Bent pushrods

[tinman58]

The rods are identical in length, as the ones I removed

 

[CJD]

Another thought....is there a chance your pushrods are to long?

John

I had the same thought.. at the top of this page...

Sorry, my attention Spanish isn't that long!?

Now I'm leaning towards wrong length valve stems. The exhaust valve seats wear about 4 times faster than the intakes, so not likely that a non hardened intake seat is causing trouble.

If you can get the valve clearance, it may make it. If the clearance is too tight, you can do a good bit of damage in 200 miles. And if you have tight valve guides, you can lose the head, piston, rod, sleeve, and possibly the crank. That's what is in the path if the valve hits the piston after getting stuck.

Sorry if I'm repeating anybody else's ideas!

John

 

[TR4nut]

Well unless the head has been skimmed a lot or you have a very high lift cam I don't think there is much chance of the valve hitting the piston - the TR engine design isn't an interference type engine.

I'm a little surprised you couldn't get to an acceptable lash setting though - I know if valves recess then you can lose the gap, but when you are setting them from scratch isn't there typically quite a lot of room there if you back the adjusters all the way up? I'm thinking closer to 0.2 or so? Again makes me wonder on poolboy's and John's thoughts on pushrod length.

 

[Hap Waldrop]

an the valve is working it's way up in the bowl, if the valve lash tightened up because of this, it could indeed cause excessive valvetrain pressures and bend the the pushords,

You lost me there, Hap. Can you explain that a bit more?

BTW, I had severe VSR on a head that had hardened seats installed. WHile it certainly helps, hardened seats are not necessarily a "magic bullet".

If the valve is recessing into the head/bowl, then it is moving upward, making for a higher valve stem hieght, thus reducing lash, or elminating it altogether, thus increasing the amount of pressure on the valve to the rocker arm, then the rocker arm sends that pressure down the line to the lifter and cam lobe, also if you had the sort of recession shown in your picture you could also have valve spring bind. Add reground non hardened camshaft and entry level lifters to this equation and you got a recipe for diaster.

Randall, if you had a valve recess with a hardened seat insert, then I would be looking at the person who installed the hardened seats. Bottom line what happens most commonly with heads that do not have hardened exhaust seats is the cast iron seat area at the exahsut valve get compromised, because it was never intended to run with hotter burner unleaded fuels, and it simply will not hold seal for very long. What one normally finds is a seat are that looks pitted , almost like rust pitting, you an cut or grind a new seat in normal valve job, but it will not last even a few hundred miles without substantial valve leakage. Thats why every modern cast iron head in production since say 1980 has hardened exhaust seats inserts. We did alot of leak down testing a few years back with head running unleaded fuel with out hardened exhaust seats and it would lose 25% of their seal in less than 200 miles, when it was first confirmed at less the 2%, but when hardened seat were installed, they held their seal, well the jury is still out on that one because the test head is still in use, and with many leakdown test still has no more than 3% leakages several years later. I guess I've rebuild a good 200 LBC cylinder heads, and for the last 7-8 years every one of them has gotten hardened exhaust seats, we even install them in the race heads that run on leaded race fuels. Anyone in these days and times who is rebuilding a old British cylinder head and not installing hardened exhaust seats, and thinks that is acceptable method, is simply kidding themselves, IMHO, it is not "maybe to do" thing" it is a "must do" thing .

Most classic street car owners simply do not test perforamcne whether it be leak down test or a chassis dyno, they just assume it's all ok because it is running decently, and what they do not know, can't hurt them. Here's the deal, no matter if you have a nicley ported head, bump compression ratio, higher lift camshaft, if the engine is not effictnet at the vlaves and is leaking there, then you're losing perforamcne. I do constant leakdowns on my race engines ,and if I see leakdown numbers on valves as high as little as 5%, then I pull the head and lap the offending valves to increase seal, because that is lost HP. In street engine, it would not that uncommon for a engien to hae as much as 30% exahsut valve leakage, and the owner not know there as a problem, but consider that could cut performacne as much as 20%, valve seal is ultra important to good performacne, without good valve seal, you can't have it.

 

[tomshobby]

I have been looking for a photo I took of an exhaust valve seat before I had my engine rebuilt. It had a few very clear and precise impressions in it which I assume were made by bits of a broken ring on its way out. It left no doubt that the valve seats in my engine were very soft.

The engine had 44,000 original miles. When I purchased the car it was running rough and the compression was poor. I wanted to drive it a little so I could better decide what needed attention so I had a valve job done. It was obvious that it was the first valve grind and little was taken off. When I pulled the head for a total rebuild the seats were pitted.

As far as push rods bending. shave an 1/8th or more from the head, put in a lumpy cam, install new valves and don't check the stem length, don't check the valve springs for binding. All good ways to mess up the valve train geometry. Probably more going on than just bent push rods.

 

[Hap Waldrop]

Tom, typically when I removing that much from Triumph cylinder head, I would order a set of shorter custom tubular pushords, shorter by the same amount I took off the head. You can get them from Smith Bros. Pushords, custom made to your specs, and they are not expensive, less than $100 (for 4 cylinder, a little more for the 6 cylinders) shipped to your door. This is how you measure them, measure the entire lenght (minus what you need them to be), then deduct the dept of the top cup, get a rough measurement of the width of the cup and bottom, get the 5/16" diameter tubular pushords. Smith Brother is a great company, they will make and ship them normally the same day you order. Hope this helps.

 

[tomshobby]

Hi Hap,
My engine was put together correctly. After 33,000+ miles it runs great and used less than a pint of oil on our 4,000 mile trip this summer.

I was just expressing my frustration because it seems so many don't and ether they or the next owner end up like CJD asking after something like this happens.

 

[poolboy]

or PB..

 

[Brosky]

I had to put shorter push rods in my engine when the head was shaved.

And I only had three lifters that looked like the two on the bottom left, so I got mine before it got really bad.

 

[CJD]

PB...did you figure out what caused that?

John

 

[poolboy]

"PB...did you figure out what caused that?

John"


Just a bad combination. Leave out one of the following and things would have probably been just fine.
S2 Cam Profile
High Ratio Roller rocker arms 1.55:1
Shaved head resulting in 9.3-9.5 CR
And last but not least, shims under the Valve Springs.
More than likely the destruction began on day 1 from spring bind. The cam's lobes concaved the lifters and over time they just began to disintegrate.
At least that's the theory.

 

[tomshobby]

"PB...did you figure out what caused that?

John"


Just a bad combination. Leave out one of the following and things would have probably been just fine.
S2 Cam Profile
High Ratio Roller rocker arms 1.55:1
Shaved head resulting in 9.3-9.5 CR
And last but not least, shims under the Valve Springs.
More than likely the destruction began on day 1 from spring bind. The cam's lobes concaved the lifters and over time they just began to disintegrate.
At least that's the theory.

It was the cost of the education that hurt.

 

[poolboy]

I guess there are a few more factors to consider. Since I bought the car with several thousand, if not more, miles on the engine, I don't know about the cam break in procedure or the oil that was used. But, in the end the post mortem was spring bind.

 

[CJD]

If it's any consolation, a couple bent rods is really a good outcome. Through the years, every major mechanical failure I have had was precipitated by the valve train. The results can be MUCH worse! Some examples:

- New cam not broken in correctly ground 2 lobes flat in 30 minutes of running...of course all that metal wound up all through the new engine.

- brand new roller cam and lifters trashed from coil bind. (back when that set up was several $k)

- A nickel pushrod guide broke, allowing the rod to cock on a chevy, which popped the keepers off, so the valve went down the cylinder. It was a brand new guide...and engine.

- Not checking piston clearance broke the tulip off a valve from the valve just barely touching the piston at high speed. After 2,000 miles the tulip broke off in the cylinder. You guessed it...new motor.

I guess you can tell, its always a screw up on my part, and usually from not checking every clearance within the valvetrain. I now check the installed height, open height, seat pressure, fully open pressure, piston clearance, and I use that really thick break-in lube from GM on every new cam installation. Of course, there are still the normal checks, like seats and guides.

So, I would REALLY prefer a couple bent rods!

John

 

[tinman58]

After about 200 miles onSunday, There is a little tell tale sign of the problem. The exhaust pipe is very grey from hot exhaust. I could feel the lose of power for the last 50 miles or so... Started on removing the motor, apron rad.and interior is out.

 

[apbos]

You will be done in know time Dan. Looks like we should have good driving weather for the next 10 days. Do you have a machine shop lined up?

Paul

 

[tinman58]

Hi Paul!!
Long time no hear. Yea I have a shop in San Leandro. I am going to balance the drive train crank, pistons etc. this time, I may need a new head for the TR do you have any ideas?

 

[TR3driver]

If the valve is recessing into the head/bowl, then it is moving upward, making for a higher valve stem hieght, thus reducing lash, or elminating it altogether,

That much I agree with.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] thus increasing the amount of pressure on the valve to the rocker arm
[/QUOTE]Uh, no. Since the spring is now allowed to expand beyond its usual installed height, there is actually less force once the lash is adjusted. And the same amount if the lash doesn't get adjusted, since the rocker is holding the stem & spring down (rather than the valve head against the seat).
<div class="ubbcode-block"><div class="ubbcode-header">Quote:] also if you had the sort of recession shown in your picture you could also have valve spring bind.[/QUOTE]Again no, it doesn't work that way. The VSR means the valve stem stands up taller above the head and the spring is expanded, not compressed. Since the stroke remains the same, you cannot have coil bind (if you didn't have it before).
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Randall, if you had a valve recess with a hardened seat insert, then I would be looking at the person who installed the hardened seats. [/QUOTE]Look at them for what? Softening the inserts?
Although I can't prove it, I believe the problem was very high 'seat' pressure, caused by the racing valve springs I used. But I don't propose to repeat the experiment.
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Bottom line what happens most commonly with heads that do not have hardened exhaust seats is the cast iron seat area at the exahsut valve get compromised
[/QUOTE]
Actually, I claim that most heads without hardened inserts do just fine. Being run with leaded fuel leaves a lasting effect that can easily last the rest of the life of the engine if it isn't run hard for extended periods. I replaced the head above with one that was totally stock (actually the one I removed when installing the one above) and it went another 40k or so miles with absolutely no signs of VSR.

The trick is that, once you disturb the exhaust seat surface, then they need to be hardened, because the lead only penetrates a tiny amount (similar to case hardening).

<div class="ubbcode-block"><div class="ubbcode-header">Quote:] valve seal is ultra important to good performacne, without good valve seal, you can't have it. [/QUOTE]

Absolutely! A car engine is basically a glorified air pump; if it leaks then it cannot perform as it should.

 

[Hap Waldrop]

Randall, do a fresh valve job on head without hardened exhaust seat that you see pittng in the seat area, do leak down test, you'll probably see a good number as for seal, if the valve job is done right, then go drive a few hunded mile and do it again, I think you see it's not so good now, testing proving results.

As for what I said about a valve recessing, if the the valve recesses into the bowl the stem height grows on the head, the lash get tighter, sure the valve spring can't increase pressure, in fact it would lose seated pressure, but neverhteless the stem is higher, make sense?

 

[apbos]

Dan
I think I saw a listing for TR parts on craiglist. Short of that you can use my rebuilt TR head and replace it if you should need to replace yours and one is not available.
Paul

The B/E is coming along 60 % in primer