5 replies to this topic

[manag00]

Hello,

 

I just had a full engine rebuild and part of that included a more aggressive camshaft, milled head, etc.

I had to set the timing via timing gun, I turned the distributor to set the timing but could not set it and it was still 5 degrees off.

 

My question is: if I adjust the cam gear (retard or advance it) should I be able to get the timing on the crank shaft pulley to line up?

 

Liviu

[rustycivic]

The timing you're referring to is spark timing, and your cam should have been degreed when it was installed, especially if you milled the head as well. Basically after milling the head and the new cam, plus a cam gear, true TDC is now off from the timing marks and you need first to pull spark plug no.1 and drop a long screwdriver into the hole, then rotate the motor counter clockwise till you see the screwdriver begin to drop again, this will help you find true TDC on the crank, the second half is a little harder, even worse with the motor in the car, but you need a degree wheel of sorts and a dial gauge. You need to look up proper procedure for this, but basically you need to find TDC for the cam as well, then adjust the cam gear, sorta ignoring the numbers on it, to your new "0" position. This is your motors true TDC, then you can set your spark timing from there. 

 

Also to consider is your distributor springs might be crapped out and not giving you the correct advance. 

[anjin]

The crankshaft pulley will still give you the block tdc accurately. 

 

Milling the head means the distance between the cam and crank pulleys is shorter, and that automatically causes a timing difference, You can adjust for that with an adjustable camgear, but that should be less than half a tooth on the timing belt.  If the head was milled 30 thou then that's the shorter distance on the belt you need to adjust for, for example.

 

If your camshaft is a regrind, then there is the potential for the slot for the distributor to be out as well. That one is way more difficult to solve.  And of course with the more agressive cam then normal timing may not be what you want to end up with anyway.  It is an excellend starting point, however.

[manag00]

How do you know how much you need to degree the cam timing and can it be done with the engine in the car?
Anjou, you are right, the crankshaft pulley still gives me TDC but when the crank pulley is at TDC the camshaft gear marks do lot line up horizontally, it's like they are off by one tooth.
To give you an idea: head shaved .040, block resurfaced, aggressive can, 10.5-1 compression.
Who should I see to play around with the cam gear and tune it? Machine shops or tunning shops (I doubt they will mess around with old technology)

Thanks

[rallyxcrx]

While changing my head gasket, getting ready for the next race, my cam rolled out of the engine bay and on to the floor, bending my adjustable cam gear. I threw on a stock cam gear and went racing. With .030 off the head, and the cam timing set as close to the marks as I could get it, the car ran good, with a bit more torque than usual.  Since I'm a backyard mechanic, I just set my cams on the marks and go, while serious racers degree cams, and adjust them on the dyno. Dave

[manag00]

Thank you rallyxcrx. I think I will just take it to a tuning shop where they will figure out all the details. Better than screwing around myself and then damaging some thing.

 

LIviu