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Author Topic: Blown headgasket checks. One simple one not so simple.  (Read 6372 times)
1970_347
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Location: Maine

« on: September 27, 2013, 02:30:58 am »

pull the radiator cap.. stretch some sandwich wrap across the filler neck.. push it in slightly with your finger.. to make a dent.. \/  place a rubber band around the outside to hold it in place and make it kinda air tight.. crank the engine over.. make sure the bag did not inflate.. change from \/ to /\ that would indicate a blown headgasket.

then with a radiator pressure tester.. and check that the cooling system holds pressure.


basic test is identical to a cylinder leak down test.. except i take the valve core out of my compression tester hose and hook that directly to the quick connect on the shop air hose..  the cylinder leak down tester hose has a restriction..  the compression tester hose with the special low pressure valve core removed flows a LOT of air..   when i rotate the engine to the various cylinders to check each one at TDC on the compression stroke.. ( where the rotor is pointing at the wire to that spark plug.. )  when i find one that leaks into the radiator.. i leave the setup there and call the customer..  i usually have some kind of tapered plug or radiator pressure adaptor with clear vinyl hose on it and looped over the hood latch.. partially filled with coolant or water...

when the customer gets there.. i show them the failure by hooking up the air hose to the compression tester hose... when bubbles start coming out the radiator.. i have proven a leak in the head gasket or combustion chamber..

this does not show up the leaks that happen in the exhaust ports past the valve seats.. but a long term radiator pressure test will show those up  perhaps a bag over the tail pipe on that one also..


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1970 Mustang
347 - world products heads, mild cam,
performer RPM intake, Holley 750 4160 carb. C-4, 8.8  rear.

Drive train going to change quite a bit soon
69 Merc
The Ricer King
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« Reply #1 on: September 27, 2013, 09:58:27 am »

For any head gasket problem that I've ever had a simple compression test told me which bad gasket it was and which cylinders were being affected.
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Robert's 1969 Mercury Montego (FordStrokers 408W, QFT 850cfm RQ-AN, Super Victor, 1" aluminum open spacer, CamMotion HR .624"/.609" 251*/256* 108* LSA, 1-3/4"x3-1/2" headers, Dynomax Ultra #17224 mufflers, C6/4R100 trans, 8"/9" 5500 converter, Broader Performance manual V/B, 9" 4.56 Detroit Truetrac, Hoosier Pro Street 31x12.5R15 on 10" rims)

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Thanks to Jim "Woody" and Nicole Woods @ FordStrokers 408W, Westminster Performance Transmission (W.P.T.) transmissions, TCS Performance converters, Broader Performance valvebodies and last but not least a BIG thanks (always) to my friends here and abroad in the World!
BirdMan
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Location: Topeka, KS

« Reply #2 on: October 09, 2013, 10:08:21 am »

Also the sparkplug will be rusty and the amount will be dependent on amount of leak and how long the engine has been run this way.
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