Adjustable cam gear question.

[Mazda Carnage]

The car has been running fine for months with the stock cam gear but even before I assembled this engine this issue was a concern.
The car is fast in boost but has nothing before, minimal pedal achieved boost, keeping up with slow traffic was annoying and gas millage (without speeding ) is horrible.

So I installed (after slight modification) Larkens adjustable cam gear.
The reason I installed it is because I am currently running a head that's been shaved 0.020".... the outcome is the distributor no longer sits in the proper position to achieve correct ignition timing.

*My understanding is: the Cam and crank line up matching valve and piston movement (of course) Via the timing belt. Any change in the cams positioning would be noticeable at the distributor because the cam dowel and distributor slot are set in the cam. The distributor is fixed in the rear housing holding it sensor fixed with it, the distributor teeth move with the cam.

Going on * when I set the ignition timing and the distributor no longer sits in the same position it means the actual timing between the valves and pistons is off even though the spark timing is set at the correct degree with the timing light.

So assuming that Distributor, cam and crank key way pulley... are to spec, head/block height and timing belt length would be the only thing affecting the distributors position?
Can the distributors position be used to line up the cam and crank using an adjustable cam gear?
Is the correlation between the timing belt gears and distributor as direct as I think on these OBD1 cars or is there something I'm missing?

[ademan]

Originally Posted by Mazda Carnage

The car has been running fine for months with the stock cam gear but even before I assembled this engine this issue was a concern.
The car is fast in boost but has nothing before, minimal pedal achieved boost, keeping up with slow traffic was annoying and gas millage (without speeding ) is horrible.

So I installed (after slight modification) Larkens adjustable cam gear.
The reason I installed it is because I am currently running a head that's been shaved 0.020".... the outcome is the distributor no longer sits in the proper position to achieve correct ignition timing.

*My understanding is: the Cam and crank line up matching valve and piston movement (of course) Via the timing belt. Any change in the cams positioning would be noticeable at the distributor because the cam dowel and distributor slot are set in the cam. The distributor is fixed in the rear housing holding it sensor fixed with it, the distributor teeth move with the cam.

Going on * when I set the ignition timing and the distributor no longer sits in the same position it means the actual timing between the valves and pistons is off even though the spark timing is set at the correct degree with the timing light.

So assuming that Distributor, cam and crank key way pulley... are to spec, head/block height and timing belt length would be the only thing affecting the distributors position?
Can the distributors position be used to line up the cam and crank using an adjustable cam gear?
Is the correlation between the timing belt gears and distributor as direct as I think on these OBD1 cars or is there something I'm missing?

shaving the head wont have any effect on aligning cam gear and crank. you can shave .040 of it and still set/line the crank and cam up

[Zach]

Also, what does the FSM say about this? Remember the stock cam pulley is four way adjustable and mentions it there I believe.

[chief tool]

I agree with the above also, there should be no reason why a head thats thinner should change the way the cam and cranks are aligned.(with no timing belt installed)

Big question is.....on an unmodified car what is the cam position when the cam wheel is installed at "1" and the crank is at TDC.

If you knew that you could work backwards from there and position the cam in that spot.

shaving the head will retard the cam, but according to my calculations its roughly 0.5 degrees for 0.02" which is not alot.

(0.020" /Cam wheel dia * Pi) * 360 degrees

Maybe start with the adjustable wheel in more or less the stock position, and road tune it, with a few degrees either way, I remember reading on Mazda 626.net that one member got good performance on his 2.2 NA with 6 degrees of cam retard, which is not what I would have expected.

[gtdreamdxbudget]

Originally Posted by chief tool

I remember reading on Mazda 626.net that one member got good performance on his 2.2 NA with 6 degrees of cam retard, which is not what I would have expected.

thats highly unusual, i remember my NA's bolt loosening enough for it to rotate to 0 deg, and it ran fine until it got to the upper RPM's where power started dropping off.. i've found 12 deg advance works great for the NA motor

[STW]

Retarding the cam means the valves close later, when at high RPM there's still flow into the cylinders. The dyno results were very consistent with the theory; retarding cams decreased power at low RPM but improved the top end. Advancing the cam makes the valves close early and is effectively the same as installing a shorter duration cam.

[gtdreamdxbudget]

wait.. my bad.. i was thinking ignition timing, not cam timing....