Ford 640 with high compression pistons

Dakota Vogel

New User
I am currently restoring and rebuilding a ford 640 that I bought with a wagner loader. The motor was ceased when i bought it.
For the engine rebuild it needed new sleeves and pistons. I had bought a sleeve and piston sets, one set per cylinder. At the time of buying them the the high compression piston sets were only $2 more than the standard set. As of current time having the tractor completely rebuilt and restored the total $8 I spent to have a more power full tractor has been the most headache including $8 I've ever spent
Here the kits I used: item number 160840 on yesterday tractors website. Nearly $100 a kit now but only about $50 when I bought them back in January 2023.
Everything I've done to the motor: had the block blasted and cooked. I then resleeved the motor my self. Then sent it to a machinist who honed the cylinders because they shrank a little, and also decked the block and the head about a total of .023" off both combined. I replaced everything that the motor contains other than the cracked, cam, and rod.

The motor does not want to start. I contacted the manufacturer of the pistons, Reliance power parts, and was told the high compression pistons run on factor ford motor setting. That was not working for me, I new it wasn't going to work as I'm adding compression. Originally when I cranked it over it would have no effort of starting, have spark and fuel, the exhaust would spit vaporized gas. Started playing with timing, dropped it from 8 degrees timed then up to 20 degrees in 2 degree increments then dropped it back down to 15 degrees timed as that sounded the best. When I crank the motor on the starter the cylinders will pop now, but not every cylinder will pop in every combustion set. It will also have an occasional back fire. The little combustion that it does have isn't very strong but that is also only on the starter, motor doesn't run by its self. You might think it's a carb thing but it's not, motor gets fuel. I've messed with the needles and nothing gets better. Messing with the needles shouldn't have anything to do with a motor starting, there only there for idle control.
I recently started playing with valve last. I brought it down from the recommended .014 to .016 range down to .010 the up to .025 range, still nothing and doesn't even want to make as much popping sounds.

Is there anyone out there that have used high compression pistons on there mid to last 50s ford tractors
And is there anyone that would know the motor setting that the tractors need to run.

I know there's 2 factors for me, I have high compression pistons and I've reduced the block and head making a little more compression.

I'm on a few Facebook groups and the only "glorified" answer I've gotten from people is " your electronics are bad" and "your distributor is 180 out". There not, I've checked

I've been working on starting this motor for 2-3 hours a day for the last 3 months, I'm starting to feel very defeated. Not a good feeling for my first serious motor build.
Tell us how do you know the timing is correct, does the term "on the rock" mean anything to you.

Also what's the compression numbers.

Did you replace any other parts, parts like the exhaust manifold.

This post was edited by Hobo,NC on 07/03/2023 at 01:49 pm.
Always go back to basics...Does it have compression, don't guess. Is the distributor in correctly, bring #1 to compression and check the rotor to the cap. Firing order/, are the wires on correctly?
These are the most common things causing a new motor to not start. Of course it needs good gas, been down that road on old tractor new motor old gas.
I'm with Hobo, what's your compression numbers?

By way of comparison, I recently rebuilt a 1957 283 Chevy. The block had to be bored so I bought new
pistons. The originals were flat top, the new ones had valve relief notches in them (I was told that flat
tops were not available). Engine runs fine but averages about 125 PSI per hole, which is lower than what the
factory manual specifies.
I doubt very much the high compression pistons
have anything to do with this problem. Since you
had it hot tanked you must have had the cam out.
Im wondering if you could have it out of time with
the crankshaft. Remove the valve cover and all the
plugs (for easy cranking) and find top dead center
with a piece of wire down the spark plug hole. At
TDC on intake stroke, the intake valve lever should
be tightening up, or tight, and the valve should start
opening as soon as the piston starts down. If the
piston is part way down before the valve opens, or if
it opens before TDC, then youll have to recheck
your cam timing. Cam out of time will also cause
compression to be way down.
Distributor turns clockwise - firing order is 1-2-4-3 and #1 is the front cylinder. Are you wired correctly?

Agree with others, pistons are unlikely to be the factor associated with inability to start. Fuel, compression, and spark. One of those 3 is missing/wrongly timed.
ALL have replied with good answers. I concur your problem isn't mechanical; most likely electrical. I'll just add that incorrect wiring accounts for 99.98% of all non-
starting issues regardless if you have the OEM 6V/POS GRN or a 12V switcheroo setup going. Which are you using? You need to go thru and verify the entire wiring system is
correct. Also, on an engine rebuild, never just buy a kit until you get the block boiled and inspected, a qualified shop is best. Ya gotta know what sizes you need in
order to get the right kit. Get your manuals and verify wiring. Take no shortcuts.

Tim Daley (MI)

t sounds like you are so convinced that your problem is compression so you are not going to listen to anything else that you are told. So I will say: YES! you are correct! your problem is compression is too high. But please, what is your compression? Also, You state that the motor is getting fuel, which is nice, but it is oh so much nicer when the fuel is getting to the spark plugs. A RICH mixture is required for cold starts. That is why they have chokes. Are your plugs getting wet with gas?
Would like to suggest just one more thing to you is
high compression in any motor does not cause
starting problems. It causes operational problems if
compression is too high. The numbers you have
shown did not even raise the ratio 1/2 a point,
depending on the shape of the combustion
chamber. The only unknown factor is how much
more compression ratio is built into the pistons.
Even if they raised it a full point you are still under
8.0. I dont think there is anything wrong with the
parts you installed or the machine work you had
first thing would be dist is 180 degrees out of time. You timed it on the exhaust stroke and not on the intake stroke. You could just move the spark plug wires over two holes on the dist, to check this.. remember that there are two time you get tdc,,, and one is correct and the other is the exhaust stroke. What is your compression? do you even have any? did the valves stick, or pistons hit the valve and bend them so they dont seal? CHECK COMPRESSION.. If it is normal, then you need to check spark and gas. Does the engine run when you lightly spray in starter fluid while cranking?? IT SHOULD, unless you have a spark or compression problem. You could be a tooth off on the cam timing which will give you problems and if too far off, low compression, and valves hitting pistons. again, what is your compression? Have you put a timing light on it? Also what plugs and what gap. Get the japanese plugs for best results, as most of the china made american brand plugs refuse to fire over 120lbs of compression.
I built a motor for a 600 project with high compression pistons. I used a head from a 2000 that had the smallest combustion chambers and had it cut .050 . What Fritz said is correct even at that the compression is so low to start with that I doubt that I had 8 to 1. Not enough change for timing to be a consideration. If its popping you are getting fire and gas just not at the right time. It sounds to me that that the distributer and or firing order and cam timing are out. Even I have made that mistake over the years once or twice and many times corrected others mistakes. It's not the pistons.

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