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TR6 TR6 put put sounds, part 2

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ichthos

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As soon as a couple of you mentioned compression, I decided to take compression readings. In order from front to back they are: 190, 185, 30, 170, 180, 185. Obviously the 30 is a red flag. Wouldn't this mean there is a burnt valve, not a blown head gasket? I don't like the 170 reading, but I read that the cylinders should be within 10%. The 170 is low, but seems acceptable. There is no water in the oil, and there is not any oil in the radiator fluid. Any thoughts or suggestions?

Kevin
 
ichthos said:
...compression readings. In order from front to back they are: 190, 185, 30, 170, 180, 185. Obviously the 30 is a red flag. Wouldn't this mean there is a burnt valve, not a blown head gasket? ...
Click to expand...

Actually you could have a burnt or stuck valve, or worse a hole in a piston. And no, it cant be the head gasket, as you would have low compression on at least 2 cylinders.

Try the compression test again, but this time put some 30wt oil into the cylinder before attaching the gauge. If compression goes up, its rings or piston crack. If the compression stays the same, its valves.

What is the condition of the plug that came out of #3? This also can tell us a lot. Spark Plugs

Rev the engine a few times quickly and see if your getting any blueish colored smoke out of the exhaust. If yes, then that's oil your burning. If not, then I'm willing to bet your intake valve is not closing all the way, and the 'put put' sound is the sound of a backfire into your intake manifold.

If you feel lucky, and when I did this trick I felt lucky and it worked, you can try spraying some water into your carbs at about 3000 rpm. I'd start with about 1/2 a cup per carb barrel. Yes, the engine will seem to hate this, and it will run like poo during this. What this does is blast the carbon build up off the valves, and in my lucky experience it unstuck my piston rings (which were stuck bad enough to allow for massive blow-by and I had oil shooting out of my dipstick hole!)
 
Kevin - #30 is clearly an issue (sorry, I know this stinks). Can you let us know the plug condition, smoke, and wet compression test as Pete suggested?
 
Yup... 30# is not good. But I'm going to disagree with Pete and say that it <span style="font-style: italic">could</span> be a head gasket. They <span style="font-style: italic">can</span> blow out the side of a single cylinder. All this will be revealed, of course, if water trick (a good trick!) fails to cure the problem. Then the head will have to come off...
 
My internet was down yesterday. In any case, I squirted oil in cylinder number three and there was no change - still 30 pounds. I am going to have to pull the cylinder head anyway - can you normally tell if the valve is burnt just by looking at the part of the valve that faces the piston? I have a second engine I bought a while back. The engine had serial numbers just a few away from mine (it was pulled from a 69), and the price was too good to pass up. I was thinking of just putting this head on my engine and see what happens. The worst that would happen is I woul be out time and a head gasket it it doesn't work. I am paying to have my carbs built professionally, and I am not thrilled at paying hundreds of dollars more right now. What do you think of the idea?

Kevin
 
I'm not sure what your reasoning is on having to pull the head anyways, but, when you do... turn it upside down, lay it nice and flat on a old towel or something you can get lots of gas on, then pour gas into the head. If the level goes down the valves need to be lapped or replaced, and the head needs to me cleaned or lightly machined. If the leak is slow, then clean the head and valves then re-lap the valves. If the leak is fast, and I would assume it is with only 30psi, then the valves should be replaced, head cleaned or machined, then lap the valves.

Personally, since your pulling the head anyways, I would replace all the valves with the new Harded-Seat valves and have the head professionally cleaned and machined. It can't hurt to replace all the valve springs at this point too.

ichthos said:
...can you normally tell if the valve is burnt just by looking at the part of the valve that faces the piston? ...
Kevin
Click to expand...

Not normally. Its the valve seat that matters anyways. And yes, if its burnt badly on the seat you can usually tell right away. But the best way to tell is the gas in the head test I mentioned.
 
Kevin,

Go purchase an intake manifold; Vacuum diagnostic gauge.
Do this before you start ripping the top of your engine off.

dale (Tinster)

vacgauge.jpg
 
ichthos said:
Ever since my last cross country trip my car has not been running like it should have. For lack of a better description, it makes a mild put put sound when accelerating, and is especially evident at lower speeds. I experience a slight reduction in acceleration power. This came on sort of gradually during the end of my trip. <span style="font-weight: bold">I adusted the valves - no change.</span> I found there was a vacuum leak, and a tear in one of the air valve diaphragms. I repared them, but there is still no change. The linkage does stick slightly on the carbs, so it is difficult to get the timing perfect, which also effects adusting the carbs. I am getting a second pair of carbs rebuilt professionally, and I should have them back in two weeks. There is rarely one nice fix for a problem in this car. Are there any things I should be checking while I am waiting for my carbs?

Kevin
Click to expand...

Andy, in an earlier separate thread about this problem Kevin said he already adjusted the the valves resulting in no change.
 
I tried keeping the engine rpm up to 3000 rpm and ran one quart of water spray through the carbs - no change. Still the same put put sound. After finally finding a vacuum guage, I took a vacuum reading. The needle moved rapidly between 18 and 19 inches, maybe a little more. I still think there is something wrong with the exhaust valve for cylinder three. What do you think now? What should I do now?
Kevin
 
Pull the head.
Remove all rockers.
Insert plugs.
Turn it over, fill combustion chanbers with kerosene or solvent.

See what port gets wet.

However:

If you have a flat cam (can't remember ever seeing one in an LBC, but troubleshooting just the same), it can do strange things.

Also, I have experienced a head gasket blown from one cylinder to the outside....once that I remember.

Makes a "putt-putt" sound, causes the vacuum gauge to go wonky at idle.

So, make sure all the rockers move roughly the same amount, pull the head, inspect the gasket carefully, wet the chambers, see what valve is bad.

Quick and dirty, if it's just one, pull that valve, inspect the seat, lap a new valve to it and re-assemble.
That is, if you want the summer out of it and plan on a full rebuild this winter.


If you want it right, have a knowledgeable (on LBC) machine shop do it, including magna-flux.
There really isn't a good reason to do it halffasst if you intend on keeping it and having it dependable.


Dave
 
ichthos said:
... I took a vacuum reading. The needle moved rapidly between 18 and 19 inches,...
Click to expand...

Rapid movement on the vacuum gauge suggests that 1 cylinder is out of whack. Also, with such a small change like that, it could also suggest that one (or more) spark plugs are gaped too close. A regular, evenly-spaced, downscale flicking of the needle would indicate one (or more) of the valves are burned or warped.

How does the gauge look under rapid acceleration? Does it even out, fluctuate more, Drop to 0, stay the same, so on?

Vacuum gauges are almost one of those things where you would have to be there to tell whats going on for certain. I tried to find this website I've seen many moons back with great animated examples, but have had no luck so far. If I do find it, I'll post it. Maybe someone else has it bookmarked and can post it before I pull my hair out looking?
 
pjsmetana said:
BINGO!
https://www.imperialclub.com/Repair/Fuel/VacuumGauge/index.htm
Click to expand...

You may move to the head of the class Pete! Spot on!!

Now Kevin has confirmation he's heading down the
correct path to diagnos his problem before ripping
things apart. He had a bit of difficulty locating a
vacuum test gauge but finally found one.

Kevin's had the vacuum testing procedures for a while
and began preliminary testing last night. I can't wait
to find out why his cyl. N0 3 is so low. My personal
guess is sticky valve from carbon build-up. The gauge
should tell!!

best regards,

Dale (Tinster)
 
Tinster said:
You may move to the head of the class Pete! Spot on!!
Click to expand...

All right... but can I keep my Dunce Cap?
 
pjsmetana said:
Tinster said:
You may move to the head of the class Pete! Spot on!!
Click to expand...

All right... but can I keep my Dunce Cap?
Click to expand...

You ain't no dunce, Pete. You took a suggestion and ran it down pretty good.

Good on ya mate!

Dale (Tinster)
 
I am trying hard not to remove the head until I am sure of what the problem is. I had already cleaned and gapped the spark plugs earlier to get rid of that variable. I am having a hard time reducing the idle, but even with the lowered idle, the needle is bouncing evenly between 16.5 and 17.5 inches.When I rev the engine, the needle drops, but the needle is then steady. I removed the valve cover, and I could not hear or see anything different in the valves from #3 cylinder. So now what?

Kevin
 
So, all the rockers moved about the same with the cover off?
A one-inch flutter isn't much, but it's an indication.
When you rev it, it is supposed to drop, then steady.

Next is a leakdown, or at the very least, apply service air to #3 and see where the noise is coming out.
 
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