I bought a 66 f-250 with a 352 in it, it was donated to breast cancer research and i bought it on ebay. I drove it home 50 miles and it ran pretty good after i finally got it started. The next morning I was going to take it to register it, but when i started it it ran like crap. I pulled some plug wires and found it was not running on all cylinders. Pulled the valve covers and found push rods on intake valves 3,5,6,7. bent so bad you couldnt twist them. I checked the timing marks and seems ok rotor pointing to #1 with timing mark lined up. It seems to me the only thing it could be is bent valve stems not allowing valves to open. I put 120 psi in the cylinders and the valves are sealing, one i could hear a little air passing to the carb.

I think I have no choice but to pull heads?
looking at the heads this motor was probably rebuilt at some point.

Thanks, Robert

 

How old is the gas?

 

Old smells real bad, I replaced the bent rods and turned it over by hand and bent the new ones again.

 

Get all of that bad gas out.
You're going to need to free the valves. Once they are free, replace the pushrods, make sure they are no longer binding by turning it over by hand and watching the valves. Use fresh gas, start it and see what happens. It's likely the bad gas that caused them to seize.

 

Cool I will try that thanks! That would be sweet if i didnt have to tear it apart already.

 

I would like to know your out come of what works out for you! please keep us posted.

 

I will do that.
Heres another question, I got the push rods at autozone all they had were .030" longer rods so I got 16 of them they said this would cause no problem.
Is this true?
It has hydraulic lifters.

Thanks again Rob

 

A 352 has adjustable rocker arms, right? If so, then the longer pushrods should not hurt. If anything, they can help because the new adjuster screw position provides a slightly better rocker ratio.

 

there was no adjustment screw on/in the rocker...
...and all of the rockers are all mounted on one long shaft,...
you have to put in a sample length pushrod and see how much lifter plunger depression that you got.
many ./ most every NEW engine had different lengths as needed FROM THE FACTORY....

if the engine ever had a common valve and seat "grind' or head gasket resurfacing..then the pushrod length would obviously change...

there is no positive mannor to know what length...

9.620 is the right length you need.
but that is when the rockers are new...
as rocker wears, the pushrod length will also change...

this doing it WRONG,
is the number one reason that FE engines have leakey valves and burn out valveseats...

///knock bang ETC....low compression...

after you FIRST observe how much wear is on the rocker pushrod SEAT,
then
you can check the needed length with an adjustable pushrod...a PAIR of adjustable pushrods makes this a lot easier, especially since you have to remove the rockershaft and all of the rockers to be able to do it properly each time...( some individual rockers he can actually just "push' over because the rocker is only held in place on the shaft with a spring..)

as said, it is COMMON to have to use MANY different lengths pushrods in a FE engine..
as said, have seen many that had four or five different lengths

the ball ends on totally stock units have been found after wear to be shaped like a "football" instead of ROUND.

and many of the cup ends are worn flat inside the bottom....

and no telling what the rockers will look like.

I would also think about replacing the hyd. lifters for some new ones! Just remember to pump them up before starting the engine!!!! This is easy to do with the right 1/4" drive deep socket, a long 8" or longer extension.... take out your dizzy, (marking where its at before you take it out) get a good drill and run the socket down to the oil pump drive shaft and run the drill till you see oil coming out of ALL the hyd. lifters

 

Being the truck was a donor it was probably revved way beyond valve float (ie the crap was beat out of it for ****es and gigggles). This will bend the push rods.

It is common for FE engines to bend push rods as they are over 9 inches long. Some of the longest in any engine. I have a 68 T Bird special 390 that when i pulled it apart also had four bent push rods.

To replace them i would pull the intake and replace the lifters and install new stock length rods. Clean up the rockers, shafts and access their condition also. Replace if worn. Non stock length rods are make up for milling and other valve train mods. For a street engine the stock push rods and lifters rockers will do fine. If you are looking for racing or RPM then the push rods need to be matched as each one will have slight variance.

Garbz

 

Personally, I'd pull the heads and do it right. It's not hard , it's the messiness and time involved that have many people trying to take the shorter route. Inspect the heads, lifters and valves, they could be in need of some major attention from the sound of things.That way you can see a much more complete picture and do it right.

 

Instead of saying FE pushrods "are over 9" long" how about lookin' in the truck parts catalogs for the correct info.

1965/67 F100/350 352 & 1968 F100/350 360/390 before change L2: C4TZ6565B .. Pushrod / 9.62" long.

C8AZ6565A .. Pushrod .030" U.S. / C4TZ6565D .. Pushrod .060" U.S. / C4TZ6565C .. Pushrod .060" O.S.
----------------------------------------------------------------------------------------------------
1968 F100/350 360/390 from change L2; 1969/76 F100/350 360/390: C8AZ6565A .. Pushrod / 9.59" long.

C4TZ6565B .. Pushrod .030" O.S.

No FE engines w/adjustable rockers were installed in any F100/350's, nor in passenger car 352/390's after 1962 or with 410/428 engines.

 

I wouldn't pull the heads just yet. This wouldn't be the first instance I've heard of where bad gas caused valves to stick and bend pushrods. It's very easy to fix and eliminate the bad gas as a problem. If it does it again once the valves have been freed and good gas is being used, then dig deeper.

 

Im gonna change the fuel tap the valves free and new rods and give it a try I will let you know.

 

Bill they are over nine inches long. therefore my statement is correct as to the propensity to easily bend during float or other abnormal occurrences in the valve-train. One really does not care just how long in this statement.

The parts book is fairly useless in this case as after almost fifty years or a even multiple rebuild's there could be anything in there.

A typical case of longer is not better.

Welcome back from Vacacay.

Garbz