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Author Topic:   head gaskets
pmiracing
Dirt Full Roller

Total posts: 44
posted June 26, 2005 07:01 PM  
some how we blew both head gaskets on our motor. it's a 351w ford with only 5 nights on it and it blew through the number 1 and 6 cylinders. this motor runs about 200-210 every night and this week we ran 2 laps in our heat and it blew all the water out and was 270. this after packing track for 45 min. running about 190-200. I have never heard of both gaskets going like this the odd thing is the motor never lost power but I found water in the cylinders and pulled the heads to find the gasket material behind the rings eaten away. Any ideas on what caused this? its a fresh 9-1 motor with stock replacement pistons.

nine finger
Dirt Forum Racer

Total posts: 76
posted June 26, 2005 07:29 PM  
did you retorque after initial run in.

powerglides
Dirt Freak

Total posts: 374
posted June 27, 2005 04:40 AM  
Are the heads angle milled? Sometimes the water passages are on an angle and get too close to the chamber as the heads are milled.

akadirtracer7
Dirt Freak

Total posts: 217
posted June 27, 2005 05:53 AM  
what gaskets are you using.If there fel-pro 1101-2 toss them just blew a set 2 weeks ago they pulled the rings inbetween 3&4 and 7&8 the block was decked and the heads milled this is a new 408 I built 13.3 to 1 I think the intake fit just enough to seal the water passages.when I put new gaskets on I had to shave the bottom of the intake down.The gasket were only .002 thicker than the other set but enough to cause problems.If the gasketis in the chamber at all it will burn it up, I also went .060 bigger on the bore size of the gasket.My buddy tore up 4 motors with the 1101-2 his damaged the block and head i got lucky it was just the gasket. hope this helps

Steve Dupree
Dirt Freak

Total posts: 316
posted June 27, 2005 06:27 AM  
Well we run the same motor at 9.5 to 1 and use felpro we run between 210 and 235 and nock on wood no problems. But we always sevice are heads if just to make sure they are straight.

pmiracing
Dirt Full Roller

Total posts: 44
posted June 27, 2005 04:53 PM  
I looked at the heads today and the decking job my engine builder did is a little rough. if I run my fingernail across it it will chatter a little. the heads are flat but it looks like they had the feed speed on the mill too fast. It's not bad but could this cause it? I did retorque the heads and I don't know what gaskets they are. The rings are fine but behind them is eaten away. Also one of the cylinders that was leaking was about 180psi. with all others being 150. why would a blown cylinder have more pressure?

Steve Dupree
Dirt Freak

Total posts: 316
posted June 27, 2005 07:01 PM  
Probally because of water in it also i wanted to tell you torque the heads to 112 ft. lbs. Alot of books show different but we have an old michell and it says 105 to 112 we have always put are at 112. I dont think if flat what you found caused it ill bet you torqued to 90 or so like alot of books say and that not enough. If the machine shop is close have him clean them up again on the sevice. He probally just had dull bits. Felpro gaskets no spray and 112 ft. lbs. Torque in correct sequense also use the three step method 90,100 and then 112. Middle out to each side and back and forth on torquing. Both middles,then move left both left then move to the right of middle both of those and so forth.

eenfield
Dirt Maniac

Total posts: 116
posted June 27, 2005 08:47 PM  
I forget the technical term, but different gaskets require certain finishes on the sealing surface. Some take a finer finish, some take a rougher finish... Maybe your machinist had it right.

akadirtracer7
Dirt Freak

Total posts: 217
posted July 06, 2005 06:12 PM  
also when you torque the heads you do it the first time then leave it sit a while .Then come back and loosen the bolts one at a time and retorque then move on to the next one.Then after you run it the first time let it sit until its totally cooled down,like the next day then retorque them and again by loosening a bolt then retorque one at a time...

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