Red motor cam change

[lxhatch_jim]

Hi lads. Myself and Dave (aka Dave_EH) are planning a cam change including a conversion to straight cut timing gears on a 186. Being young and wet behind the ears we are in need of a little help regarding finding TDC.  

Assuming that the harmonic balancer hasn't slipped, should the harmonic balancer mark be at the long timing mark on the block before the cam is removed? We are assuming that the long timing mark is standard timing which is 6 degrees so is that really TDC? The “screwdriver down the spark plug hole” method has been suggested but we are dubious about its accuracy.

To further complicate the issue, the new gears enable cam advance/retardation adjustments to be made without removal cam removal…….apparently

Any help would be much appreciated.

Cheers
Jim â€" attempting to live the dream.

[Ed]

Jim,

on the motor the TDC mark should represent TDC unless balancer has slipped as you mention.

your 6 deg static timing means your ignition fires 6 degrees before TDC.  

TDC always remains where it should be at top of the stroke.

when u use a timing light it fires when no1 fires and this is what you are adjusting when u advance or retard the spark.

i usually check TDC on no 1 using a screwdriver just to be sure.

oh I degreed my cam in to be sure the cam was at spec, my timing gears allowed adjustments too but I didnt know enough to make any adjustments, so i left it at spec.

was on a 308 but the principle is the same.

Cheers

Ed

[Dr_Terry]

Hi Guys.

Be careful of timing marks on Holden Red 6 cylinders.

If the timing case is off an EH to HG (149, 161,179 or 186) then the long mark is actually 5 degrees BTDC not zero TDC. The marks below it are 7 & 9 degrees BTDC.

The 173 & 202 HQ onwards type are more conventional in that they show true TDC & each mark below that is 2 degrees BTDC.

My advice is, if you're a bit new at this is to get a pro to check it out before you re-assemble it.

Dr Terry.

[Dave_EH]

Thankyou for the replies on this topic.

With the basics now under control does anybody have much knowledge on asymetrical timing?

Would this be recommended under any circumstances?  The timing gear allows for this to take place?

Does this basically make the cam milder or lumpier?

regards
Dave

[lxhatch_jim]

This is a good question Dave