Technical 265 Mopar Flathead compression readings

I recently purchased a 265 Chrysler Spitfire engine and the compression readings as follows;
1. 138
2. 140
3. 30
4. 30
5. 35
6. 140
Ironically another used 251 used chrysler flathead engine that also reads low in cylinders 3 and 4. What would cause this? coincidence?
I have squirted some oil on the 3,5, and 5 cylinders but no climb on the PSI at all.

I recall someone providing advice on how to check the valves for leakage and adjustment. A leakdown test would require the cylinder to be tested to be on TDC. How would I verify that each cylinder be on TDC when I test?
My apologies if these questions seem basic but engine mechanics is not my forte.

 

Low compression on adjacent cylinders can indicate a blown head gasket. Look for timing marks on the front pulley to find TDC. There is another way that is very accurate, that applies to Chrysler flatheads. There is a small pipe plug in the middle of the head, over the #6 cylinder. Take it out and you can drop a screwdriver down on the piston. You can turn the engine by hand and tell exactly when the piston is at TDC. #6 and #1 rise and fall together. The others are at 120 degrees.

Oil would bring compression up if the problem was bad rings. Since it didn't, the problem must be bad valves or (long shot) broken pistons.

If the engine has been out of commission for a long time the valves may be stuck. Or, could be pistons or head gasket.

There is a simple device that screws into the spark plug hole that allows you to pressurize the cylinder from an air hose. If you do this and you can hear a hissing from the carburetor, you have a bad intake valve. From the exhaust, bad exhaust valve. From the adjacent cylinder spark plug hole, bad gasket.

It could be the best thing would be to take the head off and have a look. Head gaskets are not too expensive. In a pinch you might be able to reuse the old one if it is not blown and you soak it in water overnight.

 

Have you tried to turn the engine over or get it running? If not, maybe you should spray some penetrating oil in the cylinders leave it a few days and turn it over with the starter, put the spark plugs back in and try to start it. It may be nothing worse than a few stuck valves from sitting.

 

Thank you guys for the input. I'm leaning to doing a leak down test and I'm assuming that each cylinder that is tested should be at TDC.
I got the engine so cheap that I didn't ask the PO many questions but I do recall him saying something about a leak. I'm guessing a head gasket leak.

Motor hasn't sat for more than 6 months by PO but I'm going to start it, check for stuck valves and compression test again.

Would I be able to see stuck valves from the side of the engine while it's running?


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you'd probably be able to see stuck valves when you crank it over by hand, more easily.

Might not even run the way it is? or it might? be fun to see.

How much does a new head gasket cost?

 

Looks like a head gasket is going to run in the 30-35 dollar range. The head is going to have to come off anyway if there is no compression. Stuck valves, burnt valves blown gasket all need the head off to repair. If it was me I would pull the head and go from there.

 

I have been reading a lot about these old sixes. Stuck valves seems pretty common.
Actually running it may unstick the valves, would at least give it a shot before tearing into it.
Maybe removing the valve covers and a little persuasion is all that is needed.
But if the engine has only been sitting 6 months ... something seems awry.

 

Correct me if I am wrong, I thought the spitfire 6 was a flathead?

 

Yes sir, it is a flathead, valve covers are on the side of the block not the top.

 

Yes the "Spitfire" head on Chrysler cars, nothing special except the embossed casting design.
I is definitely a side valve L head engine...

 

I have the engine on a cradle and I'll be installing an Edmunds aluminum head anyways. But I think I will open up the side valve covers start the engine and see if there's an obvious stuck valve.
Would like to play with it for a bit before opening her up.

Thank all of you for the great input.




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Again, I think stuck valves will be easier to see if you turn it by hand or the starter. know it was obvious when I did it with a Ford flathead that had two stuck valves.

I like your engine stand, except for the small casters. I built mine the same way and found the cherry-picker legs won't go under the engine stand, so taking the engine on and off is a bitch. The next time, I'll use larger casters (also, easier to roll around) or spacers to get it high enough.

 

Tubman, I want to make this engine so fast that I was afraid that bigger caster will allow the engine to take off!! Lol.

I makes this stand in a rush and it seems to hold up pretty well and rolls smooth. Not to crazy about not being able to remove the oil pan because the cradle is against the oil pan bolts.


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I'm assuming you can see stuck valves via the side covers when turning by hand?


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It is suggested you adjust the valves with the motor warm and running, here is a youtube video showing a valve adjustment.

 

My only point is, you should be able to see if the valves are operating properly by turning over the engine with the cover off. I saw one photo where the tappet was stuck in the up position, this leaves the valve open and as the cam rotates, it does not lift the tappet that is already lifted and stuck.

 

Perfect. Thank you! I will check this weekend


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Lots of good advice given here! We used the "side covers removal" (or "minor exploratory surgery") method to diagnose a similar problem in my daughter's '56 Plymouth's flat six. Turned out #4 exhaust valve was stuck wide open and we ended up pulling the head when efforts to free it through the side opening failed. It now purrs like a kitten!
With regard to reusing a head gasket, I couldn't get a new one for the ten dollar replacement 202 c.i. Hudson flat six engine in my '54 Jet oval track racer back in 1973 after freeing up some stuck valves that it had. A racing buddy had told me to spray both sides of the old gasket with rattle can gloss enamel (colour optional) and torque her down. Worked like a hot damn! Copped a third place in the Championship race and got a big trophy and kiss from a cute trophy gal! Good luck! Regards, Dave.

 

I once heard that silver or gold metallic paint works best because of the metal or copper in the paint. I decided to go with Silver metallic on my last flathead new gasket replacement.


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I spun the motor with the side valve covers off. All the valves move freely. I'll be removing the head shortly.


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I got a bit impatient and removed the head without doing a complete leakdown test to identify the issue.
The head is off to the machine shop to determine evenness and shave some off if possible.

No valves are stuck when spinning by hand and no noticible leaking by looking at the gasket. I'm assuming the problem could be a slightly warped head? The good thing i have three, will get all resurfaces so I can't try other and check if the compression even out.

What else is recommended I do to the valves while the head is off?

 

. Also check compression rings by pouring light weight oil in cylinders..if rings are good it will take time for the oil to drain down..if it drains faster in the cylinders in question your rings are bad ....also buy some lapping compound and lap the valves....

 

Thanks choptop. I'm going to try the oil.

 

If you are hopping it up (high compression head, multi carbs) better tear it down and check crankshaft, bearings, oil pump, rings and valves. An old engine will often go on for years if you baby it. If you hop it up it will blow up in a few weeks. Have seen this happen more than once.

You need a ring and valve job anyway from the sound of it. Spend the money for a gasket set, rings, and possibly bearings and grind the valves. Parts are cheap for those motors. If everything is up to specs you will be surprised how it purrs.

O ya, while you have it apart would be a good time to install a reground cam and have the flywheel lightened (old time speed secret for whippier acceleration).

 

If you want to know what one of those motors is capable of in good condition check this out.

http://www.allpar.com/cars/desoto/suburban-1951.html


My favorite quote- at high altitude at 70 MPH it smooths out like a perfectly balanced turbine. This in a 5000 pound DeSoto 8 passenger limousine with 4:11 gears and 185,000 miles on it. While towing a trailer at 10,000 feet elevation.

 

Thanks. That is one thing I was debating doing. I'm just afraid to keep going the extra step and never get the car on the road.
I do have a buddy that has a machine shop that can do the work at a great discount t for me but worries me if any engine rebuilding shop can do the work on these old flatheads or not. The last 236 flathead I took him, he had tons of questions and I decided to pull the engine out. I never did get that engine done. This will be my fourth engine I've owned but never got one on the road. The PO of this one says it was freshly rebuilt no more that 2-3k miles on the motor. It does look to be in pretty good condition and hoping that it was just a warped head or a leaking head gasket.

Thanks for the advice.

 

All oil has maintained same lever across pistons.

 

Anyone know of a local shop in SoCal, San Gabriel Valley preferred, that can lighten the flywheel?