Technical 265 Chrysler Flathead 6 Diagnostic

Cooling system is clean too. The br*** water tube was near spotless.

 

An in frame rebuild is possible on a six. I wouldn't think the rings are broken as there are no scratches in the bores.

 

I see no evidence of broken rings.
No scratches and the ridge up top is minute.
Okay so torked head back down had cyl 5 and 6 soaking in MMO it drained off.
Ran a final hand bomb compression test.
Here's the finale.
Cyl 6 won't rise over 55.
Might have to look at that piston or friggin well start her up.
Got a bunch a little things to do like swap on truck oil pan and pickup. Etc.

 

Are you guys sure on that spec of .015 or .020 taper? I think you have the decimal point in the wrong place.

 

Although you say that burnt valves are not obvious, you still could have a valve that is not seating well and thus the low number on #6. I'd do another leak-down after hitting the valves with some 400 wet paper.

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Well Im not making it up..lol Its exactly what is in the Chrysler Industrial Flathead 6s manual. Because it sure would not be .002 or .0015 taper.

The thought has crossed my mind 4 sure. However on 3 consecutive leakdown tests with cyl 6 at TDC no leaking out intake or exhaust valves.
So most likely not a valve issue Im leaning toward stuck ring or a broken ring.

 

I am astounded that Chrysler would say put it back together with .019" taper, but I believe you . It seems like it would smoke like a chimney. Times have changed!

 

Believe me, I was astounded too. I expected. 007 to .010 at most. Very loose tolerances. No wonder they soldier on when damaged to death.
The .020 taper seems like a cone...lol

 

I know my eye sight is not the best but I'm not seeing any ridge in those pictures, certainly not enough of a ridge to cause trouble.

Since you have the engine out you could strip it inspect and measure crank, bearings , oil pump etc. Hone cylinders and put it back together with new low tension Moly rings. Check valve stem clearance, lap valves, etc. If it was rebuilt recently (not many hours of running) this plus new gaskets should be all it needs.

If it's a real poverty row project you could just free up the rings, lap the valves and cross your fingers.

Did you speak of a mild hop up with cam, shaved head, shaved flywheel, dual carbs and dual exhaust?

A few rust pits in the cylinders won't hurt anything. Unless the rust patches are big enough to snag the rings. Look at the holes in a 2 stroke cylinder. Small pits will soon fill with carbon and get smoothed over.

 

Start it up outside of the truck. A engine don't need to be in a vehicle to run. I think after it runs a bit the compression will increase.

 

Moly rings need a very good hatch to seal. Stick with cast iron.

You guys are getting "mechanics disease" also know as "If it isn't new it must be replaced"

Clean it up and run it. Decking the head a tad might help, maybe not. If it was a 265 Chevy V8 guys would put it in stock. The 265 dodge probably makes 2x the torque of a Chevy 265.

 

All good stuff. Recent rebuild early 80s....lol how many hours after who knows.
I have dual carbs and exhaust nothing else.
Im not gonna shave head just yet. I may put on a 218 head for a compression boost.
Im gonna try and run her see whats what.
Thanx

Great idea just need a bell, manifolds and carb. I dont have spares right now.
See what I can dig up.
Thanx

 

Pretty sure the plan is you just stated.
And gobs of tork as you stated like 225 ft lbs at 1600 RPM.
Compression by hand is damn near normal in 5 cyls.
Its a brute of an engine compared to even early V8s

 

Flat Six I am looking at my Chrysler Corporation of Canada Shop Manual covering 1949 - 50 - 51 - 52 Chrysler, Dodge, DeSoto and Plymouth cars. In the Engine - 7 - 15 section under Reconditioning Cylinder Walls it says 'Maximum allowable taper .0015" Maximum out of round .002" A good job should show no more than .0005" out-of-round and .0005" taper. If they are badly scored or out of round they should first be bored with a reliable boring tool and then polished with a hone.'

This is much tighter than the usual .007 rule of thumb and much, much tighter than the .015 and .020 you quoted. Suggest you check your manual again. If I missed something give me the chapter and verse and I will check again in my manual.

 

Here you go Rusty, and a tidbit of 265 comparison to early HEMI in trucks.

 

Cc the 218 head before you put it on!
With the Plymouth flatty the early heads had larger chambers and poor design. The 56 head with .060 off was quite a jump in compression. Like .5 of a point!

 

You will have to use your best judgement, I hope your engine has no where near .020 piston slop.

 

Most likely just use 265 head. Get her running and see whats what.
At 100 psi compression by spinning by hand in 2 to 3 strokes not bad.

 

Okay so tried hole 6 this AM. Got 75 PSI 1st crack 2nd time 60.
Added some oil no change. I suspect valve leaking some possibly.
When hand cranking it hits 50 psi on first pull. All other cyls remain 100+

 

I bet the valve is sticking in the block. Crud on the stems will do that. Make sure the lifter is on the base circle of the cam and give the offending valve a whack with a rubber hammer.

 

Okay so had a peak in another Chrysler shop manual.
The tolerances for outta round are friggin huge, cyl taper .030 rebore, and outta round .004.
Very forgiving to say the least.
Compression at 100 psi acceptable spec too.
Here is the page from my 40 through 49 Chrysler shop manual.
Pic of lifter chamber very friggin clean in there.

 

You could just pull #6 piston, and clean the carbon off the ring groves. Then you can insert one of the rings into the cylinder and measure the end gap at a couple places in the cylinder, then you will know how much tapper your cylinder has.
Your spec sheet also gives an acceptable ring end gap, so you will know what shape the rings are in. Gene

 

I can't see an engine where the rings are moving .020 every time the piston goes up and down lasting very long. I have been around farm machinery all my life with the age of a Super 92 2000 hrs was about the average life if the air cleaner was serviced I don't see a lot of ware in a second time around engine My question how much side to side movement can you get when the piston is at the top.

 

UPDATE Extra Extra Read All About It
Okay today pulled #6 piston to see whats going on.
Some surprises,
3 ring pistons
Some not surprises
Rings rusty stuck in lands.
Some dirt on bearing at some point
Put top ring into cyl, HUGE GAP...yikes
Sime pics 4 you.

 

Do you have another set of rings for one cylinder? Or, clean those, oil up and put back together? They won't get rusty when running. Not sure what to do about the ring gap at bottom of cylinder. Does the bore measure within tolerance?

 

No measurements yet.
But ridge was hardly nothing.
Ring gap is friggin huge.
Not sure what Im gonna do yet.
I wont **** around with it a half ***ed job before I get mad and off to my favorite engine builder who's company rebuilt it once in early 1980s.

 

It might be at the point of beyond my experience on this.
If I tear in further it might as well be pro built.
Nice that it has 3 ring pistons though instead of 4

 

Okay so put a ring into hole 6. The ring is off 6 piston, top ring.
Huge ring end gap. Those rings wore right down.
The bore has a slight ridge only and placing piston upside down in hole has .008 clearance on side. Yes I know thats bush league. I have no dial gauge and don't know how to use 1 anyway.
The pistons are 3 ring which are not factory. But .040 over and 2 x 1/16 compression rings and a 3/32 oil wiper.

 

So, stack a bunch of feeler gauges together and measure the end gap at the top and again at the bottom and see what the difference between the two measurements are.

Your clearance between the piston and the cylinder wall is not bad. Those old blocks were tough. If the ring got stuck on the piston, it could wear down pretty fast.
The bearing doesn't look too bad either, if the crank looks that smooth, your probably OK there as well.
It looks like a tear down, clean up, a hone job, new rings, bearings and gaskets and you will be good for another 50,000 miles. Gene

 

Thanx Gene, they sure wore out.
Will try as you mentioned in the morning see what I can come up with.
No wonder a cyl leakdown test was such a failure...lol