Hello All,

Well, we have discovered low compression on 3 cylinders... about 50 psi and think it is a ring/cyl problem.  The main symptom is a rough idle. 87,000 original miles

We are making room in the barn to park it and would like the membership's input on how to remove the engine.

1) The side door is only wide enough to maybe move the block thru.

2) The front opening is too small.

3) Remove the entire front fiberglass piece!

4) Remove the engine from the bottom

5) Remove one of the front windscreens


Thanks  Steve




Tags: Allegro Engine Removal, Class A Allegro Engine Removal, How to remove the engine in an Allegro Motorhome

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Thanks for the replies.

I figured that with something this old there would be more restoration work than routine maintenance. My first objective will be to get it mobile. After that, I'll see what it needs.

I'm going to look at it tomorrow.

  Jim, not being there nor having run any compression or leak down checks, if only 3 cylinders exhibit lower compression, might the problem be valves on those cylinders instead of  rings or cylinder?? If the other cylinders are acceptable and close in PSI to each other, its easier to pull the heads then the entire engine would be my guess. Then if you end up having to pull it all the heads are already off.

 Rough idling you mentioned may be vacuum leaks or valve problems ya know.

 Just a thought, your RV your money your call, its always fun to hear peoples opinions on such, to each their own, however.

 Best wishes God Bless and Merry Christmas

  John T 

Thanks for the suggestion, but the original poster had the issue back in 2010. This is why I hate bringing up old threads but this was a near perfect match for my issue and I was hoping Steve would provide a post mortem since so much time had passed.

But....sounds like Steve got lucky and just needed some top end work. "Mine" (it isn't mine yet) threw a connecting rod. At a minimum the block will need sleeved, but the rod may have damaged it beyond repair. I haven't see it yet. Going to look at it in about half an hour.

If all it needs is an engine I'll snag it. 454 blocks seem to plentiful and relatively inexpensive. I can rig something up to get the engine out the door. I actually have a rig for dropping FWD drivetrains out the bottom of cars, I'm sure I can tweak it in such a way that I can use it to lift the engine into the cab.

Why do you suspect the piston/ring/cylinder area instead of the valves?    Have you tested to verify?  Having a few bad cylinders would be rare unless the engine was severely overheated and run that way.

If you haven't already done this - you need to check compression after squiring oil in the spark-plug hole.  If after adding oil -the compression stays low - the problem is a valve and not the cylinder/piston.  If it DOES rise after adding oil  - then I guess you are on the correct track.  Like I said though, that would be rare unless some sort of disaster took place.  Rings rarely wear in modern engines.  The cylinder walls get scored, piston ring-grooves get overly wide, rings get scratched, etc.  So when it does happen - you often cannot fix just by fixing or replacing pistons and re-ringing.  

If you had pistons and cylinders in such bad shape that compression cannot rise above 50 PSI - then it ought to smoke something awful and foul plugs when it's running.  I.e., if compression leaks down, then oil will leak up.

I assume since you want to pull the engine - you plan on boring the cylinders oversize - or just replace the engine?

By the way, even if you had a few cylinders so bad that you only read 50 PSI when testing - that's only at 300 RPM I assume when cranking with the starter motor.  Once the engine runs and RPM is well over 1000 RPM, those worn cylinders would make enough compression to fire.  A compression reading is a measurement of compression leakage in a certain time-frame.  Any cylinder that makes 50 PSI when cranking will make more when the engine is running IF it's a cylinder problem.  Not the case if the problem is a valve or valve-seat.

I looked at it - I'll post a new thread for opinions.

Related to this thread, though, I think the block is salvageable. Seems like a wristpin came loose. Pushed the piston into the head. Lots of bent things, but I'd be willing to bet I could sleeve the cylinder. Even better would be if I could get away with boring it out. In any event, engine needs to come out.




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