Thread: Franklin S4 centreline

Cam timing is a pita but want do do it right. Last time I used kelford settings on the fs4s but didn't work that well. Think it was 106/108 iirc.

Maybe the method had something to do with it. Are you saying once the dail gauges are hooked up, you only start measuring 0 deg from the point where the valve opens 0.4mm?

It is hard to read the degree wheel from exactly where the valve starts to move. If you measure from a certain lift (manufacturers use various values) to a certain lift from closed then it is easier to be precise and you get more repeatable results. Whatever value you use so long as it isn't ridiculous it will be within few degrees due to the ramp rates not being symmetrical but I used 0.4mm for comparison to the Nissan stock settings. I agree it is a pain in the arse but once you have your cams set to a known position you can use the adjustable gears to move them without having to measure each time.

Yeah this is what I'm after.

Thanks for the help guy.

Ok guys busy installing these cam gears right now. I know the issue came up in another thread, but there wasn't a definitive answer. Are the specs mentioned above in terms of degrees at the crank or degrees on the camshaft? The camgears are marked as each mark = 2 deg crank.

So, if my cam is set to say 100 deg ATDC and I want it at 104 deg ATDC I need to move it 2 marks on the camgear pulley correct?

Or

is it crankshaft degrees in which case to get from 100 to 104 I'd move 4 marks on the cam gear.

Lobe centres are in crank degrees.

If your intake cam lobe centre is 100deg and you want 104, you retard the intake cam four crank dregrees on the cam gear. With your gears, its two marks (1 mark = 2 crank deg).

Likewise, If the exhaust lobe centre is 100 and you want 104, you advance the exhaust cam two marks (4 crank deg) on the cam gear.

SR20-AUTECH

I would add you won't be able to get the camshafts to the lobe center you want without knowing where the piston position is. Finding true TDC is the first step. A degree wheel on the crankshaft is a must, otherwise it's a guess. The "put a screw driver in the sparkplug hole and rotate the engine to the highest position" does not cut it.

Word.

Thanks for the input guys. Just completed the cam gear installation. AFR's on idle went from 14.7 to around 13.0. Seems about right since the there should be some bottom end compromise in order to move the powerband higher up.

It's late here and I don't want to wake up the neighbours so I'll take it for a road tune tomorrow.

Ok just measured up the cams. I have first generation FS4's. My results are somewhat surprising, and nothing like what has been posted up before.

I used the piston stop method to get TDC and we measured the cam centrelines about 4 times each. The results where repeatable so I'm quite sure of the numbers.

Intake - Low lobe = 90
Exhaust - Low lobe = 122
Low lobe LCA = 106

Intake - High lobe = 90
Exhaust - High lobe = 120
High lobe LCA = 105

My cam sprokets where both set to 8 crank deg advance while I was doing the measurements so I had to adjust the values back to get the numbers above. In other words the actual centreline for high lobe intake was 82 and the exhaust high was 128.

The numbers vary a lot from the 115 intake centreline and 100 exhaust centreline that was posted up before. Perhaps the Franklin cams just differ from batch to batch, who knows.

What was interesting was that the centrelines of the high and low lobes are the same for the intake and very close for the exhaust. Kinda confirms what someone mentioned before about there not being a compromise between performance on the high and low lobes. If the low lobes are set to make good power then so do the high lobes.

Does anyone know if the clearances affect the measurements and if so how?

Gonna adjust the cams tomorrow to the desired centrelines and will see how the car runs.

Also, given the previous numbers posted up we were wondering if the cams were perhaps switched around.

Looking at the ramp angles the intake cam has the very sharp agressive opening ramp and a smoother closing ramp.

The exhaust cam has a smooth opening ramp and an aggressive closing ramp. Does this seem consistent with what is expected?