How on earth can I 'make' accurate timing marks ?

[Hybrid_From_Hell]

Hmmmmmmmmmmmm

Just got in from trying to get a mates V8 4.6 racer to run, he had megasquirted it, and I guessed he had done something

wrong / missed / stupid, but in fairness not really - he had followed my thread and with a bit of help had it all correct

What it turned out to be was timing, gawd knows what he had, but it was Waaaaaaaaaay out

Nowm, before you all go "Pratt" he has a good reason - the V8 in Questions has NO Timing Marks

None, Ziltch, feeeerucall

Its a 4.6 from a late GEMS powered P38, non thor unit

On the timing cover there are no marks, or TDC Indicators, and the pulley equally has nothing on it,

just a drive belt for the serp belt and thats it, so when he rebuilt it he got his calcs wrong re what

was TDC and built it up - with the timing he had it was never going to run.

To fix the poblem, and just to get it running I did a big time bodgeification on it - I got a spare spark

plug, removed the centre electrode, drilled out the center and welded in a 2" section of a old V8 Pushrod

the passenger rocker cover removed and the engine turned by hand until both vales closed, then it was backed ioff

the sparkplug pushrod combo screwed in and the engine re rotated until in jammed

At the point a Mark had been dremmelled into the casing, and a mark was placed on the pulley again with a dremel, then the

combo bodgo tool removed engine rotated past TDC the thing screwed back in and engine reversed up till jammed and then another

mark on the pulley

TDC was then simply the exact point between the two marks that then we refixed the trigger wheel in relation to TDC and VR Sensor

all then lined up with the new timing TDC mark on the tinming cover

Engine then started

He did cartrwheels as it has eluded him for some weeks now, I tuned MS by ear for 6-8 degrees etc and left, but its a bodge

So, what I am desperately thinking (and failing to resolve) is how I can equally now work out easily the 2 degree gaps Before

and Aft TDC without taking the pulley off and trying to even out the timing marks around the pulley edge, that would be a nightmare,

as would a session with a dividing head (crossed my mind and dismissed )

So, ideas please so that I can get the timing solid on MS better than a guess, the MS reads wild spark as I have

big time trim in it after the bodge above, matey is chuffed enough, but I'd like it to be more accuarte on base timing settings

Ideas ?

Nige

[Dave W]

Are you using the GEMS OEM crank sensor ?

If so you just need to know what position the missing tooth is in on a standard GEMS setup and there's no need to have a mark anywhere else. I have it written down somewhere from the last GEMS MS install I did.

As it's GEMS rather than Thor you should even be able to run EDIS off the OEM sensor if you really feel it necessary.

Another possibility, if you're using an external timing wheel, is to use a 2 channel scope with a channel on each sensor, that way you can compare the position of the external wheel relative to the OEM one.

Obviously this all assumes the GEMS flywheel is still fitted.

[Hybrid_From_Hell]

Hi Dave

Nope Engine came without most / all Gems stuff was crashed P38 I think

nothing gems left on it sensor inc.

He's using a Trigger wheel I made him, plus the Ford sensor and Bracketry,

was an auto but now mated to an LT95 with a flywheel from a old carb V8

Thoughts ?

Nige

[FridgeFreezer]

I thought the GEMS flywheel was 60-2 hence unsuitable for EDIS that said they're supposedly quite rare in manual form anyway, or they were when I last looked.

Anyway, aside from that you could certainly use the gap to take the timing mark from as they need to be accurate.

[Dave W]

FF - yep you're right GEMS is 60-2 not 36-1, must be past my bed time

HFH - You're method for finding TDC seems about as good as you'll get, maybe you'd get slightly better with a dial gauge but probably not much. Is it practical to rotate the toothed wheel to the correct position ? At the end of the day, once you have the toothed wheel set up correctly there's not really much reason to have any timing marks ?

[Bowie69]

I did exactly what you did Nige(albeit with a caphead bolt and a nut ground down to a sleeve), and then played with the trim in MT to get it to sound better, still not 100% sure it is quite right, maybe someone has a better idea...?

[will_warne]

Nige, I'd try finding TDC again with a dial gauge - at least that way you can be certain where it is. Then mark the timing case and pulley with something like a narrow nibbed pen. As the mark only needs to be temporary I'd concentrate on getting TDC marked really accurately in the short term so you can get the trigger wheel to the correct position.

[Aragorn]

The mid point of the above should get you a TDC mark thats as accurate as you'll manage. DTI down the plug hole would also work.

You can then calculate the distance between the TDC mark and your desired mark using some maths...

(3.14 x pulley diameter) / 360 gives you the distance round the pulley for one degree.

So if the pulley is for example 200mm in diameter, 3.14*200/360 = 1.74mm

so if you want a mark for 8 degrees, you can simply measure 13.9mm (1.74*8) round from your TDC mark and make another mark there.

HTH

[FridgeFreezer]

You could buy some timing tape from Real Steel, once you have a known mark you just line it up & stick it on. It's calibrated for the diameter of the damper.

[Bull Bar Cowboy]

Yes, method as posted is about as good as, although dial gauge with a ball end probe down the plug hole works OK ……….

Another method will be to use a manometer water gauge. Just use a picec of wood to clip a piece of plastic pipe on in a U shape. Then seal the end of the pipe into a broken plug. Fill the U with a little water and once you know the valves are closed then btring No1 up to compression ………….. the level will rise and fall as you come up to and go past TDC ………..fiddly but it works

I guess the most obvious method has been missed ……………..I have thought it through and can see no reason why I wouldn’t work…………..If you are using EDIS then disconnect the SAW signal and EDIS should default to 10 BTDC. Make sure the sensor is exactly in the centre of the 5 tooth after the gap. With both valves closed on No1, line up the sensor to the centre of the 5th tooth. Mark the timing cover exactly in the centre of the gap (missing tooth) . This mark should correspond to 10 BTDC with the engine running. If it doesn’t, then move the trigger wheel slightly to achieve the 10 BTDC setting. TDC can then be measured back with an angle gauge, but having a 10 degree mark should be OK for what you need.

[Night Train]

I would use the dial gauge in the plug hole method to find TDC and then mark the pulley.

To find the 2 deg increments have you thought of buying a cheap protractor from the stationers and placing it on the pulley and then marking off each degree mark you need?

[p76rangie]

So, what I am desperately thinking (and failing to resolve) is how I can equally now work out easily the 2 degree gaps Before

and Aft TDC without taking the pulley off and trying to even out the timing marks around the pulley edge, that would be a nightmare,

as would a session with a dividing head (crossed my mind and dismissed )

So, ideas please so that I can get the timing solid on MS better than a guess, the MS reads wild spark as I have

big time trim in it after the bodge above, matey is chuffed enough, but I'd like it to be more accuarte on base timing settings

Ideas ?

Nige

I take it from your question that you have found TDC and are just attempting to mark the timing marks so you can set the timing at say 6 degrees before TDC. If this is correct, just measure the diameter of the pulley and divide by 180 and that will give you the distance for 1 degree of timing. That is, the pully turns twice for every one turn of a distributor, so you divide by 180 instead of 360.

[Aragorn]

I take it from your question that you have found TDC and are just attempting to mark the timing marks so you can set the timing at say 6 degrees before TDC. If this is correct, just measure the diameter of the pulley and divide by 180 and that will give you the distance for 1 degree of timing. That is, the pully turns twice for every one turn of a distributor, so you divide by 180 instead of 360.

You need the circumference of the pulley/damper, not the diameter. (ie 3.14 x D)

Also, the timing is based on crank degrees, not cam degrees!

You dont have to buy a timing tape. Some sticky tape, pen, ruler and calculator is all you need to make your own!

Alternatively you could knock it up on the PC once you've calculated the spacing, and print it onto an adhesive label, or even just some paper as a template then scribe it onto the pulley.

[Bull Bar Cowboy]

Here you go Nige ............... you should be able locate accurately 20 BTDC and then go back 2 teeth ....... then just use the Real Steel timing tape and centre pop the relevant marks.......... however, I still think using EDIS 10 BTDC default will be the quickest method, but the below should be easy........

From the P80 up 99MY manual..........

The crankshaft position sensor is the most important

sensor on the engine. It is located in the left hand side

of the flywheel housing and uses a different thickness

of spacer for manual and automatic gearboxes. The

signal it produces informs the ECM:

- the engine is turning

- how fast the engine is turning

- which stage the engine is at in the cycle

As there is no default strategy, failure of the CKP

sensor will result in the engine failing to start. The fault

is indicated by illumination of the malfunction indicator

light (MIL) on North American specification vehicles.

The output signal from the CKP sensor is obtained

from the magnetic path being made and broken as the

reluctor ring teeth pass the sensor tip. The reluctor

ring has 35 teeth and one missing tooth spaced at

10°intervals. The missing tooth is positioned at

20°after TDC.

[p76rangie]

You need the circumference of the pulley/damper, not the diameter. (ie 3.14 x D)

Also, the timing is based on crank degrees, not cam degrees!

You dont have to buy a timing tape. Some sticky tape, pen, ruler and calculator is all you need to make your own!

Alternatively you could knock it up on the PC once you've calculated the spacing, and print it onto an adhesive label, or even just some paper as a template then scribe it onto the pulley.

Sorry, I meant around the outside, My fingers just typed the wrong word. You are also correct about the crank degrees.

[Bull Bar Cowboy]

I take it from your question that you have found TDC and are just attempting to mark the timing marks so you can set the timing at say 6 degrees before TDC. If this is correct, just measure the diameter of the pulley and divide by 180 and that will give you the distance for 1 degree of timing. That is, the pully turns twice for every one turn of a distributor, so you divide by 180 instead of 360.

I had to read that a couple of times to fully understand it ....... I think..

Written like that, then yes I think is incorrect as you are making the timing relative to the camshaft ………. i.e. 2 degrees of crankshaft rotation equals 1 degree of camshaft rotation. Unless you were going to the measure the angle in Radians .. 360° equals 2 radians or 1 radian equals 180/ degrees………it might be an easy way to mark up the pulley circumference.

The ignition firing point is a crankshaft angular measurement that is relative to No1 piston at TDC on the compression stoke…………i.e the zero degrees reference point of a circle............the actual point of firing is relative to the speed of the piston, and speed of the flame front, which is dependant on the design of the combustion chamber ........ I think we have been here before

[RangeyRover]

Nige,

Attached is a timing tape that fits a 3.9

Ignore the chevy reference, it was adapted from mez.co.uk

I will produce a better one with the correct references and a "check line" .

Maybe this will help others.

RR

Visio-timingtape.pdf

[Dave W]

I thought the GEMS flywheel was 60-2 hence unsuitable for EDIS that said they're supposedly quite rare in manual form anyway, or they were when I last looked.

Just an update on this, I've been working on an R reg P38 4.6 Range Rover today with a GEMS system and it has a 36-1 crank trigger. I was sure when you said it that I've come across them as 60-2 as well so maybe there are two different versions. I didn't have time to check the position of the gap relative to TDC though to see if it would be compatible with EDIS.

[zim]

An extended DTI gauge into cylinder 1

G

[Aragorn]

60-2 is a bosch setup, so i'd imagine the later bosch engines will use 60-2!

[LandyLee]

Laser used to sell a dummy spark plug with a central probe which could easily be dti`d to set up TDC , used it loads , years ago,