[Tony Wheeler]

Originally Posted by Malcolm Towrie

Your post and its annoyed tone puzzle me, Tony.

I think you've misread me Malcolm. It happens sometimes in this kind of forum. It's probably my lame attempts at humour. I assure you I'm not annoyed!

Originally Posted by Malcolm Towrie

You say the motor is running well, yet it has 2 cylinders with 30 psi compression.

Yes, that's what you reported Malcolm: "The carrier was running OK last summer and fall in parades and displays. It started and ran OK just before I did the compression test two days ago, even with horrible compression on 4 of 8 cylinders."

It's not uncommon to find minimal compression in several pots on these old flatheads. They'll still run happily for many years to come, and if restricted to parades they'll probably outlive the owner. Even in hard use they remain indestructible - my F15A road truck shows 40-70 psi in all pots and rattles alarmingly when cold, but after warm up I never hesitate to wring every last screaming rpm out of it through the gears. I'm sure Jacques if he's reading this will attest to its performance up steep mountain tracks - albeit at 4000 rpm! In practice, apart from a thirst for oil, it's a perfectly serviceable motor, and I enjoy not having to nurse it like a $5000 rebuild.

Of course, being accustomed to modern motors, it can be quite disconcerting to see readings of 30 psi, and the natural response is an overwhelming urge to pull the heads off and investigate. Perhaps that's why most owners avoid performing compression tests! However, we need to remind ourselves that compression tests are purely diagnostic, and pots showing 30-50 psi at cranking speed will still produce plenty of power.

Originally Posted by Malcolm Towrie

Yes, it starts and drives, but it is not a well-running motor IMO.

This seems at odds with your earlier report Malcolm: "The carrier was running OK last summer"....."but it is not a well-running motor IMO." I guess it comes down to one's definition of "motor running well". To my mind, if a motor is firing on all cylinders, and drives the vehicle satisfactorily, it's "running well". It may be down on power, but that's a different question. That's generally tolerable on MVs, thanks to plenty of gears and no need to keep up with traffic. Indeed, lack of power is arguably essential to the MV driving experience!

Of course, I fully understand your earlier point: "the owner likes his equipment to be in good condition". Particularly when: "This carrier is in very nice, restored condition and the engine was supposed to have been rebuilt." I too would be keen to address low compression issue in such a vehicle. I was merely urging forethought and proper diagnosis.

Originally Posted by Malcolm Towrie

the tapping the valves idea was suggested and it was easy to do, so why not?

I suspect there was some misunderstanding / miscommunication here Malcolm. It wasn't immediately clear from your initial post that YOUR motor was already running, and in Ron's discussion of stuck valves it wasn't immediately clear that HIS motor was not running! Again, it's inevitable with this kind of information exchange. As you say, no big deal in this case.

Originally Posted by Malcolm Towrie

So as a newbie to these engines, with the heads so temptingly accessible, it seemed a simple job to pull both the heads and intake manifold and check for ALL the various top-end related issues that could be causing this, AND fix them in the time we had available. All in one fell swoop.

Yes, it's always tempting to whip off those heads, but in practice it achieves very little. Unlike OHV heads you can't send them away for a valve job! Unfortunately the "quick fix" you were hoping for does not exist on flatheads, because the "top end" is actually in the block.

Originally Posted by Malcolm Towrie

Of course, now I know it isn't that simple to pull the heads, nor is it that simple to do a valve job on these engines, so we'll just run the old girl as-is until there's a space in her schedule to do the work.

I think that's basically what we were advocating Malcolm, as the time frame seemed unrealistic, and the diagnosis unconfirmed. As Lynn says: "if the engine has become tired you might end up with a big job on your hands." Another possibility yet to be ruled out is broken rings, which can also occur in a poorly rebuilt motor. If I were you I'd be keen to complete the wet and dry comp test, and if it all points to valves as we suspect, I'd be keen to remove the intake manifold and check clearances.

Anyway good luck with it Malcolm and keep us posted with any developments.

Cheers,
Tony