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Make your own adv cam gear?

496truck

496truck

New member
Joined
Jan 16, 2012
Location
Carver, Ma
Has anyone done this before? Am I crazy? Or just doing it wrong?

As a homeowner and a dad I can find a million other places to spend the dollars it takes to buy an adjustable timing gear, new or used. Even the "affordable" incrementally adjustable gear from IPD is almost $100.

After installing my RSI stage 1 cam I was slightly sad at the loss of low end torque, where most everyday street driving is needed. But loved how that cam pulled in the upper RPM range. Not very often, with an auto trans anyway, do you get the chance to pull those RPMs. At least not here in overcrowded New England. After a bit of research I had read that most users gained a bit of low end torque back by advancing the cam about 4*.

I had an extra cam gear lying around. Advancing the cam gear 1 belt notch is about 10* (well, according to my count and math it was 9.something close enough to 10), which is more than I was looking for. So, why not make a timing mark 180* off and drill a new hole for the cam gear locating pin? I made some marks 1/2 a tooth forward, scribed some lines on it, center punched it and drilled a new hole. At this point I have about a 4-5* advanced gear.

I plan on swapping this in Wednesday unless someone has a good reason for me not to. Will add pics too.
 
496truck said:
I plan on swapping this in Wednesday unless someone has a good reason for me not to. Will add pics too.
Click to expand...
360/38 is 9.something, you're right, but that is cam degrees. Crank degrees is twice that, so if you advance it one whole tooth, it will be 18.something crank degrees.

Your 4.5 degree mark is 9 crank degrees unless you did something different. You can for sure do that, but I think it would be better to have more accuracy than just measuring and center punching it, like if you have a rotary table or some other way to rotate it a certain amount.
 
Avalanche used to make them from stock cam pulleys..
 
Poik said:
360/38 is 9.something, you're right, but that is cam degrees. Crank degrees is twice that, so if you advance it one whole tooth, it will be 18.something crank degrees.

Your 4.5 degree mark is 9 crank degrees unless you did something different. You can for sure do that, but I think it would be better to have more accuracy than just measuring and center punching it, like if you have a rotary table or some other way to rotate it a certain amount.
Click to expand...

Now, correct me if I'm wrong. Advancing/retarding the cam is done in cam degrees not crank degrees... right? It's been a loooooong time since going to school for this stuff so a brief double check using pics of Volvo adjustable cam gears, specifically the Nuke gear, shows a 5* increment is approx 1/2 a tooth.
nukecamgear.jpg


tryingbe said:
Put the stock camshaft back on and problem solved...

$$$ made back too.
Click to expand...

I almost considered this but really like everything else the RSI cam improved. I am willing to sacrifice a little top end to gain more low end as long as it still breathes like it does through the rest of the range. Someone else mentioned other "insert letter here" cams but I don't know which cams to look for, nor where to find them, nor if they are slotted for the head mount dist.
 
I marked and drilled one to correct head/block height. Worked well
I think you can get it down to about 5deg by hand. About 1/2 a tooth.
I started a pilot hole with a super fine dremel bit.

Shrink/grow the wheel and you will see how fine the hole needs to be.

CrankDegreeWheel2.jpg
 
I just wallowed out the hole a little to the right, and used a flattened piece of safety wire for a shim, once the bolt is torqued down its not going anywhere. 3-4 degrees out on the edge of the pulley is a tiny bit of movement down where the locating hole is drilled. This was on the advice of my machinist of course. I'm in the process of installing the engine right now, so I don't have any feedback on whether it moved the powerband at all. I'm running a B21FT with an A cam and a big turbo so we shall see, I'm thinking laggy unless this little trick helps out.
 
If using aluminum it should be "hard anodized" shouldn't it? IPD's first ones wore quickly.....
 
496truck said:
Now, correct me if I'm wrong. Advancing/retarding the cam is done in cam degrees not crank degrees... right? It's been a loooooong time since going to school for this stuff so a brief double check using pics of Volvo adjustable cam gears, specifically the Nuke gear, shows a 5* increment is approx 1/2 a tooth.
nukecamgear.jpg




I almost considered this but really like everything else the RSI cam improved. I am willing to sacrifice a little top end to gain more low end as long as it still breathes like it does through the rest of the range. Someone else mentioned other "insert letter here" cams but I don't know which cams to look for, nor where to find them, nor if they are slotted for the head mount dist.
Click to expand...

you say one tooth is X degrees but you're only looking at the high point; the belt has to slip both a high and low spot to re-engage the cogs.

also correct ME if i am wrong but those marks are in 2* crank rotation for each increment
 
Early IPD adjustable gears were a stock gear with center cut out and then a circular plate bolted to center and slots on outer edge to allow outer part of gear to move relative to center, I have one somewhere seems it wouldn't be hard to replicate
 
Coupe' de Grace said:
you say one tooth is X degrees but you're only looking at the high point; the belt has to slip both a high and low spot to re-engage the cogs.

also correct ME if i am wrong but those marks are in 2* crank rotation for each increment
Click to expand...

Not talking about slipping the belt here. As stated in the first post, rotating the cam gear one belt notch forward = 10* (approx). What I did was drill a new hole for the cam alignment pin 1/2 a tooth forward of the timing mark. This keeps the belt and gear in the same place but rotates the cam 5* (approx) forward.

And, yes, it's a minimal amount off compared to the original hole. But I didn't feel warm and fuzzy wallowing out the original hole and using a shim to push the cam forward. A straight edge, some scribe lines, a sharp punch and some drilling was easy enough.

Crank rotates 2x as fast as the cam. So, 1* of cam rotation = 2* of crank rotation. You adv/ret a cam based on crank being stationary at TDC. So, you are right but crank * doesn't come in to play when making a cam adjustment.
 
VB242 said:
I just wallowed out the hole a little to the right, and used a flattened piece of safety wire for a shim, once the bolt is torqued down its not going anywhere. 3-4 degrees out on the edge of the pulley is a tiny bit of movement down where the locating hole is drilled. This was on the advice of my machinist of course. I'm in the process of installing the engine right now, so I don't have any feedback on whether it moved the powerband at all. I'm running a B21FT with an A cam and a big turbo so we shall see, I'm thinking laggy unless this little trick helps out.
Click to expand...

Why do you always post about something you haven't actually done?

Airfrix said:
NONE of posted URLs in this thread are good ! :grrr:
Click to expand...

There is only one IMG that is broken.
 
You know, I will have some seat time very soon scotty d, within the next day so I will report back immediately with my findings. Why are you constantly trolling my posts?
 
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