Was running perfect - suddenly no compression

[REX55nord]

Hello all,

 

I recently rebuilt (complete teardown) a Model "30" Chrysler industrial engine, date code 1954.  I was quite impressed with myself last year when I buttoned it up - and it fired right up and ran like  sewing machine.  Sat over winter - and wouldn't start...just backfired (mainly out the exh, but on occasion thru the carb.)  She flooded out, so I let her dry out for a week.  In the meantime I checked the carb...all seemed good.  Also checked the ignition - it looked a little weak (color) to me, so I checked the electrical good; swapped acouple of parts from other engines/spare parts - still looked the same, so I got back to looking at the engine proper.  I discovered this afternoon that there is no compression on ANY cylinders (using the thumb test - I haven't put a tester to it)  I mean NONE.  What on earth would make a perfectly running engine suddenly not start and have little to no compression?? 

[P15-D24]

Have you checked the tongue on the head bolts?

[Don Coatney]

I am not familiar with the tongue head bolt check  .

 

But with  no compression across the board I would suspect there is a valve issue. Either all valves are stuck open or the cam is not turning. Remove the valve covers, spin the engine and inspect the valve action while spinning. 

[MBF]

Yup-what Don said......

[REX55nord]

No, I haven't checked the head torque but will do.  I can't imagine all or most valves would be stuck, since it had been running so good.  As far as the camshaft, the distributor is turning - does that not mean the camshaft is turning?

[Plymouthy Adams]

a spinning camshaft will open the valves..it WILL NOT close them...that is a function of the springs and proper valve guide clearance..free of carbon rust and such...

[MBF]

Hanging valves in a flatty is a common problem if they're not run regularly especially in humid areas

[_shel_ny]

Sat over winter - and wouldn't start...just backfired (mainly out the exh, but on occasion thru the carb.)  She flooded out,so I let her dry out for a week. ......................................................... What on earth would make a perfectly running engine suddenly not start and have little to no compression?? 

 

 

As Don said..........   stuck valves.......   You have listed classic examples of what would happen if the valves are sticking............. open...............    

[Dodgeb4ya]

You weren't running old gas?

[_shel_ny]

The 12 or so years that I had my car I always started the season (April or so) with the gas that was in the tank when parked. (November or so)

 

EDIT: I guess that is not the total truth. I filled, or primed the carb with fresh gas to replace that which had evaporated to get it fired up, then ran the stale gas.

Edited October 27, 2014 by shel_ny

[Plymouthy Adams]

DodgeB4ya makes a very wise statement..this new blend of fuels we have today goes stale in a short time past 30 days on the average...if it sits for a long long time the volatile components evaporate and metabolize into an mixture that is quick to gum up valves and valve guides..(am not a chemical engineer, the process I do not know so just putting it into words to let you know it is not good stuff when aged)   oh it is usually not noticeable till the engine has ran a bit through it and then left to cool..it is not recommended by warning even at majority of gas pumps to buy and store todays fuel past 30 day limit..

[NiftyFifty]

Best way to put the engine away at the end of the season, without a big mess is to get it slightly warm then let it idle and take off the air breather and stall it out with a dump of sea foam, or the sea foam intake cleaner....their both just a little oily and it leaves that as the last fluid on those parts vs today's ethanol gas

[REX55nord]

Thanks to all of you who weighed in on this - it really has helped me think it through.  Yes - I'll definitely check the valves - not only check if they're hanging up but re-check the lash, now that it has run a bit (since rebuild).  Does anyone object to setting them cold, as this is what I did before (I know they will need to be set with a slightly greater gap).  Another question: should I consider replacing the valve springs with nos or aftermarket - which might have a little more zing to them.  Note that I re-used the original springs - I checked them for matching height and saw no problems with any of them, but I did not check their strength.

[Plymouthy Adams]

you do not need more zing...zing in these engines are undue pressure on the tappet faces and the cam lobes themselves..when you rebuilt this engine you had checked to make to ensure the spring deflection pressure was correct and the  length was also in tolerance..if they passed at that time, they should still be good to go

Edited October 27, 2014 by Plymouthy Adams

[Don Coatney]

I did replace my valve springs when I rebuilt my engine but to the naked eye I could not see a difference. I set my lash when cold and I have not had any issues in over 40,000 miles. When you adjust the valves error on the loose side. Slight ticking is acceptable. If you adjust them too tight it can lead to burned valves.

 

[Dodgeb4ya]

I would not attempt to adjust the valves before making sure they are all free and you have run and completely warmed up the engine. You said it ran very well up to this issue so I doubt the adjustment changed much.

After it's running though I too would re check them.  HOT!

[REX55nord]

Thanks for the feedback on valves and springs.  I'll proceed with all of the advice in mind.