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Back in the 70s I built my share of engines
I am 62 now and thought I would restore am old truck.
I now own a really clean 69 F-100 360
I need to decide to ether build a motor or use this one
I know nothing about the truck except the motor is clean like it was just rebuild. Really clean!
Pulled the PCV valve and no blow-by Sounds good when it is running but an exhaust leak makes me not want to run it much
Pulled the plugs and they all are a nice toasty brown and no signs of oil
Compression, throttle wide open,,, test #1 and #3 are 100psi dry but #5 is 80 dry and 95 wet, #7 is 45 dry 60 wet
I checked the rockers to see if maybe the intake wasn't opening Everything looked good on a dial indicator
Why are the plugs so nice looking if it has bad rings? Plus no blow by
Do you think the exhaust manifold leak trashed a valve or actually the exhaust valve in 2 cylinders dropping the compression?
I drove it home 15 miles with the leak
If I totally rebuild the motor, plus rebuild the rest of this truck, I will never sell it for what I have in it
Not planning on selling it but you never know
I am into any input before I decide my next move
I don't think the compression came up enough between the wet and dry test to be bad rings. Also, oil rings and compression rings are separate on most engines so the compression rings could be worn and the oil rings be fine.
#5 and #7 are side by side so you could have a blown head gasket between the two?
My first mistake was to assume the cylinders were odd on the right and even on the left. If it is 1-4 on the left and 5-8 on the right.... My problem I saw so far is #7 and #8
Motogotor - I think you have a made a good point. It could be a blown head gasket. I did not test the other side because I figured it was a bad motor. Today I will check the other 4 cylinders so I can be sure it is just the 2 that are side by side
I assumed that I should get 110psi or greater so I felt like none of them checked great. I also assumed the exhaust leak warped the exhaust valve
With the short stroke of the 360 (3.5") compared to the 390 having the longer stroke (3.750"), would the compression be closer to 100psi???
I dont have a leak down tester and I am not sure what i would learn by testing "leak down" If it cant build more than 50 psi it must be leaking somewhere... Right?
It doesnt have any rust or bondo. It has new duel exhaust and new radiator, everything works. 3 on the tree that I will put on the floor later
Slack in the manual steering and original style manual brakes
I dont have a leak down tester and I am not sure what i would learn by testing "leak down" If it cant build more than 50 psi it must be leaking somewhere... Right?
pressurizing the cylinder can tell you where your leak is at. You can look for where the escaping air is going like exhaust, out the carb, crank case or cooling system.
That is exactly what I need to do. Not leak down but hook it to a compressor and listen to where it is leaking
Great idea Thanks!!!!
I looks like all the shortages will make it near impossible to buy a long block I has 2 companies tell me if I placed the order it could be over 6 months to get a motor
