View Full Version : Need help my head is tapered

04-11-2015, 12:13 PM
I decided to use the surface grinder at work to machine my head. It left the head with a .015 taper from front to back.
I brought it to a machine shop and had it done professionally thinking that they would make it flat again but they told me that they levelled the head according to what I had done. So they took off about .004 to resurface it. But it's still tapered. Will this affect the performance or will it not be noticeable? I don't want to spend another $125 to get another head machined if I don't need to. Help please!

04-11-2015, 01:56 PM
sorry bro, it has to be flat. Otherwise you will have head gasket problems for days.

04-11-2015, 05:28 PM
that's exactly what I'm worried about what do you think my options do you think I should get another head or try to fix this one?

04-11-2015, 08:32 PM
but it is flat, just ever so slightly wedge shaped. I actually don't think that would be a problem.

personally, Id run it. I doubt its an issue.

and do you mean front of motor to back of motor (length of the engine) or do you mean wedged intake side to exhaust?

04-11-2015, 10:30 PM
So it's tapered exhaust to intake valves where the intake valves are affected in having more shaven off then the exhaust valve side. The head is flat it was done professionally. The guys at the machine shop were mildly concerned.
Will there be more compression in the intake side or am I just paranoid. I don't have the time to take the head off again my wife will kill me! Lol
I have a 95 celica gt with a 5fse engine. I'm putting 264 delta grind cams and a custom intake manifold plus a piggy back apexi neo 2 with ebay 4-1 headers plus I did a amature port and polish, put new valves in and laped them. Please tell me this won't blow my gasket having the head tapered?

04-12-2015, 02:26 AM
well being a performance build I would be slightly more concerned, but .015" is .3mm. looking at that in terms of a thickness gauge Im having a hard time visualizing how that would cause an issue. You could do a little math to figure out what that translates to in valve deflection at the bottom of its stroke. That would be my biggest concern, not what it does to the compression chamber.

Are you using stock bore and stock compression pistons? 5S pistons do utilize valve reliefs so Id want to know that that ever so slight angle isn't going to create an interference. I don't think it does.

You need to know the valve stroke, and the stock angle of the valve then plug in the angles and distances to a little geometry equation and figure that out. but I also don't know the gap between the valve face and the relief on the piston.

Another option would be to place some modeling clay on the top of a piston then bolt the head down with a spare head gasket and rotate the engine, disassemble and verify you have clearance. I know that sounds like a pain in the ass, but its better than putting it all together and finding out you have an inference issue.

Im totally not concerned about your head gasket sealing or blowing because of this issue. I really cant think of any reason this should be a problem aside from valve clearance.

04-12-2015, 01:28 PM
Yes stock Pistons and bore. It's a mild build at most. I was thinking Couldn't I put the clay in then bolt the head and push down on the valves manually to see if there hitting. I don't want to set it up then take it apart. The clearance should be more than enough to offset .015 thou. I read that someone on here shaved off .100 thou. which seems like a awful lot.

04-12-2015, 06:29 PM
If you wanted to do the clay trick to be sure, you would need to put a piston at TDC then fully torque down the head with a headgasket (wasting it in the process since you couldn't remove the head without damaging it) in place, then rotate the cams by hand...at a minimum. The 5S is a non interference engine so you don't have to worry about cam timing. You couldn't push a valve by hand because how would you know how far to push it?

Regarding how much was shaved, its not a question of that. That would affect how deep the valve enters the recess in the piston. its a matter of the fact that angle of the valve changes, and so the face of the valve lands slightly more in towards the center of the piston. Ive tried to figure the math on it but cant wrap my brain around it.

All that said...I personally would put it all together and cross my fingers when I fired it up. I really don't think that amount of head thickness difference is a problem. Ive got to think that there is at least that much variation just in castings from the factory to think .3mm is going to cause you any problem with clearances.

Run it. It will be fine.