brnt exhaust valve or blwn headgasket or neither??

[Lazy JW]

There is absolutely nothing invalid about his compression test. A bit cumbersome, perhaps, but perfectly legitimate.

#1. Probably is a bad head gasket. If you pull the head and it WASN'T the head gasket, your old gasket is now ruined. Definitely need a new one. The only way I would EVER attempt to re-use an old head gasket is if I were stuck on top of a mountain and didn't feel like walking out cuz it just ain't gonna last very long.

#2. If you find a burned valve but the seat looks decent (no huge gaping holes) then just buy a new valve and one of those suction cup gadgets plus a little tube of lapping compound and lap the thing to fit. I would lap them all for that matter.

#3. Install new seals on ALL of the valves after lapping.

#4. Start saving for a PROPER head rebuild, it's looming on the horizon
Have fun,
Joe

 

[Anonymous]

Changing the head gasket on these engines is a piece of cake. We just changed it on Joshyxs 250 last weekend. All you need is the head gasket and valve cover gssket. You can re-use the carb gasket. Just remove valve cover and loosen rocker shaft bolts enough to remove push rods. Then you can remove head bolts. You dont have to remove exhaust manifold. Just disconnect the pipe from it . The head should come right off. Make sure all gasket mating surfaces are clean before re- installing head gasket. You can re-use the head bolts, just make sure you clean the threads real good. You need a torque wrench to tighten head bolts. Tighten in 3 steps to 75 ft.lbs. Follow the order for tightening head bolts that is in the Falcon Performance Handbook. That should solve your problem and get you back on the road. These sixes are a blast! Have fun!

 

[63comet]

Heh BC, did you ever find out what the problem was? I am experiencing the exact same symptoms. Just curious.

 

[rommaster2]

I would be interested to know too, mostly because mine was fouling the #5 plug, and now is starting to foul the #6. It doesnt smoke, and doesnt over heat however every now and then runs alot hotter then it should. I'm probably gonna change the head gasket, and when i do maybe even put on an aftermarket valve cover.

I'll have to look at my chiltons manual to see how hard it is to do it, you guys say it should be easy, how long would you guys figure it would take? I would like to know because the time i get to work on my bird now is very rare and especially when my friend can help too, if it takes very little time we could just do it at the college after school, worst case scenario i figure that i'll find out something esle is wrong, but it works fine right now so i'd just be in the same spot.

If this thing wasnt my daily driver when i had the head off i'd use the school to mill the head and put bigger valves in, but i dont have the time right now to get that done and its already been rebuilt last year so yeah whatever .

 

[63comet]

Well, here is what I found out, I pulled the head this afternoon, took me about 1 1/2 hours to pull off head and clean off head gasket. Thats right, clean off the head gasket, I have never had one bake on the head and block like that and what I found was the gasket between 3 and 4 cyl. looks like they didn't seal at all. I had to scrape off the gasket with a putty knife from both surfaces. The gasket material seperated from the metal strip. I then turned the head upside down and inserted spark plugs with vaseline on the threads and filled each combustion chamber with gasoline and let them set for 30 minutes with absolutely no gas leaking by at all. So I am putting it back together when I get home from vacation in a week and try it again.

 

[rommaster2]

gasoline? How could you tell none was leaking, the darn stuff evaporates so quickly.

 

[63comet]

not if you fill the whole combustion chamber.

 

[mugsy]

I've done all my compression tests by myself. All you need to do is use a compression tester that has a threaded end that screws into the spark plug hole. Also, I have used a screwdriver/bailing wire to hold the carb all the way open. Do as mentioned above, take ALL the plus out to perform the test. Personally I remove the power feed to the coil so the ignition system is not energized; but thats just a personal preference. And depending on the connector on the end of the wire, you might need to wrap it with electric tape so it doesn't ground itself in the engine compartment.

Do the test "dry" and then repeat with about a tablespoon of motor oil in each cylinger (pour thru the spark plug hole). This is the "wet" test. If the pressure rises significantly between dry and wet tests then the rings are bad. If the pressure is about the same then the valve(s) are bad. And make sure to use motor oil, not WD-40 or some other thin oil. The oil needs to be thick enough to form a seal between the rings and the cylinder walls.

I would also think that if the "leak" is between two cylinders, then those two should read low on the compression test. Just makes sense to me

When I read the original post my first thought was point gap/dwell is too low. You said the ignition system was OK, did you check or re-set the dwell/gap?