Curt

Porken, I have a 79 and would love to do this next time I do the timing belt. Is your prototype adjustable? or does it just bolt on to one place. and how did you mount it to the block. were there holes there already to bolt to or is that a bracket that its bolted to.

Very good idea and seems to be relatively cheap and easy to do. Like I said im very interested. I would buy a pattern from you for sure.

PorKen

Curt,

The bracket is slotted to move the pulley up and down for adjustment.

I put studs into the mounting holes for the power steering pump rear support and serrated stainless steel nuts to hold it down.

My next iteration will replace the PS pump rear support (which is a simple steel part from the factory). This bracket will eventually allow having the covers remain in place and the cam timing pulley position will be adjustable via a bolt, like the power steering and alternator tension bolts. (You will have to cut a hole in the side of the center cover.)

Curt

Okay, sounds like a great plan. I have to pull both cam covers due to multiple leaks. So that means I will dig a bit deeper and replace the belt, water pump, rebuild the tensioner and hopefully bolt on the adjustable cam timer.

John Speake

Hi Ken,
Interesting project ! Excellent work............

Is it possible to mount your idler in such a way that the belt tension is not afected as it is moved ?

Do you need to move it, do you think you have sacrificed power or torque in some parts of the rev range after optimising/equalising the the timimng on both cams ?

Certainly, it would be the best solution to go for a flywheel TDC triggered ignition system. This would get over the problem of the ignition timing varying with cam position.

Are the early crankcases machined with the boss for the flywheel position sensor ?

Are you planning to do some (G-Tech or RR) peformance figures to show the benefit of the system ?

Regards,

BC

I'm sorry. I still do not get it. How is that tensioner advancing both cams?

Curt

Brendan, it appears to me that when the tensioner is on it pulls on the belt which in return pulls both cam gears forward. At least thats what I get out of it looking at the first picture on the first page. When you do that it advances both cams the equal amount. but it also advances the timing because the distributor is run off the drivers side cam. So you must reset your ignition timing back to spec, but your cam timing is now advanced a few degrees. I believe he said that one tooth equals 7 degrees and I think he was only advancing the cams about half of that.

Someone correct me if im wrong, but I think that is the idea of it.

My question is, why couldnt you remove the cam gears and take them to a machine shop and have a new keyway cut into them for the 3-5 degree advance. Does that take aware from the strength or is it too hard to have that done and get it precise enough.

Curt

Forget that last comment about cutting a new keyway in the cam gears. After thinking about it I realize that would not work. There would be slack in the timing belt on the tension side. and since one tooth is too much advance you cant just slip the belt on one tooth advance. so you must use the roller on the tension side to pull those cam gears forward that 3-5 degrees. Duh, I hate when I dont think about things.

Weissach1982

This is very interesting and I'm wanting to figure out how to make a bracket and what kind of parts I need to make this work. But I have a few questions. How would you reset the ignition timing to stock? And what if the belt were to slip off the tensioner or the bracket break, what would be the result to that? And is there any problem with leaving the timing gear covers off?
Thanks,
Cory J.

Lizard928

if the bracket were to break the tension would become loose, possibly loose enough to skip teeth, although what material is the roller bolted too? and what guage?

PorKen

Let me reiterate that this version is not variable while driving, it gives a fixed advance only.

Also, the additional idler roller doesn't effect the tension on the belt, it's purpose is to create a few extra centimeters of travel for the belt between the crank gear and the left cam gear.

The sequence for installing the pulley is as follows (left is driver's left):

0. Check the ignition timing with a timing light.
1. Position the cams at their marks with TDC on the balancer.
2. Unscrew the tensioner bolt to release tension on the belt between the right cam gear and the crank gear.
3. While applying light pressure on the driving side of the belt with your hand (between the oil pump gear and the left cam gear), rotate the crank counter-clockwise slowly until the pointer shows halfway between 0 and 10 degrees advance. Watch that you are not moving the cams while doing this; you may need to unscrew the tension bolt further if necessary.
4. There will now be some slack in the belt between the oil pump gear and the left cam gear.
5. Install the advance pulley taking care not to rotate the crank or cams.
6. Turn the tensioner bolt in a few turns, then follow the procedure for checking the tension using the Kempf tool.
7. After resetting the belt tension, when the cams are at their marks, the balancer will show roughly 4 degrees advance.
8. Check the ignition timing with a timing light. The amount of advance over the previous check will show the amount of advance created.
9. You may want to retard the timing to your previous setting. I found that I could run an additional amount of ignition advance with the cams advanced.

John Speake,
I haven't been able to figure a way of making a variable system without have an additional pulley to capture/release the belt on the slack side of the crank gear. The tension would be constant; the belt would be longer on one side of the crank gear or the other for a given advance/retard.

I don't know if moving the advance around would help enough to be worth the trouble and expense. This simple device has given me the most noticeable grunt of all my stratagems, for the least effort and cost.

I haven't had the chance to check if my top speed is diminished. I am beginning to believe that tuning the cam timing has optimized the modifications I have made so far. Especially in regard to the large exhaust system I fitted. It apparently has moved the torque level back down into the usable range. For example, while merging onto the freeway this morning, going about 40 I floored it, the slushbox auto shifted to 2nd, and I was going over 90 before I had time to look down at the speedo.

Previously I had little real power under 3 grand.

I am drawn to buying a G-tech pro, but can't justify it, yet, and I would like to do some more repairs before putting her on the dyno (Rolling-Road).

BrendanCampion - I hope the instructions explained it a little better.

Curt - The strongest option would be to machine new keyways in the steel crank gear.



Weissach1982,
a.) Turn the distributor.
b.) Opportunity to test if your engine is non interference.
c.) None that I've thought of, except the fear of dropping a tool or a timing light cord 'into the mix'. I think that the belt must run cooler, thereby extending it's life?

Lizard931,
a.) See (b) above.
b.) 3/16 steel plate.

drnick

porken, such a cool mod!

do i understand rightly that what you have achieved is to correct for in-built discrepancies in the cam timing between the cylinder banks? or is it between the crank and cams?

what are your thoughts on applying this in an interference engine, and what about your top end - any noticeable drop in power?

PorKen

drnick - thanks mate!

The first setting I tried was just to get the two cam marks to be the same distance to their respective pointers (split the difference). This means that neither of them is right in the center, but at least they are closer together in terms of being in sync with TDC on the balancer. Then I advanced it a little more for grins. It is it is now 4 degrees advanced at the crank, or 2 degrees at the camshaft with the cam marks centered as described.

2-4 degrees at the crank (1-2 at the cam) shouldn't be a problem. Of course, YMMV.

Ideally on any engine you would pull the heads and use Plastigage to verify that you have at least (0.15?) of clearance between the valves and the piston at the advanced setting.

It doesn't seem to have had a negative effect. I was driving today and it pulled hard from about 40MPH to the auto shift point from 2nd to 3rd at over 90MPH.

What's best is the response between the pedal going down and going faster. I used to dread accelerating at low speeds and waiting that seemingly endles time for the engine to cam in.

BC

As Mr. Top-um-hat said this morning on "thomas and freinds" while my 1yr old and I watched....

I don't know... I just don't know

But thats not really the issue. Your doing it and it works. Thats all that counts.


Anyway - I think you should get a 4spd auto like I did with my deceased 81 - That would really wake that car up. ALOT.

Trust me - that whole highway merge experience changes remarkably. Better gas mileage, better cruising performance, etc.

Weissach1982

Porken, what kind of roller did you use on that bracket? What dimensions was the bracket cut to fit to the rear powersteering pump bracket in order to mount the roller to tension the belt? I think I worded that right, you catch my drift don't ya lol I'm kinda sleepy so forgive me.
Thanks,
Cory J.

Rufus Sanders

I think Brendan has hit on a more traditional way to do this, which is simply re-gear to put the power curve where you want it vs. road speed. A bracket and an idler are so much simpler, but what is the real effect here?

It sounds like the torque curve has been shifted backward toward lower RPM, but maybe it's something else. - Ruf