Camshaft Timing

[Twinky]

After seeing many unknown camshaft profiles for sale lately I have been pondering on how to actually measure the camshaft. So I decided

to try to make up a contraption and see how I go. After finding bits and pieces around the workshop I slaped them together to make this:

 

 

So I gave it a quick measure and came up with these interesting specs:

 

Exhaust Spec

Camshaft duration at .005" lift =220 degrees

Total Lobe lift = .224"

 

That duration just did not look right what so ever so I checked and double checked.

Went on the net to see if I could find anything out and I came accross an article that stated that alot of companies

over exagerate thier camshaft specs, stating the duration from when the camshaft begins to open. Seems to be the case here.

 

One question, does anyone know what the rocker ratio is on the 4k??

 

I'll do some more thorough testing shortly an post the results

[camerondownunder88]

Nice jig :(

 

Rocker ratio on ALL K motors is 1.5

 

Cameron

[altezzaclub]

Rollas hell, that's BF1942 I see there!! :(

 

Nice rig- We did the same in the car with the Datsun 1600s, being SOHC it was easy to mount a dial guage and protractor.

 

Now you need a few cams to try out! You should get nice cam curves on graph paper.

[Twinky]

Rocker ratio on ALL K motors is 1.5

Hmmm then it makes the total lift at .336" on the exhaust which is nearly what it should be for intake :dance:

 

Rollas hell, that's BF1942 I see there!!

 

Yeah I still fire that up every now and then.

 

My protractor is an old radio tuner face with a scale stuck on it's face. The connection to the cam was originally connected to a giant variable capacitor.

It's cool because it has two gears, enabeling me to go at 1/4 turn speed and normal speed. It's something like 20 turns for 180 degrees on normal drive and 80 turns with 1/4 drive.

The stands were the most difficult part of it because it took a little bit of work to get them right. They are just a solid bar cut down to the width of the camshaft wheel, hole drilled down the middle and then threaded to bolt onto the stands. A bit of angle held up by some 2mm ally sheet, drilled and tapped with brackets on the ends to hold the camshaft still while rotating.

The dial guage I had to borrow from work, worth over $1000!!!! Don't drop that thing!

 

There is a guy selling an unknown camshaft here in adelaide but he lives in loberthal, I work up north so it's hard to get to him without taking up a good portion of the afternoon.

When I have a free arvo I'll go get it and do some testing.

 

Anyone in Adelaide want thier camshaft measured???

[philbey]

Good work, but if you think you're getting accurate results think again.

 

I did the same on mine but be warned:

- have you taken into account the diameter of your tip on the dial gauge.

- Getting your dial indicator shaft aligned directly through the cam axis is very, very tricky. Just slightly off and your specs will change.

- Your rig, while creative, will be problematic as you have no hard connection between your camshaft and your mag base. the slightest nudge of your support or even that tea towel will cock up the job.

 

You will get inaccurate results, and I dare say that this is why you reckon your specs are out. Cam grinding is a straightforward machining process and it's very easy to produce accurate, repeatable dimensions. Any claim that they overstate their specs is bullshit.

 

I just used my engine block as a jig when I had it on the engine stand, and a protractor drilled and screwed onto the front of the camshaft. At least when it's mounted into a block, your cam is perfectly centred and you can mag base straight to the block.

 

Also, I measured at 5 degree increments and plotted my timing curves in Excel. I also made sure I degreed it at maximum lift (because it was in between two degree points) Next time I will do it at 2 degree increments, I wasn't happy with my plot.

 

My lessons learnt, I wouldn't do it this way again.

 

Next time I do this I will:

 

1. Install the cam in the block

2. Fit a solid lifter (hydro lifter engine), perhaps even turn one down so the top of it is perfectly flat.

3. Run the dial indicator straight off the lifter

4. Mount my protractor to the Crank and not the cam. This allows more accurate degreeing as you get 720 degrees of crank rotation to the cam.

 

The reason the lifter method will work is because you are measuring exactly what is being transmitted to the valve, and you only have to make sure your dial gauge interfaces nicely with a flat surface. Measuring straight off the lobe means you add a sideways friction force to the dial gauge as well.

[ke70dave]

i agree with what philby sais.

 

howeever twinky i stilll love what you have made!!!

 

might be better idea to get a nice chunk of perfectly flat steel and mount your gear to it (its prolly going to be heavy), get it machined flat perhaps. i would also avoid using those poly bases on your mounts as any flex will give inaccurate results. (same deal as the tea towel)

 

i do like philbys idea of doing it in the motor, but thats not really practical if you don't have the motor appart at the time i guess.

 

but nice work though!

[Trev]

Someone should cut up a stuffed block so you can use the cam section.

[Twinky]

Yeah the pics were only for presentation, the measurements will be made on a measuring table that we have at work. The table has a magnet switch on it to energetically clamp what you are measureing to the table (meter square metal table). Those bases do not wobble in the slightest because of the whieght distribution.

This jig was only designed to make comparisons between a stock camshaft and an unknown camshaft. If I wanted to know the specs of a cam I would send it away.

If I wanted to do it accurately I would have machined a one piece design with the camshaft sitting in a bearing carrier. But I really can't be bothered.

Basically with the current jig I use a spirit level to level off the camshaft (not a bubble but a digital scale). The uni joint on the spindle allows the protractor to sit at an incline if needed but i have a stand for it at work. I took it home because I can't take photos at my work being a government department.

 

But yeah I know this thing is not %100 accurate but it gives me a base to start with and to compare with. After all, if you don't change the setup you can directly compare to another

even with mistakes made, for instance I measured the lift on the stock camshaft and even if that value was wrong I can say that if the unknown camshaft measured at .050" more lift then I know that the unknown camshaft has xxx more lift than the standard.

 

I like to work on first principals which is partly why I made it this way, as simple as possible.

[philbey]

Measuring lift is as simple as putting a vernier caliper across the lobe, that's probably more reliable than a dial gauge anyway!

 

The thing with my proposed method is that you don't unecesasry variables; you're measuring the cam in the exact spot it will reside: the motor.

 

Never fear. You know the score. A couple of V blocks on a mag surface table will be fine, no need for fancy machined bits!!

 

Just a question, where you buying your dial gauges? Because for 1000 bucks, you got stitched up!

[Twinky]

I did actually use the calipers to measure the lift and I got near the same result. My guage wasn't 90 to the cam which let it slip a bit.

We have all the machinery at work to do it so I could just ask to use them but meh, i couldn't justify using a mill for an hour for a home job.

Not my dial guage, was bought over 10 years ago by the government. Some Swiss manufacturer, it is quite sensitive and can accurately display .0005" incriments with a full scale of .45" and an secondary .05 incriment guage. So it's not too shabby.

I did look at buying my own guage but the good ones won't see a price tag of under $100.

[philbey]

check ebay mate, plenty of well priced Mitutoyo gear. Mitutoyo is Jap and make top notch gear.

 

I got one of these on ebay for 28 bucks. Perfect nick, brand new, just a tiny crack on the edge of the lens.

 

 

But I sold that one to my mate and bought one of these on Ebay for 70 bucks, secondhand but in perfect condition.

 

Accurate to .0008in. (although mine is Metric)

[Twinky]

Wow that is cheap for Mitutoyo, especially when I get stuff below cost from them....

[philbey]

yeh, the first one was NOS, box was trashed but the gauge was absolutely spotless. The digi was overrated to but used.

[Twinky]

Well finally I got my arse into gear and made a graph.

 

It is a shitty Xls graph so the res is shit. I made the measurements in 1 degree incriments.

 

This is only the intake camshaft, #2 Cyl

 

 

It's not the best graph but it does show the slowing down on one side when the valve is closing, compared to the other side which is far more aggressive.

Edited September 2, 2010 by Twinky

[ke70dave]

nicely done, good to see some actual results.

 

never occured to me that the opening/closing would be different. i always thought cams were symetrical....there you go hey.