bmwe21.net forums

Greeting everybody, my first post here so sorry for any mistakes. I have a '81 316 e21 with manual transmission, on which a put a 300 degree Dbillas camshaft and 2 dellrorto DHLA 40 H. The problem is, whenever i accelerate it, it will bog down, like it's flooded, but if i keep the pedal accelerated after 1-2-3 seconds it will run like it should. This only happens bellow 3500 rpm. I attached a video , you can see fuel spitting out of the left carb.

Specs: Dellorto DHLA 40
idle:58
Air:180
Fuel:130
synced with a vacum meter, flotors adjusted to correct position.

Thanks in advance!

i also ported the cylinder head

Since you have remove the standar intake and carb, you lost vacuum advance. You can correct it, givin some advance, between 15-20º at 3000rpm and.
Maybe more.
I have a program, that give you a basic configuration to start tuning carb. It is for BMW M10, for Weber DCOE or dellorto DHLA. That is for standar engine. Run under DOS.
If you want, I can send it to your email.

Regards.

i would be much obliged if you could send it by email. So you are saying i should use the strobo light at 3000rpm, not at 2200. i will try the 15-20 degrees advance and will come back with more info , thanks!

You can download the program here:
http://www.s262612653.websitehome.co.uk ... ETTING.EXE

Run under Windows 32bits.

Little bit more info.

Top End Performance:
...

DO NOT hookup the distributor vacuum advance to the intake Manifold. That does not work and is a common mistake we see. If you do that you will pull full advance at idle then as soon as you open the throttle it loose vacuum and the timing will retard quickly causing a big stumble or flat spot and very bad throttle response.

When running Sidedrafts you need to either get a centrifugal advance distributor or leave your vacuum advance disconnected and just run more initial timing. You usually need 12-14 degress advance at 1000 RPM and 36 degrees total by 3000 RPM for the carbs to react properly. These timing numbers are baseline estimates only and can vary from car to car. You have to make sure you do not have a detonation problem from too much advance.
....

They usually tuning BMW 2002, M10 2.0, you can start tuning your engine from these settings and change to get the correct tuning for your engine.

Thanks, i already disconected the vacum lines from the distributor and tomorow i will use the strobe to start tuning from this recomended settings. Today i took down one of the carbs that had a pump jet full with junk...replaced it. Will be back tomorrow with more info and hopefuly good news!

Also, one quick question, do you have any idea if a MSD ignition box + Coil will have any benefit , as i have one just standing around?

If do you have high compression and run over 4000 rpm most time yes. Ignition is more accurately and better at idle on winter.
If you are a quiet driver, you will not feel the difference.

In my 316, I do not have ingition module, so I install a pertronix ingition to eliminate points and have less maintenance. Happy with that upgrade.
Int the future, I will install "Second Strike" (Pertronix) wich is a rev limiter and a spark amplifier. It is like MSD 6AL, but from Pertronix.

Sorry to gate crash, I'm suffering a similar problem to yours with the bogging, my idle is also terrible. It revs slight between gear changes at the moment to which is annoying the hell out of me.
I've got 55 idle jets but have been told to use 45s? Seems small compared to what you have? My hydro carbons are 2000 plus on idle.... :/

i'm not sure what hydro carbons are (is that the amount of bad gases that come out of your car?)...did you try the classic way to tune them? http://www.s262612653.websitehome.co.uk ... htm...also check the flotors level...i disconected the vacum lines from the distributor and there is a slight improvement...but it still boggs for 1-1,5 secs before working like it should...my distributor is in a point that if i retard or advance it,the idle speed drops...if you have the option, try different setups to see if the carbs have anything to do with it...for example i went from 130 gas 180 air to 180gas-240 air and there us a slight improvement...just play around with them

My idle has a mind of its own, when I change gear the revs rise slightly before dropping (possible air leak on spindles I think) and then it bogs up and cuts out I'm going to disconnect my vaccum tomorrow like you said as I've a feeling it did run better without it especially under load and the revs didn't go up during gear changes I don't think.
Hydo carbons are unburnt fuel. Even when I adjust the mixture it's still so rich that's why I thought I had the wrong idle jets, I've got 55s at the mo and was going to try 45s??? I've never had such difficulty setting up a pair of carbs before, but these are my first set of dellortos.

When I say it bogs up and cuts out, it takes a little while if you leave it idling, it will idle at 1100 then slowly get slower until it finally conks out

dellortos have a mind of their own...that's for sure )if you disconnect the vacum lines for good be sure to block the vacum holes on the carbs and also fix in place the central plate of the distributor... today was the national work day so no work on my biemmer but tommorow i'm going to spend the entire day trying to figure it out...will come back with more info

Do 45 idles seem too small to you? I'm pretty much running a healthy but stock engine with some light porting work (was meant to be keeping this on standard haha)