head gasket opinion

[nmainehunter]

I am going to use Cometic gaskets. Are the copper better than the layered? Thanks

[JW113]

My experience is that the multi-layered type tend to not leak...

-JW

[RTMike]

No copper MLS all the way

[aswracing]

MLS every day of the week and twice on Sunday.

Just be sure to use the MLS-specific torque procedure. The factory procedure, when used with MLS head gaskets, may well cause a stud to pull up out of the case. We sold almost a thousand engine kits last year and this is a really common mistake among customers who don't bother to read our kit instructions. A blown head gasket accompanied by a loose head bolt a couple hundred miles down the road is the usual result. Then they find themselves time-serting the stud hole in the case.

[nmainehunter]

Thanks, MLS it is!

[nibroc]

what is MLS?

[FXDBI]

what is MLS?

Multi layer steel.     Bob

[1340evo]

how good do the surfaces need to be.. it says 'perfect'... whats perfect

[Ohio HD]

Perfect means completely clean, surfaces flat, no nicks or dings in the head or cylinder surfaces.

[1340evo]

Guess mine are perfect then... whats the best base gasket to use the with?

[Ohio HD]

I have no idea what the best is, but I prefer Cometic SLS gaskets.

[1340evo]

Not much in the UK, but Spain has some, but expensive. do you use .010" or .020" ?... and if you use the .030" MLS head gasket, whats the torque procedure?

[kd]

I usually choose base gaskets based on deck height requirements. Have you measured it?  What are your goals? I am in Ohio's camp with MLS Cometic head and base gaskets. Myself and most others choose the .030 head gasket as a way to control detonation.  It would be better to have some information on your build and components.  One component doesn't necessarily suit all situations.

[1340evo]

I still need to assemble it, a rough measure before had my pistons at -.007 on one jug and -.012 on the other... this is common by all accounts, but I've not put the new pistons in as yet so don't know where they sit. I will do it this weekend and assemble with no base gasket to see what I have. I've already CC'd the heads so know where they are.
Im not chasing increased CR but would like to get them equal by skimming the head I guess, from a vibration point of view...

[kd]

That's good planning and good planning usually pays dividends.    FYI, in the quest for a combination of 0 deck and .030 quench, Cometic will make your gaskets (head or base) in any size you ask for provided they have the dimensional stock to cut them from. They don't charge extra for that service which to me is a great example of their customer service.

Your other option if pistons are below deck is to clean up the gasket surface with the excess material you have. You get true gasket surfaces out of that also.

[1340evo]

Okay, so I've measured up, cylinders on with no base gasket.. not easy to do as you need to try hold the piston, and measuring both sides of the piston over the pin, it does vary on both pistons side to side, by 0.12mm on the front and 0.14mm on the rear when measuring the deck height!.. but anyway, here are my averaged findings

Front head CC 81.6     Front pistone proud 0.284mm
Rear head CC 81.0      Rear piston proud 0.185mm

My pistons are . 010 oversize and the bores measure 3.504 inch with my verniers.

I get 0.4cc differance in them (so maybe not worth bothering with?), but need the CR if I use a .020 base and a .030 head or .045 head gasket ?? whats optimum with a EV27 cam?

[kd]

Put some tape around the pistons before you slide the barrels on to stop them from rocking.  The piston diameter above the rings is smaller than the sides and skirt and it will rock. The measurement is taken over the center line of the wrist pin on each side and compared to the deck of the cylinder gasket surface next to it when tightened down. Each side may be a tiny bit different (maybe .001") so use and average for each hole.  If you prevent the piston from rocking you should get a decent measurement at the pin. I didn't do a conversion to metric but there is a difference showing up that may be a result of using the front and rear of the piston where rocking has affected it.

[1340evo]

Did that, packed the top with tape so it did not rock.. two layers of masking tape at 12, 3, 6 and 9 oclock so it held it. measured over the pin LHS and RHS, and thats where I'm seeing .12 and .14mm ... (0.005").. they are cast top so maybe not that accurate?
both the same way also.. lower on the LHS, higher on the RHS?

[1340evo]

 

[kd]

I am sorry but I don't understand what you are doing or looking to accomplish. You are giving volume numbers.  Deck height is a distance measurement, not volume. (even though it ultimately will make a difference in volume if not even).  It is mostly used to determine head gasket thickness to set quench (squish) and control detonation or pinging.  It is agreed that .030 is optimum. Stock will be about .045 and provides less swirl in the combustion chamber gasses. For example a piston that is .003 in the hole will give .033 squish with a .030 gasket.  If it is .023 in the hole with no base gasket you would choose a .020 base gasket and a .027 head gasket to get .030 squish. In the real world a .030 is probably as good (giving .033 squish) but some of us OCD people go for exact.    It is nice to have even compression and no detonation.

Again, how much is it in or out of the hole if measured from the cylinder head gasket surface to the top of the piston in distance. Can you give that in thousands of an inch?  I take it you are still measuring without a base gasket.

[1340evo]

yes, average piston proud (out of the hole) is

Front 0.284 (0".011)
Rear 0.185 (0".007)

with no base gasket

I then go on to calculate the cc differance that the .004 makes, and it about 0.6cc, which is the differance in the cc of my heads...

[kd]

If your not building a blueprinted engine, a .010 base gasket the front will be .001 out and the rear .003 in.  You have them off so there is the option to trim the rear .003.  A .030 head gasket will work fine, or you can go .036.   The .030 head gasket is optimum to prevent pinging.

Have you measured the head gaskets you took out?  Having the head cc's match the volume of the difference in the deck height is spooky.  If it was apart before and in the hands of an OCD builder it could have been intentional because the relative volumes even out.

[JW113]

I know I'm just off in the woods here. But, is this any of this going to make a difference on a bike ridden around between home, work, and the local pub?



Just keep the pistons from hitting the heads, and all is good!


JW

[1340evo]

Hi All.... Whilst it's out I may as well get it as right as I can....

Yes, strange how they add up to be perfectly the same?

Strange about the angle on the piston top.. having looked at the pistons, there is no rubbing whilst I've been doing this other than front and rear where you'd expect it? Wonder if you can get a rod adjuster to tweak them straight, although they should of been checked when the bottom end was done?