Cam Timing

[daffyflyer]

OK, so my new engine idles like crap.

Im pretty sure the cam timing is off, any tips on how to get it right?

I had #1 at TDC, and set the dowels on the cams to 12 o'clock, but how can i tell if its a tooth off?

Anyone done cam timing who'd like to share?

[de Bounce]

Fairly detailed procedure here.
Clicky
Near the end of the article.
More for replacing the belt but does identify the the alignment marks!

[daffyflyer]

Yeah, Had a look at that already, but will read it again incase i misunderstood it!

I dunno.. i seem to have it right (as far as all the marks go). just not... right...

They aren't stock cams though, Tighe 805s so that might not help, i know it should not idle very well on a stock ecu, but this is like BRAP BRAP 2000rpm idle, which i think suggests its not quite right..

[ampz]

You should be able to count 19 teeth of the timing belt between the 2 cam sprockets.
(credit to Sabretooth as he posted it in this thread).

I couldn't quite remember 19 (thought it was 22 for some reason, but that may be another car) but I usually confirm this by counting them before disassembly and writing with chalk on the garage wall same as torque settings when pulling things apart or putting them back together.

[Atmo]

I'm not sure if this is the issue, but I fitted some reground cams to my Laser's BP (using lash caps) and "out of the box" the inlet cam was 6 degrees advanced, while the exhaust cam was 3 degrees retarded. Using the standard ecu this gave the engine a similar BRAP BRAP type idle as you describe and it was an absolute dog under 4000rpm. The dyno run revealed that the power band had moved up the rev range by 500rpm.

The only way to overcome this was to use adjustable cam pulleys. Once fitted and the cams dialled in correctly, drivability down low was vastly improved and the idle settled down a lot. I've not had it back on the dyno yet, but the difference was very noticable.

Best of luck!

[CT]

Simplest way to ensure you have the cams at the right position is to make sure the crank is at TDC on the marks first. Then, the inlet cam should be pointing to 9 o'clock and the exhaust cam shoud be pointing to 3 o'clock. There should also be 19 spare teeth between the cam wheels that are not touching the cam wheels.Check the cam wheel marks and they should perfectly line up.

[daffyflyer]

Ok, Thanks guys.


CT with your method, what marks are you using? there are 2 notches in each gear right?

I was using the cam dowels both at 12 o clock.

Will try counting the teeth between gears too Cheers.



Whilst it will be good to have it running ok, I won't get the strange "does that have a modded 13b in it?" looks at the lights anymore lol

[JMather]

Have you checked your timing with the timing light? you may just need to adjust the cam angle sensor.

[daffyflyer]

Have you checked your timing with the timing light? you may just need to adjust the cam angle sensor.

Naw, its not "my ignition timing is a bit fruity" idle, its, my valves open while stuff is burning still idle

[Mr Morlock]

The quest was how to check the timing. Usual story is tdc and line the cam marks up before removing belt etc. Counting teeth seems sound. However on old engines tdc could be determined a number of ways- inserting a cork in the plug hole- probing carefully and seeing where the rotor button was pointed. I am not quite sure what is the most reliable method on the 5 but I would be verifying tdc and rechecking the timing marks and teeth. If you have modfied cams then perhaps timing adjustment ( not on the gears) has to be varied.

[daffyflyer]

As specified by one of the manuals i had (the veloce one) I put the engine at TDC (Using the ol' screwdriver down #1 plug hole trick!) then set the I mark on the intake cam to point up and the E mark on the exhaust cam to point up


Idles sweet @ 1200rpm ish, and feels very strong - YAY!


It did start running like crap and refusing to accelerate at all after a while though, but i suspect that i may not have put enough tension on it and it might have skipped a tooth on the belt.

Anyway, i now know what im doing, so thats a start!


Also that 19 teeth thing seems wrong, the belt would need like 2 inches of slack to have that many teeth free as far as i can see.

[daffyflyer]

Oh, and for future reference, best way to find TDC that i have found is put a screwdriver down #1 plug hole and turn the motor over with a socket on the crank pulley

[Mr Morlock]

daffy that sounds an ok way- the cork or finger assures that it is on compression stroke.

[kazjim]

If these are aftermarket or reground cams, then the timing point will be different ....

Example - i had some Cams bround by te Famous Graham Russel ( http://www.russellengineering.com.au/ ) Using Stock Mini Cams (1100 ones...)

The Grind we decided on (now being sold as the RE-13T) had to be installed advanced with a 10' offset woodwuff key !

Basically when they regrind the cam they move the centrelines all over the place ...

Sounds to me like your exhaust is a little advanced and the intlet possibly a little retarded !

I've had the same sound, but that was when we were experimenting with LCA profiles and retarding the Exhaust to give a bigger hit to the Turbine . . . ended up a little hotter than expected !

Anyway, I'd be contacting te grinder / company and seeing where it should be timed in to ....

i use a Degree wheel on the Crank and a Mag-base Dial guage on the inlet / exhaust lobes and work out the timing from there based on the grinders notes...

Cheers
J

[daffyflyer]

Thanks Kazjim - Got it fixed now anyway, turned out I had my own timing marks wrong.

Once i followed the manual properly, it all worked fine and runs like a charm :