Actual RX-1 Cam specs?

[TurboTony]

Does anyone know what the cam specs really are?

I'm debating about getting a set of adjustable sprockets and moving my lobe centers around a bit when I have the head off to do the shim.

I have a small degree wheel that I hope will fit so I can measure the lobe centerlines and see just what is the factory specs.

I was kinda hopeing that someone else had some numbers to validate mine.

Tony

 

[KbxSrx]

I have a set of cams and gears if you want to run them under a mic. (and crank, rods, pistons, etc)

 

[TurboTony]

How much do you want for just the gears?

Tony

 

[KbxSrx]

I dont know the price, but dont think I want to split them up.

 

[TWIN TURBO]

Cam specs taken from American Snowmobiler.
In.=268deg.Lift=7.30mm
Ex=276deg.Lift=7.75mm
Intake cam Open=BTDC 31 deg.
Close=ABDC 57 deg.
Exhaust cam Open= BBDC 60 deg.
Close= ATDC 36 deg.
Overlap= 67 deg.

These are RX1 Apex's are different

 

[TurboTony]

Any idea how that was measured?

As in at zero lash"advertised" or .050 lift?

I'm not sure how Yamaha would pubilish the cam specs, I'm kind of used to the automotive ways.

By those numbers the intake centerline is at 103 degrees and the exhaust is at 102 degrees. If I'm caluctating this correct the LSA is 116 degrees. That sure seems small for an engine that revs to 10,200

Tony

 

[TWIN TURBO]

I never checked these numbers but I would think these spec would be SAE. specs. On automotive engine with flat tappets I believe its .006 liftter rise. Not sure if its the same for overhead cam motors. Will find out.

 

[TurboTony]

I bolted on a degree wheel today and measured the cams as best as I could. Man those valve and buckets are tiny.

Anyway, this is what I got, all measured at .050 valve lift

intake opens at 10 degrees btdc
intake closes at 40 degrees abdc

exhaust opens at 35 degrees bbdc
exhaust closes at 16 degrees atdc

With those measurements I have the following

intake 230 duration 105 lobe center
exhaust 231 duration 99.5 lobe center
102 dehrees lobe seperation.

Dave has been using 114 degree lobe centers and lobe sep and found some good numbers on the dyno, so that is what I will be setting the cams to.

I bought a set of Graves slotted gears to save me the hassle of slotting the stockers.

Just thought I'd give an update for anyone interested.

Tony

 

[SUPERTUNER]

The many RX1 engines I have built seem to fall into 103 int. 102 exh.

Due to the actual "event timing" (aka valve lash) you will want to use this formula:

OPEN + CLOSE +180degrees divided by 2 minus OPEN (or smallest number)

I have also degree'd cams to close down on the seat. A typical intake closing time (just when the valve seats on the valve seat) would be 50 to 51 degrees depending on overall cam timing. 50 to 51 degrees would put total cam timing around 106 degrees.

Remember too that when building a NA engine with high compression you need to check intake and exhaust valve to piston clearance. Need a minimum of .040" intake P to V and exhaust .090" P to V. Of course these numbers will get you around 17 or 18 to 1 compression. I highly doubt anyone is that high!

Freddie Klies
www.easterncycleperf.com

 

[JohnGalt]

anyone have some dyno sheets comparing stock to tweaked timing?