TDC and Damper . Engine experts in 'ere

[GJUK]

Hi guys,

Help me out with this if you can.

Before removing my existing distributor I took off the rocker cover on my big block 400 (the right hand one as you look at the car from the front), turned it over clockwise until number one (front right) was opening and then closing on the inlet and a little more until both the pushrods on the inlet and exhaust valves could be spun freely by hand.
Once there I checked on the damper and was happy to see a nice big pressed in factory dot, lined up with 0 on the TDC gauge original to the engine. I marked this with tipex so it was clear. Happy days...

Got the new distributor in, same place (there abouts). Car fired up and didnt really like it. TDC could not be seen at this point with a timing light (I think it was hiding under the strip of metal right at 12 would be on a clock fave) So from what I can see the damper is not moving around.

I moved the distributor until the car was more happy by ear, turning it clockwise which made it worse and then anticlockwise. by a good 15* or so.

The timing light was showing TDC as being no where near the factory gauge showing 0-20 advance (which is around 11 to 12 on a clock face). In fact it was picking up the mark I had made on there at about 1-2 on a clock face, where there is no gauge to show what advance/retard you are running.

I'm confused to say the least. The engine is not original maybe I am doing this wrong (it was going well and to plan until the timing light came out ).

The timing light is working, I have two, they both show the same. I am working on No1 for sure.

Regardless of the above the car runs like a dream, pulls clean 0-5500 rpm with no bogs or miss fire. I'm guessing I am at about 16* advance at idle with 35ish all in. But I'd like to find out the logic behind the above.

Thanks!

Jon

[db]

Just throwing a curveball out there... could the damper be on back to front? I expect it would only fit on one way, but you never know!

Other than the, I'd say the dot you think is tdc, isn't. Maybe tdc was on a long-since-lost sticker?

As you say, the main thing is it runs good!!

[morgan]

This - Cool idea. Should be more accurate than thumb test ?

http://www.wikihow.com/Find-Your-Engine ... nter-(TDC)

[Pete]

Did you have #1 on the COMPRESSION stroke when you did the first bit?

Normally I drop out the spark plug and feel for compression as I find TDC - you could have been on TDC on another phase of the cycle.

Standard dampers usually have lines cut into them, not dots.

Sometimes standard Dampers move on the rubber so they are not representing TDC correctly but that is rare.

The only real way to find TDC with the head on is to have a locking bolt through and old spark plug, turn crank one way to the stop - mark the damper, rotate the other way to the stop - mark the Damper; and then the mid-point between these is actual TDC.

[morgan]

OK. Thats odd. First post came up invisible (for me ??) Try again -


This - Cool idea. Should be more accurate than thumb test ?

http://www.wikihow.com/Find-Your-Engine ... nter-(TDC)

[Blue]

Did the dizzy just plug in or did you need to alter any wiring? If the 2 wires from the dizzy are connected the wrong way round, you get exactly those symptoms.

[Pete]

Good call, Blue - I think it knocks the timing about 30 degrees.....

[GJUK]

Did you have #1 on the COMPRESSION stroke when you did the first bit?

Hi Pete, yes I did. I took the rocker cover off and watched the inlet open and then closing, just as it closed I took the reading and checked both the pushrods were free by hand.

Normally I drop out the spark plug and feel for compression as I find TDC - you could have been on TDC on another phase of the cycle.

I didnt do this but did watch the inlet close.

Standard dampers usually have lines cut into them, not dots.

Hmm, mine has lines (at each 90*) and one dot. The line and dot were where I marked TDC.

Sometimes standard Dampers move on the rubber so they are not representing TDC correctly but that is rare.

I read this, I think it is not moving however.

The only real way to find TDC with the head on is to have a locking bolt through and old spark plug, turn crank one way to the stop - mark the damper, rotate the other way to the stop - mark the Damper; and then the mid-point between these is actual TDC.

Might have to get one of these TDC stoppers I've seen for sale, all the rage in the US it seems for finding TDC.

Thank you.

---------------

Did the dizzy just plug in or did you need to alter any wiring? If the 2 wires from the dizzy are connected the wrong way round, you get exactly those symptoms.

Hi John. MSD dizzy plugged straight in to MSD 6AL-2 box, no crimping cutting or sellotape involved. The manuals said to connect direct to each other and it only goes in one way the plug in question.

Let me upload some photos to show.

Thanks guys.

Jon

[GJUK]

Morgan

I can see your message but if I quote it my message is blank also.

Morgan, I can see your link if I try to quote you (thanks, for the link, I worked out how to get TDC just a bit stumped by this...)

OK. Thats odd. First post came up invisible (for me ??) Try again -
This - Cool idea. Should be more accurate than thumb test ?

edit, removed URL code, forum doesn't like it (thanks for the link)

[GJUK]

First picture shows the mark Made when I found TDC. The engine damper had a dimple and a line exactly where the 'degree marker plate' was showing Zero. (engine had run since then so it is not showing as lined up as it was having found TDC).



Below shows where the above white line was being picked up, timing light connected to number 1 lead, engine at idle ~850rpm.

[DaveMadders]

Did the dizzy just plug in or did you need to alter any wiring? If the 2 wires from the dizzy are connected the wrong way round, you get exactly those symptoms.

And we've had moulded out of the box wiring connectors made the wrong way round (think that was MSD) so needed switching round

[GJUK]

Did the dizzy just plug in or did you need to alter any wiring? If the 2 wires from the dizzy are connected the wrong way round, you get exactly those symptoms.

And we've had moulded out of the box wiring connectors made the wrong way round (think that was MSD) so needed switching round

Interesting. I will tomorrow check the colours of the cables and report back. Maybe this is the issue.

Thank you!

[Dave999]

OK before you cut off any moulded connectors

Does your timing light work with MSD? **

AND

you need to take into account that old dizzy and new dizzy will differ in a number of ways. The cap position in relation to the body, and the rotor, when at 0 mechanical advance, in relation to the relutctor star on the shaft will vary between the 2.

and you got it more or less in the right place


i.e the rotor was pointing in the general direction of cylinder no.1 lead


on top of that the electronics in your 2 ignitions have their own delay it will be small, as in milliseconds, but it is enough to have an impact

the timing curve in electronic distributors differed to those in the points distributors for this reason

MSD distributors were based on a ford designed GM HEI copy Not Chrylsers design

chrylser US at least were pretty random in their QA when it came to tollerances and machining of distributors and produced so many variants of the same thing as CR cams and petrol changed that what is right is hard to check.


**
also your MSD MultipleSparkDischarge probably does 2-3 sparks for every ignition event up to approx. 3000 RPM. that will play havoc with certain timing guns


all in all I'm not surprised your timing is further out than anticipated.


set engine to TDC firing stroke we found it at the NATS 2 years ago.

use a marker to mark the distributor directly below no.1 tower on the cap
take off cap and extend the mark up and over the top edge of the case so you cane easily align the centre of the rotor with it

put in the distributor with the rotor pointing at no.1 mark exactly.

Look down to the pickup, a point of the star should be nearing or just past the pickup centre point.

choose the closest point and turn the distributor so that it lines up exactly, point of star with centre line of pickup
make a mark on the edge where the rotor now points.

put at dot between them

turn dizzy so that rotor centre line aligns with the new mark

put on cap and lock it all down

Now provided you did all this with the motor at TDC on the firing stroke
car should start
timing should be on or few digress from TDC at idle

idle will be slow
tailpipe will smell of unburnt fuel and will eventually go black

but you should see your TDC mark at the tab on you timing cover

wind in the appropriate initial advance now


Dave

[GJUK]

OK before you cut off any moulded connectors

Does your timing light work with MSD? **

Hi Dave, thanks for the reply.
Though no official documents stating it does, others have posted saying that it does work with MSD

AND

you need to take into account that old dizzy and new dizzy will differ in a number of ways. The cap position in relation to the body, and the rotor, when at 0 mechanical advance, in relation to the relutctor star on the shaft will vary between the 2.

and you got it more or less in the right place


i.e the rotor was pointing in the general direction of cylinder no.1 lead

Yes, I only looked at the rotor position and shaft that mounts to the cam not the body of the dizzy.

on top of that the electronics in your 2 ignitions have their own delay it will be small, as in milliseconds, but it is enough to have an impact

the timing curve in electronic distributors differed to those in the points distributors for this reason

MSD distributors were based on a ford designed GM HEI copy Not Chrylsers design

chrylser US at least were pretty random in their QA when it came to tollerances and machining of distributors and produced so many variants of the same thing as CR cams and petrol changed that what is right is hard to check.

Interesting.

**
also your MSD MultipleSparkDischarge probably does 2-3 sparks for every ignition event up to approx. 3000 RPM. that will play havoc with certain timing guns

Bananarama! has multiple sparks below 3000 rpm. Though my timing light shows only 1 (that my eyes can pick up).

all in all I'm not surprised your timing is further out than anticipated.

set engine to TDC firing stroke we found it at the NATS 2 years ago.

use a marker to mark the distributor directly below no.1 tower on the cap
take off cap and extend the mark up and over the top edge of the case so you cane easily align the centre of the rotor with it

put in the distributor with the rotor pointing at no.1 mark exactly.

Look down to the pickup, a point of the star should be nearing or just past the pickup centre point.

choose the closest point and turn the distributor so that it lines up exactly, point of star with centre line of pickup
make a mark on the edge where the rotor now points.

put at dot between them

turn dizzy so that rotor centre line aligns with the new mark

put on cap and lock it all down

Now provided you did all this with the motor at TDC on the firing stroke
car should start
timing should be on or few digress from TDC at idle

idle will be slow
tailpipe will smell of unburnt fuel and will eventually go black

but you should see your TDC mark at the tab on you timing cover

wind in the appropriate initial advance now


Dave

I'll do this Dave, though I think I must be near enough there or there abouts now with it. If it was anywhere out it wouldnt run like it did the other day. The smell of the fumes are a lot less than they ever have been. It ran and pulls great.

Maybe I need a better timing light than my £50 draper thing I bought as a quick fix some months back.

[Dave999]

cheap timing guns work better with MSD than some of the more expensive ones


if what you have works stick with it

Dave