Hi guys! Ran into grief trying to give my daughter's '56 Plymouth with a 230 inch flat six a compression test just now. Warmed it up and pulled #1 plug and screwed in the compression gauge hose. Pulled the coil wire and tried to crank it over but it wouldn't go. Seemed like it was seized. Tried the starter a couple more times and it did a hard partial turn on one of the tries. The car does have a bad ring gear but I can always turn it over by hand and get past the bad sections and it starts fine. Tried to turn it by hand but couldn't (sprained my thumb in the process!). Pulled the starter and noted that the ring gear was in a spot with good teeth and starter itself seemed fine. Put it back in and tried again several times. Nothing. Then it hit me. There is an adapter on my comp. gauge that I had left on which has longer threads. The plug's reach is very short - SHIT! Unscrewed the hose from the plug hole and with a flashlite noticed just a slight indentation in the carbon buildup on top of the piston. The bottom face of the brass adapter on the hose seemed fine and not flattened. Any thoughts on what I've done? Jumped a few teeth on the timing chain or ???? Any help greatly appreciated! Regards, Dave.
bench test the starter, you probably just need fresh charge on battery. if your still wired for 6V grab a 12V battery for your test, it will spin it over plenty fast.
The plug on a Dodge six is over a valve, not a piston. If you didn't ram it too much, you should be fine, though a weak timing chain could have jumped. If it did it was due for a change anyway. Put a ring gear in it while it's in for the chain!!!!
Im speaking from the top of my head. but in pretty sure you are safe. The engine was turning over with the help of the starter when it hit the piston/valve. And then it probably did not have any high speed. All force put on it later have "only" put pressure on it. No Imapact force if you get what i mean. Turn it over a couple of revolutions, and check down the plug hole so everything seams OK.
Thanks for the fast replies guys! 55dude: the car is 12 volts and I had charged the battery within the last month. It spun the starter over just fine when I warmed the engine up in preparation for the comp. test. I will check the specific gravity to make sure. I also had the starter checked out some time ago when I was diagnosing what turned out to be the shot ring gear. Thanks! R Pope: Thanks for the education as to valve/piston location. It's been some years since I've had a flat six apart! I may have to pull the timing cover to check the chain. It would work out fine as in addition to the ring gear and (maybe) the chain, the rad needs to be done as well! Thanks! Mr 42: Hi Lars! Yes, I see exactly what you mean by just pressure and not force - very good point! When I get it unstuck I will check down the plug hole. Thanks! Best regards, Dave.
UPDATE: Tested the battery and it's right up - 1275 on all cells. Still seized up tight. Starter engages but doesn't crank it. Took out the rad and will take it down to get checked out as it has a leak. Will pull off the front engine mount and timing cover to see if anything is amiss there. Boy, the crank pulley sure has a super size bolt holding it on! Will post again as I delve into it! Regards, Dave.
Normally the procedure to run a compression test is to pull all of the plugs first. That lets the engine spin easier. Also have the throttle plate wide open to let air flow in. Are you sure nothing dropped down the spark plug hole that might have gotten on top of the piston?
Mr48chev: Thanks for your response! Yes, I thought of that after that pulling all the plugs might been better! Nothing got down the plug hole as I backed the plug out so far and then blasted the cavity under the plug's sealing ring with air to remove some loose crud that was there plus there was nothing small and loose on top of the head that could have bounced in. Thanks again for your thoughts! Regards, Dave.
Sounds to me like you'll find the problem when you get that timing cover off. I could be well wrong but I think you're gonna find the timing chain has somehow locked up. Those timing chains get pretty sloppy on the Mopar sixes.
while im not familiar with the internal architecture of a mopar 6, it is possible to knock #1 rod out of the block when the timing goes out and the rod hits the cam. this happening with yours maybe?
Rockabillybassman: Yes, I'm hoping it's something "simple" like the chain! I recall many years ago having an English Ford Consul four banger which had a chain so loose it wore a large set of grooves in the inside of the timing cover. Made a hell of a racket! Thanks for your reply! blue collar stu: Ouch! I hope it isn't that bad, but if I find nothing amiss under the timing cover, the side cover will be my next removal.....and then the head.....followed by the pan! Thanks for your thoughts! Regards, Dave.
The Jalopy Journal
