Camshaft Timing Predator / Honda / Clone

[bob58o]

Anybody ever try retarding a stock camshaft by 1 Tooth?

I just counted 48 teeth on my Predator camshaft.
360 degrees / 48 Teeth = 7.5 degrees per Tooth.

Say you removed the governor, got a billet rod, upgraded the valve springs, advanced the ignition timing... You know, all the things needed to allow more RPMs.

I think Piston to Valve Clearance would be ok on a stock engine.

I wonder if it would run and what the powerband might look like?
Like if you could get 6k or 6500 out of a stock cam straight up, would you be able to get 7k or 7500 after retarding it 1 tooth?

Hmmm? Who wants to try it?

 

[Whitetrashrocker]

Dunno but here's my Briggs.
70 tooth, 5.14°

Most cam degree changes on race cars are a few degrees. Jumping a tooth on these cams are on the larger size of a jump.

I did not jump mine when I put it back together because I just wanted to kart and not clay the head again.

 

[mckutzy]

I don't know about a tooth skipping, but I have heard about twisting the gear position a few degrees... That is the gear shrunk on the crank shaft...
Here's a tool for it....
http://www.kartworks.ca/index.php?main_page=product_info&cPath=178_164&products_id=1919

The back of the plate they don't show you, but it has 3 gears welded on to it(former crank gears), they hold the crank gear in position while you use a bar to move the crank.

 

[bob58o]

I don't know about a tooth skipping, but I have heard about twisting the gear position a few degrees... That is the gear shrunk on the crank shaft...
Here's a tool for it....
http://www.kartworks.ca/index.php?main_page=product_info&cPath=178_164&products_id=1919

The back of the plate they don't show you, but it has 3 gears welded on to it(former crank gears), they hold the crank gear in position while you use a bar to move the crank.

I am aware of turning the gear on the crank, but I was just wondering if skipping a tooth is a cheap, easy mod that might give some DIY speed demons some extra top end power. I am curious if 7.5 degrees is too much?

Aftermarket cams seem to have an ICL between 102 and 110 ish. Wonder what stock is?

 

[mckutzy]

As for the finer details idk.... But another search came up with this from bobs...

https://karting.4cycle.com/showthread.php?20428-Holy-Moses-Cam

They do some explaining and also other types of tools made...

 

[bob58o]

As for the finer details idk.... But another search came up with this from bobs...

And I found this...
How appropriate.

"This stuff is not rocket science although some make it out to be"

 

[Whitetrashrocker]

Like I said earlier, a few degrees is what most cam tuners play with. 1-3°

Moving it 5-7° is alot.

I've heard of it being done but I don't have any first hand experience.

 

[bob58o]

Like I said earlier, a few degrees is what most cam tuners play with. 1-3°

Moving it 5-7° is alot.

I've heard of it being done but I don't have any first hand experience.

If I didn't think it would require a billet rod, it would be fairly cheap to test.

Remove Gov. (Free)
Retard Stock Cam (Free)
HD Valve Springs ($10)
Advanced Flywheel Key ($10)

For $20 (plus a billet rod), you might be able to easily shift the power band to higher RPMs. Perhaps make peak TQ at 4000 RPM???

Might need a higher Idle RPM, so might need a high stall clutch.

---------- Post added at 10:49 AM ---------- Previous post was at 10:42 AM ----------

And since I just purchased a flywheel for a hemi predator that I don't own yet. Maybe I will test this when I get one.

Soon I might have enough spare parts to build one.
No extra cranks at this point though.

 

[Whitetrashrocker]

Billet rod not required. Just slap it in and go man.
Just remember...

 

[Whitetrashrocker]

And to answer your signature, thermodynamics. Not enough matter in space to hold heat. Now a surface pointed at the sun is extremely hot while in the shade is below freezing. That's just the radiation. But you should know this already.


Unless your a flat Earth lemming and then the answer is simple. The heat is held in by the firmament, and there is no such thing as space.

 

[bob58o]

I looked at 3 cams in the CL series from DynoCams.
All have stock lift and duration.
Still not sure where the Intake Center Line is on a stock cam.

CL1 - 5200-5800 RPM
ICL 108.5

CL2 - 6200-6700 RPM
ICL 112

Then there is a CL2R (R for Retarded 2 degrees)
Says 2 degree retardation shifts power band around 200 degrees.

CL2R 6400-6900 RPM
ICL 114

Since 108.5 to 112 gives a jump of 1000 RPMs and 112 to 114 only gives a jump of 200 RPMs, it makes me think the stock lift and duration might not allow enough air for the engine to breath properly if it were retarded any further.

Since I don't know the ICL on a stock cam (it may be 108.5 like the CL1?), not sure where 7.5 retardation would put it. If stock is 105, then 112.5 would probably be ok. If stock is 108, then 115 might be too much.

Now if you add in some ratio rockers when retarding the stock cam one tooth.... You might have something? Since you are changing the cam timing to run at higher RPMs, then you should add some lift to give more air so you make power running at those high RPMs.

 

[bob58o]

Wait, hold the press.

Isn't 360 degrees on the cam equal 720 degrees on the crank?
So would turing the cam 7.5 degrees mean it changes the changes the ICL by double that? 15 degrees?

 

[ezcome-ezgo]

Pause the show.
Stop the train.
Suspend disbelief.

 

[Whitetrashrocker]

Wait, hold the press.

Isn't 360 degrees on the cam equal 720 degrees on the crank?
So would turing the cam 7.5 degrees mean it changes the changes the ICL by double that? 15 degrees?

See why a tooth is a big jump now?