I asked this question question about four years ago when I first got my 74 2.0 Liter with dual Dellorto 40 carbs - "If you have dual carbs, what is your max advance timing that you are running?", but did not get many responses. Now, before I receive tirades stating that "The advance timing for a 914 is 27 degrees", yes we all know that that is the timing for an unmolested fuel injected car. But if you have experience with carbs, you know that it is damn near impossible to run at 27 degrees with a dual carb set up. What I want to know is how close to 27 degrees has anybody run successfully with carbs. When I first got my car, I could not get it to run decent without being at about 33-34 degrees advance. After sorting things out over the years I have been able to get it down to 30 degrees, providing smooth running with sufficient torque. This has given me some peace of mind, as we are all aware of the hazards of too much advance. Unfortunately, I do not know what cam I am running, as the P.O. did not leave sufficient data behind, and he had passed away before I got the car.

So, can other carb equipped owners chime in with the following:

Type and Size of Carbs
Cam - Original or Carb Cam
Type of Distributor
Degrees of Advance Timing

Thanks All,

Ansbacher

I will be interested to see responses because I have wondered if more advance would add anything performance wise. It starts easy and runs well.... head temperatures are good. I have my timing set at 27 degrees. It has a Mallory distributor set at 11 degrees at idle and the total advance key is locked at 16 degrees with gray advance springs. Elevation here is about 2200 ft above sea level.

2056
Dellorto 40's
Webcam
Mallory dual point with Pertronix ignitor II
27 degrees advance

I have an engine I built with 40 webers on it and I'm having hard time to get it running below about 45 tdc. I have 103 mm cylinders,it's been stroked, and I don't' know what cam it has. This is my first big motor and I'm at a point where I don't know what to try now.[size=1]

Total displacement? Look for a number on the top of a venturi. Maybe a 28, 32 or greater.

I have a Raby built 2430, it came with the following from his shop

Type and Size of Carbs: 44 EMPI HPMX
Cam - Raby
Type of Distributor: Mallory
Degrees of Advance Timing: 12 at idle (1200rpm) and 28 at full advance 3000rpm

Dale,

A lot of perceived timing issues can really be carb issues. I'd recommend giving your dual carbs a thorough sync and adjustment, maybe clean out the idle circuit and re-set the idle air mix screws. This is not hard to do and has done wonders for me in other cars. Even at 3000-rpm, you may be using only the idle circuit/jets if that is how your carbs are set up. syncing and making sure both linkages open at exactly the same time is critical.

2056
Dellorto 40's
Webcam
Stock (FI) dizzy
29(ish) degrees advance

Starts easily, idles well, takes throttle well. As mentioned, very sensitive to near perfect carb synchronization. The slightest bit out of synch, and it idles and accelerates poorly.

I run the hex-bar set-up which many have derided, but it works for me. Just replace the ball ends once a year or so.

Wow, with the responses that are coming in (BTW Thank You) it looks like I'm still too far advanced even at 30 degrees. Looks like I may have to readdress everything to try to get it down in the upper 20s.

sdoolin: Yeah, I have the hex bar setup too, and it is EXTREMELY sensitive to balance adjustments to the point of ridiculousness.

Thanks all and keep the numbers coming in.

Ansbacher

I thought more people would chime in.

Boomingbeetle said that Raby set his up with 28 degrees of advance so that may be the best place to run it.

I haven't checked mine in years and I was curious so I put a timing light on it a couple of hours ago. My light is an analog light with a dial on it and it actually looks like my timing is closer to 10 degrees at an idle (950rpm) and 26 degrees at 3500 rpm. I also have the much maligned cross bar linkage and I may leave the timing where it is so that I don't have to adjust the idle which is kind of a pain to get just right.

DRLA 45s with main jets reamed "3 sizes larger than" 162
FC442 465 lift 280 duration STD Base circle -- I have been advised this is the wrong cam for my 2366cc engine
Ignition 123 Bluetooth dizzy
Total advance 37º @3500 RPM, 36º @5000 RPM
We found it idled better with 20º advance @1000 RPM

We arrived at this tuning on the dyno on a cool day using premium fuel while debugging carb problems. With any more advance than this, pinging would reduce the performance. I might have to back it off as the weather gets warmer?

I think the *part throttle* performance (thus fuel economy) would be improved if I also tinkered with the vacuum curve (discussed in another thread) but so many other problems with my car I haven't gotten around to it.

Click to view attachment

Jake used to say to find what the engine wanted and was happy with.
The acceptable range is 27-32. At 32 or above, the engine has other issues that need to be addressed.

My 2056 when I was running carbs ran at 29.5 advance (Mallory Unilite).

Zach

History lesson. Out of the box DRLA 40s came with 34mm vents, 40 Webbers came with 28mm vents. That's why the ads of the day were able to make the better flow claims. I woild be surprised if his were other than 34 mm.

I run 28 degrees of mechanical advance with 163/86b cam, DRla 45's & Mallory Unilite with vacuum advance.

Depending on which distributor you are running, I'd still set @ 28 degrees. You are going to see the most difference with advance @ idle. I don't recall what you will see with a 050, but I'm certain that it is close to a Mallory @ idle. Unless you have a recurved 009, advance @ idle with be very high to make the 28 degree number as the curve is very short.

Regards

Mine seemed to develop the most power at 36-37, though it's possible I'm confused about something. What issues should I be investigating?

Look at the screen shots of the jetting and timing specs of the Raby engine fs in the classifieds. You're running substantial advance. Be careful.

For what it's worth, be well aware that cruising on straight & level your throttle plates are barely cracked above idle position, so you're operating in transition. How I know is that my 2316 has a TPS readout. The scale on the TPS is from 4 at idle to 50 at WOT. Cruising at 55-60 the TPS readout is at 4. Slight pressure on the accelerator to get 5 or 6 on the TPS results in speeding up to 70 or so. Carbs (and for than matter f.I. systems) are challenged to provide correct operation across the full range....just food for
thought...

Interesting.... my DRLA 40's came with 28mm vents and I had to find a set of 34's. I always thought they flowed better because of the design of the progression circuit.

My timing as set at 26-27 degrees at 3500 rpm and 10 - 11 degrees at an idle. I played around with it and bumped it up to 32 degrees and then 30 degrees and it ran like a truck.... felt like I had attached a weight to the flywheel. Put it back to 26 degrees. I guess it must have to do with the cam and c/r every engine must have a spot where it runs best. So much for adding some advance to get more performance.

I aim for 28, but 30 is fine. Any more than 32 is way too much.
The big thing is that it doesn't ping under load, problem is with a noisy aircooled it's hard to hear ping. Near my house I have a highway with a long uphill grade and a concrete dividing barrier, driving close to the barrier I can really hear if the engine is pinging. If I hear ping I back it off till it stops.

Also ditch the hex bar and get a better linkage, make sure they open equally. #1 reason for dual carb issues is a shitty linkage.

I spent some time way back when setting up the crappy crossbar and It works fine and don't really have any carb issues.

I was just playing around to see if I could squeeze something more out of it with some extra timing.

34 vents may make it harder to tune, maybe try 32mm. Bigger vents kill the venturi effect.
Not saying you can't tune it with 34 vents, but that's getting to the size I'd start considering 44/45 size carbs.