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Valve problem(still!)

Dne'

Dne'

Well-Known Member
Hi ya'll!
Finally got feeling well enough to work on my stang! Herb(my motorman) came over yesterday and we re-assembled my 289.
Review: We had the motor running a few months ago, but broke no. #8 cylinder intake(?) rocker arm, bent the pushrod, and bent the valve. What the machine shop discovered was the guide through the head was worn side to side allowing the rocker arm to 'walk' off the top of the valve stem. I removed the head then, Herb had that valve guide/valve replaced.

Herb had stated that we should probably pull the other head at that time and put in different studs? I forget, but I was having enough back n neck problems and didn't want to pull the other head, so I said let's just get it running as cheaply as possible. At that time I just wasn't physically able to do work!

Yesterday; put the head back on. Herb put a special rocker arm that stays on the valve stem. He adjusted the valves, then We put the valve cover back on, went to crank it, and immediately started popping back through the carb! :cry. Pulled the valve cover and the new rocker arm was broken in half just as before and bent the pushrod! If I or Herb knew what was wrong, it would have been fixed~ so I for certain don't know what's wrong! Herb will be coming over sometime during the week to check something on it.

What are your opinions? Should I opt for different heads? Herb said he could get me a set of aluminum head complete for 850.00, but I'm not excited about spending that much more money!
thanks,
dne'
 
What the machine shop discovered was the guide through the head was worn side to side allowing the rocker arm to 'walk' off the top of the valve stem.
Click to expand...

Valve guides on a rebuilt cylinder head will not be "worn". I thought that this was a rebuilt engine?


Something is seriously wrong, but heck if I know what it is.... two broken rocker arms in a row on the same cylinder/valve..... wrong lifter? wrong spring? wrong pushrod? improperly machined camshaft?
 
I'm with Dave here.....a rebuilt engine will not have worn guides. Sounds like someone didn't do the job correct. Sounds like you could have a valve to piston clearance issue also. Not knowing your engine builder.......and that head was not right.....how can you be sure it is all correct?

I would pull both heads and have a good (different) shop go thru them or get the alum. ones. Also, before cranking with the starter, hand crank it for several revolutions with a ratchet, then crank with the starter but the coil wire pulled. Do this cranking with the valve covers off to watch the problem areas.

It is all pretty simple....just finding the bad spot is hard sometimes.
 
Is this a stock cam or one with higher lift? Did you install different springs? Is there any binding in the spring?
 
"66gt350" said:
Is this a stock cam or one with higher lift? Did you install different springs? Is there any binding in the spring?
Click to expand...

+1 Only time I've presonally seen this happen, it was spring bind. Springs got mixed up, and the one that got mixed in had lower lift capability. Broke pretty much everything.
 
more thoughts

THank you guys! It seems like it'd be a simple thing to figure out! on the second go around, he replaced the lifter, pushrod, rocker arm, and (I don't know what they replaced at the machine shop to be honest regarding the valve,guide, nothing had been said about worn valve guides). When the head was off, I didn't see any sign on the piston that it had been touched by a valve. But the amount of pressure to break a rocker arm must be immense!

I'm embaressed to say 66gt350, I don't know~ I don't even know what cam is in the motor, much less what springs are in it. I hire someone to do what they do best and at least expect favorable results.

I"ll be anxious for him to come back out this week to see what he's thinking!

I had this idea that maybe the valve was stuck(an idea mind you), so I just went in the garage, took a lady foot prybar, put a nut on the rocker arm stud, and was able to make the valve open with no restrictions and sounded like it was seating ok judging by the sound it made.

About the only thing that makes any sense is the hole in the head where the push rod comes through. The "hole" don't know how to describe it(oblong hole) is worn to where the pushrod could have slop(side to side) and possibly allow the rocker arm to slip off to the side of the valve tip/end, and break it/and bend PR. But this new rockerarm was designed to stay atop of the valve via the guides that are built into it, unless it was just able to Jump off of the valve tip! So, this is the theory that I'm kind of sticking with for now. I just wish we had started the motor with the valve cover off!
 
The "hole" don't know how to describe it(oblong hole) is worn to where the pushrod could have slop(side to side) and possibly allow the rocker arm to slip off to the side of the valve tip/end, and break it/and bend PR.
Click to expand...

The hole doesnt keep the push rod in alignment, the rocker arms do with the old rail-style rocker arms.

Without knowing what has been changed with the motor its a crap shoot. My best guess is that it is a coil bind issue. Rotate the motor over until one of the valves is completely open. Measure between the spring coils with a feeler gauge. You need to have at least .060" of clearance between the coils. Check both the intake and exhaust valves in case you have a split pattern cam.

If that checks out okay then you need to make sure the pushrods are the correct length. It is possible that the push rods are too long and they are collapsing the lifters too far or completely bottoming them out.

Do the rocker arms break when it is idling? Reved up?
 
"6t9mach1" said:
The hole doesnt keep the push rod in alignment, the rocker arms do with the old rail-style rocker arms.
Click to expand...

'65-66 heads do have oblong holes that serve as rod guides. These older motors did not use rail type rockers. That change came in '67 IIRC.
 
a little more info

Hi, the first time(a few months ago), we just got it running long enough to hear it run. I got a wrecker to haul the stang to the muffler shop for the exhaust system. I started it, and pop pop pop!
This time, I forgot to hook up the hot wire to the distributor and it got turned over quite a bit until I realized why the motor wasn't getting fire! Tried again, started immediately and the pop happened, so we didn't run it more than 10 seconds!

I just got off the phone with Herb and asked him what he is thinking; He stated that the new cam has a pretty high lift rate, and perhaps that particular valve had some machine work back in time, or the valve seal could be compromising the situation. The head still sounds like it will need to come back off whatever he finds he also said!

I'm thinking about calling him back to ask, should I just go ahead a pull the head now instead of waiting for him to come over. I've got it down pretty good to get that head off! lol

"You need to have at least .060" of clearance between the coils." now this sounds like something I could inspect right now except for the valve/rocker arm in question(I don't have a rocker arm/PR for it right now). actually I'd be happy if the head is ok! I honestly don't want to purchase another set of heads. So a rail style rocker has the little tabs that keep the rocker arm on the valve? Thats what Herb had put on yesterday. So, it's starting to sound more like a spring, or valve guide problem? especially since the lift of the cam is pretty high.

"6t9mach1" said:
The hole doesnt keep the push rod in alignment, the rocker arms do with the old rail-style rocker arms.

Without knowing what has been changed with the motor its a crap shoot. My best guess is that it is a coil bind issue. Rotate the motor over until one of the valves is completely open. Measure between the spring coils with a feeler gauge. You need to have at least .060" of clearance between the coils. Check both the intake and exhaust valves in case you have a split pattern cam.

If that checks out okay then you need to make sure the pushrods are the correct length. It is possible that the push rods are too long and they are collapsing the lifters too far or completely bottoming them out.

Do the rocker arms break when it is idling? Reved up?
Click to expand...


THis is what is in the motor::
Materials list, supplied by EPWI from Houston.
Pistons: Sealed Power #273P flatop pistons, with #E-251K moly rings.
Bearings: Clevite "P" series
Gaskets: FelPro 260 series gasket set, with neoprene rear seal, and positive valve seals
Valves: NEW Engine Pro valves (1.78"x1.44") and new 90# seat pressure valvesprings
Camshaft: NEW Engine Pro camshaft (218`/224`@.050" with .465" lift- 110` lobe center)
Pushrods: NEW Pioneer #EP279 moly pushrods
Lifters: NEW Sealed Power hydralic lifters #HT-900
Timing set: NEW Engine Pro timing set #3014 silent link chain and gears
Rod bolts: ARP 5/16" rod bolts for strength and reliability
Oil pump: NEW Melling #M-68 pump with #68-S oil screen and #IS-68 driveshaft

Machine work.
Block: Clean and magnaflux, then bore and hone 289 block .030" oversize (21-30 ra finish)
Crank: Grind .020"/.020" undersize, chamfer oil holes and micropolish for long bearing life (8-10ra)
Rods: Install ARP bolts-resize big end to factory specs-match weigh rods (each end) as set
Heads: Clean and magnaflux-surface with CBN cutter- 3-angle seats in head- Hardened exhaust seats-replace guides (press-in iron guides)- positive valve seals- hardened 7` keepers- NEW 1.78"x1.44" stock valves- enlarge exhaust ports to gasket size, streamline exhaust guide for increased flow.
Balance assembly: Match weigh all rods and pistons- use correct bob weight to balance the crank, with flywheel and balancer installed.

External components.
Edelbrock #1406, 650cfm carb with electric choke and vacuum secondaries.
Edelbrock #2121 Performer intake manifold
Clean and install customer timing cover and balancer
Chrome steel valve covers
Reinstall customer distributor and provide NEW wires and sparkplugs. (Denee, I will need to pickup the distributor!) Another option is NEW ProForm HEI style ready to run dist. for $175.00 extra. This has the coil in the cap, and much HOTTER spark than the original.
 
"Dne'" said:
Hi ya'll!

Yesterday; put the head back on. Herb put a special rocker arm that stays on the valve stem. He adjusted the valves, then We put the valve cover back on, went to crank it, and immediately started popping back through the carb! :cry. Pulled the valve cover and the new rocker arm was broken in half just as before and bent the pushrod! If I or Herb knew what was wrong, it would have been fixed~ so I for certain don't know what's wrong! Herb will be coming over sometime during the week to check something on it.

dne'
Click to expand...

Check the rocker stud for miss alignment or off center.
It sounds like the rocker is hitting the stud when opening the valve at the high point.
I had one snap off a stud from doing this, a slight grinding to the rocker hole to lengthen the hole solved the rocker from hitting the stud.
 
IIRC, it doesn't take too much bigger of a cam or springs to start wreaking havok with the rockers. It's been a long, long time when I helped a buddy rebuild his engine, so I don't recall the exact cam and springs he installed. He went with a slightly warmer cam and springs, and he was bending pushrods and breaking rockers. He ended up having to get a new set of rockers that were stronger than the stock ones, and didn't have anymore problems with the rockers breaking.
 
Dne', I think it's really time to cut the ties with this guy. He thinks that .465 is a high lift cam? That's maybe stock, possibly just north of stock. It's not considered a high lift on anything bigger than a 250 CID engine.

With rocker arms falling off, he's just now getting around to rail rockers?

You've got to cut this guy loose before he bankrupts you!

I haven't followed the entire story, but do your heads have slots or round holes for the push rods? If they are round holes, rail rockers are essential.
 
some photos

IN person the hole looks more worn than in this photo, but even so, doesn't look bad enough to me to walk the rocker arm. Herb hasn't charged me extra for coming to my home, nor for parts, I'm going to let him finish his work; if he hadn't become such a friend, I'd probably be looking for someone else, but I've become very fond of him! I don't have very many friends except for family, so i'm going to stick it out with him. He drives all the way from across town, and Houston is a big town/city! And if I need "other" mechanical info, he helps there too! Anyway, I'd rather not be having to take my motor back apart, but I'm getting pretty good at it! lol So, Wednesday he'll be back out to do whatever he's going to do. Let's see what happens!
Thanks everyone!
dne'

IMG_8988.jpg


IMG_8989.jpg


IMG_8990.jpg
 
I'd be installing some guide plates for one thing. Your wear pattern on the valve looks good though. I'd have to lean toward a spring or cam issue. Possibly that lobe is not right. Just a guess though.
 
Since your heads have the narrow slots rather than the larger holes, you should not be using the rail type rockers. That could be the reason for the latest breakage. That doesn't explain the first breakage, though.

Frank
 
"apollard" said:
'65-66 heads do have oblong holes that serve as rod guides. These older motors did not use rail type rockers. That change came in '67 IIRC.
Click to expand...

Gottcha...learn something new every day :)
 
Dne',

I can't see anything amiss within your photos', but thanks for psoting them. It's always nice to have a visual.

Since this exact same rocker arm has failed TWICE in a row....

I'd rule out the rocker arm as a possibility.

It has to be one of the following:

1. Wrong valve spring installed. It's possible when the heads were being re-assembled that the head builder lost his mind for a second and switched and intake and exhaust valve springs.

2. The stem of the new replacement valve was not cut/sized properly.

3. Wrong length pushrod.

4. Far-fetched, but anything's possible.... the lobe for that valve on the camshaft was not machined properly causing excessive lift.

5. There's an obsrtuction within the lifter bore preventing the lifter from seating (doubtful)

6. The lifter is defective, again doubtful.


While I'm doubting Herb's skill level, he is trying to "make good" on this problem and he's still working for free. Stick with him for now and hopefully between him on site and us here we can figure all of this out.
 
I still can't explain it!

Herb called me and told me the story~ in short these are the wrong heads~ he admits a mess-up. I say,It's just bizarre why this one valve caused problems and not the others. He said IT may have had some machine work back when, made it a little different than the others. I'm not quoting what Herb said, just generalized, he put it much more professionally! Anyway, he's preparing another set of heads and will be ready in about a week. I'd still like some roller rocker arms even if you don't see them!

Tomorrow, like I have nothing better to do, I'll take the existing heads off. My most unfavorite part of the disassembly is the hedders, and lifting the heads off(I'll get my brother to do it)! I like hedders, but hate them at the same time! lol
dne'
 
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