TheSamba.com :: View topic - Vaccum advance vs. 009 - which is better for off-road?

Mon Aug 30, 2004 3:34 pm

I've read articles & threads here on vaccum advance vs. mechanical advance distributors - some say mechanical advance is better (I forget the pro-mechanical arguments), others say vacuum advance is better because the advance comes on quicker, and you get more of it, which helps the engine run cooler and gets better mileage. However, I've never seen this debate come up in the context of baja bugs / dune buggies.

I brought this up at my local shop, and I was told that mechanical advance is better for a baja bug because it gives you more power off the line to get the big tires moving. (not just because they were trying to sell me a 009 -I already have a 009 and was thinking of switching to vacuum advance).

Anyone have thoughts on which is better for a baja bug? In my particular case, my baja is 75% street driven, stock d/p 1600, single 34 PICT-3, and will not be running huge tires - just 215 75R 15's in the rear (27.7" overall tire diameter).

Tue Aug 31, 2004 8:16 am

I got a Subaru turbo just recently and I need to get a mechanical advance distributor now because I think the pressure will through the vacuum advance way out. So that’s a plus for the 009.
Paul

Tue Aug 31, 2004 2:53 pm

I am just speaking from personal experience, but I found the vaccum advance to work the best on a stock DP motor with a stock 34 pict carb. If you do decide to go with the 009 you will need to slightly modify your 34pict carb, or you will more than likely have the dreaded "flat spot". Drilling or chainging the main jett and blocking the small hole in the butterfly is easy to do. You will see a noticeable gain, but gas mileage will suffer a little.

SHMO

Tue Aug 31, 2004 5:56 pm

SHMO What would you change the main jet too? My sons running the same Carb motor etc, And definately has a flat spot that wont go away, He also runs a 009, On my car I run a run a 009 distributor, 1600 single port with excellent response.

Wed Sep 01, 2004 7:23 pm

my vote is the mechanical advance 009

i use it on my rail.

i had a vaccum advance, switched to a mechanical advance and saw a big improvement

Wed Sep 01, 2004 8:29 pm

I had good luck with upping my main jett size to 1.35mm. I also plugged the small hole on the throttle plate with an aluminum pop rivet. I Put a tiny dab of locktite on the rivet before securing it to the throttle plate to assure it would stay in place. One thing I forgot to mention was the accelerator pump. I don't recall where I set it, but remember that a few notches either way would make the flat spot much more noticeable. I "think" I ended up using slightly more fuel from the accelrator pump. Moving the the accelerator pumps notches towards the rear of the car will provide a bigger "pump" of fuel, and moving the notches to the front will provide less fuel. I spent some time playing with the pumps adjustment.

Before you even start a carb tune, make sure the car is timed properly and it is brought up to opperating temps.

Hope this helps

SHMO

Wed Sep 01, 2004 8:36 pm

I had good luck with upping my main jett size to 1.35mm. I also plugged the small hole on the throttle plate with an aluminum pop rivet. I Put a tiny dab of locktite on the rivet before securing it to the throttle plate to assure it would stay in place. One thing I forgot to mention was the accelerator pump. I don't recall where I set it, but remember that a few notches either way would make the flat spot much more noticeable. I "think" I ended up using slightly more fuel from the accelrator pump. Moving the the accelerator pumps notches towards the rear of the car will provide a bigger "pump" of fuel, and moving the notches to the front will provide less fuel. I spent some time playing with the pumps adjustment.

Before you even start a carb tune, make sure the car is timed properly and it is brought up to opperating temps.

Hope this helps

SHMO

Sat Sep 04, 2004 8:27 am

I have the same engine and carb right now and I'm using the 009. I just had the jets reemed (not sure what size) but it still has a bit of a flat spot. my engine runs great but I cant dump the clutch and expect to floor it without the flatspot occuring. I have 29"X7" tires on 15X5" rims in rear.

I have a new vacume advance distributor that I'm going to install. All the mechanics I've spoke with and even the one that just reemed the jets to my carb told me the only way I'm going to get rid of that flatspot, that's caused by the 009, is to switch to a vacume advance. Ontop of that it will increase the mileage as mentioned in previous replies.

Scince we practically have the same engine I suggest the vacume advance. My engine also seams to idle high with the 009. Timing is at 10 degrees BTDC mixtures on the carb are good but still idles too high. I'm hoping to fix this problem with the VA Distributor. hope this helps

Sat Sep 04, 2004 5:54 pm

Dan,

if your flatspot is just off idle, you should spend some time playing with the accelerator pump. I bet that's your culprit. Granted you will proabably never completely cure the problem, but I was able to correct mine to the point where drivability was almost as good as stock. I would also question the professionalism of any mechanic who would drill out a jett. That is a total "backyarder" trick. Nothing wrong with that and it does work, but why modify a 2 dollar part. it is like using the same gasket twice.

You really should set your timing at full advance also.

SHMO

Sun Sep 05, 2004 5:12 pm

SHMO wrote: Dan,

if your flatspot is just off idle, you should spend some time playing with the accelerator pump. I bet that's your culprit. Granted you will proabably never completely cure the problem, but I was able to correct mine to the point where drivability was almost as good as stock. I would also question the professionalism of any mechanic who would drill out a jett. That is a total "backyarder" trick. Nothing wrong with that and it does work, but why modify a 2 dollar part. it is like using the same gasket twice.

You really should set your timing at full advance also.

SHMO

I know the cure. A vacume advance distributor.... :wink: I'm pretty confident the mechanics I take my car to know what their doing. But then again..... I'm not posotive but I think he replaced the jet with a new one but does it really matter when its a new carb and has new jets?
The first time I took my car to the shop the mechanic timed it at 15 BTDC. Then they changed owners and got new mechanics except for the guy that was working on my car. One of the new owners timed my car at 10 BTDC. The original mechanic just stood there and didnt say a word .... :?

The only time I didnt have a flatspot was before they did my jets and the choke was constantly on. But now my carb is working the way its suppose to and I'm happy with my engines performance, its actually running the best it ever has right now.

So its pointless to install an 009 in a stock engine if all your getting is less performance and a bit of a flat spot.

Tue Oct 05, 2004 10:20 am

I would not use a 009 unless it is an old german one...all new are mexican or brazilian, poor quality......instead use one from porsche 912... I don't remenmber the #, but they are almose exactly like 009, but they have brouder advance curve....you can set your initial timing lower and still get plenty of advance up high....I replaced the 009 in my 1600 and lost the flat spot immediately...Also most alpha romeo DOHC motors have the identical distributos. you just have to change the gear at the bottom. it is an easy way to get high performance. even electronic ignition with knock sensor...

Tue Oct 05, 2004 11:28 am

DanGreen1 wrote: The first time I took my car to the shop the mechanic timed it at 15 BTDC. Then they changed owners and got new mechanics except for the guy that was working on my car. One of the new owners timed my car at 10 BTDC. The original mechanic just stood there and didnt say a word .... :?

They both got it wrong, although the new owner was probably closer. The 009 must be timed at full advance. Static time it to TDC to start it, then hold the engine at 3000rpm and set the timing to 28-30 degrees BTDC and don't worry about where the idle falls.

Thu Oct 21, 2004 10:26 pm

Ive got a stock 34 pict and a 009 and have heard of the flat spot all over but I dont have it. I did have it for about a week after I installed my new 34 pict but after setting the timing and adjusting the carb it went away. guess I got lucky. :)

Fri Oct 22, 2004 1:38 pm

Could someone please explain "Flat Spot" to me. I try to read and understand most of the postings here, but this one is just not coming to me.

Fri Oct 22, 2004 1:58 pm

Okay, in the simplest of terms, when anyone is talking about the "flatspot' they usually mean a condition where there is a hesitation, sluggish acceleration, and no power just as you accelerate. so instead of hearing waaaaaaaaahhhhhHHHHHHHHHHHHHHHHH from your trusty engine, a nice steadily increasing sound of power unleashed when you step on the pedal, you hear wuh.....wuuuuuaaaaaaaaaahhhhhhhhHHHHHHHHHHHHHH.

Fri Oct 22, 2004 2:19 pm

I see.. Well that would suck. I'm against Flat Spots!

Thanks for the explanation.

Fri Oct 22, 2004 4:38 pm

I think Nicksan's experience just goes to show how important it is to have your engine properly timed before you try adjusting the carb.

Fri Oct 22, 2004 5:17 pm

My 1835 has had a flat spot for years, and everything but the 009 has been changed, so I need to ask- -what would the correct vac adv dist be? I'm not too familiar with them.

Fri Oct 22, 2004 7:47 pm

What kind of carb are you running? Check out this site here for Kadrons. On this site it says that the vacumm advance is much smoother than a 009 or mechanical Dist. They are referring to that when using Kadrons but It might be true for other carbs also.

http://www.lowbugget.com/