FunK73

iTrader: (6)

So I put the DHLA48 on the car today and I've run into a bit of an issue. The car has a real nasty issue where it boggs/floods/leans out the engine if i give it the beans under 3k rpms. Heres some of the facts

Dellorto DHLA48, Racingbeat modified and jetted according to stock 12a guide.
Stock exhaust manifold/cat delete pipe/stock muffler
Timing is set a hair counter clockwise of the TDC mark at idle (supposed to be 2 degrees below top dead center i heard) I'm not running vac advance.
Stock fuel pump at the moment to a FPR set to about 2.5psi

Now the question is what could be causing the bog? Is it because my exhaust isnt flowing enough? Timing off? Need to upgrade the fuel pump? (I have the proper carter pump to give it the extra fuel flow it needs just havent gotten it in yet) I should also mention, it bog at partial throttle, not necessarily full throttle.

Here is a video to try and give you a better idea of whats going on. Its hard to hear over the clutch fan but you can see that is the rpms are above 3k, every time i give it gas, itll misfire and take off. However, anything below 3k it bogs big time. Seems like the lower it is from 3k the worse the bog is. As you can see, when hovering at 2800rpm, it bogs pretty bad then goes, but from 2500rpm, it just kills the engine. Kind of makes me think it might have something to do with timing.

http://www.youtube.com/watch?v=lpkn7QNByyw

Ideas?

t_g_farrell

iTrader: (1)

Seems like the spring for Dell tuning. Your issue sounds like you need to adjust the
idle mixture screws first and then verify that the AP is squirting a reasonable
amount when the throttle is pressed. You will never completely remove the bog
but you should be able to get it to a minimum. Also you can't expect to just mash the
throttle under 2k and not have it bog a bit. Nature of the beast.

Heres a site that can help you out and it even has the RB instructions on setting
things up.

www.gruntled.com/Dellorto

Siraniko

iTrader: (13)

clogged idle circuit

FunK73

iTrader: (6)

Is there any easy fix to that wacky? Like carb cleaner or seafoam or something? And wouldn't the idle not be nice and smooth?

I know I won't be able to mash it too much down low in the rpm range, but the way its running now seems a bit excessive. I've tried mixtures in and out, different jets all around, and I still can't give the gas more that about an inch of pedal travel without it misfiring/killing.

I am however going to be testing out a header tomorrow and I'll be swapping the fuel pump too. It just doesnt seem like its a fuel issue at this point though, it seems like it would be too rich, not leaning out because of lack of fuel in the bowls.

j9fd3s

iTrader: (3)

carb cleaner, pull whatever you need to, to spray thru the idle circuit.

i'd also make sure the accelerator pump works.

i agree with wacky, the idle circuit either isn't delivering enough fuel, or the main circuit is coming on too late.

FunK73

iTrader: (6)

so you guys think its going lean rather than flooding out? I should also say that the car seems to be idling pretty rich as it sits in that video. It occasionally would pop out the exhaust when it boggs

FunK73

iTrader: (6)

Also, after the car has been sitting over night, it takes FOREVER to fire up the next day. Almost as though the float bowl is emptying. I've heard of this issue with the nikki being common, but not much on it with the side drafts. I'm going to take the lip off tomorrow and check the level, but any things that would cause this kind of issue too?

snivley whiplash

iTrader: (4)

pm sent

hoang5659

iTrader: (14)

i am having the same issue but not as extreme. i put a DHLA48 about a week ago on my streetported 13b. i am new to carbs so keep the tips coming. i will watch this thread and check out the link posted above. you guys rock!

pinoyremix

if you have the choke hooked up..it shouldnt be hard to start...mine..i have to turn it over atleast once to get it primed with fuel...i don't have my choke hooked up...i watched the video...the thing about these carbs is that the idle jets really affect how it runs...i also when starting have to ease into the throttle when starting from a stop..after that..its pretty responsive...just the nature of the beast...

pinoyremix

i would also recommend getting a afr gauge...i have a aem one and it works great for turning the idle mixture screws to get your fr and idle right where you want them...

Siraniko

iTrader: (13)

AFR wont work for this issue.

take apart the dellorto with jets out venturies and the accelerator pump underneath the carb. brake cleaner and compressed air are your friend. while you are at it, replace the AP's gasket as it is the common source for fuel leak. just buy a sheet of gasket from partshouse and make your own. If you havent noticed, Racing Beat added a gasket in there so it will squirt more gas.

hoang5659

iTrader: (14)

+1 on the choke. i just put one in and it really helps keep the engine turning until its warmed up. before i would have to rev it until it was warm. only then it would hold an idle. i am still working out the kinks in mine also. i might have to tear it down like wacky said. but i am not ready for that just yet.

patmac6075

iTrader: (26)

Watching patiently as I too have a Dell48 ready to install.
Any bits of wisdom would be appreciated....anybody know where I can get a RB Dellorto accelerator bracket? Right now I'm fabbing up my own and it looks like smegma!
PS already read through Grunteled.com about a fifty times.

FunK73

iTrader: (6)

Mine is holding an idle fine when its cold, but its REALLY rich. However when I richened up the idle screws, it seemed to idle like garbage, but getting on the gas seemed a bit better. Also seems like theres no power up top. Guessing thats a jetting issue seeing as how I've got 250s in there at the moment.

Also Im wondering if trumpets could have anything to do with the issue. I bought the carb without and trumpets on it, but I had a couple that I had on my DHLA40, and as far as the websites were telling me, they should still work. Is there a specific size trumpet for the 12a application?

j9fd3s

iTrader: (3)

see, if you gave it a little more fuel, and the hesitation got better, it was lean. you just need to figure out how to get the idle proper, and that area richer. wacky would have you put in a bigger idle jet, i'd try a smaller air corrector. what basically is happening is that the idle circuit only flows so much fuel and the main circuit isn't delivering enough fuel yet, so it stops running. wacky adds more fuel to the idle circuit, i get the main working at a lower rpm. i think either way works

the no power up top is probably cause its jetted for a header/full exhaust, and you are still stock, its probably way rich up there. its also possible adding the exhaust changes, or fixes the hesitation, so i'd do that first

you do want to have the trumpets on there, they smooth the flow of air into the carb. the only thing that would make them engine specific is that you can tune the length of the intake with them.

1984se

what fuel pressure regulator are you using?

diabolical1

iTrader: (3)

you've received some really good ideas and advice in this thread and i'm not telling you to disregard any of it, but here's my take. i think you need to take care of the issues you mentioned before you go ahead and start trying to fix your problems. by themselves, they may not be the root cause, but i think in tandem, they could be a big part of it - particularly the exhaust and timing. instead of guessing, i think you should get a timing light and know for sure where you are.

likewise, i think the exhaust is key in tuning an aftermarket carburetor. i ran my car for a couple years with the stock manifold and cat delete, but i noticed a difference when i put on my exhaust system. it wasn't night and day, but it was notable.

if your fuel pump is in decent shape, it shouldn't really be much of an issue until you get upstairs in RPM, but if it's less than decent, who knows?
i fought a somewhat uphill battle when i was tuning my Dell'Orto. when i first installed it, mine started and idled great but ran like ****! i got some really good adivce on this board so if you have a spare moment, you can look up some of my old threads - it may help, it may not. if i recall, tuning on my 13B got me topped out at 230 jets. my 240s started showing negative effects upstairs, so if your 12A is stock-ported, i think you should also get some jets and start jetting down when you get the exhaust and timing sorted. i know every engine is different, but i think 250 is probably too much for you.

FunK73

iTrader: (6)

Timing is on the dot now according to the racingbeat suggestions, fuel pump is in, and the regulator (which is a holley low pressure) is set as well. No notable differences. Looks like I need to start looking for a header and jetting changes.

Would the stock exhaust/cat delete mean I should be jetting leaner than what is suggested by racingbeat for an engine with the header?

Should also mention, started the car after the pump was in tonight and it was a chilly one out there. It idled like a champ (no choke) at a grand, and progressively the idle got rougher as the engine warmed.

The float bowls are also emptying over night.

t_g_farrell

iTrader: (1)

The float bowls are probably being siphoned back down the fuel line when the
pump turns off. Since its starting pretty well cold and not exhibiting flooding issues
I don't think its draining into the engine. I always let my fuel pump run for a few
seconds before I crank it over so the bowls will fill up.

Those 250 jets are too big for a stock port with a RB SP full exhaust much less
your cat deleted stock system with a muffler. 230 is whats used on stock port
12A or 13B. The 250 might be good for a SP or BP. So yeah the exhaust will cause
you issues but not at idle or initial throttle tip in. I wouldn't worry too much
about it while you sort the carb out.

Your idle jets are set too rich. Before you can tune this carb you have to get it
not only to operating temp but as hot as possible. It tunes differently cold vs hot.

The way to tune the 2 idle jets is to first make sure they are both at the same
starting point for number of turns in or out. Then turn both screws in about 1/2
turn and let it settle down. Keep doing this until the idle smooths out and picks
up to a peak, then back it off about 1 turn. Adjust the idle speed and repeat
until it idles @750 rpm or so. I have mine idling at 900 rpm so there is some
variance as in all carbs. Your trying to get the idle adjusted to just be slightly
rich by taking them down to the leanest setting and then backing them off a bit.
This is the old school way to tune a carb and it works on all carbs.

Once you get the idle setup correctly then move on to the AP and make sure its
squirting correctly. Just look in the venturis right after turning it (so theres gas
in the bowls) and tip the throttle bit. You should see some nice squirting action
from the center venturi into the carb throat. If not then you need to adjust the
AP or fix it if its not pumping anything.

This all assumes a nice clean carb with no clogged passages. A clog anywhere in
there can cause all kinds f strange behavior. Also make sure the idle air needles
and seats look ok. I buddy of mine had an issue with a Dell he bought where the
idle air needle seats had been broken out and the needles could never be
adjusted correctly.

Siraniko

iTrader: (13)

once the engine is running, tun the idle screw clockwise and once the engine is almost dying, back it out until the the idle is smooth. its that simple lol

FunK73

iTrader: (6)

Ok here is the updates as of today.

Upgraded the fuel pump, and its regulated to 2.5psi

I jetted the carb main jets to 180 to see what happened, it was noticeably worse. If I pegged it while holding the rpms at 4000, it would kill the engine. However, when I put the 250s in, its not fixed, but it is better. It only kills if i hold it at anything under 3k and peg it. Not much better than 230's

Idle jets are set to 75, and the idle is silky smooth at 1000rpm. Idle screws adjusted as such

Timing is set at TDC as instructed by the RB set up for the 84-85 12A.

Spark plugs are new as well

I can also really tell that the carb is stuggling up top in the revs. It gets up to about 5k in a hurry but 5-7 is a real stuggle it seems. Its smooth, but theres almost no pull from the engine.

So the moral of the story seems to be that the engine is running lean, but the maximum jets I have are not enough to make it right. However the exhaust still is pretty rich so I'm not sure how lean it actually is. I'm thinking I might have to wait until April when I'll be getting my header, and grab a wide band and go from there. Maybe work on trying to clean the carb up a bit as well in the mean time.

DarrenTRS

iTrader: (1)

Not sure what help this will do but this is the jetting for my stock-port, emissions deleted 13B with a stock exhaust manifold and straight back exhaust. I've never had a wideband on it but I did know [little autometer dummy narrowband] it ran a bit rich until I started having fuel pump issues, so hopefully this might be of some kind of help.

Main Jets: 2.2
Main E-Tubes: 7772-8
Idle Jets: .75
Idle E-Tubes: 7850-8
Starter Jet: .95
Starter E-Tube: 7482-4
Pump Jet: 80

FunK73

iTrader: (6)

Thats pretty close to stock really.

Main Emulsion Tube #7772.8
Main Fuel Jet #230
Main Air Jet #230
Idle Holder/Emulsion Tube #7850.4
Idle Jet #75
Accelerator Pump Jet #90
Needle and Seat #300

Siraniko

iTrader: (13)

there are times in life when you say **** it, ditch the book, forget about the wideband and use common sense. you said at 2.5 PSI, your motor is struggling between 5-7K RPM. That right there is an indication of fuel starvation. also which spark plug wires are you using?