Race Engine Forum UK

Hello Guy !

I need to make additional marks for the ignition timing on the crank pulley , can you please explain me how can i do this ?

I've been reading this : http://guy-croft.com/viewtopic.php?t=104 , but is it possible to find true TDC with the head fitted ? (trough the spark plug hole maybe ?!)
Also how should i draw marks on the pulley ? TDC is 360deg. right so first mark must be 0 or ? (i wish to make marks - 30 , 31 , 32deg. for total/dynamic ignition timing , and also mark lower degrees - 5 , 10 , 15 etc. for the initial/static ignition timing ..)

Thanks !
Damir

Damir, sorry for the late reply.

Yes of course you can do that job with the head on, you put a round bar down the plug with piston no1 just before TDC, remembering the crank turns clockwise viewed from the crank nose (front pulley end), set up a dial gauge on the bar and a protractor on the pulley and do the setup same as described in that article. I use a an old spark plug body drilled and reamed and a piece of silver steel round bar for that.

Worth noting that on inclined valve engines like the Fiat TC you have to watch that the valves don't 'grab' the bar - because they will bend.

The first thing is to make a pointer bolted to the crankcase front, then you find true tdc - you will know by know of course that there is a significant 'dwell' phase around tdc where the piston doesn't move at all and true TDC is at the middle of that phase. Mark tdc by filing the front pulley opposite the timing pointer.

My favourite way of doing ignition timing is to have one single mark for TDC and to use a 'variable delay' timing light which allows you to read off the ignition timing by turning the dial on the timing light to align the pointer and tdc mark at any speed.
If you don't have a strobe like that then, yes, you need to mark up the front pulley in addition to TDC with say, 5 or 10 degrees advance, (whatever the static advance is) and maybe the max advance figure of 35 degrees or whatever.

Looking at the crank front pulley, it rotates clockwise so the first mark that should appear as the crank is turned toward TDC will be the max value, then as it gets nearer TDC the 10 and 5 and then finally the TDC mark itself will align with the pointer.

The photo shows a pointer and mark on a TC unit that I did lately for client in Latvia. If you use a the round pointer like that it is vital to ensure the alignment of the timing light is correct when setting timing, because you can get major parallax error, which is why I sent the photo to the client. In this respect a blade pointer is better, as shown on engine 04.061

Hello Guy !

Excellent thanks !

So you say if i buy this adjustable strobe light i need to draw only TDC mark ? and adjust the strobe light to flash lets say 30deg. point the light at this TDC mark turn the distributor and watch when TDC mark on the pulley aligns with mark on the pointer and then the ignition timing will be adjusted on 30deg. ?

Kind regards
Damir

That is correct yes.

This is the absolute best on the market.

http://buy1.snapon.com/products/diagnos ... leType=all

Sorry for the link but I ain't got one. I've only got a cheap one from Chiner that I rarely use and I'm definitely not featuring that on this site!

GC

Hello !

Ok. then i will buy myself one of these adjustable strobe lights .
(Must admit i didn't use this tool before and i really didn't know that you can buy an adjustable strobe light , this is something new for me !)

Thanks Guy !

Kind regards
Damir