Milled head...anything special I need to do?

[renobruce]

My head going on my 78 GS1000 project has been milled .015" Do I need to use any special gaskets or should I be OK with the standard ones? I see that Wiseco offers a copper base gasket that is .020" Do I need it?

[salty_monk]

I guess the only thing it would do (if there is still valve to piston clearance) is to up the Compression ratio. As mine runs on 87 I guess you may need to run a little more retard or move to premium.
As you're putting slotted cams in it it shouldn't mess with the timing.... can't think of anything else to check for..... (presuming the tensioner can take up that much slack in the chain).

[49er]

My head going on my 78 GS1000 project has been milled .015" Do I need to use any special gaskets or should I be OK with the standard ones? I see that Wiseco offers a copper base gasket that is .020" Do I need it?

What pistons are you running? How much squish area do you need? Are you increasing the valve lift over stock? What volume is taken up by the stock gasket ?

All these questions need consideration before you decide to fit that copper .020" base gasket. Did you mill the head to correct a bow in the head surface or just to bump up the CR ? If you were correcting a warp, you will now have different volumes in the chambers of each cylinder!

[psyguy]

have a look in your manual on what the piston-valve clearance is ( i think it's like 1-2mm)
so, i dont think you NEED a thicker gasket, but using it would bring things to factory spec a bit more
as mentioned, you'll get a marginally different cr using a regular gasket

[renobruce]

What pistons are you running? How much squish area do you need? Are you increasing the valve lift over stock? What volume is taken up by the stock gasket ?

All these questions need consideration before you decide to fit that copper .020" base gasket. Did you mill the head to correct a bow in the head surface or just to bump up the CR ? If you were correcting a warp, you will now have different volumes in the chambers of each cylinder!

I bought the head already milled. It was done along with the porting and valve job.

I am running Wiseco 1085 pistons.

I plan on using some aftermarket cams, but nothing too radical.

I just measured the stock base gasket...it is also .020", same as the one offered by Wiseco. So no gain there, just a different material. I assume those copper gaskets are better for high compression?

I looked in my manual and I don't see where there is a spec on valve to piston clearance in the service specifications.

[renobruce]

[salty_monk]

If you have valve clearance then the extra CR would be a benefit. I would say that's what they milled it for as all those other mods are performance related..

You could always do a trial fit with no gasket, put some putty on the top of the pistons & turn it over slowly by hand to see if they clear. Of course that means fitting your cams so you'll be committed to them at that point I guess one way or the other.

If they clear with no gasket they will definitely clear when you add the gasket in.

Dan

[chef1366]

Are you going to degree in the cams?

[renobruce]

Are you going to degree in the cams?

Yes.......

[salty_monk]

Bruce,

Just a thought, do a dry run with the old stock cams with some putty on the top of the pistons... you should then be able to measure how much room you have & thus how much lift you have on your go faster cams....

Dan

[SqDancerLynn1]

You shouldn't have any problems BUT as with any preformance
engine you should trial fit everthing just to make sure at a bare
min I think you need .060 piston/valve clearance.

[49er]

I bought the head already milled. It was done along with the porting and valve job.

I am running Wiseco 1085 pistons.

I plan on using some aftermarket cams, but nothing too radical.

I just measured the stock base gasket...it is also .020", same as the one offered by Wiseco. So no gain there, just a different material. I assume those copper gaskets are better for high compression?

I looked in my manual and I don't see where there is a spec on valve to piston clearance in the service specifications.

Your Wiseco Pistons should give you 10.25-1 when fitted with their head and barrell gasket. By milling .015" off the head your CR will be raised marginally, perhaps to 10.75-1. This will be quite beneficial, but may cause valve clearance problems. Your stock clearance should have been around .080". I don't know if the Wiseco pockets are stock depth or deeper. If they're deeper, you should have enough clearance.
If stock or less, the increase in valve lift and milling could reduce clearance to below .050". That's cutting it a bit fine. You really need to fit up the head and measure clearances at TDC after the power stroke.
The copper gasket will be easier to remove than the stock ones. No baked on material to scarpe off mating surfaces at any subsequent rebuilds!

[renobruce]

I think you need .060 piston/valve clearance.

Your stock clearance should have been around .080".

Where are you getting this information? I check in both my 1000 and 1150 manuals, and I don't see where they give this specification.

[Nessism]

Manufacturers don't typically provide valve clearance information. It's the hot rod folks that typically figure out this kind of stuff.

I doubt skimming the head 15 thou will make any difference if all the parts were stock. With hi compression pistons and a hot cam though, using clay to check clearance is a good idea. The 1.5mm clearance sounds about right. You might want to talk to the cam manufacturer to see what they have to say.

[Big Jay]

Piston to valve clearance changes when you move the cam timing. With the Wisecos, you should have plenty if clearance. Minimums would be .040" intake, and .065" exhaust if you have good aftermarket valve springs. If not, make the exhaust .085 minimum.

Jay