cylinder head temp

[autronicDSM]

after i have my head decked and buy cometic head gasket to try it out i'm installing cylinder head temp gauge. reason i'm doing it is i thought i never warped the head but i keep blowing coolant to overflow tank and overheating under boost. when i replaced head gasket it looked like it never been used so obviously head is warped.

here's my question, at what temps does head start to warp...i tried looking on yahoo but only result i get are for airplanes and seems like 400F is the safest before engine might seize.

 

[insane147]

are you sure it s your head that warped, the block deck could be marred or warped also. where would you mount the cyl. head temp sender anyhow??

 

[autronicDSM]

CHT probe mounts under spark plug. it looks like O-ring with a wire attached to it.

 

[GTM]

Originally posted by autronicDSM
after i have my head decked and buy cometic head gasket to try it out i'm installing cylinder head temp gauge. reason i'm doing it is i thought i never warped the head but i keep blowing coolant to overflow tank and overheating under boost.
...

First things first, have you done a "Block Check" using the special tool and fluid???

I keep reading about all these "blown" head gasket problems but never read that anyone ever tested for combustion gas in the cooling system. People these are invaluable tools, buy, rent, borrow or pay someone for the normal 15 min of testing. "Block Check" is patented name but you are looking for the tool and fluid which changes from blue to yellow if combustion gas is present in the cooling system. These things are too blasted hard to pull down only to mis-diagnose a problem.

So why isn't it a water pump sucking air through the seal, that will cause it to pump water and yet not leak water.

" when i replaced head gasket it looked like it never been used so obviously head is warped.
"

I'm not convinced, have you checked it or had a machine shop check for warpage, had it machined??

"
here's my question, at what temps does head start to warp...i tried looking on yahoo but only result i get are for airplanes and seems like 400F is the safest before engine might seize.

"

I would think the DSM and other watercooled engines would be higher, perhaps 500ºF. Do you have an oil temperature gauge?? If you see more than 270ºF you are in danger of breaking down the oil and then ruining the engine.

I believe most mfg recommend 600ºF when straightening a warped aluminum head. I've done a couple of 2L Nissan SOHC successfully using a 20 ton shop hydraulic press, coating the top of the head with oil and heating with torch until it's smoking pretty good. Since most organic compounds will burn at 500ºF or lower and I didn't have a 600ºF thermometer it was my temp control. While heating I applied the press pressure and left it to sit overnight and then slowly released the pressure. Took about 3 passes of this to bring them into specifications but never had any problems, didn't even machine them, just dressed with a mill bastard file. These were my own engines so I could afford to take the chance, too many things could go wrong. Remember just because you mill a warped head you have done nothing for the camshaft bore, so if if it was .020 warped and you just milled the head the camshaft is going to be in trouble.

I have "0" experience with warped blocks, from what I read it does happen, again a good straight edge and go-no-go feeler gauges will reveal the truth. When I did my son's valve job the head gasket showed no evidence of leaking, no real reason to check for warpage so just slapped another back on. Time will tell if that was a mistake.

Cheers,
GTM

 

[GTM]

Originally posted by insane147
are you sure it s your head that warped, the block deck could be marred or warped also. where would you mount the cyl. head temp sender anyhow??

Re: cylr head temp sensor there are several choices.

Here is a great site for some inexpensive instruments if you are on a budget, they also have some pro equipment $$$$. These are aircraft instruments so no pretty neon colors to match the seat covers but accuracy is 1%-2% so not lab quality but better than the pretty ones.

http://www.aircraftspruce.com/catmain.php?dest=cathome.html

Click on "Instruments",then "CHT gauges", then "MICRO 1000" the 2 1/2 square mount is $61.75, 2" round $54.95 plus the sensor further down the page. On the left is the spark plug mount, middle is for threaded installation and the right is for an exhaust pipe. If I'm not mistaken you can just use 18 ga. wire for extensions if needed.

Please note metric pipe thread is not the same as NPT pipe, close enough for a blind hole but not for where fluids are present.

They have EGT gauges for about the same price so that along with an oil temp, and boost gauges will be added to my son's instrumentation.

There are other sensors types available, don't know if this site has them. Some of these are about the diameter of a quarter and 3/8" thick, they use a flat piece of spring steel of which one end is bolted to an existing hole, the other end just presses the sensor against the surface for a topical contact. The ones I'm familiar with are good for 400º-500ºF but they do make lower temp contact sensors. Household washer dryers, hotwater heaters, coffee makers etc.

Just think what you could do with a half dozen of these disk sensors and a rotary switch, tranny housing, radiator core, Intercooler, underhood and one for the drivers seat when thing get really exciting.

Cheers,
GTM