• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Top Dead Center

Share this page

Aww, go on and pull th' head and find TDC with a dial indicator! :jester:

...ya still should do the "mark the damper" from both directions of rotation but you:
A) Have an excellent reason for NEW TOOLS,
B) Can dream up all manner of excuse to fuss with valves/guides/springs,etc.

:laugh:
 
DrEntropy said:
Aww, go on and pull th' head and find TDC with a dial indicator! :jester:

...ya still should do the "mark the damper" from both directions of rotation but you:
A) Have an excellent reason for NEW TOOLS,
B) Can dream up all manner of excuse to fuss with valves/guides/springs,etc.

:laugh:
Click to expand...
Holy Bat-Poop! I guess when you've got 29K posts you can get away with that! Us mere mortals have to carefully couch our feelings in language that won't get our threads yanked!
 
TOC said:
DrEntropy said:
Aww, go on and pull th' head and find TDC with a dial indicator! :jester:

...ya still should do the "mark the damper" from both directions of rotation but you:
A) Have an excellent reason for NEW TOOLS,
B) Can dream up all manner of excuse to fuss with valves/guides/springs,etc.

:laugh:
Click to expand...
Holy Bat-Poop! I guess when you've got 29K posts you can get away with that! Us mere mortals have to carefully couch our feelings in language that won't get our threads yanked!
Click to expand...

Jus' tryin' to be helpful, Dave. :devilgrin:

We all know in our hearts we truly want to understand th' mystical inner workings of th' infernal combustion engine.
That takes dedication, patience and a truckload of SierraHotel TOOLS. :wink:
 
Actually, Dr. Entrophy is not only being helpful but I believe he is right about the head and the dial indicator...

If I use the little Top Dead Center Indicator through the spark plug hole, I foresee a possible problem. The piston rises straight up, but the Indicator enters at an angle. And if it is necessary to get this exactly right, that angle may give a false reading.

I think I'll depend on the mark on the pully and the proper use of a timing light instead.

Ah, yes, the siren song of those "mystical inner workings of th' infernal combustion engine." Argh... Tie me to the mast, crew members.
 
The dial indicator is subject to the same error possibility that your spark plug hole indicator is. The piston doesn't move for a few degrees before and after TDC.

The piston stop/timing disk style doesn't have this problem.
 
Many thanks, Dr. John.

Like so many other things connected with this car, I'm going to have a friend of mine who knows these procedures well do the check for me. I'll watch and learn.
 
Do not trust the existing damper marks. It's possible that they loose a degree of accuracy per 10,000 miles on the engine.
If they were that accurate, you could use them to accurately install a cam, rather than the usual ritual.
Depends what you want to do. Set the timing, they're Ok to get you close, but not for finding the true sweet spot for your particular engine with that particular mileage on that particular day, with that particular fuel.

You'll notice or discover that the ignition timing as recommended by Lucas was by an initial Vacuum reading followed by a road test or running conditions.
Check out "Timing..Final Adjustment" about half way down:
https://mgaguru.com/mgtech/books/lts_otcc/Session3_CoilIgnition.pdf
 
Hi, Poolboy,

Thank you for the link. It is very interesting, and I will read it with care. But it is probably far more information than I need for what I want to do, at least at this time.

All I want to do is to check the timing of the engine. I've done this before with American cars and it was pretty simple... but that was 30 years ago. Perhaps I am under the false assumption that checking the timing on the Triumph should be about as simple.

As for the engine, it was completely rebuilt about a year ago and has about 5000 miles on it.

I'm not sure what you mean by "the existing damper marks." The only dampers I know of are the dampers in the carburetor suction chambers and dampers in the suspension.
 
Ed - The timing marks on the crank damper, harmonic damper, damper pulley; like alot of things on the cars it has several names.
 
SkinnedKnuckles said:
Ed - The timing marks on the crank damper, harmonic damper, damper pulley; like alot of things on the cars it has several names.
Click to expand...

Except the a stock TR2-4 engine doesn't have any kind of damper on the crank pulley. And the pulley is drilled with a mark for TDC, and while it can be installed off (there are six bolts in the pulley that mate to the hub, and the hub can only go on one way), it should be easy to tell if it is right.
 
Brent,

Can you tell me where I would find any of these mentioned in the standard manuals? I don't find any of them mentioned in the indexes.

You are not talking about the hole in the fan pulley and pointer on the timing cover, are you?
 
Ed, Poolboy and Skinned Knuckles have TR6s, which have harmonic dampers, while TR3s just hane a hole drilled in the pulley. I guess they thought that the TR3 has dampers like their cars. That's why the TR3 manual does not mention a damper.
 
That's right. I'm not familar with the older fellows.

But what's Ed talking about when he said this ? The drilled hole ?

"I think I'll depend on the mark on the pully and the proper use of a timing light instead."
 
LexTR3 said:
Brent,

Can you tell me where I would find any of these mentioned in the standard manuals?
Click to expand...

Penciled in the margin of my Haynes? :smile: Never said those were official names. And yeah - my mistake. Was referring to TR6.
 
poolboy said:
That's right. I'm not familar with the older fellows.

But what's Ed talking about when he said this ? The drilled hole ?

"I think I'll depend on the mark on the pully and the proper use of a timing light instead."
Click to expand...

Yes, the TR2-4 engines have a small hole drilled in the back half of the crank pulley, that (if the pulley is properly installed) will line up with the pointer on the timing cover to indicate TDC.

There isn't any scale, so to use a timing light, you need an "advance" timing light.
 
LexTR3 said:
Hi, Poolboy,

Thank you for the link. It is very interesting, and I will read it with care. But it is probably far more information than I need for what I want to do, at least at this time.
Click to expand...
Oh then let me completely overwhelm you, Ed.
You got to have something to do after you run up those thousand miles.

I'd see about getting that changed, BTW ! :driving:

https://mgaguru.com/mgtech/books/lts_otcc.htm

https://www.acecom.com.au/TR6_images/LucasFaultDiagnosisServiceManual.pdf
 
Thanks Darrell ! I'll see if I can retain that information.
 
poolboy said:
Thanks Darrell ! I'll see if I can retain that information.
Click to expand...

With so many things in common between the TR models (at least 2 thru 6), it is easy to get surprised by something that changed.
 
Ken, surprised me too.
TR3Pulley.jpg
 
Back
Top