Slotted cam gears, opening overlap; Any experiences? Worth it?

[LA Mike]

Steve,

Here in SoCal you can get a set made at a very reasonable price. I go tohttp://www.bakerprecision.com/ in Long Beach. Take your old ones in to their shop and they will make them while you wait.

LA Mike

[threejagsteve]

Hello, LA Mike,

That's about 33 mi. from me... straight through downtown, to East L.A., then through Compton... the scenic route!

Simi Ed also told me about a place in Northridge.

But thanks for the thought!

Cheers,
threejagsteve

[FeralJuggernaut]

Along the lines of  fabricated braided lines...   I got a clutch line made for about $50 including stainless ends, while I waited at a marine/engineering shop.    That should expand your options a little bit.   

[threejagsteve]

Thanks, FJ! Yeah, I hadn't thought of checking marine applications suppliers.

And to everyone else, sorry for hijacking this thread... I didn't mean to, I just had one quick queston.

________________________________

To make up for it, I'll post the observation that it MIGHT be possible to see if slotted cam sprockets would be helpful by just bumping the cams a tooth along the chain - remembering that cams rotate at half crank speed, you can calculate the change by dividing the number of teeth on the sprocket by 720 (two crank rotations) to get the number of degrees each tooth changes the cam timing. For example, if there are 48 teeth on the cam sprocket, each tooth would move the timing by 720/48 = 15 crank degrees.

If a one-tooth movement provides a noticeable (and desirable) difference, then it might be worth investing in slotted sprockets to get it just right.

Warning: I'm not recommending this; just positing the possibility. If you try it, it's at your own risk, and I'm not responsible if you break your motor.

Cheers,
threejagsteve

[andyb]

Stock cams spec to around 104/104.5 centers.  15* in either way is far too big of a change to run well.  The typical range is going to be from 103 to about 108 for a typical naturally aspirated motor.

[RichBaker]

 The difference between a YZ-F and the sister WR-F engines is cam timing..... one tooth on the exhaust cam. IIRC, the WR was one tooth retarded from the YZ engine. If I advance my WR cam one tooth, it'll be the same as a YZ engine......

  One TOOTH on the exhaust cam.....

[threejagsteve]

Stock cams spec to around 104/104.5 centers.  15* in either way is far too big of a change to run well.  The typical range is going to be from 103 to about 108 for a typical naturally aspirated motor.

That was just an example... I haven't counted the number of teeth on a cam sprocket, so that would be the first order of business for someone exploring the feasibility of the idea.

Cheers,
threejagsteve

[threejagsteve]

Just ran across a picture of an FJ cam gear on eBay... By my count (twice to be sure), it has 46 teeth. 720/46 = ~15.652174 degrees of crank rotation per tooth.

Cheers,
threejagsteve

[TRoy]

Is anyone looking for some slotted cam gears? I've still got the ones that carey gave me umpteen year ago.

They've got about 45* of adjustability   

[TRoy]

15.652174 degrees of crank rotation per tooth.

THE TOOTH? YOU CAN'T HANDLE THE TOOTH!!! 

[andyb]

Not if you want to run decently, anyhow.

They're like $50, or you can kick TRoy's ass and make him send you his.  Do it right!  Maybe you'll be able to get his lunch money too...

[Pat Conlon]

Bumpity bump.

[racerrad8]

Cam timing;
        Since I really haven't played with it in over 10 years, I am a little rusty on what I did. As most of you know, I have been racing and building Legend race car FJ1200's since 1994. I started playing with modifications with our rulebook to try and find more power.

My results were mixed at best. While I could note a better powerband per rpm range at differing settings the other end of the rpm range lost power significantly.

The most notable change I was able to make was with cars that run on a road course type track where they see higher sustained rpms. I was able to do this by widening the lobe centers of the cams. the actual degree of opening time did not seem to make much difference, but the widening of the lobe center by 2-4 degrees made a big difference at the top end of the power band before the rev limiter kicks in.

I tried to use this theory on a oval track cars, but with the wide sweep of the power band from the corner to the end of the straight, there too much of a negative affect on one end or the other.

The other issue I have had with almost all of the engines that I installed adjustable cam gears on was slippage if the cam gear on the mounting bolts. I am not sure if this was due to the abuse we place on the engine as far as the heavier weight of the car, idle to wide open, or the banging of the gearbox, but most of them slipped at one point or another.

Since most of the racers need to work on their driving skill to decrease track times, I have returned to using stock cam gears on all engine except those that have been built several times and the deck heights of all of the components are getting short. This allows me to degree the cams back to a visual center on the cam cap and I have not had anyone complain about power.

The question you posed about temperature difference within the engine based on cam timing would seem to be minimal. The core idea between the cam design & timing is to increase cylinder fill & pressure. In my opinion if you are able to increase cylinder fill with a higher volume of fuel/air your temps should actually increase.

One simple thing that I have done to every engine that comes through my door including my two bikes is to advance the ignition timing by 5-6 degrees. This wakes the engine up throughout the powerband, improves fuel economy and the engine seems to run cooler. I have gone as high as 10 degrees, but carbs and ambient temps play a major role in that application. There are advance rotors available on the aftermarket that bolt right on. In the case of the Legend car, we have to use the stock rotor. So I slot the holes of the ignition plate to the shadow of the mounting washer to obtain the timing advance.

Heat Issues;
While we are here in the Central Valley of California, we still see heat days of over 100 degrees. While this seems to be an issue that comes across the group every couple of months, I believe this is really not an issue. Imagine taking the engine, putting it in a car sideways, putting fenders and a hood over the top of it and racing it at wide open throttle on the hot summer days...

We have had to become very adaptive to the engine to obtain any type of durability from it. This engine is air/oil cooled. We have had to make the oil cooling system so large that some cars carry 6+ quarts of oil. We have air ducting running to everywhere possible to try and transfer heat from the cooling fins of the cylinder and head.

We still see enough heat on the cylinder head to soften the aluminum enough to absorb the washers under the head nuts. We have seen many times 500+ degrees of cylinder head temp at a head stud and many people see oil temp in excess of 350 degrees. Yet this engine runs that way week in and week out throughout the country.

In my opinion, the air cooling system designed by Yamaha works very well. In stop & go traffic obviously the air cooling goes away.

That is when oil cooling must take over to help transfer the heat way from the engine. This winter, I plan on designing a oil cooler system that will increase the cooling capacity of the system. My hope is to use two small fans on the cooler for those stop and go moments. The addition of the bigger cooler plus the additional capacity of the spin-on oil filter should help cool when there is no air flow.

I mounted an oil temp gauge on my bike last week and will be taking it out for a ride next week to get some base runs to document oil temps.

I have thoughts on how to make a system, and I will be making mounts & hoses that will hopefully still fit the stock application of the bike. There might be some minor modifications to be made, but by looking at my bike, I see lots of space to make it better.

Carbs;
David come up with my answers almost everytime...The only thing I have done to improve the cleaning of the carbs is the purchase of an ultrasonic cleaner. It gets the smallest jets clean everytime.

Randy - RPM

[threejagsteve]

One simple thing that I have done to every engine that comes through my door including my two bikes is to advance the ignition timing by 5-6 degrees. This wakes the engine up throughout the powerband, improves fuel economy and the engine seems to run cooler. I have gone as high as 10 degrees, but carbs and ambient temps play a major role in that application. There are advance rotors available on the aftermarket that bolt right on. In the case of the Legend car, we have to use the stock rotor. So I slot the holes of the ignition plate to the shadow of the mounting washer to obtain the timing advance.

Randy - RPM

And no knock running on CA's 91 octane pump premium?

Thanks for all that typing, Randy -- it was very informative!

Cheers,
threejagsteve

[Pat Conlon]

Ok Randy that answers that....Many thanks for sharing your wisdom and experience with us!

On the ignition advance plate: IIRC Vance and Hinds used to offer a 5* (or 7*?) advance plate for our FJ's but I have not been able to locate a vendor, do you have a source? Any in your stock?
I have a 5* advance plate on my '92 and I like how it wakes the bike up...
I have been looking for a advance plate for my '84 1100 but no go so far...

Thanks again Randy...