This is a mini DIY on how to fix a warped head at home. This method is also called lapping.
It's a good idea to check your head during a rebuild when you have it off, or after buying one used.
How do you know your head is warped?
For a water cooled motor you'll be burning coolant, possibly over heating, or smoking more.
For an air cooled motor you should see fuel gather outside the jug around the head gasket area, and sometimes you can hear the leak.
OR you bought your head used from Minkia38 on Ebay.
A warped head will hurt your performance at best and toast your motor at worst.
To fix it tape a piece of wet or dry 400-800 grit sand paper to a flat surface. I like 400 because it works fast.
The yellow powder coating over spray tells me my head is warped and there is a low spot in that area
Spray some cutting oil or light oil on the sandpaper I used WD40. This keeps the paper from instantly clogging up with aluminum making it useless.
Keep the old plugs in to keep grit and aluminum out of the threads.
Move the head, pressing down slightly in a figure 8 pattern for a few minutes.
A good eye will be able to see the warpage as parts of the head that aren't touching the paper or parts that look dull compared to the fresh sanded parts.
Keep goin and spray fresh oil on the paper every now and then. I also wipe the sandpaper off with a rag to keep it cutting fast.
For my head it took a good 20 minutes and I would consider mine to be pretty bad.
You will know when it's enough by the whole sealing surface looking uniform or all the same.
For the record I don't think mine was leaking because the powder coat filled in the low spots but I'm not the type of guy to knowingly run something I know is wrong.
You might be curious like I was as to any performance increases since in a way you just milled off material from the head. Well here my compression before and after 20 minutes of work.
I gained about 6 psi- not enough to affect my tune, and in no way a substitute for having Flotek mill your head which would also fix any warpage.
Before:
After:
It's a good idea to check your head during a rebuild when you have it off, or after buying one used.
How do you know your head is warped?
For a water cooled motor you'll be burning coolant, possibly over heating, or smoking more.
For an air cooled motor you should see fuel gather outside the jug around the head gasket area, and sometimes you can hear the leak.
OR you bought your head used from Minkia38 on Ebay.
A warped head will hurt your performance at best and toast your motor at worst.
To fix it tape a piece of wet or dry 400-800 grit sand paper to a flat surface. I like 400 because it works fast.
The yellow powder coating over spray tells me my head is warped and there is a low spot in that area
Spray some cutting oil or light oil on the sandpaper I used WD40. This keeps the paper from instantly clogging up with aluminum making it useless.
Keep the old plugs in to keep grit and aluminum out of the threads.
Move the head, pressing down slightly in a figure 8 pattern for a few minutes.
A good eye will be able to see the warpage as parts of the head that aren't touching the paper or parts that look dull compared to the fresh sanded parts.
Keep goin and spray fresh oil on the paper every now and then. I also wipe the sandpaper off with a rag to keep it cutting fast.
For my head it took a good 20 minutes and I would consider mine to be pretty bad.
You will know when it's enough by the whole sealing surface looking uniform or all the same.
For the record I don't think mine was leaking because the powder coat filled in the low spots but I'm not the type of guy to knowingly run something I know is wrong.
You might be curious like I was as to any performance increases since in a way you just milled off material from the head. Well here my compression before and after 20 minutes of work.
I gained about 6 psi- not enough to affect my tune, and in no way a substitute for having Flotek mill your head which would also fix any warpage.
Before:
After:
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