Messed something up pretty bad

250mav

Well-known member
when i got my blue 72 250/c4 mav it had a little bit of a miss. swapped in new plugs and it went away except a very slight miss around 50 and up in 3rd

so since last night on the way home from the beach it started to get a little worse. figured the plugs were fouling again.

im driving today and she just sputters to a stop and i roll into the speedy gas. i give 'er a min to cool down, go buy a drink and giver 'er a crank. it doesnt even sound like it was close to wanting to fire but a big thick cloud of white smoke comes out of the oil cap and through the dip stick. poped the timing chain was my first thought. so i pulled the dizzy cap and then spun the fan. the crank was turning as was the rotor so the chain is still in one piece since the dizzy is spun off the cam and i was turning the crank. tho the thought of a skipped tooth is still present. the inside of the cap looks very good as do the internals off the dizzy tho i dont claim to be the least bit knowlegable about points. but noting looked dirty or ate up or anything like that.

eventually after letting it cool down for about an hour i limped it a few miles up the road to my girl friends house. it felt like it was on 3 cyls and didnt have anything to offer above 30mph

im dealing with some very excessive crank case pressure and also smoking exhaust. but shes' missing so bad the tail pipe smoke could be from that but it looks more like oil then running rich

at this point i havent even put a wrench to it. im going to pull the plugs first and see what they tell me. i'll post some pics too to get a 2nd opinion

i look foward to hearing you guys thoughts
 
Possibly a sheared distributor rollpin? Check your base timing and plug order. Could anyone have swapped the leads around?

Has a vacuum hose come off anywhere?
 
well heres the plug out of the #3 hole

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run a compression check if you get a chance.

pull your valve cover and see if anything looks out of place also.

def signs of some interaction of parts though.
 
Geezzz,that sucks '250',I'm sorry to hear it :( . You've got back-up transportation,right :unsure:: ~OO6.
 
its too dark to take a clear pic so i'll put it up tomorrow.

anyway, i just finished taking the head off. on top of piston #3 theres a hole big enough to stick about 3 fingers into and the valve its self is down in the oil pan somewhere.

on a more postive note theres NO damage to the cylinder wall so i should just be able to pull the motor and slide in a new piston. the intake valve and combution chamger look a little scared but i think the heads OK. just needs 2 new valves put in.

my everyday car is my 1976 250 comet 4dr, so yea im OK

that car is beat to the ground and this new maverick was in 100x better shape. sheme it happened like that.

:cry: :cry: :cry:

and we were just at the beach enjoying our selves yesterday too

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damn, that sucks. you might not even need to pull it out, just drop the pan, pull old piston out, hone, and slip the new one in. you'll have to get on your back, but i replaced rod bearings and rings like that on a friend's car once, it wasn't hard.
 
yea thats probably what im going to do. i didnt cound on the wall not having any damage. i was ready to pull it out and get a new one


so where can i get individual pistons and valves at? Napa maybe?
 
It may be a bit more involved than replacing the piston and valves. I would want to know why the valve decided to poke a hole in the piston in the first place. You might check your timing chain and gears too.
Doug
 
well now that i got out there in the sunlight im not feeling as optimistic about the condition of the cylinder walls

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I just suffered a similar problem on my winter car (Izusu Amigo). On that car I had a performance cam w/ slightly more lift and I suspect that the extra lift (over 60,000 miles of use) fatigued and broke the spring. Once the spring broke there was no tension on the valve stem keeper. I have no idea where the valce stem ended up at. Link to modern art (used to be an aluminum head) http://i290.photobucket.com/albums/ll27 ... 280018.jpg Link to the ventilated piston http://i290.photobucket.com/albums/ll27 ... 280023.jpg. I also intent to swap in a new piston but in my case I also get to spend $500 on a replacement head.

On the positive side, I rushed the '78 200 replacement engine into my Falcon in mid June and it has been my daily driver since.
 
Exact same thing happened to me.

I also managed to crack both the block and the head.

I think it was my #2.

Not sure what caused it, suspected spring failure.
 
My Lincoln had been sitting for a year or so, and when I started it up, it soumded like a diesel w/ all the valve clatter. I could not get above 40 mph. The exhaust valves had rusted to the cast iron guides and it bent 7 of the 8 push rods. You might check all your push rods while the rocker arms are off. Maybe a valve job is in order.
Doug.
 
Did you find any clues inside the valve cover as to what let loose on the top end? Was the spring in one piece? Did the keepers show signs of heavy wear?
 
the retainer in the top of the spring was broken into a few pieces still sitting there. the spring was still inder the rocket tho in the right spot
 
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