1966 Mustang 200 Mild Rebuild

Hello Everyone 1st post here - I’ve done a lot of reading on this forum and think I’m ready to jump in.....but I need help/support. Sorry for the long post I wanted to get the basics covered in one post.

Car History:
I have a ‘66 Mustang convertible 200 Sprint that was my Dad’s and has been in the family for 45 years. He purchased it with about 40k miles in ‘75. It currently has 105k miles and has been sitting for about 5 years. The interior/exterior was redone in late ‘88/'89 and was relegated to parade and Sunday afternoon drive duty - no engine work was done. My Dad kept it in a heated garage until I brought it to Arizona (still garaged) about 15 years ago. Engine ran and drove good for many years. I drove it occasionally on weekends until about 5 years ago when the engine started making a knocking noise at idle. I didn’t have time to do anything with it so it has sat in my garage since. I recently retired and would like to bring this old girl back to life.

What I want out of the car:
Not a daily driver but something my wife and I can take reliably to a local small towns (1 to 1 1/2 hour away for lunch and a day out), country roads so very little if any highway (60 - 65 mph max) - do want to have 2-lane passing power, grocery getter - yeah when I want to drive it and local around town fun to drive car.

Observations & Actions:
I drained the fuel and put MMO in the pistons. Manually turned it over - no sound that I could hear and turned smoothly. Rebuilt the carburetor (1100), new fuel-filter, new battery, new plugs, rotor & cap, already had pertronix and fired her up. It started without much effort. Ran it for 5-10 minutes. Adjusted the idle a little but would not idle below about 700-800. Still making a knocking noise at idle. Sat for a couple days. Ran a compression test. Dry (1-6) was:160, 170, 170, 175, 174, 169. Wet (1-6) was: 165, 175, 175, 179, 179, 175. I think this is promising - Yes? Pulled the valve cover (at some point adjustable rockers had been installed - who knew?) and found several severely worn and deformed pushrods. Cups were deformed and very loose (no preload). Could this be a lifter problem or did they just bleed down? Upon further investigation I found the rocker arm shaft to be severely plugged with gunk. After some cleaning all the rockers rotate with some drag but they bind with minimal side pressure. Could this be the cause of the knocking sound? Oil pressure gauge has always read in the normal range. In addition, I found the PCV all gunked up (no rattle either) and the vacuum line & grommet crumbled when I removed the valve cover - vacuum leak - could this be part of the idle issue?

Thoughts on next steps:
New rocker arm assembly (or rebuild existing), new push rods, maybe lifters (not sure I’m looking forward to pulling the head). Eventually a new oil pump (gasket is leaking and needs replaced anyway) and timing chain. I checked the slack in the chain and it is 4-6 degrees (back and forth) of crank rotation to observe any rotor movement. I’m not sure I have the ability to pull the engine (don’t have room or hoist/lift) and do any block work. Maybe pulling the head and oil pan will decide for me once I can see the cylinders.

I did purchase the handbook and have read it cover to cover several times. Just not sure of my abilities for doing an engine rebuild. It has been 40 years since I have done anything like this.

Questions:
1) Thoughts on lifter replacement - Part of the knocking? Just bleed down? Replace anyway?
2) Could the rocker arm assembly condition cause the knocking?
3) Should I just purchase a new/rebuilt rocker arm assembly vs trying to rebuild existing?
4) Could the timing chain slack cause the knocking or wear on the rocker arm assembly? Could this have caused Piston/ring damage?
5) Should I pull the head? If I do what else should be done - only want to do this once.
6) If I pull the oil pan what should I look for to determine if additional block (piston/ring, cylinder, crank, bearing) work is required?
7) Anything else? What am I missing - I’m sure a lot?

Thanks for your help.

Troy, welcome aboard. Sounds like you have a nice ride.
The compression looks great.
Get it on the road & since it sat for 5 years, check the brakes for proper operation.
If i can help you on any distributor options, just give a shout, Bill

Troys66":13n6nxja said:

Hello Everyone 1st post here - I’ve done a lot of reading on this forum and think I’m ready to jump in.....but I need help/support.

Questions:
1) Thoughts on lifter replacement - Part of the knocking? Just bleed down? Replace anyway?
2) Could the rocker arm assembly condition cause the knocking?
3) Should I just purchase a new/rebuilt rocker arm assembly vs trying to rebuild existing?
4) Could the timing chain slack cause the knocking or wear on the rocker arm assembly? Could this have caused Piston/ring damage?
5) Should I pull the head? If I do what else should be done - only want to do this once.
6) If I pull the oil pan what should I look for to determine if additional block (piston/ring, cylinder, crank, bearing) work is required?
7) Anything else? What am I missing - I’m sure a lot?

Thanks for your help.

Click to expand...

Welcome to the Ford Six forum Troy's66, sounds like a very nice car. Thank you for providing such great details about the condistion of the engine. In answer to your questions


1. Maybe and this would then require removing the head to inspect them for wear to the base, more detail below.
2. Yes this is very likely due to your description on their condition. More detail below.
3. Maybe depends on your abilities, tools, and equipment you have to work with the rocker arm bushings would need a small arbor press to install them. More details below.
4. Yes this quite likely on a severely stretched timing chains. A loose timing chain won't cause wear to the rocker assembly, pistions, or rings. More details below.
5. Maybe, however you can do most of the repairs without pulling the head, untill you get to wanting to replace lifters and or the camshaft. More details below.
6. When you pull the pan you can then if you wanted to also pull the Main caps and Rod caps to check out the crankshafts bearing surface and bearing inserts condition and their clearances.
7. If you decide to go deep inside and find that the engines parts are in good shape you can get a rering kit very reasonable. Unforchanately you won't be able to see the condistion of the cylinders or lifters without also removing the head first. These rering kits give you a full gasket set, Rod bearings, and a ring set, to this you can also add a set of main bearings (and other parts) for a very low budget overhaul that will probally more than meet your planed goals for your Mustangs usage and to be very reliable. Usally at this point for anything more than removing the head with the engine in the car people will go ahead and pull the motor out for this kind of work however it can be done in the car if need be. Recently a site member did this on his 1962 a Falcon for a very low cost with decent results. Check out site member "bones92" Budget Rehab / Overhaul to see what it takes.

Budget Rehab / Overhaul
viewtopic.php?f=1&t=80834

For a more spefic Mustang spefic 200 rebuild (engine pulled for building) check out site member echo1955 excellent series videos to get an idea of what's involved in a mild performance engine rebuild.

Mustang engine rebuild
viewtopic.php?f=1&t=77528

You didn't mention your budget for this mild engine rebuild. I do think your engines condistion is probally much better than in the first example (of the 62 Falcon) so you can probally get even better results you just need to decide how far you want to go inside the engine. But for sure rebuilt rockers and new push rods, adding the needed new peplacement timing chain set along with cam and lifters, rings, bearings, fresh gaskets, compleate set of freeze plugs for head and block, a real good cleaning, and a fresh valve job would give you a very good running stock engine for a reasonable cost for your planed use.

Since you have such good oil pressure and cylinder compression readings I think you may have already found a few possable sources of your knocking noise. At this time you might not need to pull the head off unless you really wanted too. But yes for sure do work on fixing those rocker arms cleaning them thoroughly inside and out. After you have checked them out throughly you will know if you need to rebuild them or replace them with a rebuilt set from your discription it sounds like there is eigher shaft and or rocker arm bushing damage from a lack of oil. A new replacement shaft and the rocker arm bushings are avaible and it will make the engine run better and also be quieter. Pictures of the rockers and other parts would be helpful in the diagnosis. You could rebuild them yourself if you have the ability it's not hard or decide to have them rebuilt or get an exchange set, Rocker Arms Unlimeted is a good company to contact for their rebuilding or exchange services http://rockerarms.com

After you have fixed the rockers arms, replaced all the damaged push rods, and adjusted the lifter preload you could run the engine to see if that was a source of your knocking. Check out all your push rods to see if any of them happen to be bent, if they are you will for sure need to replace them and those that you said that were badly damaged in the cups and ends. If you find any bent push rods be sure to check the valves in that location still open freely. Do keep the push rods all in the order they came out so they go back in the same place if they are reusable. V. I. / (Vintage Inlines .com) our site sponsor may be able to help you in getting the new push rods or a compleate new set as well as the rocker shaft and bushings.

Yes if the push rods were loose the rockers will need to be adjusted after you get the rocker arms back in good working condition. Hydrolic lifters usally aren't a sorce of knocking sounds but they can make a ticking sound and with the looseness and damage to the ends that you have described that's very likely. If you decide to pull the head right away then you could inspect the lifters for wear to their base (that rides on the camshafts lobes) and or replace them if you wanted. At that point though you might also think about a replacement camshaft to go along with the new lifters. Along with a fresh valve job with back cutting, resurfacing of the head, and enlarging of the carb's intake mounting base hole to a minimum of 1 3/4 inch for better flow or also so if you ever wanted to use a different carb at a later date you will be ready,

Yes that gummed up PCV and deteriorated hose and Gromlet could be a very likely cause of the high idle RPM, cleaning or replacement of the PCV and hose / Gromlet parts should really help you be able to tune it better. That's the next thing to try since you have allready done a compleate tune up and carb rebuild hope your fuel tank is nice and clean too. Check how clean the inside of the engine is while its apart and clean up as much of the grime and sludge inside as you can so there's good oil flow and oil return flow back to the oil pan.

One other known cause of engine knocking on some of these inline six engines is from an oil pan has been dented in badly after running over a curb or hitting something, have seen this many times. If your going to be replace those pan gaskets, and or the rear main seal that's a good time to also clean out and fix any damage to the oil pan or replace it with another. While the oil pan is off that's also the time to pull the front timing cover to replace that sloppy timing chain set and yes sometimes they can be a source (if they are really loose) of a knocking sound as well as poor engine Performace. You have a good basic plan of what you want to do, let us know what you find out and how far you want to dive into the engine as you keep working on it. Take lots of pictures of all the parts, hope that answered some of your questions, good luck Edited with addistional info.

that's a bit long and varied history for me to follow. May B justa "bound up top end" chewed the cups.
Examine both ends as U roll ona known flat plane? I would not do a rebuild at this point. Thats if you have the cash, time, etc and wish to start at the beginning, all over again. I like the way U gave a gentile start rather then just 'jumpin it awake'. Sometimes you can tell if damage is old or new. Look & see if U can.
As you know 150, 300 rms lower would B nice, not sure Y that is unless auto transmis (forgot what U said).
I'd run it and keep an eye, ear, nose and hand onit 4 awhile B4 any long (1 - 2 hr) trips. Work your way up
after a slo start. PR now, no lifters or cam w/o some proof of need. This is not what we think of as an 'interference' motor.

After 3 - 6 mo some more thoughts might be put into a DSII/carb upgrade and some use as a "real car". Shame to just come out on 1/2 doz Sundays 1/2 the year where you live...

Hi, It sounds like you Mustang was not treated to regular oil changes, and there is sludge in the engine. So make sure the oil feed to the rocker shaft from the back of the head is cleared. When you run it with the valve cover off you should see plenty of oil at each rocker arm. As mentioned, I would get a set of cupped push rods from Vintage Inline. Usually the rocker shaft will clean up real good. I remember a section in the Performance Handbook about the rocker shaft. If that doesn't take care of the noise you will have to keep digging.
So of course the tune up will help. I would probably change to hoses and belts, and keep the old ones for spare parts.
The timing chain set is a little worn, probably from poor lubrication, but I would put that job on hold for now.
As Bill said, make sure the brakes are in top shape. I would think the wheel cylinders are rusted. Also on my 66 Mustang I changed the original master cylinder to a dual bowl from a 67, there is a simple kit to add the second brake line from most of the Mustang parts houses.
I would just do one job at a time until it is running like new.
Good luck

Howdy Troy and All:

And welcome to THE FORUM! Yes, it is that good. And you've got a gem of a project. Enjoy!

You're already got some good advice. My advice addition is to take it one step at a time. It can be a little (or alot) intimidating to tackle everything all at once. You know you have a problem up on top. I'd start there. Yes, a bent/damaged push rod could cause the noise. I start by completely disassembling the rocker arm shaft and rocker arms. Clean, Clean, Clean! FYI- oil is transferred up from the oil pump through the back head bolt, through the head to the back rocker stand then into the rocker shaft and then from the back to the front rockers. It is a not-unusual problem on engine that have not been serviced regularly and been allowed to sit for extended periods of time. Oil sits in the rocker arm shaft and slowly, along with time and neglect, turns to SLUDGE- blocking oil from getting through. Does this sound like yours?
Most caused wear is where the rocker arm balls contact the pushrod cups. Next is the rocker arm shaft. Both due to lack of lubrication. Clean and inspect all very thoroughly. The inside of the rocker shaft will require particular attention to get clean. Check the out side of the shaft for gauling. Replace bent and excessively worn pieces.

Once this is done get it running with a oil system cleaning additive to the new oil and filter. This process will take quite a bit of driving to start to clean years of neglect. Change this cleaning oil and additive often- maybe every 500 to 1,000 miles. Pay attention to noises, temperature, vacuum reading, idle and driving qualities. Once you have this done (and it's quite a bit) you will be able to assess the rest of the engine. The next likely problem area will be the hydraulic lifters, but one-thing-at-a-time. That's my two cents, for what it's worth.

You have a GEM of a car. Take your time and treat it right. Enjoy!

Adios, David

Thanks for all the feedback. Lots of information to digest.

I did watch the Echo1995 videos prior and would love to have an engine that looks like that but probable won’t go there. Budget - I Don’t Know - I want it to run good and look acceptable but won’t be doing car shows. Not afraid to spend $1-2k on this if required.

Ran into a potential issue today that may cause me to pull the head after all. I removed #2 pushrod to verify length and the lifter came out of the pocket with it and fell back into the engine. It is currently laying on its side between #2 &3 cylinders. I spent an hour with a extension magnet and wire trying to coax it back in position - no luck. Any ideas on a quick fix?

I have ordered pushrods, timing chain, oil pan gasket kit and several other items - so will be waiting on delivery. I see VIntage in-line has rebuilt rocker arm assembly on there website. If they have stock I will probably go this route.

Oil pan is in good shape no dents - I dropped it today and pan looks very clean - no metal and very little gunk. I know my Dad treated this car like a baby. Changed the oil & filter with Mobil 1 every year and only put about 1000 - 1500 miles per year. I have done the same except for the last 5 years while it sat. Still not sure what caused all the rocker tube gunk.

I will try to post a few pictures if I can figure out how soon.

Thanks all again. Stay tuned.

"... Changed the oil & filter with Mobil 1 every year and only put about 1000 - 1500 miles per year. I have done the same except for the last 5 years while it sat. Still not sure what caused all the rocker tube gunk. ..."
the sitting, worse thing for a vehicle. Time turns a benifit (oil) into a bas*^%d.
If U have a long gun brush (cleaning kit) push it dwn the insde of that rocker shaft.
Compressed air, kero, gas &/or other solvent is ur best friend now...

On your Budgeting I think with carful selecting of the parts and doing as much of your own labor you should be able to do these repairs. From your compression test and great oil pressure, experience tells me your engine is still in reasonably good condition.

That's unfortunate on the lifter coming out usally they don't on older engines but it's a good sign that the bottom end is very clean. But don't give up you might still be able to get the lifter back in its hole. I have a number of tools that I have used over the years for these type problems. Severial different strength magnets on rods, a few home made items, plus a four finger grabber tool (see below link for an example) that has helped me many times. This last one you can use to grab the top edge of the lifter to move and start it back in the lifter hole. Use a small Rod or stiff wire to help guide and hold it before releasing the grabber tool. Good luck

Grabber Tool
https://www.homedepot.com/p/GrabEasy-24 ... /202505170

Yow, trying to get a lifter back into it's bore reminds me of this video:

Robotic Surgery peeling and suturing a grape
https://youtu.be/KNHgeykDXFw

Another thought if you succeed in getting the lifter back in its hole. May not happen again but when you go to remove any of other push rods I would spin them with your fingers to break lose any oil suction or grime that's holding the push Rods to the lifters. Good luck

I finally got the lifter back in it's pocket. I had a 4-finger grabber and a wire - took a little time but all is good now. All the other pushrods are out - I was a lot more carful removing them.

Yes I pulled the oil pan and the bottom end is very clean. Is it possible that the PCV plugged and little to no vacuum caused the rocker arm shaft to plug up? With no oil flow to the top end caused the pushrod damage?

At this point I think I will put it back together with a new rebuild rocker arm assembly and oil pump and see what happens. This car ran really good until just before the knocking started. The other thing that I remember happening just before I parked it was the idle was off (Would die after it warmed up). I thought this was an issue with the carburetor but now think it was a vacuum leak.

Thanks Guys

Still waiting on parts but I have another question.

On the Rocker arm assembly I see that on the Vintage inlines (VI) website they have a 1.6 HR Assembly - Would this add any value to a mostly stock car? I may upgrade the distributor in the future but won't likely go any further. I see a little information in the handbook but not a lot of information (Wakes up a stock cam car in the lower RPM range - HB). Also VI hints that the spring would also need to be upgraded - to what? I saw somewhere that the springs can be replaced with the head still on the car but this may be more then I want to dig into. Would it be a good idea to purchase the HR assembly or better off sticking to stock? Springs? What other can of worms would the HR open up for me?

Thanks again

A few picts for you pleasure.

Thank you for the pictures they do help to see problems. I can see at least two of the push rods that are bent at the top section next to the rocker adjuster cup, make sure that those two valves are not stuck. One of them is #6 In. The other is near center of engine but I can't tell a referance to eighter the front or back of the head. Yes lack of proper oiling to top end parts can cause push Rod wear, Rocker Arm Shaft wear, Rocker Arm bushing wear, Valve tip wear, eventually valve guide wear, and valve seal damage. I think you have caught the problem early and due to not much use there should be only minimal wear or damage. While you have it apart this far be sure to clean the heads oil passages going to the rocker assembly, the rocker assembly, plus the top of head and the it's oil return passages going back down through the block into the oil pan.

Yes the 1.6 ratio rocker arms will give a little boost to a stock engine because they increase the lift and duration some. On the valve springs many people use the Hi Performace 289 or 302.V8 springs for a little more spring seat pressure this would give a slight increase in useable RPM range over the stock set of valve springs. Replaceing the valve springs and valve stem seals is an easy job with the head still on the engine. Going to a better distributor like the later DuraSpark II is a great up grade too that will give you much longer lasting tune ups, faster starting, better performance, and better economy. All those Mod's together will make it run noticeably better. Congrats that's sure one great looking Mustang Sprint Convertible, good luck.

Hi, you got a beautiful Mustang Sprint out there, very nice. And being in the family to me makes it even better.
Well you don't have as much sludge as I was expecting. I've seen engines so caked with so much sludge that the crud would be caked everywhere, that the moving parts would leave carvings in it and the drain back holes would be plugged with it.
Personally, I'm cheap, and I'm a fixer, and I have refurbished many rocker shafts back in the 70's. I would clean the parts in kerosene and scotchbrite. At least save yours for later if you got a new one by now. Also save the good push rods in case you need one later.
I think a few high RPM runs through the desert could have done the push rods in, allegedly.
It is not a big job to change the valve springs with the head on, you just need the correct valve spring compressor, and a way to keep the valves from falling into the cylinder. Mechanics use compressed air, but a rope down the spark plug hole will do. More often this is to change the valve stem seals, which you should do if you decide to dig in.
If this was my engine, the choice would be either new 1.6 rocker arm, new springs and seals and push rods, or fix the rocker arm assembly, change the push rods, and see what happens.
Good luck

HOwdy Back Troy:

WOW!! What a beauty! ENJOY!

On the 1.6 rockers, the cost for the small gain is questionable- unless you have more money than time. The difference between 1.5 stock rockers and 1.6 rockers at the valves is about .030", about the thickness of a matchbook cover. Given your description of your intended use for this car, I don't think you'd notice the difference.

I'd be inclined to follow Ron's suggestion- clean and replace bent parts and run it. If you have to do valve stem seals, add a .030" valve spring shim to increase spring pressure, while it's apart.

IIWY I'd save my money, look for a later cylinder head to rebuild, modify and have ready to swap onto your engine when it become for a valve job.

Enjoy the ride.

Adios, David

Another note I'm not sure has been mentioned. New rocker shafts are available. As are the end plugs for you're old one. If you find your shaft is worn and get a new one be sure to de-bur the holes in it. On your old shaft, definitely remove the old plugs and clean it through. Also, Berrymans carb dip does a wonderful job of cleaning up the towers, rockers and springs between them. Be sure that the oil holes in the rockers are clear as well. Good luck!

Rocker Arm Shaft:
MELLING MRS652 or SEALED POWER RS619
FORD# C3DZ6563A

Plugs:
DORMAN 555007
These are a 17/32" steel cup plug

Pushrods:
SEALED POWER RP3076

chad":jkgi2bev said:

"... If U have a long gun brush (cleaning kit) push it dwn the insde of that rocker shaft.
Compressed air, kero, gas &/or other solvent is ur best friend now...

Click to expand...

once U have the shaft ends off & internals clean put these back on/in:
R. Shaft Plug Ends:
DORMAN 555007
These are a 17/32" steel cup plug

Hey Troy, curious on what you ended up doing here as I am in a similar situation.