Bringing a 640 Back To Life (was Newcomer)

[tderrick]

I bet you have a couple of burned up valves. The originals cant handle unleaded gas, even with lead substitute with any load on the engine (ok for parade duty or idling around the yard but that is about it). Most old Fords have had them replaced years ago. A compression check will tell you quick.

I'm afraid you may be right... I think I'll bring out my local tractor mechanic
to do some tests. It may be out of my hands by now...

 

[Soundguy]

A compression test kit is under 20$ at harbor freight.

a dry test followed by a wet test will tell you compression, and ring wear vs valve wear.

IE.. low compression that comes up on a wet test is ring /bore wear.. low comp that does not come up on a wet test is valve wear..

( wet test is dumping in a tablspoon of oil in to the cyl.. it seals the rings for a few seconds.. )

soundguy

soundguy

 

[tderrick]

A compression test kit is under 20$ at harbor freight.



soundguy

soundguy

Would you send me the part # of a good one??

 

[wolc123]

All I do is turn the engine over with the key off and my thumb over the spark plug holes one at a time. Use your $20 to buy a few of the valves you are going to need. Dont skimp and just replace the burnt ones, as the unleaded gas will get all of them eventually.

 

[Soundguy]

Unleaded gas does not destroy valves.

With the exception of war time models, ALL ford tractors left the assy line with HARD valve seats.

Tetra Ethyl Lead was NOT a valve lubricant.. it was an anti-spark-knock / ping addative to help modify the low octane fuel used back then. Prevented or helped prevent pre-detonation.

A thumb test is an ok go / no go if you are looking for a stuck valve or trying to find TDC on a comp stroke.. but it is absolutely not calibrated, and a 20$ harbor freight comp tester can be a usefull diagnostic tool.

dry vs wet,vs leakdown tests are vcalid measurment of combustion chamber health..

Don't 'skimp' on tools and guess about parts!

soundguy

 

[wolc123]

S.G., Would you care to bet that he has burnt valves? Do you know how many hours are on that tractor, no reason to worry about ring wear. Unleaded gas does take out old Ford valves, I have seen it happen several times first hand and so has my good friend and mechanic down at the town highway garage.

 

[Soundguy]

I don't bet on anything.. I use a tester and leave the guessing out of it.

I've seen WAY more low comp numbers due to bad rings than valves.

that's not to say that valves never have problems.. and that's not to say HE doesn't have a valve problem.

the concept of unleaded gas destroying ford engines is about like bigfoot.

soundguy

 

[tderrick]

We'll find out soon enough about the valves...

 

[sandman2234]

A little squirt of oil and a pressure tester has sidetracked many a mechanic's valve job proposal, that often would have required the engine to be torn back down after the mechanic was done with the valve job. Usually they get the valve job and tear it down, getting you to spend some money, then hit you with the sight of a ridge at the top of the cylinder, saying you would be better off to go ahead and fix this while you have it torn down. Puts more money in their pockets.
David from jax

 

[Soundguy]

Yep... I've seen lots of life pumped back into an engine with a set of rings, a set of mean and rod bearing shells, and a ridge reaming.. and sometimes a lil hand lap on a valve if one looks bad...

I'd never just tear down for a valve job based on faith.. without a compression ( and leakdown ) test to see what all is going on..

Blind faith is good for religion..not so great on fixin engines...

soundguy