| [ Total Views: 501 | Total Replies: 11 | Thread Id: 22552 ] |
|
|
 4 of 50
Commited Dubber
Posts: 71
Threads: 21
Registered: September 12th, 2003
Member Is Offline
Theme: UltimaBB Pro Blue ( Default )
Mood: BBrrrrrrr!
|
| posted on May 6th, 2004 at 06:10 PM |
|
|
top dead centre
Does anyone have a U-bewt method of finding TDC?
I have a '77 bus and the plastic timing mark component is missing from the rear of the fan housing AND I cant seem to get hold of one in a hurry.
Thanks
|
|
|
 Bizarre
Super Moderator
The artist formerly known as blue74l
Posts: 12780
Threads: 734
Registered: August 25th, 2002
Member Is Offline
Location: Abbotsford, Sydney
Theme: UltimaBB Pro Blue ( Default )
|
| posted on May 6th, 2004 at 06:51 PM |
|
|
hmmmm..... take #1 plug out and put a pencil in there and turn the motor over by hand????
:thumb
Futue te ipsum!!!
|
|
|
tassupervee
A.k.a.: Knob Jockey
Custom Title Time!
That really hurts doesnt it!
Posts: 1171
Threads: 25
Registered: September 21st, 2003
Member Is Offline
Location: Huon Valley SouthernTasmania
Theme: UltimaBB Psyche Blue
Mood: Moody!
|
| posted on May 6th, 2004 at 07:11 PM |
|
|
Your a cruel man '74 LOL
If you have or can beg borrow steal a vernier caliper with a dial indicator you can find TDC close enough.
Extend the caliper right apart and just insert the tail of the caliper down the plug hole as close to perpendicular (in line with the travel of the
piston, not in line with the plug hole) as you can and then seat the base of the caliper onto the plug hole and gently wind the engine over watching
the dial indicator until it stops moving.
You will need help to get this right as it takes a bit of patience to hold the vernier steady and keep a bit of pressure on the top of the vernier to
work as a dial guage.
Works for me!
L8tr M8
E
Im not a complete idiot, quite a few parts are missing....
|
|
|
AdrianH
Officially Full-On Dubber
Posts: 257
Threads: 20
Registered: March 5th, 2004
Member Is Offline
Location: New Zealand
Theme: UltimaBB Pro Blue ( Default )
Mood: rebuilding again
|
| posted on May 6th, 2004 at 07:54 PM |
|
|
Heres what I have done, taken out the ceramic core of a spark plug, tapped it for an M10 bolt, wound the bolt through, rounded off the end that is
exposed in the cylinder and wrapped a bit of insulation tape around the end (so it doesnt fall off !!!)
Make sure the cylinder is on the compression stroke, put the bolt?plug thing in, wind the engine slowly untill it contacts the bolt, mark the pulley,
wind the engine back the other way till it contacts again, mark the pulley. Half way between the two marks is TDC.
|
|
|
1303Steve
A.k.a.: Steve Carter
Scirocco Rare
Posts: 8650
Threads: 564
Registered: August 27th, 2002
Member Is Offline
Location: Sydney, NSW
Theme: UltimaBB Pro Blue ( Default )
Mood: Parrot Heading
|
| posted on May 6th, 2004 at 09:45 PM |
|
|
Hi
I just reread your post, I was going to suggest Adrians method, but dont try it with a Type 4 motor, the plug goes in at the wrong angle.
Buy a new timming scale.
1302Steve
[Edited on 6-5-2004 by 1302Steve]
|
|
|
4 of 50
Commited Dubber
Posts: 71
Threads: 21
Registered: September 12th, 2003
Member Is Offline
Theme: UltimaBB Pro Blue ( Default )
Mood: BBrrrrrrr!
|
| posted on May 7th, 2004 at 08:53 AM |
|
|
AdrianH, That is ingenious!
I have tried the pencil/pen in the plug hole. The angle is all wrong and I lost the tip in the cylynder. It was only plastic and I ended up turning
the motor over, problem fixed.
As the piston gets towards the TDC there is very little piston movement compared to crank handle movement and this is the problem I guess. Turning the
crank both ways and getting the mid point between two contacts is awsome,
Tried to buy a new timing scale from Import Advantage in Brisbane but they had run out and dont expect any more for 6-8 weeks.
Thanks
[Edited on 7-5-2004 by 4 of 50]
|
|
|
cumonghia
Commited Dubber
Posts: 70
Threads: 26
Registered: March 29th, 2004
Member Is Offline
Theme: UltimaBB Pro Blue ( Default )
|
| posted on May 8th, 2004 at 09:01 PM |
|
|
can you get your finger in the plug hole? take out the rotor so it wont start, and get someone to crank the motor over, with your finger sealing the
sparkplug hole. soon as air hisses past your finger yell stop! thats it. done that with inline fours and sixes, works fine.
[Edited on 8-5-2004 by cumonghia]
|
|
|
tassupervee
A.k.a.: Knob Jockey
Custom Title Time!
That really hurts doesnt it!
Posts: 1171
Threads: 25
Registered: September 21st, 2003
Member Is Offline
Location: Huon Valley SouthernTasmania
Theme: UltimaBB Psyche Blue
Mood: Moody!
|
| posted on May 9th, 2004 at 07:19 PM |
|
|
Errrrrrrrrr,,, I dont think he is wanting to know when a particular cylinder is on compression dude, he wants to find actual top dead centre.
Unfortunately, pencils and fingers in the plug holes are not too good at determining TDC with any certainty. Only close enough.
The suggestion using a bolt in a gutted plug and winding the engine up till the piston contacts, marking, then winding the engine backwards untill the
piston contacts again, marking again and measuring half the didtance between the two marks is as old as the hills, accurate and an excellent
suggestion that I had completely forgotten about!!!.
Of course, a dial guage is correct but not all have acess to one, same as my olde fashioned methode of using a vernier caliper with a dial indicator
as a substitute for a dial indicator.
L8tr
E
Im not a complete idiot, quite a few parts are missing....
|
|
|
4 of 50
Commited Dubber
Posts: 71
Threads: 21
Registered: September 12th, 2003
Member Is Offline
Theme: UltimaBB Pro Blue ( Default )
Mood: BBrrrrrrr!
|
| posted on May 10th, 2004 at 10:10 AM |
|
|
Thanks tassupervee
Since you mentioned the caliper method I have been mulling over using a simple pressure gauge that uses a manometer or long peice of clear plastic
tubing into which water can climb(so indicating the pressure).
A bulb of some sort can sit in the cylinder and act as the resevoir and pressure transducer. As the piston cranks on the water is propelled from the
bulb up the tubing and into view. When the water stops climbing, that is TDC.
Hmmm, now I think of it a caliper might be a bit easier
|
|
|
tassupervee
A.k.a.: Knob Jockey
Custom Title Time!
That really hurts doesnt it!
Posts: 1171
Threads: 25
Registered: September 21st, 2003
Member Is Offline
Location: Huon Valley SouthernTasmania
Theme: UltimaBB Psyche Blue
Mood: Moody!
|
| posted on May 10th, 2004 at 07:27 PM |
|
|
Bwaaahahahaha I gotta say that method is equally ingenious!!!
Good stuff.
L8tr dude! LOLOLOLOL
E
Im not a complete idiot, quite a few parts are missing....
|
|
|
4 of 50
Commited Dubber
Posts: 71
Threads: 21
Registered: September 12th, 2003
Member Is Offline
Theme: UltimaBB Pro Blue ( Default )
Mood: BBrrrrrrr!
|
| posted on May 15th, 2004 at 07:04 PM |
|
|
In the end I eyeballed the piston in the cylinder via the spark plug hole and I had a mate cranking the pulley and 'got a feel for the topography of
the piston.
Then I got in line with one edge of the plug hole and said stop when a line/mark/familiar landmark on the piston came into view. A mark was made on
the case in line with the pulley notch.
Next, I kept cranking in the same direction and when the piston came back after TDC I stoppped at the same point as before. The two stop points were
marked in the case and in-between is TDC.
I then did a full service and she runs fine
PS the timing mark (7.5 BTDC) was found by measuring the pulley circumference and dividing C by 48 ( 360/7.5 ) You can check calcs by measuring
diameter and marking the previous timing mark.
|
|
|
tassupervee
A.k.a.: Knob Jockey
Custom Title Time!
That really hurts doesnt it!
Posts: 1171
Threads: 25
Registered: September 21st, 2003
Member Is Offline
Location: Huon Valley SouthernTasmania
Theme: UltimaBB Psyche Blue
Mood: Moody!
|
| posted on May 15th, 2004 at 11:59 PM |
|
|
Necessity is the mother of invention!
Im not a complete idiot, quite a few parts are missing....
|
|
|
4 of 50
Commited Dubber
Posts: 71
Threads: 21
Registered: September 12th, 2003
Member Is Offline
Theme: UltimaBB Pro Blue ( Default )
Mood: BBrrrrrrr!
|
| posted on May 18th, 2004 at 10:57 PM |
|
|
Feedback:I managed to get hold of a plastic timing gauge today and the above mentioned method of finding TDC was spot on but the timing mark was a bit
out (-2.5 degrees)
|
|
|
tassupervee
A.k.a.: Knob Jockey
Custom Title Time!
That really hurts doesnt it!
Posts: 1171
Threads: 25
Registered: September 21st, 2003
Member Is Offline
Location: Huon Valley SouthernTasmania
Theme: UltimaBB Psyche Blue
Mood: Moody!
|
| posted on May 19th, 2004 at 07:36 PM |
|
|
Good stuff dude.
L8tr
E
Im not a complete idiot, quite a few parts are missing....
|
|
|
