944 16V twin CAM GEARS mod
12-04-2005, 11:12 PM
#16
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With attention to detail and good instruction, I don't see why a good local machine shop couldn't hybrid a set for you. I have a laithe and spare parts, I was thinking about making an adjustable gear for the 8V motors. Never did it so far, too buisy playing with everything else.
The Dodge one is basicly the same deal, I'm thinking considerably cheaper tho, that and more readily available. About the 968 one, I'm not so sure it will just bolt on or require modification, haven't looked into it too far.
I think the cost of regular maint. changing belts, chains, tensioners vs the initial cost of the retro fitment and just having a belt to change is a good deal. I'll be looking into it further as I put this project together.
Being a toyota guy, are those pulleys used on other toyota 4 cyl motors? I'm thinking that they could be had for cheap from breaker yards if they come from a comon car like a tercel or a corrola????
The Dodge one is basicly the same deal, I'm thinking considerably cheaper tho, that and more readily available. About the 968 one, I'm not so sure it will just bolt on or require modification, haven't looked into it too far.
I think the cost of regular maint. changing belts, chains, tensioners vs the initial cost of the retro fitment and just having a belt to change is a good deal. I'll be looking into it further as I put this project together.
Being a toyota guy, are those pulleys used on other toyota 4 cyl motors? I'm thinking that they could be had for cheap from breaker yards if they come from a comon car like a tercel or a corrola????
12-04-2005, 11:15 PM
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As far as I know and can tell, all the pulleys are straight cut(unless the 944S is different). This sounds waay too doable, I'm liking this conversation, lol.
12-04-2005, 11:36 PM
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Pros/Cons:
Originally Posted by 968.net
Below are photos of David Raines' own 16V Turbo. It runs external cam gears for a few reasons, with advantages and disadvantages: this setup is considerably safer than the internal chain which has a history of failure when the plastic ramp wears down. Most people don't bother to replace the ramps (which are available separately from an aftermarket supplier in Canada), and the chain breaks. Since this car is raced frequently, the belt is changed often and this setup makes it much easier. It also makes individually dialing in the cams much easier. However, it requires putting a 1" high hump in the hood to clear the intake cam gear, at least in a 951.
12-05-2005, 12:35 AM
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first of all, I'm not a toyota guy. I just parted out an 88 supercharged MR2 thats all.
I'm pretty sure that all 4AGE engine have them as well as the 4AGZE. This includes corolla and MR2's and probably others. I dont know if the 90's generation of MR2's work or not.
I also have a suspision that some honda cam gears would also use the 944 type belt.
I'm pretty sure that all 4AGE engine have them as well as the 4AGZE. This includes corolla and MR2's and probably others. I dont know if the 90's generation of MR2's work or not.
I also have a suspision that some honda cam gears would also use the 944 type belt.
12-05-2005, 12:37 AM
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Originally Posted by MoonBoy
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12-05-2005, 12:55 AM
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thats a good point about the motor height.
I just had a closer look at that picture of the 16V motor with the twin cam gears (Moonboy's picture)... they have 34 teeth, the MR2 cam gears have 36 teeth.
I think that they might work. A bit of a backyard special though.
So you get the machine shop to make you a plate that bolts onto the camshaft (blue colour in MoonBoy's picture). You get them to drill 5 holes in the MR2 cam gears for the retaining bolts (see picture), and remove the centre part. The 'blue' plate that bolts to the camshaft will have many holes for adjustability.
I just had a closer look at that picture of the 16V motor with the twin cam gears (Moonboy's picture)... they have 34 teeth, the MR2 cam gears have 36 teeth.
I think that they might work. A bit of a backyard special though.
So you get the machine shop to make you a plate that bolts onto the camshaft (blue colour in MoonBoy's picture). You get them to drill 5 holes in the MR2 cam gears for the retaining bolts (see picture), and remove the centre part. The 'blue' plate that bolts to the camshaft will have many holes for adjustability.
12-05-2005, 05:27 AM
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This would be a waste of time on a high compression 16v NA engine. The cam gear pulley has three mounting slots to allow for some adjustment of intake to exhaust cam timing. The FSM calls for 1.4mm lift on #1 intake valve. You can adjust this value out to 2mm or down to less than 1.4mm with the pulley slots. This will have the effect of shifting the torque curve up or down the RPM range. It has been said that above 2mm the engine runs poorly. I currently have mine set at 1.77mm and have noticed what seems like more torque at lower RPMs. It is not a great deal of change.
Anyway any adjustment more than the stock pulley slots will result in valve contact with the 10.9:1 compression pistons so what is the advantage on a NA? IMHO you would only be adding more points of potential failure for minimal gain. Don't you think the tuners at Porsche figured out the optimum valve timing for these engines? Seems easier and cheaper to remove the cam cover once in a while and change the f#cking pad! not trying to be nasty here just making a point.
If you are building a turbo 16v like Andy wants to do then lower compression pistons could be used and you could move the timing where ever you want. So it makes sense that you would do this on a turbo engine as in Moonboy's picture.
Anyway any adjustment more than the stock pulley slots will result in valve contact with the 10.9:1 compression pistons so what is the advantage on a NA? IMHO you would only be adding more points of potential failure for minimal gain. Don't you think the tuners at Porsche figured out the optimum valve timing for these engines? Seems easier and cheaper to remove the cam cover once in a while and change the f#cking pad! not trying to be nasty here just making a point.
If you are building a turbo 16v like Andy wants to do then lower compression pistons could be used and you could move the timing where ever you want. So it makes sense that you would do this on a turbo engine as in Moonboy's picture.