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Sun Aug 09, 2020 7:13 am

Im having some problems with my dual 45 dells when i accelerate from either idle to WOT or even cruising then WOT where it has a pretty noticeable stumble until the rpms catch up then it evens out.
I also have a A/F meter and by the looks of it it will go from 12-13 to 22 on the meter when this happens.
Ive tried changing all the jets to different combinations as well as venturi size and while some seem to help it doesnt seem to go away.

Info about motor and carb set up
2054 (94x74)
ponchito heads 40 x 35.5
120 cam
stock rockers
not sure if it matters but bigger oil pump since im running a 4 quart oil sump and have about 10 quarts of oil through lines and seperate oil cooler 96 pass if i remember.

45 Dells
34 venturies ( bought 36 venturies to see if it would help)
200 A/C (orignally had 180 but someone suggested the 200)
140 main jets ( have a set of 162)
55 idles (have 65 and 70)
55 pump jets ( have 60 figured since it was lean on accelleration they would help but didnt seem to change much)
#2 emulsion tube
Carbs are synced running about 4.5 on the scale

Im not the best at tuning carbs but the A/F meter has helped a little but still not my area of expertise so any help would be greatly appreciated.
thank you

Sun Aug 09, 2020 7:18 am

What about it being a slow advancing timing issue
Plus when at idle.... If you mash the throttle and it goes flat and No black smoke exits the exhaust then its lack of fuel... If you mash the throttle and black smoke exits the exhaust its over rich.
An AFR gauge is a more accurate tool to use, but old school tuning still has its place

Sun Aug 09, 2020 7:28 am

possibly hadn't really thought of that i forgot to add that i am running CB performances crank trigger kit maybe the settings that were originally set need to be tweaked Also not sure if this matters but its also in a 1962 bus even though it does it with no load its definitely more noticeable under load.

When i mash the throttle i haven't noticed any black smoke and what the gauge shows it goes super lean but that's not to say it's accurate either

Sun Aug 09, 2020 7:51 am

There are others far more knowlageable than me but your 36s will bring the mains in later.

22 on the AFR tells me the engine quit firing. Could be way too rich or way too lean.

Sun Aug 09, 2020 7:51 am

Make sure all 4 pump squirts are working. Bit of hassle in a bus. You might have to remove them to check it. Or use a mirror / torch.

Sun Aug 09, 2020 7:55 am

You need to tune the engine. Have a look at this, long read but lots of info.

https://www.thesamba.com/vw/forum/viewtopic.php?t=...start=2120

Sun Aug 09, 2020 8:51 am

the stumble is most likely a gap between the idle progression circuit and the main jet circuit . On dellortos the float height has a lot to do with this .

Make sure your float height is in spec . 5mm to 6mm . hold the top vertically I use a 5mm drill bit as a guide , roll it up with the gasket in place under the float .if you have sprung needles the 5mm should be when the float tang just rests on the plunger . It can be fiddly to get right but it is crucial so take your time .

There has been a fair bit on tuning dellortos on the samba if you do a search .Some very good information .As well as the link Badbug has given .

Sun Aug 09, 2020 10:31 am

So I was messing with it after reading what you guys said and the links shared I put in the 140 main with 180 a/c and 55 idle with 55 pump jets its almost gone still has a little stumble but not nearly as bad as it was im thinking maybe it was too much fuel like someone stated in that link might still have to pull apart and check the floats. I did notice however if I raised the idle to able 1200 rpm its almost non existent. I think at that point im in the progressive ports right? Would that mean that I need bigger idle jets or vise versa

Sun Aug 09, 2020 2:45 pm

Keep reading the article your answers are in the thread i posted.

Sun Aug 09, 2020 7:10 pm

Bad bug wrote: Keep reading the article your answers are in the thread i posted.
X2.
The real gold is in the first 10 pages. But the thread is worthy of reading all the way through. At least once.

It took me three days to get through it. I'm a little slow! :lol:

Sun Aug 09, 2020 9:48 pm

67rustavenger wrote:
The real gold is in the first 10 pages

I was going to say this but i need the original poster to have a eureka moment. Yes every bit of the thread is good. I will walk this walk soon when i assemble and tune my own engine.

Sun Aug 09, 2020 10:44 pm

Oh i didn't even get to the first pages it started me off on the last pages and I was working backwards but ill check it from the beginning

Sun Aug 09, 2020 10:52 pm

I have DRLA 45: on a 2276, and did quite a bit of tuning with a programmable ignition. Every point up the RPM/Load range needs to be measured and tuned in order. The thread linked is a good start. Although the DRLA has some of its own characteristics, and that tuning thread is heavy on the Weber side.

As for the off idle stumble, and it being smooth from 1200 RPM up. I’d venture to say this is a result Your carb being slightly large for the engine. As a result the butterfly’s are almost closed at idle, and they have to move far enough to uncover the first progression hole before the fuel starts flowing. If you back the base timing down, you will have to open the throttle to achieve the same idle speed, this may help. Your gonna have to find the balance between base timing and throttle plate position for a smooth start. With programmable ignition this is fairly easy and full advance is not challenged.

Jet sizes for a given flow, vary by manufacture. I’d expect to be in the 57-58 idle jet size on a set of 45s. That said, I’ve seen 55’s that flowed the same as factory 58s. Check AFR at 1800-2000 ROM and adjust idle jets if needed.

As mentioned, it’s a waste of time to chase your tune until fuel pressure is set at 3 PSI +\- 0.25 and the floats are confirmed at 5-6mm. If the floats are too high it will bulb over and read rich. If the floats are too low you will have a lean spot on transition around 2600 +\- 200 RPM.

Mon Aug 10, 2020 2:56 am

When you finally get pissed off enough, send them to Dave at Blackline. I had a brand new NOS set of 45s that I couldnt get the flat spot out of. He put them on his mule motor , tuned them, and I got them back, perfect.

Mon Aug 10, 2020 7:19 am

sounds like you're in the same boat as I am with my 45's on my 1968cc .
Mine goes lean at the initial throttle, It is sucking more air than fuel when it opens the throttle. You can feel it and hear it.

I am waiting for some Berg grooved venturies, I have the 30/34 on order. They don't list the size on the web site, but I e-mailed and they said they can do them.

180 airs I get a big lean spike

200 air, 56 idle, 132main , with the 200 air the spike is gone, but at light throttle cruise, it goes into the 17's on the AFR

Mon Aug 10, 2020 8:31 am

That 140 main seems small to me.
150 sounds more like what it would want.
You can try the 162 to see if it helps the stumble.

Mon Aug 10, 2020 8:55 am

Ohio Tom wrote: That 140 main seems small to me.
150 sounds more like what it would want.
You can try the 162 to see if it helps the stumble.

EXACTLY what I was going to say.

Mon Aug 10, 2020 10:53 am

Ohio Tom wrote: That 140 main seems small to me.
150 sounds more like what it would want.
You can try the 162 to see if it helps the stumble.

John would recommend coming up slowly on the jet size from 140 to 145.

Mon Aug 10, 2020 5:08 pm

im going to see how the 200 a/c with the 140 works first then ill have to order bigger jets from 145-155 and see how it goes and just play with combinations. Also might play with the timing on the crank trigger program because at idle im running about 12 ill have to double check with the computer ill try and get data log on like the ones that were posted and maybe thatll give a little more info