Hello looking to see if anyone else has had a similar issue. Fresh 50 mercury flathead Builder/specs unknown Fresh looking motor in the valley and in the pan. Turns over smooth. cylinders/rods looked good from below when I dropped the Pan. One first start cranked and got good oil pressure @60. 2x2 new strombergs set @2 psi. Fired up temp was rising and @3min in motor just stops. I check the fuel pressure and fire again. 2 min pass it locks up again. I let it cool. And try again and adjusted the timing. This time it went alot longer. I burped the thermostats and @190 motor locked up. Tried to spin the crank with the bolt and it was seized. Let it cool till the next day and it spun over by hand. Fired the motor. No knock or ping sounded good at at @190 again locked up. Talked to my local flathead builder and he thought the electric fuel pump was to strong and washing the cylinder walls and causing the pistons to seize. Also I have a sbc converted dizzy with new ignitor 3 electronic ignition and new petronics 3 coil. New plug wires and plugs. New fuel pump just replaced tonight. Still spins when cool. And will fire when motor cools down. Any thought would be appreciated . Thanks
If the fuel pump is overriding the needle/seat in the carbs enough to wash the cylinders at operating temperature, you'd probably be seeing some black smoke out the exhaust. It certainly sounds like there is not adequate piston-to-wall clearance. Heads are easy to pull, I'd be looking at the cylinder walls for severe scuffing. Or have a look with a bore scope.
2 PSI is a happy place for those Strombergs. If it was pissing enough fuel to wash the walls to that extent it would run like crap and your oil would smell like corn fuel. When it "locks up" does that mean you cant spin it even by hand? I'd be pulling the main caps and bustin out the plasti-gauge. Either that or those piston rings are on the snug side.
I'd opt for the piston/cylinder wall clearance being too tight. Once the pistons heat up they seize. When cool they let go and will run. Agree with heads off and have a look at the bores. For the cost of a couple of gaskets you may save a lot of angst and money.
I had simililar with a '50 cushman eagle. Long story short, rebuilder didn't gap the rings. It would start, run, lock up. Good Luck!
Thanks all I'm thinking it's something with the rings also. Letting her cool now and will look tomorrow and see what I can see. Just hoping I didn't ruin this block.
My Brother bought a 390 block to replace one that had a cracked cylinder Ran great at idle for a few minutes then would quit, let cool down, start up would quit We pulled it apart and found no evidence of of anything out of the ordinary We torqued the main caps with no inserts to check for size The front main in the block revealed a crack in the middle of the oil hole There were no marks or such on the front main inserts Hope ya find an answer ...... strange things happen sometimes Ricky.
Is it only doing this at idle? Had an electronic ignition in one of my cars and it would just stop running. Not a hesitant stop but a sudden sharp stop as if someone had unplugged my car.This is 1982 when this was happening so no internet yet. Had to use microfiche at the library. Anyway, after I checked the distributor, I found that one of the wires under the plate was broken but it would make contact with itself after the engine cooled down and then it would restart. Drive it or idle it for a bit and it would do it again. I fixed the wire and it never happened again.
Pic of your pistons if possible? I had that exact problem back in 1968.2 of my pistons(36-21 stud) did not have the slot cut all the way down to the bottom of the skirt.
If you get into it deep enough check the ring end gaps at both the top and bottom of the bore, at least as far as the lower range of the ring travel. Make sure the bores don't have excessive tapeer. And as oldtom already mentioned, make sure the ring grooves aren't varnished or carboned up. Also make sure the cam turns smoothly and freely and that the lifers have sufficient clearance in their bores.
What transmission is in it? Buddy of mine had a similar problem with a T5 in his. Input shaft was bottomed in the crank locking the motor up. We had to cut an 1/8 inch off the nose of the input shaft.
Hard lesson learned may years ago.........I pull down every engine I get, even crate engines..........Have found lots of loose parts, unacceptable clearances, poor quality control, and/or ignorant engine assemblers.
I would guess insufficient piston to wall clearance, but as posted previously it could be upper ring gap is too narrow, dirty ring lands or even a cam or crank clearance issue. I'd start with pulling the heads, looking for visual clues and mic the bores. If the bores mic out (with the rods/pistons in place) I'd move to the bottom end. If it does prove to be insufficient wall clearance or ring binding and the scoring isn't bad, you could get off with just a light hone and some rings. And some hours of work.
Pulled the drivers head and 5, has some scuffs but 6 looks like it hit something and has some issues up top on the piston. 7,8 look good. It's std but pistons 5,6 look older and 7,8 look new
So for whatever reason. 1,2,5,6 pistons are trash. But the rest are ok. Going to talk to my local flathead guy tomorrow and hoping the cylinders can be honed.
"Fresh rebuild". Someone wise on here (I know, long shot) once said "a non running engine is just parts. Pay accordingly"
Piston to cyl wall clearance too tight. Look at the cyls real good measure carefully.Plus pay attention to cyls out of round. lippy
That ain’t gonna buff out! Take some Works toilet bowl cleaner to the cylinders. It will take the galled aluminum off of the cylinder walls without hurting the bores. They might not be too bad. (Old small engine trick. Saved a lot of overbores.)
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