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I recently needed to replace the heads on my 1966 289 engine because one of the heads had cracked just above the front lower head bolt near the #1 cylinder. I bought some rebuilt replacement heads with the same C6 0E casting numbers from a reputable supplier. Immediately after installing them I broke a #3 exhaust valve rocker arm. I also found that 6 of the 8 exhaust valve push rods were bent. :sadcry: During the investigation into why I thought this may have occurred I found the source of this problem to be the fact the valve springs were in a coil binding situation when the valve was fully open. It turns out when the replacement cylinder head supplier rebuilt these heads the valve spring assembled height he used was 1.55 inches – significantly lower than 1.75 to 1.78 inches which is what is specified in 1966 Ford Mustang shop manual. I also measured a number of the valve springs and found they went into coil binding at about 1.17 inches. This means the total valve travel before spring coil binding is about 0.38 inches. Since the specified exhaust valve lift is 0.38 inches this confirmed my suspicion that it was truly spring coil binding that created this problem. And yes, I did check the valve to piston clearance and found it to be much greater than specified 0.082 to 0.152 inches, so I know the problem was not associated with the valve hitting the piston. When I contacted company I bought these heads from they indicated these were stock replacement valves and could not offer any explanation why there was a problem.

Has anyone else had any similar experiences?
 

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I'm surprised at the 1.55 installed height that's the height for a I6 not a V8, did they install shims under the springs, or used shorter valves, or different retainers and keepers. Good Luck.
 

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Another thing to consider is 1966 is the year Ford switched from non rail rockers to rail type rockers. The earlier head used non rail rockers with hardened pushrods and the pushrod holes are oval shaped. Also the valve stems don't stick out as far over the valve spring retainers. The later style has circular pushrod holes and rails on the sides of the rockers to keep them centered on the pushrods...

The geometry between the 2 is different and I've heard of (reputable) builders mixing and matching the 2 before. If you get the shorter valve stems with rail type rockers, then the rockers come in contact with the spring retainers. Also using the wrong length pushrods can lead to other problems. Confirm if you have the early 66 or later 66 style heads and then double check you have the correct associated components...
 

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I'm surprised at the 1.55 installed height that's the height for a I6 not a V8, did they install shims under the springs, or used shorter valves, or different retainers and keepers. Good Luck.
There are no shims under the valve springs and the retainers / keepers appear to be the same as the original. Not really sure if the replacement heads have a shorter valve as I no longer have the original heads that would allow me to check this out.
 

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Another thing to consider is 1966 is the year Ford switched from non rail rockers to rail type rockers. The earlier head used non rail rockers with hardened pushrods and the pushrod holes are oval shaped. Also the valve stems don't stick out as far over the valve spring retainers. The later style has circular pushrod holes and rails on the sides of the rockers to keep them centered on the pushrods...

The geometry between the 2 is different and I've heard of (reputable) builders mixing and matching the 2 before. If you get the shorter valve stems with rail type rockers, then the rockers come in contact with the spring retainers. Also using the wrong length pushrods can lead to other problems. Confirm if you have the early 66 or later 66 style heads and then double check you have the correct associated components...
You are quite correct that Ford changed over from a non-rail rocker arm to a rail type rocker arm in mid-1966. There are at least two valve types that were used with different valve tip lengths (the distance between the top of the valve stem and the top keeper groove). One of these has a valve tip length of ).370 inches and the other is about 0.20 inches longer. Both were used with rail type rocker arms - and shorter has sufficient clearance to not interfer with the valve spring retainer as you incorrectly indicated may occur.

Again, my problem seems to be associated with the valve springs coil binding. The only variables that can account for this are camshaft lift, rocker arm ratio (the product of these two results in total valve lift), installed valve spring height and how much spring compression travel there is before the valve spring binds. With the valve spring height set at 1.55 and the springs binding at 1.17 inches that means there is a maximum spring compression travel of 0.380 inches - and since the specified valve lift is also 0.380 inches spring binding is probably occuring!

Again, I guess may real question is does anyone know if there are stock 289 Ford valves that are about 0.23 inches different in length when measured from the face of the valve to the lower keeper groove. I suspect there are since this appears to be my problem, but I have not been able to identify these two different valves.
 

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Look under the rocker (or remove it) and visually check how much of the valve stem is sticking out above the spring retainer. It will be obvious if you have the longer or shorter ones. The shorter ones will be almost flush and the longer ones stick out about 1/4"...

Are your rockers rail type or not? Do you have pushrod slots or holes?
 

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Discussion Starter #7
Look under the rocker (or remove it) and visually check how much of the valve stem is sticking out above the spring retainer. It will be obvious if you have the longer or shorter ones. The shorter ones will be almost flush and the longer ones stick out about 1/4"...

Are your rockers rail type or not? Do you have pushrod slots or holes?
The problem is not with the valve tip length. The valves that I have have the shorter - 0.370 inch valve tip length - and there is more than sufficient clearance so only the rocker arm tip comes in contact with the top of the valve stem and no other portion of the rocker (be it the rails or any other part) comes in contact with the valve spring retainer throughout the complete engine cycle.

Once again, the source of my problem is the valve spring assembled height. The major factors that contribute to this are the distance between the valve face and the upper keeper grove, the distance between the cylinder head valve seat and the cylinder head valve spring seat and the retainer / keeper being used. Since the cylinder head is basically the same, the retainer / keeper are the same and only variable seems to be the valve and the dimension between the valve face to the top groove of the keeper.
 

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...and shorter has sufficient clearance to not interfer with the valve spring retainer as you incorrectly indicated may occur.
It seems you have a bit more homework to do...

Again, I guess may real question is does anyone know if there are stock 289 Ford valves that are about 0.23 inches different in length when measured from the face of the valve to the lower keeper groove.
Yes, the early style were about 1/16" to 1/8" above the keepers. When combined with the rail type rockers they will indeed come in contact with the retainers and eventually lead to a dropped valve...

The problem is not with the valve tip length. The valves that I have have the shorter - 0.370 inch valve tip length - and there is more than sufficient clearance so only the rocker arm tip comes in contact with the top of the valve stem and no other portion of the rocker (be it the rails or any other part) comes in contact with the valve spring retainer throughout the complete engine cycle.

Once again, the source of my problem is the valve spring assembled height.
And knowing is half the battle...

My assumption to your original question was that you had mismatched parts (springs or otherwise). We would be able to help you diagnose your problem if you told us which components you have now, or better yet post pictures...

Just trying to help buddy...:winks
 

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I think you are right DragRacer 289, you have the shorter valves, did they go to larger dia valves, if so did they use chevy std length valves which are too short they have to use the .100 longer length or more valves in fords. The installed height is too short for the 289. Good Luck.
 

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Discussion Starter #10
It seems you have a bit more homework to do...



Yes, the early style were about 1/16" to 1/8" above the keepers. When combined with the rail type rockers they will indeed come in contact with the retainers and eventually lead to a dropped valve...



And knowing is half the battle...

My assumption to your original question was that you had mismatched parts (springs or otherwise). We would be able to help you diagnose your problem if you told us which components you have now, or better yet post pictures...

Just trying to help buddy...:winks
OK, here is what I found after digging a multitude of parts catalogs and making a lot of additional measurements on my original heads and the rebuilt heads I purchased.

As it turns out there were two valve / valve spring combination installed in the 289 by Ford in 1966 – although the 1996 Mustang Shop Manual published by Ford only shows one configuration. The first configuration had a valve with an overall length of 4.867 inches and a valve tip length of 0.245 inches. The second combination had an overall valve length of 4.890 inches (about the same length is the first valve) but this valve had a 0.380 inch valve tip length. The change to the longer valve tip length was made on October 4, 1965 in order to accommodate the rail-type rockers arms. This effectively reduced the spring height by about 0.13 inches, thus reducing the total spring travel before binding by this amount. In order to compensate for this Ford also changed the valve spring. The original 1966 configuration valve spring had a 2.000 inch free length. This was changed to a valve spring with a 1.860 inch free length when the valve was changed – the 0.14 inches shorter valve spring roughly matched the amount the valve tip was changed by. This can also resulted in the initial valve spring assembled height going from 1.780 inches for the original 1966 configuration to 1.64 inches for the later configuration – again a change of 0.13 inches which is consistent with the other changes to the valve tip length and valve spring free length.

What really set me spinning about was the 1966 Mustang Shop Manual, published by Ford Service Publications, does not mention anything about a second valve / valve spring configuration. It only provides information regarding the original configuration. This is probably because the Shop Manual I have is a first printing edition that was printed in August, 1965 – and this was before the October 4, 1965 cut-in date for this particular valve / valve spring change (I do not know if there were any later versions of the 1966 Mustang Shop Manual)

In my case, it looks like the cylinder head rebuilder I got these heads from used a combination of first configuration valve springs (the longer ones) with the second configuration valves (the ones with a lower keeper groove), This was the WORST possible combination. The longer valve springs start to coil bind at about 1.30 inches. This meant that when they were installed at the nominal 1.64 inches height for the newer configuration valves there would only be about 0.34 inches of valve travel available before coil binding occurred. Since the stock camshaft results in a 0.380 exhaust valve lift, this definitely puts this configuration is a valve spring binding condition!

The conclusion and lessons learned from the experience were 1) do not believe everything that is published in the Ford Shop Manual since there were changes made to the engine configuration after it was published, 2) do not assume a parts supplier knows about all the potential changes and configurations, and 3) make sure all the parts you buy are compatible with one another and this may require some disassembling in order to confirm this. Had I done this in the first place and not gotten lazy I may have discovered this problem before assembling the engine the first time, then breaking parts and having to disassemble and reassemble everything a second time!

There is also the possibility of a third valve that has an even longer overall length than the second configuration valve were it appears Ford added an additional 0.16 inches to the valve tip length – although I do not think this third valve was used in any 1966 289 engines. I think this third configuration was introduced much later – like in the 302 engines, but these valves are exactly the same as the second configuration 1966 289 configuration except for the added valve tip length. While these third configuration valves are probably compatible with the 289 engine the extra valve tip length changes the geometry of the rocker arm slightly and could possibly increase additional side loading on the cylinder head valve guides so it would be advisable if these valves were to be used the 302 push rods should be used in conjunction with this configuration.

Again, thanks to everyone for your responses. Some may have not been applicable to my problem, but each made me think a little about what the source may have been. If any of you have any problems where you think that I may be of some assistance, please do not hesitate to contact me.

 
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