then dry and oil them immediately. Never use
solvent; it will only redistribute the grit.
· Some light vertical scoring and scratching is acceptable if it isn’t deep enough
to catch your fingernail, and doesn’t run the full length of the bore. (rm,sn)

 

Spoolin good point about the replacement gaskets, I honestly hadn't thought of that.

 

That's still 2.5 times the price and in my opinion (and possibly yours too) not done properly.

Don't get me wrong, I believe that the better way to do a decompression is with pistons. That's why I'm doing it. But I'm not convinced that the many times cheaper method of using a thicker head gasket (as I currently am) with a decent tune (I learnt that the hard way) isn't an acceptable compromise. And it's certainly a better compromise than a half baked piston replacement without rebuilding the engine.

 

I don't believe either is proper, don't get me wrong. It's a debatable opinion I would just rather leave my combustion chamber well designed and quench intact. I would recommend my "half baked" piston replacement to anyone over a 3mm headgasket. I would actually go as far to say I would recommend that over sleeving the motor because of the huge advantages of the FRM sleeves over iron sleeves. Obviously if you are going to make enough power to crack the stock sleeves (no one has done it yet) you have to sleeve it.

Anything short of a 10000+ RPM race motor full of Ti, copper beryllium, and inconel is a compromise. Which is why I still with 100% stock, if it's good enough for 600whp on the road course and I can buy replacement parts for beers and replacement motors for less than a 3mm head gasket whats the point in compromising. Of course if I couldn't get E85 and had to lower my compression I would throw some half bakes pistons in.

 

Cool, but that's not the OP's question.

 

getting back on topic....

 

I would put forward the notion that a 3mm headgasket is not a consumable item. It's longevity should be similar to that of an OEM gasket and it should last indefinitely if it is properly installed and the car is properly tuned, maintained, fueled and driven.

It's only deficit in comparison to an OEM gasket is quench shape. The OEM gasket allows the head, cylinder and piston to form a well designed quench space which is ideal for combustion. The extra 2.3mm of height of the 3mm gasket takes away from this design. That said, properly tuned this is not a problem.

As such, I also suggest that the notion that you will only get 20K or so out of a 3mm gasket is crap.

I do agree that a fully built (sleeved or not) low compression engine is the ideal solution but note that this option is incredibly expensive and time consuming for the average punter (think $5000 and possibly weeks of downtime vs something many can do in a domestic garage in a matter of hours for the cost of the headgasket) that it's not in the same ball park.

Discuss!