Thread: '66 Mustang engine issue

My son has a 66 Mustang - stock 289 - a few years back he 'freshened' up the motor - recon heads, new cam & lifters, re-ring, oil pump as well as rebuilding the auto trans - been running ok until the other week he had a miss fire and traced it to a bent exhaust valve pushrod, a new set of push rods installed and the same issue happened a few days later, on looking closer he noticed the rocker stud was badly worn on the offending valve/pushrod/rocker assembly. On checking other rocker studs it looks as if all of the exhaust studs have wear - some worse than others - at the point where the rocker contacts it - looks like only option is to at least replace all of the exhaust rocker studs and maybe the inlet studs while he is at it with either screw-in studs or like the original, push/friction fit studs. He isn't keen on screw in studs as he is convinced that the heads will have to be removed to do this so is looking into push fit studs, I have tried to talk him into screw in studs but he is paranoid about some swarfe getting into the water jacket. He removed one of the studs (and quickly found the hole went right through to the water jacket) and found it was relatively easy to hammer it back in, was it easy to do because it was the old stud, will new studs be relatively easy to hammer in, as well ?

Originally Posted by familyguy

My son has a 66 Mustang - stock 289 - a few years back he 'freshened' up the motor - recon heads, new cam & lifters, re-ring, oil pump as well as rebuilding the auto trans - been running ok until the other week he had a miss fire and traced it to a bent exhaust valve pushrod, a new set of push rods installed and the same issue happened a few days later, on looking closer he noticed the rocker stud was badly worn on the offending valve/pushrod/rocker assembly. On checking other rocker studs it looks as if all of the exhaust studs have wear - some worse than others - at the point where the rocker contacts it - looks like only option is to at least replace all of the exhaust rocker studs and maybe the inlet studs while he is at it with either screw-in studs or like the original, push/friction fit studs. He isn't keen on screw in studs as he is convinced that the heads will have to be removed to do this so is looking into push fit studs, I have tried to talk him into screw in studs but he is paranoid about some swarfe getting into the water jacket. He removed one of the studs (and quickly found the hole went right through to the water jacket) and found it was relatively easy to hammer it back in, was it easy to do because it was the old stud, will new studs be relatively easy to hammer in, as well ?

As someone who owned a repair workshop short cuts always bite. I think you will find the cam is knackered as well as the rocker assembly so it will need to be pulled out and checked. They are a simple motor to remove so it would be motor out and check the cam or remove the radiator and do it that way. If it has had metal through the oil system then it is motor out and strip it down.

One head had to be removed to replace the valve, was the cam closely examined at that time? Personally I would rather pull the motor than try and R&R a head as everything is so damned heavy on those motors. Maybe drop the oil and check for any metal content by using a magnet. If the rockers and pushrods have wear then there is metal in the oil.

Bent pushrods can cause the rocker to wear on the stud. It's possible that the valve tops are also unevenly worn due to the rocker tilting and the shape of the rocker/valve locating tabs. I think that the valves/collets are designed to allow valve rotation on the 289/302, but not sure.
I would be removing the heads and giving everything a good check over.
One low cost method of getting a better performing valve train on the 289/early 302 is to machine down the stud platforms to fit screw-in studs and hardened guide plates, and to use rockers/pivots and hardened pushrods from a 260 Windsor (around 1963 vintage) if available.
In my experience this pushrod/rocker/valve geometry works out well.

HTH,
Andrew

Yes, the valve stem tops could need a touch up as well. If all the rockers and pushrods are cactus I would be fitting an aftermarket kit. Another thought, are the valve springs stock?

The heads were handed over to a workshop at the time of the engine 'refresh' for full recon ie. new guides re-lap the valves etc so I'm assuming new springs would have been fitted at this stage he is looking at a set of screw in studs as the push/friction fit studs are just not available here - it seems as the local spares market is only geared to performance parts, if you want stock parts then the only option is to go to the US, a set of screw in studs (the cheapest) $100 for a set of 16 - they are certainly nothing fancier than a set of bolts churned out on a cnc lathe, would 16 bolts cost $100.


While I mean no disrespect to Ford, the more we look at the stock valve train setup the more it looks crude and agricultural, very much designed for cheap quick production with stamped parts and a minimum of machining, my background is in electronics and my impression of US made electronics gear from that period is that it was the best of the best, pity the auto industry wasn't the same.

Originally Posted by familyguy

The heads were handed over to a workshop at the time of the engine 'refresh' for full recon ie. new guides re-lap the valves etc so I'm assuming new springs would have been fitted at this stage he is looking at a set of screw in studs as the push/friction fit studs are just not available here - it seems as the local spares market is only geared to performance parts, if you want stock parts then the only option is to go to the US, a set of screw in studs (the cheapest) $100 for a set of 16 - they are certainly nothing fancier than a set of bolts churned out on a cnc lathe, would 16 bolts cost $100.


While I mean no disrespect to Ford, the more we look at the stock valve train setup the more it looks crude and agricultural, very much designed for cheap quick production with stamped parts and a minimum of machining, my background is in electronics and my impression of US made electronics gear from that period is that it was the best of the best, pity the auto industry wasn't the same.

It is not standard practise to replace springs in a re-build unless asked for, standard springs will keep on keeping on so to speak and don't worry about Ford's reputation, they will get over it. A mate of mine who owned a Ford used to say "The Ford will never replace the motor car". By the time you remove both heads, get the lifters out and pull the cam you may as well pull the motor out and put it on an engine stand. Maybe 90 minutes tops to pull it out.