Hey all, I think I have got this figured out but wanted other opinions. Quick background: I purchased a 78 F250 with a 400 6.6 to restore. So far I have added an aluminum intake manifold, new Holley Carb, water pump, power steering pump, double ford racing timing chain and gears, 100 amp alternator, new MSD billet dist, MSD coil, heck the whole MSG ignition, valve covers, oil pan, trans pan, fuel pump, basically the whole top end. I did not, however do the cam or valves because after I inspected the motor when I had the intake off everything looked really clean.

Here is my problem, when I bought the truck there was about 1/4 tank of fuel in the back tank that smelled bad. first thing I did was fill both tanks only to find out the tank switch valve was bad and I could not run gas from the back tank. Over the next month I rebuilt the top end and had the motor running strong. Flash forward a couple weeks and I get around to replacing the tank switch valve and spend a Saturday driving around the Nevada highways burning off the gas in the rear tank with the motor running strong the whole way. The next day I start the truck and it is missing big time. I pulled the plugs to find that the #1 and #2 plugs are fouled out #3 and #4 fouled but not to bad #5,6,7,8 all look great. Replaced all the plugs and an inline fuel filter I had put in just for the gas in the back tank. I got the motor to fire but it was only running on 5,6,7,8. Checked to see if I maybe spun the distributor but it was still tight so I pulled the valve cover to find that all four intake rods are bent, the exhaust are fine. I think there may have been H20 in the gas and caused a H20 lock which bent the rods.....any ideas?

 

What would cause the intakes to bend like that is the valves are gummed up and sticking in the guides. probably from bad fuel

 

Any suggestions as to what to do besides changing the rods?

 

If it were mine I would pull the Springs and keepers on the valves that bent the push rods, Then I would check to make sure the valves are not seized in the guides. They should operate freely, as in open and rotate freely. if you have one or more that are stuck then you would have to pull the heads and have a valve job done to them.

My guess is they are going to be tight in the guides and probably should have a valve job done

 

It would take several quarts of water to hydrolock and engine, which would never happen fron the carburetor side of things.

I am guessing your cam timing jumped several teeth causing the pistons to smack the valves.

Josh

 

several QUARTS of water to hydrolock and engine? I don't think so...any small amount over the volume of the combustion chamber when the piston is at top dead center can potentially cause damage since water won't compress...it is MUCH less than a "quarts".

 

Irregardless, the engine would have been spitting, sputtering and quit long before enough water got in there from a gas tank to bend a push rod.

 

Bullitt is right. Water in the fuel would not cause a hydro lock. You pretty much need to pour it straight down the intake. However, l'm trying to figure out how that would affect the pushrods anyway. I've seen connecting rods get bent that way but I don't see how the pushrods could get damaged.

 

MY 300 I6 had a few bent rods, but I think it was from setting in a barn for about 20 years, and the top half was seizing up over that length of time. They tried to get it running to sell it after the owner passed away.

But here you have a freshly top built motor bending push rods. I saw this years ago with a guy building a small block with a big cam and four barrel he was out having fun with it and bent a few push rods, I think his remedy was to put a smaller cam, and new push rods in it. Never really did find the cause,.........

I couldn't see how you could get enough fuel AND water through the fuel system to cause it to hydro lock and keep it running without noticing it. Guys on here say how they take their rigs up to a higher RPM, and pour a can of Seafoam down the carb and not bend rods.

 

From what I make of his post is that he didnt rebuild the heads just inspected them. I am sticking with valves seizing in the guides. Probably will have to pull the top end of the motor to fix.

 

OK,I see your right RustyTub, I wonder if the top half was torqued right? So valves seizing, are you thinking an oil lube failure?

 

Dont know exactly why they would have seized. could be a lack of oil supply to the top end or just bad gummy deposits on the stems from the motor sitting for to long.

I am curious as to what the OG poster finds when he tears it down

 

Same from me. Had the same problem. Hard to fix without cleaning the gunk off the stems.

Sorry about the old thread but there wasn't a follow up of findings and I am curious.

 

1996 F250 7.3 Diesel Running WVO. Bent pushrods in #7 cylinder, repeatedly. Is it because of the WVO; filtered but not refined? Next. There is no intake manifold. How the heck do you get to the lifters?

 

You can pull them out of the pushrod holes, but it is easier, although more time consuming to just remove the heads.

Josh