Great idea. Ford went with this non-adjustable system, and it's great if you are just taking the engine apart and putting it back together. If any head work is done though, or a aftermarket cam is installed, it can be a mess.

 

You should be able to tell if shorter pushrods are going to fix the problem without going to the trouble of installing and running them. If the pushrods are too long the problem is most likely coil-bind on the springs, meaning that the springs compress such that the coils touch each other before the maximum lift is achieved. The only other possibility is the valve touching the piston, and I think that is a very remote possibility unless the engine has been rebuilt with high compression pistons and/or a very high lift cam has been installed with high lift rocker arms.

So, with the valve covers off and a pair of straight pushrods installed on a cylinder that's been bending them, turn the engine over by hand via a breaker bar & socket on the harmonic balancer's bolt. As the engine comes up on TDC for the cylinder in question, watch the spring's coils. If they come close to closing up you need to measure the clearance with a feeler gauge to ensure they don't fully close, although at higher RPM and a hot engine the clearance will decrease.

I'm not sure what a safe clearance is, but Lunati says the minimum should be .060" on their site here - Lunati. If you have more than that your bent pushrods are because of something else, like valve/piston contact, guides that are too small, or even bent valves, and the heads need to come off to resolve those problems.

 

I'm still placing my money on excessively shimmed springs, causing coil bind. Shorter pushrods *may* help, but if the springs have lost that much tension and need shimmed this much, they will keep looking tension causing more issues in the future. Replacement springs aren't that costly, and will most likely be needed at some point down the road anyways.

 

When I rebuilt my engine I had to shim my new springs sometimes upwards of .050". What shims were used on your rebuilt heads?

 

From re-reading your original post, It sounds like the bottom end is still stock (pistons, etc.) Do you know how much was taken off the heads? Shouldn't have been more that .030".
Are you using hi-tak or a similar product on the intake gasket? Reason for asking is a buddy did that and after running for a while, the hi-tak worked it's way down the port from the gas and on to the valve seats, freezing them in place and bending pushrods. Just a thought.

 

The bottom end is all intact, as it has around 50000 miles.
As for the intake, I put Permatex ultra blue on the ends, and around the water ports. Otherwise it went on dry.
I'm not sure how much was taken off the deck when planed, and the machine shop doesn't remember either, so we are trying a couple of different length pushrods (when they come in) and see what happens.
Before trying the shorter pushrods, I want to reinstall a straight, stock length push rod, and rotate the crank a few times by hand, or ratchet, and concentrate on what is going on at the affected intake valves. I don't believe I have double valve springs, so I don't think there will be trouble with binding there.
As for not grinding off the tops of the valve stems, this may be why we were having trouble getting a compression reading, if the valves weren't closing all the way.
Will be a couple days before the shorter pushrods get here, but will post anything I find.

 

Hey Paul,

I've seen a few members on this thread outline some very concise procedures for checking everything that could be causing your issue. Take a few moments and compile that info, and run through the checks. I think you'll find your problem without just throwing pushrods at this problem.

I know it's hard to convey "tone" through the written media, so PLEASE don't take my post above as anything but just trying to help.

Check for installed height, spring bind, take the keepers off while the piston is at TDC and see if the guides are too tight, do the other check as suggested by f100jim in post #15, and you'll solve this. Don't guess, diagnose instead.

Seriously, good luck with this. I hope you find your problem.

 

I have one question are you making sure the lifter for that valve is at the bottom of its bore when tightening the rocker arms down?

I was working on a 400 one time and the center part of the lifters was stuck not allowing it to collapse which in turn bent a push rod, because it was at the top of the lobe.

 

Well, the day after Christmas, I decided to do some investigating.
With the help of a friend, after removing the pushrods and the rocker arm assemblies, I took a plastic hammer, and rapped on the valve stems.
Lo and behold, the three intake valves I was talking about (5-6-7) stuck open.
I do believe the valve guides are too tight, and the heads are coming off, and taken to a different engine shop, and have done correctly. Also taking note of the valve stem height, maybe my problems will be solved.
Will let ya all know, when the heads come back, and I find out what the engine shop says.
I'm keepin my finners crossed!

 

I am not exactly sure how they do it, but I think there is a spec for these non-adjustable heads, I am thinking it's from the head gasket surface to the top of the valve stem. I would quiz the shop about it. If they get it right, it just bolts together with no problems.

 

My son has the same problem as you. Bad Gas. The gas in the tank has so much varrnish in it from sitting that after running for a few hours it gums up the valve guide and seizes the valve in the guide. Drain and clean the tanks, put on the freash heads and see what happens.

 

I saw this today, so I thought I'd share it.

http://www.bhjproducts.com/bhj_downl...atalog_p22.pdf

 

Finally got the heads back from the machine shop.
The guy said that the guides were too tight.
So apparently what happened, is the valves didn't close fast enough for the pushrods to stay in contact with the valves, and dropped down, hitting whatever got in their way.
In the process of re installing them, and we will see if the mystery of the old pushrod bender is solved.

 

Thanks for the update!

 

Huh? I have never seen guides too tight. Especially with miles on them..