Checking head for staightness??

#1

Has anyone ever checked there head for staightness themselves? The Bently says to check it with a straight edge and a feeler gauge, but gives no further details. My head was supposedly “done” by the previous owner. I have had 30+ track days on it and now have pressure in the coolant system after cool down.

#2

It doesn’t sound like you have the head off the engine; to check the head, you’ll need to remove it. However, if you don’t have coolant in your oil, oil in your coolant and the engine is running well, I would NOT worry about your head being warped. Did you overheat? RE the pressure in your cooling sytem, how long did you “cool down” before removing the cap? It would take several hours for the coolant system temps to return to ambient and I don’t think it’s abnormal to have pressure in your cooling system even after cool down.

#3

No, I dont have the head off yet… I was just reading the Bently for some tips. There was a lot of pressure in the system 12+ hours after each race. I knew I had an issue so I was watching it all weekend. I did not have any coolant in the oil, untill recently, I pulled the car out of the garage and noticed very small traces of coolant on the dip stick. Compression checks out fine and I have not done a leak down test.

#4

I wouldn’t worry too much about the pressure; after 12 hours, ambient temp is likely very different than before running the car. Coolant in the oil is something to worry about and indicative of a head gasket leak. You could send your oil off for analysis to confirm… As far as checking for straightness, you are looking for warpage on the mating surface of the head. To check, you hold a precision straight edge against the head mating surface and look for areas that allow a feeler gauge to slide in. The biggest feeler gauge you can fit is the amount of warpage. If you do decide to pull your head, Metric Mechanic sells a head gasket that helps to prevent head warpage.

#5

I understand ambiant temp and pressure difference. 75 at time of race, 55 next morning with a lot of pressure in system … something is not right. I also get how to check for straigtness of head. I should have asked how much warp is to much? I would think the tolerance would be very small and one would not be able to tell with a feeler gauge?? I was thhinking I would send the head to a shop to check for straightness and for cracks until I read the Bently, suggesting one could check it themselves.:huh:

Metric Mechanic’s gasket prevents head warpage? Sounds interesting. I will check into that.

#6

Significant pressure in the cooling system 12 hours after the engine is shut off probably does indicate a head gasket leak or a cracked head. To check the head you first need a precision straightedge. Entry price on one is about $150. Which is about what I pay to have a head decked and valves ground. So it doesn’t make much sense to make this a DIY.

But if you have a 36" precision straightedge the procedure is to set the straightedge on shim stock, say about 0.010" thick and check the clearance in along the head with feeler gages. Do that for three-four “cuts” along the head and on the diagonals. It is a good idea to also make a series of checks perpendicular to the long axis of the head.

The slickest way of checking a head is with a coordinate measuring system. It can also be done with a dial indicator and a vertical mill with a 9x42 or larger table.

A good head will be within 0.001" of being flat. As will the block.

#7

I always send my heads to machine shops to ensure they are straight and not cracked. I once removed a head due to a bad head gasket, measured the head and everything was good. I renistalled the head and ran the car, the cooling system wasn’t holding pressure… Make a long story short, removed the head again sent it to the machine shop and it had a hairline crack where you could not see or feel. So my advice, have a machine shop check your head. Also, do not run your engine with any coolant in the oil, it will destroy the bearings.