Ideal distributor curve for 2.7 9.5:1 DC 30 on carbs?

[Neffets]

I'm running with the stock cis distributor at the moment, but would like to recurve it.
2.7
9.5:1
heads are 36/35 I/E port size
DC 30 camshafts
Zenith 40 with 34mm venturi
98 octane eu, which i think is the same as 93 octane us
Is the RS cuve the way to go?

[moneymanager]

My 2.7, very similar to yours, uses the RS curve. Hard to know if it's the best you can do, but it's very good. My car has PMO's with 36mm venturis.

[Trackrash]

I would start with a curve similar to what the early S used, considering your high compression.

Of course, only the dyno will confirm what is best.

[unclebilly]

I have a similar build but I have DC40 cams. I am running the RS curve.


In the chump car, I ran edis with a coil pack and could switch between the stock and RS curves on a 2.7 with 34mm zeniths and CIS cams. The RS curve was better at lower ambiant temps.

[JmuRiz]

Good to know, I'm going for a similar setup to unclebilly, glad to know the RS curve works well with the DC40 cam.

I'll have my dist checked (on my mechanic's machine) to see what the curve looks like and send it out (I doubt it's an RS curve right now).

[unclebilly]

Originally Posted by moneymanager

My 2.7, very similar to yours, uses the RS curve. Hard to know if it's the best you can do, but it's very good. My car has PMO's with 36mm venturis.

How are the 36mm chokes? I have 34mm in my webers but have a set of 36mm as well.

[911 SLANT]

I have a 2.7 spec. motor with 964 grind. How would RS curve do with my cams?

[snbush67]

Without knowing what your current curve really is and how your engine will react to an RS curve, its anybody's guess.


"Usually the engines best performance is given when the ignition timing is advanced close to the point of detonation. Optimal ignition timing is that which gives a lack of detonation, the lowest exhaust gas temperatures, and maximum torque." Ref: Spark advance numbers by Julian Edgar


Currently with a stock distributor you only get to choose the static timing and that's about it (max timing is relative to the static timing of course). With weight and spring adjustments you can adjust how fast it spins up to max advance, and you can slightly adjust what your max advance is by bending the weight stops.


Some people just put the distributer all in at 3000 rpms and let the static timing fall where it may. This may or may not work for you depending on how you car starts and idles, and if its a street car in stop and go traffic it might be troublesome.

[Jonny H]

Originally Posted by snbush67

Without knowing what your current curve really is and how your engine will react to an RS curve, its anybody's guess.


"Usually the engines best performance is given when the ignition timing is advanced close to the point of detonation. Optimal ignition timing is that which gives a lack of detonation, the lowest exhaust gas temperatures, and maximum torque." Ref: Spark advance numbers by Julian Edgar


Currently with a stock distributor you only get to choose the static timing and that's about it (max timing is relative to the static timing of course). With weight and spring adjustments you can adjust how fast it spins up to max advance, and you can slightly adjust what your max advance is by bending the weight stops.


Some people just put the distributer all in at 3000 rpms and let the static timing fall where it may. This may or may not work for you depending on how you car starts and idles, and if its a street car in stop and go traffic it might be troublesome.

Agree. All engines are different and respond differently to igntion timing.

One of the reasons people choose our CDI+ boxes, is if you do the 'all in' method, you can then bring your idle back by to sensible by subtracting some advance in the lower RPMs. Plus, you don't have to worry about the 'recurving' the distributor when you can add and subtract advance according to RPM.

[JohnJL]

Originally Posted by unclebilly

I have a similar build but I have DC40 cams. I am running the RS curve.


In the chump car, I ran edis with a coil pack and could switch between the stock and RS curves on a 2.7 with 34mm zeniths and CIS cams. The RS curve was better at lower ambiant temps.

Whats your static timing at idle?

Thanks