Ford Mustang Forum banner

Status
Not open for further replies.
1 - 5 of 5 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter #1
My newly aquired 66 GT started backfiring through the carburetor that got faster with acceleration. Checked the timing and everying thing seemed good. Pulled the valve covers off and found my issue (i think). One of my rocker arms was turned sideways, the push rod was bent and the hole were the push rod goes in to the valve seemed to be either altered or just worn on one side. The previous owner has put a screw-in rocker stud on this one rocker unlike the rest that is taller. You can see both issues in the picture attached. The head is the original head and the rest of the car is numbers matching. Is this head damaged beyond repair?? will it have to be replaced?? what should I do?? Please help??

Thanks in advance for your help!!!

Kyle
 

Attachments

·
Registered
Joined
·
9,200 Posts
Hello.:) I couldn't tell from that picture if this is a K code head or not, but, if it is not, I would try to find me another correctly date coded head, which shouldn't be very difficult to do, and wouldn't be expensive when you do find it. The problem wouldn't really be the push rod hole, it would be the valve guide. What probably happened was that the valve got stuck, the valve stem probably got bent along with the push rod, and damaged the valve guide, possibly even cracking the head.:shocked: However, if that's a K code head, that would be much harder to find, and wouldn't be anything close to cheap when you do finally track one down. It would be cheaper to magnaflux the head to see if it's cracked, replace the offending valve guide and fusion weld the head if it's cracked. Hope that helps.:)
 

·
Registered
Joined
·
1,161 Posts
The valve guide would be easier to fix than the pushrod guide. Once the guide is repaired, you still have an elongated pushrod guide hole to deal with. Without that being addressed, there is nothing to keep the rocker arm centered on the valve.
 

·
Registered
Joined
·
131 Posts
Regardless of whether you replace the heads or have these re-worked...spend the money (and it's not much more on top of the machine work you will already pay for) to have push rod guide plates installed when you have the head work done. Not having the guide plates is not the root cause of your problem (and from the pic I can't say for sure what is) but they are good, cheap insurance against having this kind of wear damage.

From the pic it does appear that the stud in question is different from the one next to it...but it's hard to troubleshoot things from one pic.
 

·
Registered
Joined
·
3,166 Posts
The heads that you have are an early design that uses the slotted pushrod hole as a guide for the pushrod itself. About 66 1/2 Ford went to a round P/R hole and used a slotted rocker arm (rail rockers). The valve tip end of the rocker was slotted keeping things aligned. They also went to valves with longer valve stems. You can't use the rail rockers unless you change to the longer valves.

A sticking valve caused by a valve guide problem may have led to a bent P/R (valve stuck open and kisses piston= bent pushrod). The bent pushrod wore into the slot until there was enough clearance to cause the rocker to fall off.

The cure would be to install guide plates with threaded rocker studs (the studs hold the guide plates). You will need to use hardened pushrods because of the guides. You can use your stock rockers and stock pushrod lengths. Of course this is after the valve guides are checked out.

The previous owner went with a quick fix, apparently. The possible problem with the bad valve guide and worn P/R slot wasn't addressed. All that he did was to replace the chewed up rocker stud (caused by the misalignment) and the bent pushrod. This can be done without pulling the head. I wonder why he didn't look for the cause.

The only other thing I can think of for replacing the rocker stud and having the P/R slot wear is if the pressed in stud itself worked loose. Is there a way to ask the previous owner?
 
1 - 5 of 5 Posts
Status
Not open for further replies.
Top