944 16V twin CAM GEARS mod
 

How is this done?

I assume that it requires smaller cam gears, and then a crank gear that is half the diameter of the cam gear.

The question is... is there an easy way to do it?

-find a DOHC 4 cyl motor that uses one cam gear on each camshaft
-from a motor that uses the same style belt as the 944
-from a motor that the crankshaft snout has a smaller or same diameter as 944

THEN

machine the crank gear from the doner motor so that it fits the 944
machine adapter plates for the cam gears
machine out the centre of the doner cam gears
machine mouning points into the doner gears (slots so that its adjustable)
order a custom timing belt with the correct length

I think that I read somewhere that toyota 4AGE/4AGZE motors use the same style of timing belt.

300guy

Why woud you want to go through all the hassle? I don't see any benefit in doing this.

To get rid of the chain between the two cams and the tensioner, and probably to be able to time the two cams independently

Getting rid of the expensive tensionier system that does the short little chain between the camshafts and is a big point of failure.

you dont need to find a different head. just get a 2.5L S head if you have an 8v NA.
and if you have an S2 then you already have one...

machine the pulleys like you said. then machine the head and extend the intake cam..
its will still prolly cost $$$ but why go with a completely different head if porsche already gave you one?

hassle? ive already thought of doing this..(uh..but im only 17 so maybe in my dreams)
but benefits are getting rid of the tensioner.
and even better if you get adjustable cam gears. you now have controll over the intake and exhaust cams movement individually!

You can do that with modifying the cain sprockets. Sterling on the 928 Forum did this to his Vario Cam project 928.

Here is the link. http://928sg.com/heads.htm

if you read the whole thing it says they broke off...

plus. who doesnt want big pink adjustable cam gears on the front of their engine?! :D

man i really hope no one does all this stuff before im older and have a shop to do this sh*t...

Yes, you are right. However, if designed a little better his concept could very well work.

Adding another cam gear can be very difficult. The distance and diameter of the addtional gear needs to be just right. T-belts are standard and and come in standard increments. First thing would be to determine the t-belt length, then calculate the diameter required for the extra cam gear. The problem is that the 2 cam gears have to be exactly X number of teeth apart. The diameter of the cam gear and the required distance between them might not make this project possible.

I think that you use two exhaust cams... I think that i read somewhere that the lobes on the exhaust and intake have the same profiles.

Imo... the two cam gears dont have to be X number of teeth apart... thats why the gears are adjustable.

The diameter of the gears needs to be small enough so that you can fit the two on there without them touching each other. And then the diameter of the gear on the crankshaft needs to be 1/2 the diameter. T belt length doesnt matter... I assume that a custom length belt would have to be purchased.

THIS IS INTERESTING:

I took off the cam gears and crank gear from my 4AGZE motor today ('88 toyota MR2 supercharged motor).

They use the same type of timing belt that a 944 uses - in other words, the 944 timing belt meshes with the 4agze gears. See the attached picture.

http://z31.com/unsorted/944and4agzecamgears.jpg

I'm pretty sure that the diameter of the 4AGZE crank is smaller than the 944, so this means that the 4AGZE crank gear could be machined to fit the 944 crankshaft.

Does anyone know the diameter of the hole in a 944 crankshaft timing belt gear

300guy

I was planning this for the project 949, 16V sequential turbo with dual pulleys. Really, the only thing to consider is that the cam sprokets must be double the ammount of the crank. The run in a 1:2 ratio or one rev of the cams to two revs of the crank. Shouldn't be a huge deal, just needa enough clearance between the pulleys and an extension on the one cam. I'll probably be going with custom cams anyway for the project, might as well go al the way with dual adjustable sprokets. I'm also thinking of modding a self-auto tensioner from something like a Dodge 2.5l for the cam belt too.

custom cam gears from who? How much do you figure they would cost?

Agreed, both need to be adjustable. Can you tell me any more about the dodge cam belt tensioner?

What about using a 968 hydraulic tensioner? Arent those good?

The nose of the crank is right at 1 1/16" Machining the crank pulley should not be too much of a problem. I was thinking of a hybrid cam gear. Cut the outer gear from say the toyota motor, and cut the inner part of the 944 cam gear then machine a coupling plate to match them and leaving adjustability.

exactly what I was thinking.

But it might be easier to just machine a who new centre part, rather than using the 944 one.

Its the crankshaft/camshafts that are tapered right (therefore a straight cut whole in the gears?)

BTW the 4AGZE crankshaft timing gear is a tad less than an inch... which means that it its possible to machine.

Also...

the diameter of the 4AGZE cam gears is about 4 1/4". I held them up to my 16V head and it looked like they would work... but it would be close.