Twin DRLA 36 carb problem ,guru help please


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Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Sat Jan 13, 2018 4:38 pm

I've checked my valves,static timing,point gap and inspected my pumpjet action and all four squirt the same and ok as far as I can see ,I've also adjusted the fuel pressure to 2.5psi .its ticking over fine and revs fine but if you flaw the throttle it dies or pops/flashes out of both carbs .it holds steady at high revs but you can hear it hunting a little .
My mates del book leans towards either upping the main jet size or airs if you get these symptoms on acceleration?
So I think I need to wait till I get it to a rolling road as I font have any larger mains .


flatbeat
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Re: Twin DRLA 36 carb problem ,guru help please

Post by flatbeat » Sat Jan 13, 2018 6:56 pm

All the time you're stationary and revving the engine it's only the idle jets operating. The mains won't do a thing until you're driving and under load. The mains won't kick in till 2k revs +. If it's a problem when static then it's the idle circuit...or something else....
Unless you've got a wild cam and big heads the main jet @ 115 is fine for the size of the venturis. As I said before the idle jet @ 55 is too small. To compensate, wind all of the idle mixture screws all the way in...gently!.. then wind them back out 3.5 turns each and see how it runs then. If better you deffo need a bigger idle...
Don't bother with the anti pulse....I've never needed one of them before...and I've done lots of Dells.

As a footnote Dells for some reason have a habit of really exaggerating any timing issues. I've had several,occasions setting up Dells for people having been assured the timing was correct only to find...after an hour of messing and scratching my head that the timing was off by a little. Once timed correctly.... spot on.
Turbo lag is the few seconds when the other guy thinks he has a chance.

1962 15 Window Turkis 2110 Turbo
1965 11 Window aka 'Rustina'.


flatbeat
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Re: Twin DRLA 36 carb problem ,guru help please

Post by flatbeat » Sat Jan 13, 2018 7:28 pm

Btw. Just because the pump jet actuating arm is moving doesn't mean the jet is working. The diaphragm could be split or the jet blocked....If you pull the jet to check take note it only goes back in one way....there's a flat face on the jet holder that has to line up to fit...
Turbo lag is the few seconds when the other guy thinks he has a chance.

1962 15 Window Turkis 2110 Turbo
1965 11 Window aka 'Rustina'.


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Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Sat Jan 13, 2018 8:05 pm

I've static timed it as no strobe but ended up being in same position/mark as when last strobe timed .
I've been reving over 2k. All the carbs are totally rebuilt and as new not just a quick overhaul etc . I've checked all pump jets and all work as soon as the throttle is applied /spindle turned .I will try 60 idles if I can get some before it goes in to be rolling road tuned . How to i double check the float level is correct ?


flatbeat
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Re: Twin DRLA 36 carb problem ,guru help please

Post by flatbeat » Sat Jan 13, 2018 9:03 pm

You need to take the top of the carb off to adjust the float. Usually causes over fueling and too rich if not correct...doesn't cause it to lean out unless nearly closed so starving of fuel...but if they've been rebuilt...by someone that knows what they're doing.... the the float level should be ok?
It doesn't matter how hard you Rev it when stationary....the mains won't kick in at all. You'll Rev the nuts off it on the idle jets only. Again, the mains doesn't come into play until engines under load ie driving and over 2k.
Static timings no good really. Needs to timed with a gun to get 32 deg advance at 3.5 k revs. If static timed only that could be you're problem. Seen it too many times...
Turbo lag is the few seconds when the other guy thinks he has a chance.

1962 15 Window Turkis 2110 Turbo
1965 11 Window aka 'Rustina'.


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Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Sat Jan 13, 2018 9:56 pm

Ok thanks ,so I guess as my issues seem to be leaning towards if being lean rather than rich ,I won't bother taking the carb tops off to look at the floats .I will try and borrow a strobe ,and see if I can get a set of 60 idle jets ,but will donas you suggested and wind the mixture screws out from seated position 3.5 turns and see if that improves before I buy some larger idles


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Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Sat Jan 13, 2018 10:57 pm

https://1drv.ms/v/s!AlYeK-ATh-yogntbnePrCuaWLxFM
Hopefully this will give you an idea although I'm sure you do now


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Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Sun Jan 14, 2018 11:09 am

flatbeat wrote:
Sat Jan 13, 2018 6:56 pm
All the time you're stationary and revving the engine it's only the idle jets operating. The mains won't do a thing until you're driving and under load. The mains won't kick in till 2k revs +. If it's a problem when static then it's the idle circuit...or something else....
Unless you've got a wild cam and big heads the main jet @ 115 is fine for the size of the venturis. As I said before the idle jet @ 55 is too small. To compensate, wind all of the idle mixture screws all the way in...gently!.. then wind them back out 3.5 turns each and see how it runs then. If better you deffo need a bigger idle...
Don't bother with the anti pulse....I've never needed one of them before...and I've done lots of Dells.

As a footnote Dells for some reason have a habit of really exaggerating any timing issues. I've had several,occasions setting up Dells for people having been assured the timing was correct only to find...after an hour of messing and scratching my head that the timing was off by a little. Once timed correctly.... spot on.

This morning I did as you suggested which was to wind my mixture screws out 3 1/2 turns from seated to see if it ran better .It did ,in fact I turned them out nearly four turns and the idle was smoother and it did seem to loose most of its flat spot although it still did it a bit but then it was probably due to the mixtures being all that way out .So I think 60 idles are a defo .
I would like to try possible 118,122 mains just to see as well


flatbeat
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Re: Twin DRLA 36 carb problem ,guru help please

Post by flatbeat » Sun Jan 14, 2018 12:42 pm

You'll get away with a118 but not really necessary. A 122 will be way too rich and cause bogging down. With stock heads and mild cam 115 should be spot on. A 58'idle would also be better than a 60. Don't over compensate :wink: Go to big and you'll be washing fuel down the bores and causing premature wear and thinning the oil. It'll also cost you mpg. The yanks run on the rich side to aid cooling nut not reall y needed in chilly old UK :lol:
Turbo lag is the few seconds when the other guy thinks he has a chance.

1962 15 Window Turkis 2110 Turbo
1965 11 Window aka 'Rustina'.


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Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Sun Jan 14, 2018 2:28 pm

Cheers I'll see if he has 58's and update you when fitted


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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Fri Jan 19, 2018 5:48 pm

Default
Ok quick update guys.I ordered 58 and 60 size idle jets and tried the 58's this evening . I preset the mixture screws to 3 turns out .Once warm the engine ticked over nicely and so then I tried to dial in the mixture screws .I slowly turned each one a quarter of a turn in but on each one the engine started to drop off so backed out to 3 turns again .at this setting the engine no longer pops or flashes but it does have a flat spot still if you floor it of idle ,but if you back off and floor it again it pick tight up ,no pops. So I wonder if I should try the 60 jets to see if it looses the flat spot .? It does smell quite fuely/rich but maybe that cus I'm in a garage with only the back door open .I think with the 60's I might have to wind the mixture screws in a bit .
I'm really hoping it will solve the flat spot..


flatbeat
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Re: Twin DRLA 36 carb problem ,guru help please

Post by flatbeat » Fri Jan 19, 2018 7:44 pm

No no...wind them in some more if it 'stumbles' (dies a little) when flooring it then it's too rich. With 58's I'd expect 2.5 turns out to be max needed....poss a little less. The fact that it smells too rich supports this :wink:
Turbo lag is the few seconds when the other guy thinks he has a chance.

1962 15 Window Turkis 2110 Turbo
1965 11 Window aka 'Rustina'.


Topic Author
Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Fri Jan 19, 2018 9:31 pm

So your saying wind in more .The trouble is from three turns out if I turn in about 1/4 turn it starts to stutter ? And the book says to set mixture wind in till the engine starts to stutter/ die then back out about 1/4 from this point ? Are you saying wind in till it stutters then keep going ? Sorry confused .


flatbeat
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Re: Twin DRLA 36 carb problem ,guru help please

Post by flatbeat » Sat Jan 20, 2018 12:00 am

I think you've got something else gong on then. If it's idling ok but stumbles when opening the throttle...and smells rich..then you'd expect winding it in to help. When you say engines warm are the manifolds actually warm to touch? Have you had the timing done which a gun at the correct revs etc? Have you checked the FPR is actually giving 3psi of pressure. I assume you've got the FPR before the carbs not after. Sorry but I've seen that twice!! Also the last couple of Malpassi FPR' s I've had came set at 5+ psi so check that with a guage. For the engine you state with stock heads and mild cam the current jetting should be spot on. If you've done all else above then suspect the carbs have a fault like float adjustment, sticky needle valve or whatever....
Turbo lag is the few seconds when the other guy thinks he has a chance.

1962 15 Window Turkis 2110 Turbo
1965 11 Window aka 'Rustina'.


Topic Author
Fozzy
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Re: Twin DRLA 36 carb problem ,guru help please

Post by Fozzy » Sat Jan 20, 2018 8:19 am

Fuel presure set with gauge to 2.5psi which was recomended by euro carb. I don’t have a gun but the timing was set with one and not moved since although I check static at 7.5 degrees and it’s on the same mark . I will try other jets as point of coarse today but suspect im going to have to wait till next sat at rolling road wether permitting no snow etc . It doesn’t pop or flash with the 58 jets just a little flat spot if you stamp on the throttle . As before onece that initial flat moment has passed and you then rev it it’s fine until you let it idle for a bit .

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