TDC on a Rover 4.6 V8

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garrycol
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TDC on a Rover 4.6 V8

Post by garrycol »

I need to set up the trigger wheel with respect to top dead centre on my Rover 4.6 V8. Now these engines do not have TDC marks on the pulley or a pointer.

I have the spark plug removed to observe the piston and the rocker cover removed so I can observe the valves on number 1 cylinder.

The problem is that with the piston at the top and the valves closed, the crankshaft can be moved through about 15 degrees with no observable movement in the piston.

Observing the piston movement up and noting where it stops moving while slowly rotating the crankshaft unti the piston starts going down you can estimate the half way point which should be TDC but is a bit hit and miss.

Is there a way to determine exactly where TDC is rather than the hap hazard way described above.

Thanks

Garry



unstable load
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Post by unstable load »

The most accurate way would be to gut an old plug and insert a bolt into where the electrode sits that protrudes about half an inch or so down past the old electrode depth.
Turn the piston to mid-stroke and insert the plug and then turn the engine gently until it stops against the bolt, then mark the spot on the crank pulley pointer. Now, turn the engine the other way until it touches and mark the point again.

Find the midpoint between the 2 marks and that is exact TDC on the pointer. Remember, the pointer could well be out a bit, so you will need to re-identify the timing marks if you want to use them with a strobe.
Cheers,
John

DaveEFI
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Post by DaveEFI »

If you don't fancy making your own from a spark plug and bolt, you can buy a tool which does this.
Dave
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garrycol
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Post by garrycol »

Thanks for the information - I will try making something up as there doesn't seem to be any local businesses selling piston stop tools.

cheers

garry

mgbv8
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Post by mgbv8 »

I made mine from an old spark plug. Saw off the earth strap. Remove the centre electrode however you want to do it ? I think I used vice grips and twisted it out of the plug. I found an old bolt that would slip inside the plug and brazed it is to leave about 20mm proud of the end of the plug. Then I smoothed the end of the bolt to a dome by removing a little metal.

There are many ways to make a TDC tool. The main thin is to make sure that the end of the tool is smooth as poss so as not to gouge the top of the piston. Finding TDC is then very easy by rotating one way and then the other. A couple of felt tip marks on the pulley and TDC is in the middle of those two marks :)

I have made 4 or 5 of these now and all have been lent out never to return home :)

Perry Stephenson

MGB GT + Rover V8

9.62 @ 137.37mph

Now looking for 8 seconds with a SBC engine

http://www.youtube.com/watch?v=nVscbPHgue0&list=UUqIlXfSAoiZ--GyG4tfRrjw



https://www.youtube.com/watch?v=eg3avnsNKrc&index=2&list=FLqIlXfSAoiZ--GyG4tfRrjw

unstable load
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Post by unstable load »

mgbv8 wrote:I have made 4 or 5 of these now and all have been lent out never to return home :)
Seems to be a universal problem, that...
I am still very annoyed about the Snap-On plug spanner I lent out.
Cheers,
John

garrycol
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Post by garrycol »

No one locally sells the tools so I made my own.

Image

Because of the shallow angle of the spark plug hole the piston comes up very close to TDC before touching the end of the tool but it should still be doable. I will set it up tomorrow after I have made up a pointer which will need to bolt off the timing cover near the Edis 8 sensor.

Cheers

Garry

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Post by unstable load »

Well done, Garry! Now, you need a dedicated drawer in your toolbox for the subsequent home made tools that will come along. :lol:
Cheers,
John

garrycol
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Post by garrycol »

Hi John - I have been working of cars for over 40 years - I already have that box and it is full :lol:

unstable load
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Post by unstable load »

garrycol wrote:Hi John - I have been working of cars for over 40 years - I already have that box and it is full :lol:
In that case, it's time for a second one.
Cheers,
John

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Post by SuperV8 »

How are you making/fitting your pointer?
I would be interested to see a photo.

At first I used some alloy extrusion glued to the water pump at arround 12:00 o'clock which worked great... until my aux belt snapped (because I missed finally torquing up my idler pulley), and took out my pointer.

Second version was also some alloy extrusion (section on old window frame) but I bolted in in place using some of the water pump bolts.

Tom.
Dax Rush 4.6 supercharged V8 MSII

garrycol
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Post by garrycol »

Just a bit of metal I had lying around - if the belt comes off it should be clear of the pointer. It is easy to get under a 101 so is read from under but once the trigger is set up it will not really be used.

I used a dremel to put some marks at TDC, 5BTDC and 10 BTDC on the crank pulley.

Image

Garry

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Post by SuperV8 »

Ah, ok, I used that bolt for my crank sensor so have no space down there, also my car is only a couple of inches of the ground! :shock:

Tom.
Dax Rush 4.6 supercharged V8 MSII

garrycol
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Post by garrycol »

I have posted this on the MS forum but didn't get a response.

As mentioned above the 4.6 Rover engine I am using never had timing marks on the crank pulley or a marker so I used the procedure of determining TDC through the spark plug hole on number 1 cylinder on the compression stroke - I did the procedure quite a few times and consistently got the same result and marked the crank pulley and set up a pointer.

When running on Edis 8 only in default mode, the timing light was showing 14 BTDC rather than 10 - so EDIS is either firing a bit early or my marks are a little out - it is a bit hard to tell which is wrong at this stage. I am using the highest Octane fuel I can get and I am not getting any knocking but if I have to start on starting fluid it does knock until running on petrol and on petrol there is no knocking even under load. So my thoughts are my marks are out.

When I have the entire MS3X system up and running and using the tuner program to sort out my engine map - will MS3X actually be able to work out exactly where my TDC really is or do I need to adjust the VR sensor or trigger wheel to take into account the possible 4 degrees difference.

Thanks

Garry

DaveEFI
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Post by DaveEFI »

If your TDC mark was out, then where you set the trigger wheel/sensor would also be out? As they are generally adjustable? If you are sure your TDC is correct, move the sensor in its slots to correct. If not enough adjustment, you'll have to move the trigger wheel. If it's like mine, both the trigger wheel and sensor bracket allow some adjustment.

So saying, my default EDIS setting is a couple of degrees out. I just trimmed this in the offset software setting.
Dave
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Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
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