TR4/4A TR4 Valve Recession?

[Geo Hahn]

I was getting some strange exhaust sound (rather Harleyesque at highway speed) and #3 was not firing at idle.

Investigation revealed that the #3 exhaust valve had lost it clearance... no lash at all.

I reset it to .012 (I like them a bit loose) and all is well for now, but I had to use noticably more adjustment than on the other valves (looking at how much adjustment screw shows above the pushrod).

Which is more likely -- have I burned the exhaust valve or eaten into the seat?

I'm hoping that so long as compression remains good on #3 there is no hurry to pull the head -- figuring someday I will have it off and get hardened seats installed.

Of course at the root of that thinking is the fact that we are now entering the prime diriving season in AZ. To R&R the head is simple enough but the good machine shops seem to have a month or more backlog for a small job like this.

Am I kidding myself or can I hold out until next Spring & another 3 or 4,000 miles?

 

[Moseso]

I would strongly urge you to pull the head and examine the valve in question -- and soon.

That exact symptom has preceded (twice in my automotive life) the valve head breaking off entirely, causing quite a bit of engine damage when it did. It could be, as you ask, valve recession. But it could also be the valve stem stretching. In my experience, when you lose .012" clearance in a short time, it's the, potentially disastrous latter.

As I said, I've done this twice. I will never again readjust a suddenly playless valve and hope for the best.

 

[tomshobby]

Might check to see if you have a worn cam lobe.

 

[Adrio]

Interesting that it is #3. On my TR3 it was the same thing and it was #3. Turned out to be resessed into the seat and the valve was burned. A machine shop trip, hardened seats and new valves solved the problem.

I think I drove it like that for a summer before I pulled the head. In my case driving season is only the summer and I used the snow season for the head R&R

 

[Geo Hahn]

Might check to see if you have a worn cam lobe.

That was my first thought (as I tend to expect the worst)... then I realized that a worn lobe would have the exact opposite effect, i.e. the gap would increase and the valve would not open (rather than being always open).

Interesting that it is #3. On my TR3 it was the same thing and it was #3.

Now that I think about it, it was #3 exhaust valve that finally led to reworking the head on the TR3A.

I think I'll check what the turn-around time looks like at the machine shop of choice... if it's inevitable then perhaps I will get on with it.

 

[tomshobby]

You are right, I did not think that through very well.

 

[TR3driver]

then I realized that a worn lobe would have the exact opposite effect, i.e. the gap would increase

Actually, a worn lobe won't change the lash at all. The lobe doesn't wear in the area where you measure the lash; so the only way to detect a worn lobe is to check the valve lift (or look for sparklies in the oil).

Just whip that thing off and have a look. Back when I was having head gasket problems, I could get it off in an hour. I found it unnecessary to remove the carbs from the manifolds or the manifolds from the car : just leave the whole assembly hanging on the exhaust pipe and pry it out of the way while you lift the head off the studs.

Although obviously you want to use a torque wrench when assembling, there isn't any reason you can't use an impact gun to remove head nuts. I generally used an air ratchet for everything else (except those pesky manifold nuts).

I also didn't remove the temp gauge connection, just loosen 2 hose clamps, remove the 2 bolts holding the Tstat housing to the head, then pull the housing away and lay it to the side with the capillary tube still attached. I didn't have the fuel line fastened to the housing as original, but if you do, you'll have to take that nut off as well.

 

[RonMacPherson]

You need to pull it ASAP. Either the valve is stretching, and when it breaks it "grenades" the motor, or the valve seat is receding into the head, or burning. That also can lead to explosive destruction.

 

[TR3driver]

I give up, how is valve seat recession going to lead to "explosive destruction" ?

I covered perhaps 20,000 miles with severe valve seat recession. Had to run the valves every couple 1000 miles & at the end even stuck spacers under the rocker shaft pedestals to get a bit more adjustment. Didn't run very good, but it still ran, even through Independence Pass (elevation over 2 miles) on the way to VTR 2001 in Breckenridge, CO. Finally pulled the head when I realized the spring retainers were hitting the rocker arms; but all it needs are new seat inserts and guides to be usable again.

 

[Moseso]

/bcforum/images/%%GRAEMLIN_URL%%/iagree.gif What he said...
However, a valve that's begun to stretch is a valve that's about to "release" it's head to be violently bounced from piston crown to cylinder head, for the period of time between the appearance of the REALLY LOUD BANGING sound, and the time you shut the motor down and pull to the side of the road. Even if you have the reflexes of Bruce Li, this is an entirely sufficient time to destroy the piston and -- quite possibly -- the head. Even if repairable, the head repair will cost plenty extra compared to a straight-ahead valve job. And the block will have to be entirely stripped and cleaned of the debris that used to be the piston crown.
This is not idle conjecture. I have seen it. Twice. It began with an exhaust valve that had no clearance at tune-up time. Clearance was restored. Then the valve had that much more room to stretch to the breaking point.
I certainly don't wish a head job upon Brother Geo, but I feel compelled to relate my experience with this symptom.

 

[RonMacPherson]

Randall,
If you have NEVER encountered a valve head that pulled off from a valve stem due to the valve seat receeding you have been very fortunate.

So pleas I do not understand why you choose to feel that you must try to discredit my posts... It's getting tiresome.

Always coming across as an attack or critical.

I am trying to pass on over 35 years experience in the automotive repair industry. A season as a Formula Three mechanic in Europe, two years repairing Amtrac's in Viet Nam, several published service advice inputs to American Honda(they sought to publish them, so they must have found them of some use) A season as crewchief(mostly the only wrench) on a Formula Continental where we increased the engine output over 15 horsepower due to the owner following my suggestions for cam and exhaust flow. Raced Baja in a Meyers Tow'd... Currently sitting below me is a 79 Corvette with a Ferrari Daytona kit body on it, getting finished up. a 328, a Lotus M and a 2003 Elan, besides my 75 TR6 here, two projects out in Waikele and I had two prior 6's, one in So Cal and one here, a 54 XK120M, a 40 Ford Coupe Deluxe with Chevy 265, Lasalle gearbox, tube shock conversion, among numerous other cars. And I worked on them all.

So I'll make a deal with you Randall.

If you have any questions or think my input is inconsequential, insignifigant or might be misleading to any other reader of these posts,Please do not post it so that ANYONE can think that you are attacking(as it seems you come across so frequently, not just me, but others that have contacted me regarding your posts to my posts. Please PM me and we'll see if I can explain what I am trying to say, maybe need further detail, maybe presenting it in a different format.

Okay? This is a great forum for knowledge dissemination, key to you is that you do NOT know it all, neither do I, but our knowledge can be shared with others...

 

[Brosky]

Well said. Let's keep peace in the valley.

 

[tomshobby]

Ditto

 

[Basil]

<span style="color: #FF0000">MEMO from The Emperor to Ron and Randall:</span>

<span style='font-family: Verdana'><span style="color: #006600">You both obviously have a lot of experience, and the forum I'm sure can benefit from your collective experience. However no one (not even me as hard as that is to believe) knows everything, and neither do EITHER of you two fellows. I'm not taking sides in this and I'm not locking this thread, but I am going to strongly suggest the following to both of you:

1. Respect the opinions of the other.
2. If you don't understand something, don't be a jerk and put down the other guy.
3. Ask for clarification. It may be that the other fellow just isn't explaining his thought in a way that you can understand. It doesn't mean the other person is a dolt.
4. It is ok to have honest disagreements, but be respectful in your disagreement.
5. Don't take a disagreement as a personal insult.
6. When two people clash, and both think they know everything - they are usually both half right.
7. Collaboration can be so much more beneficial to the group than confrontation.

<span style='font-size: 17pt'>Peace!
Basil</span>

</span> </span>

 

[TR3driver]

<span style="color: #FF0000">MEMO from The Emperor to Ron and Randall:</span>

<span style='font-family: Verdana'><span style="color: #006600">3. Ask for clarification.</span> </span>

<span style='font-size: 14pt'><span style="color: #336633">Funny </span>... </span>That's exactly what I thought I was doing !

Valve seat recession and the valve head pulling off the stem are two very different things. One of the differences is that one does lead to "explosive destruction" (which I'm more familiar with than I'd like to be) while as far as I know, the other does not.

If anyone knows different, please feel free to explain in either public or private.

Ron, you obviously have a lot of experience working on cars & various machinery. Believe it or not, I do respect that.

But we all make mistakes and mis-statements from time to time (I'm definitely no exception), and one of the purposes of a public forum (AFAIK) is to discuss such things. Please don't take it so personally, I am NOT trying to attack you.

But neither am I going to clear it with you before I disagree with what you've said.

 

[Basil]

<span style="color: #FF0000">MEMO from The Emperor to Ron and Randall:</span>

<span style='font-family: Verdana'><span style="color: #006600">3. Ask for clarification.</span> </span>

<span style='font-size: 14pt'><span style="color: #336633">Funny </span>... </span>That's exactly what I thought I was doing !

I really have better things to do than to get in the middle of this, but I'm going to be frank with both of you guys. First of all, Randall, I did not make that post to start a debate with either of you. You have to understand that in written communications, things can often be taken wrong because there is no verbal inflection in the written word. Ron, you should heed that lesson as well. Thus, sometimes things can come across harsher or at least differently than they are intended. For example, in your reply Randall, you started off with "I give up..." If you had been replying to me, I'll admit I would have read it as a bit more terse than perhaps you meant it, but nonetheless, it did sound like you were being rather condescending, even if that was not your intent.

Ron, you obviously have a lot of experience working on cars & various machinery. Believe it or not, I do respect that.

I expect that you are both quite knowlegable. If we can get you guys to communicate without 1) saying things in a manner that could be taken wrong and 2) on the other side of the coin, not being so thin skinned if someone disagrees with you. That way, everyone on the forum would benefit from both of your experiences.

But we all make mistakes and mis-statements from time to time (I'm definitely no exception), and one of the purposes of a public forum (AFAIK) is to discuss such things. Please don't take it so personally, I am NOT trying to attack you.

How true, no one is perfect. However, understand that this is actually a <span style="color: #3333FF"><u>private forum</u></span>, owned by yours truly. I have invested (sunk) many thousands of $$$ dollars for dedicated servers, software and high-speed data lines and more hours than I could count trying to make this the best forum possible. To that end, I decided from day one that BCF was going to be a "kinder gentler" forum, free of the flame wars and bickering that you see these days on so many other forums. If you ask any member who has been here for any length of time, you will hear most tell you that BCF is unlike (in a good way) 99% of the forums out there in its overall civility and comraderie among members. Not to toot my own horn too much, but that is no accident - it is by design. I would close the forum before I allowed that to change.

But neither am I going to clear it with you before I disagree with what you've said.

Randall: disagreeing is fine. However, you might consider tempering the tone of your disagreements. And in fact, asking reasoned questions might be better than just a shoot-from the-hip disagreement. For example, had I wanted to learn more about the connection Ron made between valve seat recession and explosive destruction, instead of “I give up…yadda yadda yadda” I might have simply asked: "Ron, that's interesting, but I'm not sure I understand the relationship between….blah blah blah. Could you explain what you mean?”

Ron: Don't take every disagreement personally. To be honest my friend, while I thought Randall could have stated his disagreement a little better, I did not read it as an attack on you. Often times on the internet, people come off differntly that they intend, or take things differently, which often gets mistaken for an "attack" when that may not have been what was intended at all. Randall said he respects your experience and he also said he was not trying to attack you. My request to you, sir, is to take him at his word.


Both of you: As I said in my original reply, I'm not singling anyone out here nor am I taking sides. Furthermore, I'm not going to debate any of what I've said and I'd appreciate it if you want to iron things out you both do so via PMs rather than here in the forums. You both strike me as intelligent, knowledgeable guys, and I really think the forum can benefit greatly from both of you.

Ok, I've just spent the better part of an hour on this response. I hope this can be put to bed now.


Basil

Basil

 

[mikespain]

Getting back to the problem in hand,there is obviously something going badly wrong with the valve,(beit recession or stretching) that needs urgent attention to ascertain the cause, and the only way is to take the head off and correct the fault, to prevent any further possible damage.Surely?

 

[2wrench]

The worst I could envision for the Forum, is to lose
differing experiences or points of view from the
really true mechanics among us.

Please agree to respectfully disagree, if necessary,
for the benefit of the truly ignorants such as myself
who need to hear what each of you have to say on any
given subject.

My comment is designed to preserve the most valuable
among us still coming here.

With best wishes and much appreciation to all,

 

[RonMacPherson]

Russell,Your caveat was that you stated you adjusted the valves every 1K miles. Not many owners who'se seats are receding are going to do that workaround. Most people even acclimate themselves to a little "noise" and slight running rough, especially at idle, because at rpm the other cylinders help mask the idle roughness, until the engine makes a loud noise, quits and won't turn over.

I've seen a great quantity of engines(that's what I do, examine mechanical failures) where the valve seat has receded and then the stress put on the valve stem at the head snaps the valve. If it is rotating at any rpm level it grenades the motor.

It's really quite easy if enough of the engine pieces are still identifiable to determine if it's seat recession or stem stretch. I've seen both frequently enough where I can identify the cause of failure.

others posted while I was typing this response, meant to go to russel

 

[Don Elliott]

George - I'm a late arrival on this thread and I would like to relate to you my experience. I rebuilt my engine in 1989 while I was doing my restoration. After the rebuild, the head was like new in 1990 when Canada announced that there would be no more leaded gas after 1990. So I could have pulled the head to have inserts installed in this "new" head, but I thought, being a mechanical engineer who always worked in R&D, that I'd see how long it would last on "unleaded petrol" before I would have to put the inserts into the cast iron head for the exhaust valves. It was about 35,000 miles later that I had to re-gap the rocker/valve clearances back from 0.012" gap because they were getting closer to 0.002" faster and sooner than normal. About every 1000 miles, the gap clearance was getting down to 0.002" or less. I knew it was time to do something about it. So I pulled off the head at 43,000 miles and found that the seats had recessed into the cast iron head almost 1/32" and the edges of the valves were so thin, some had become as sharp as a razor. If I had left it any longer, I could have had an explosive event (whatever that means).

It was then that I had 8 new valves, 8 new valve guides and 4 inserts put into the head for the exhaust valves by an engine re-build shop and since then I've had no problems. Since then, I've driven another 54,000 miles and only once have I had to make a minor adjustment for the gaps on a couple of valve clearances.