TR6 TR6 Compression

[erstearns]

Was installing a rebuilt dizzy and using a compression gauge to determine #1 cylinder compression stroke to roughly set timing.

I was hand cranking with a wrench. What should the compression be approximately? I assume that it would be somewhat less than when cranking with the starter or when running?

Any guess?

 

[Tinster]

Was installing a rebuilt dizzy and using a compression gauge to determine #1 cylinder compression stroke to roughly set timing.

I was hand cranking with a wrench. What should the compression be approximately? I assume that it would be somewhat less than when cranking with the starter or when running?

Any guess?

<span style="color: #000099">Eric, I know not alot about such things but I think
there are better methods to set the initial timing after installing
a new dizzy. (Compression will vary from car to car. You want to look
for uniformity)

I am thinking you need to static time your car. This will give you an idea
and then I'm sure the Triumph Experts here will correct my blunders and
help you out.

I did this task once and as I remember :

I took my valve cover off so I could watch the No. 1 cylinder valves opening
and closing, as I turned the engine fan by hand. I also pulled the spark plug
from Cyl No. 1 so I could see inside and place a long, thin wood dowel.

When the No.1 piston was near the top I watched the valve open and then
looked at the fanbelt pully for a timing mark. I did this several times until
I got close to piston at top with timing markers near each other.

Now, with distributor cap off, disconnect the low tension (skinny) wire from
the dizzy to the coil. Allligator clip a wire with a small lightbulb to the
dizzy spade and connected at the other end of the wire to the positive (red) pole
of the battery. If you are near TDC for cyl No. 1, the small light should come on.

Loosen the dizzy locking bolt on the right side and slowly rotate the dizzy
counter-clockwise until the small light blinks OFF. You have now found where
cylinder No. is located inside your dizzy. Put a small mark on the dizzy body
and on the dizzy cap for future reference.

Tighten the dizzy bolt, install the cap and spark plugs wires. Hopefully the
engine will fire up and you can fine tune the timing.

I think this is how I did it. If not, the experienced guys will correct my blunders.

good luck,

tinster

</span>

 

[poolboy]

Eric, about that compression. When you run a compresion test, aside from some other things you do, the compression is pumped up by multiple piston strokes.
You won't get a true reading of the compression with a single stroke.
I have an old engine; back in December with 98k miles, my readings were from a low of 142 to a high of 148.

 

[erstearns]

Thanks Tinster, your method makes sense and is similar to what is in the various manuals. My use of the comp gauge was merely to determine which pass of the timing marks was on the compression stroke. I have not determined if the TDC mark on the pulley is exactly accurate with TDC of #1 piston but I will use a method similar to yours to static time.

My concern was that the compression seemed low, even for hand cranking. Once the old girl has all her pieces and parts in the proper place I can pursue that more diligently.

Thanks

 

[AltaKnight]

To get a true compression reading you need the following
1) A warm/hot engine
2) All plugs out to facilitate cranking at speed
3) Throttle wide open, wedge the pedal
4) Carb Air valves blocked open
5) As poolboy noted several (6 to 8) compression strokes on the starter per cylinder

Any reading you get turning the engine by hand means nothing (other than a hissing noise means you must have a piston/rings of some sort in there).

 

[erstearns]

Thanks Graham, thought the data was useless. As you can see from my initial post I suspected as much but given the depth of knowledge here I thought it worth asking. Always looking for something else to worry about.

Thanks

 

[AltaKnight]

Always looking for something else to worry about.

Thanks

<span style="font-weight: bold">Eric, you must be a fellow alumni with Tinster!</span>

 

[Tinster]

Always looking for something else to worry about.

Thanks

<span style="font-weight: bold">Eric, you must be a fellow alumni with Tinster!</span>

:lol: :lol: :thumbsup:

tinster

 

[martx-5]

This is something I wrote in another thread when Dale (Tinster) was having problems with getting the timing and firing order straightened out. Anytime you bring the timing mark up to the pointer, you will either be at TDC on #1 or #6 cylinder. The method below will get you on #1, and describe how to static time the engine to get it started.

"The first thing we want to do is get back up to TDC like you did on a previous occassion. However, this time, we'll make one change so we can get your timing pretty close to where it should be. I don't know what kind of timing marks you have on your damper pulley, so I'll cover all the possibilities.

Remove the valve cover. Now turn the engine clockwise (as looking from the front) and look for the intake valve on #1 piston (second from the front) to open. Keep turning until it starts to close and then start watching for the TDC mark. This time, I don't want you to go all the way to the TDC mark.

If you have degrees marked on your damper, bring it up to the 10 deg mark BTDC (Before Top Dead Center). That would be to the right of the TDC mark as you're looking from the front.

If you don't have degrees marked, but have two marks, align the FIRST mark (the one to the right) with the pointer.

If you only have one mark, stop the rotation about 3/8"-1/2" before the TDC mark.

This will put you at about 10 deg BTDC. You'll see in a bit why were doing this. Make sure both rockers on #1 cyl wiggle just a little to indicate they are closed.

Now, pull all of the wires from the distributor cap, including the coil wire. Take off the cap. Loosen the distributor and rotate it into position so it looks like the pictures of the other distributors in this thread. They looked like the advance mechanisms were pretty much parallel with the engine block.

Attach a test light or voltmeter to the coil. Do this on the (-) side, the wire there should go to the distributor. If using a voltmeter set it at DC volts, and clip the red (+) lead from the voltmeter there. Hook the other end to the negative on the battery. This goes for the test light or the voltmeter.

Turn the ignition on, but DO NOT CRANK THE CAR OVER, or you'll have to start over again.

If the test light is on, or the voltmeter registers, turn the whole distributor CCW, until the light goes off. Then turn it back until it just lights. Tighten the distributor.

If the test light is off when you turn on the ignition, turn the distributor CW just until the light goes on or the meter registers. Tighten the distributor.

You have just set the timing statically. You can put the valve cover back on now.

Look to see where the rotor is pointing, and see which tower on the cap it lines up with. That is cyl. #1. Put the wire in and hook it up to #1 plug. Continue around the cap in a CCW manner with the rest of the wires. 1-5-3-6-2-4... put the coil wire back on.

Start the car."

 

[Trick6]

martx-5
You explained how to static time the TR6 in very such clear terms making a daunting task inviting. Very impressive.

Just wiggle the rockers and not the valves.

One can static time any engine following your instructions. Just know your firing order when you are reconnecting the spark plug wires to the distributor cap.

 

[martx-5]

...

Just wiggle the rockers and not the valves...

Good catch. I corrected it. Thank you.

 

[Tinster]

Thanks again, Art.

I guess I learned my lesson well.

tinster :thumbsup:

 

[erstearns]

Thanks all. Timing set at about right, will finish when all the beads and bangles are hooked up. With point"less" ignition the test light method works a bit different but can get you close if you understand where the magnets are. I tested it with an induction light and cranking with the starter and "close enough" for now.

Once the steering rack is aligned and bolted down, aluminum rad installed with elec fan, GP shroud, newly rebuilt bergs from Jeff P, new manifold and exhaust from Stebro etc......will be time to see if it coughs to life.

Several long necks from now.

Eric