Head clearance service limit question

[brynden29]

Hey guys,
I have searched here and on Talk and cannot find anyone with a similiar issue. I am in the process of rebuilding my engine. The head is done and I am going to get it today. Here is my problem

The stock head size is 5.197 inches. The service limit is 5.185 inches, my head is 5.165 inches after being resurfaced. So it is .02 inches under the service limit. The machine shop guy recommends me using a head saver shim. I am not sure I want to do that.

Here are my questions:

1. Is a head shim a good idea?
2. Can I use my head being that it is .02 under the service limit? Will the valves hit the pistons?
3. Should I get a new head?

I plan on running 18-20 psi on this built motor if that makes a difference. Thanks for the help guys.

 

[fwdmaster]

your fine with your head,the valves won't hit your pistons,the good thing is that your compression will be raised up a little

 

[brynden29]

your fine with your head,the valves won't hit your pistons,the good thing is that your compression will be raised up a little

Thanks for the reply. Not that I don't believe you, but have you run a head that is .02 under the service limit?

 

[fwdmaster]

Thanks for the reply. Not that I don't believe you, but have you run a head that is .02 under the service limit?

Yes I have,my compression on all 4 cylinders were 185 and still is after a year of abuse,my car runs great with no problems

 

[donniekak]

I have seen heads that were milled down so far the valves protruded past the surface of the head. Might be a problem if you run cams with more lift than stock though.

 

[brynden29]

I am running stock cams. So it sounds like I will be ok.

 

[brynden29]

Just a little more info, I am running Wiseco 8.3:1 pistons. They do have sizable valve reliefs in them. Thanks again for your help. I do not want to mess up my freshly built motor!

 

[talon187]

if your so worried run a thicker headgasket to make up the diffrent like a mitsu 4 layer

 

[jrohner]

I have seen heads that were milled down so far the valves protruded past the surface of the head.

The head on my 1g talon is like that slightly.

 

[brynden29]

if your so worried run a thicker headgasket to make up the diffrent like a mitsu 4 layer

I ordered the Cometic MLS head gasket. Do you think that will be thick enough? It says it is .051".

 

[donniekak]

Get an old headgasket and put some playdough in the valve reliefs in the pistons. Crank it over a few times and take it apart. Measure the thickness of the playdough and that is your clearance.

 

[asd_gst]

i work at a machine shop and we've milled heads more then .020" for people before when the limit on the head was around .004" being the limit to how much it can be milled. if anythign check your valve clearance.

 

[brynden29]

Thanks for the replies. I am going to use the "playdoh" method tonight. I have a paper HG that I am not going to use so I am going to put playdoh on my valve reliefs and turn the crank over a few times to check the clearance. I will post the results in case someone else is ever in my same situation and does a search.

 

[TurboAnything]

By the way the factory manual says .008 is the cut limit. No worries though i have run heads with more cut off with no issues.