Setting cam timing

[up2nogood]

Just wondering if it's as simple as aligning no1 piston TDC with the 'back' of the cam on no1 firing?

Or should I be retarding the timing slightly for more torque?

[mike 90 RR]

OK .... It's after 12 ....

[up2nogood]

slow day......

[mike 90 RR]

Just wondering if it's as simple as aligning no1 piston TDC with the 'back' of the cam on no1 firing?

Or should I be retarding the timing slightly for more torque?

Yes ... you set the "piston 1" to TDC ... No to ... set to "visual" back of cam .. You have to set it up to marks on the gears to get it right ... as it is easy to be 1 tooth out

Advance the Distributor to get more response from the motor


Which motor are you working on? .. Are you installing a new cam?


Mike
:)

[up2nogood]

4.6 with 3.9 heads. 9.34:1 block. Will be using tin gaskets and running dedicated LPG.

[mike 90 RR]

4.6 with 3.9 heads. 9.34:1 block. Will be using tin gaskets and running dedicated LPG.

.. So your using a brand new cam .... Durations set for LPG ?? (gas cam)

Mike
:)

[up2nogood]

Hmm, hadn't thought of that. Was just going to use a Dynotec PC216.

Thoughts on this?

[justinc]

Hmm, hadn't thought of that. Was just going to use a Dynotec PC216.

Thoughts on this?


PC216 would be a great cam for gas, make sure it is dialed in though. You MAY have to retard it a few degrees, I have on the last 2 I have done BUT they weren't running gas and were Low comp 3.9's....

If in doubt set it to factory marks.

JC

[RoverP6B]

With regard to camshaft timing, it was my understanding that if you advance the timing this will improve low end torque, as opposed to retarding the camshaft timing to after TDC as this will reduce low end torque.

Or am I missing something?:angel:

Ron.

[Blknight.aus]

no, your not missing anything, within limits individually both will increase low end torque.

Very Very Generally

retarding the cam a little can let the gasses flow better at low RPM BUT will hurt you at higher RPMs go too far and you can wind up with Ms. Valve Face introducing herself to MR Piston Crown and thats usually a marriage that ends in a disastrously costly divorce.

Generally with the rover engines as stock you only get to pick by a tooth mesh and not with any fancy cam adjusting gears and usually thats just way to much one way or another. If you were going to the effort of getting yourself set up with an adjusting cam gear you'd know enough to know that theres much better after market cams for rover engines than the stock ones and you'd fit one of them at the same time and to the specs provided with your new cam.

advancing the Timing puts the spark to the fuel air mix a bit earlier and raises the combustion pressure earlier putting more push on the top of the piston BUT.. When you start to hook in on the noise and the revs lift the advance then pushes you into the realms of pinging and this gets even worse when you lift off and have a decent manifold vac happening.

[justinc]

With regard to camshaft timing, it was my understanding that if you advance the timing this will improve low end torque, as opposed to retarding the camshaft timing to after TDC as this will reduce low end torque.

Or am I missing something?:angel:

Ron.

Correct. The cam design also is an important factor here, the PC216 is a middle of the road lift, good profile cam. It has excellent vac at idle and will give good mid power. The fitment to a big cube hi comp engine, IE 4.6 over a 3.5, will negate some of the bottom end reduction when retarded, but in an automatic trans application will be a good match in the 1800 to 3000 rpm rev range. The vacuum at idle will be less when valve timing is retarded, but if advanced too far the cams design characteristics will be compromised.

So, when we talk retarding cam timing in this context, it is only sometimes performed to achieve the specs with regard to lift etc that are supplied with the cam itself, which then allows the cam to work in your engine as it was designed to do. Retarding or advancing a standard cam is almost pointless and will more than likely reduce performance across the board.

JC