Twin carbs
Re: Twin carbs
Got the engine sorted now, so back on the carbs.
The colourtune seemed a bit short, so I've got the long throw extension, which gives the same thread length as the plugs.
And the SK type synchrometer sits on (not in) the Dellorto IDF, so I've ordered the adaptor for it.
I don't have air horns.....will fit K&N's when all done.
And the 60's idle jets are here ready to fit.
Nearly there now.
The colourtune seemed a bit short, so I've got the long throw extension, which gives the same thread length as the plugs.
And the SK type synchrometer sits on (not in) the Dellorto IDF, so I've ordered the adaptor for it.
I don't have air horns.....will fit K&N's when all done.
And the 60's idle jets are here ready to fit.
Nearly there now.
Re: Twin carbs
Some very useful information in this thread. So thanks to those who have taken the time to post.
1976 1.5Ti
1977 1.2Ti
1989 1.7 Sprint Veloce
1989 75TS
2003 147 2.0TS Lusso
2004 MX5 1.8S
2002 1.6 Focus LX
1977 1.2Ti
1989 1.7 Sprint Veloce
1989 75TS
2003 147 2.0TS Lusso
2004 MX5 1.8S
2002 1.6 Focus LX
- LooLooSud33Spider
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Re: Twin carbs
Dave try to run trumpets inside the K&Ns if you can. As without them you get very messy turbulent airflow through the carbs as a result they never quite go or Sound quite right .
Alfasud Ti 1984
Alfa Spider 2.0 Ts 916
Alfa Spider 20v Turbo
Alfa Spider 2.0 Ts 916
Alfa Spider 20v Turbo
Re: Twin carbs
Gulp!
I hadn't thought of trumpets.
The K&N's are 85mm high.
Will look at Eurocarb/ebay for trumpets......then I suppose the AFM will fit right into them?
I hadn't thought of trumpets.
The K&N's are 85mm high.
Will look at Eurocarb/ebay for trumpets......then I suppose the AFM will fit right into them?
Re: Twin carbs
Set of 36/45 trumpets and bolts ordered from Eurocarb.
The only ones they have to suit DRLA 36 carbs it seems.
When they arrive, will fit them before attempting to set the carbs up.
The only ones they have to suit DRLA 36 carbs it seems.
When they arrive, will fit them before attempting to set the carbs up.
Re: Twin carbs
Amazingly, the trumpets came overnight.
Looks like one of the fixings will need to be drilled a tapped?
Looks like one of the fixings will need to be drilled a tapped?
Re: Twin carbs
I had to do that on mine Dave, both opposite diagonals and remove the factory middle mount.
Re: Twin carbs
Any one on here fitted trumpets to Dellorto DRLA 36's.
Just wanted some info before I start drilling holes in the covers!
Just wanted some info before I start drilling holes in the covers!
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Re: Twin carbs
I have don e it a while ago. As keys to says carb flange needs drilling band tapping. From what I can remember there are some dimples in the casting to mark the spots. Think it was M6 10m nut.
Rsfruitbat
Rsfruitbat
Re: Twin carbs
Yes a couple of dimples.
One is directly above the support arm for the float.....so plenty of meat to drill into.
The other is above a thinner section of the cover.....not much to tap into
Did you drill through into the carb body there?
One is directly above the support arm for the float.....so plenty of meat to drill into.
The other is above a thinner section of the cover.....not much to tap into
Did you drill through into the carb body there?
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Re: Twin carbs
Your carbs are in bits right?
Re: Twin carbs
No,fitted on the car.
Will remove the covers to drill and tap.
Will remove the covers to drill and tap.
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Re: Twin carbs
Any chance of a picture to confirm what you are describingalfadave wrote:Yes a couple of dimples.
One is directly above the support arm for the float.....so plenty of meat to drill into.
The other is above a thinner section of the cover.....not much to tap into
Did you drill through into the carb body there?
Rsfruitbat
Re: Twin carbs
No chance of that I'm sorry.....if you remove a cover
and look directly under the 2 dimples on the cover, you will see what I mean.
One is directly above one of the float pedestals, and there is plenty of metal to drill and tap into.
The other dimple is above a thinner part of the cover.
Did you manage to drill and tap into this.....
or did you through drill into the main carb body?
Hope that makes sense.
and look directly under the 2 dimples on the cover, you will see what I mean.
One is directly above one of the float pedestals, and there is plenty of metal to drill and tap into.
The other dimple is above a thinner part of the cover.
Did you manage to drill and tap into this.....
or did you through drill into the main carb body?
Hope that makes sense.
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Re: Twin carbs
I definitely drilled through the dimples. If metal is thin is there room to put a bolt into the tapped hole from underneath?
I didn't have any problems when I did it and I didn't do anything fancy.
Rsfruitbat
I didn't have any problems when I did it and I didn't do anything fancy.
Rsfruitbat
Re: Twin carbs
Drilled and tapped the covers ok today.
The one over the float pedestal, I drilled a blind hole approx 8mm deep.
The other I drilled through the cover, and both tapped ok.
Got the K&N bases, and the trumpets fitted ok, and fitted 60's idle jets.
Next job is to set up the carbs.....New Years Day maybe?
The one over the float pedestal, I drilled a blind hole approx 8mm deep.
The other I drilled through the cover, and both tapped ok.
Got the K&N bases, and the trumpets fitted ok, and fitted 60's idle jets.
Next job is to set up the carbs.....New Years Day maybe?
Re: Twin carbs
Got diverted in January!
But have now got back on the sud.
The Air flow meter is a great little item, and easy to use.
The colourtune was a bit difficult to see in bright sunlight, but got a blue flame ok.
Seems to be running fine.....so its MoT time soon.
As the car was first registered on 01.02.1980 this is its last official MoT required. But lead us not into temptation ! I think I'll continue to have MoT tests......or at least what they used to call pre MoT's
Thanks sprint88qv......your twin carb set up check list is spot on.
But have now got back on the sud.
The Air flow meter is a great little item, and easy to use.
The colourtune was a bit difficult to see in bright sunlight, but got a blue flame ok.
Seems to be running fine.....so its MoT time soon.
As the car was first registered on 01.02.1980 this is its last official MoT required. But lead us not into temptation ! I think I'll continue to have MoT tests......or at least what they used to call pre MoT's
Thanks sprint88qv......your twin carb set up check list is spot on.
Re: Twin carbs
Best of luck with the test dave
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Re: Twin carbs
Great news Dave.
Fingers crossed for the mot....
...reminds me, I better start thinking about a few spring jobs to get mine ready for its mot.
Fingers crossed for the mot....
...reminds me, I better start thinking about a few spring jobs to get mine ready for its mot.
Re: Twin carbs
Dave out of interest what reading was you getting with air flow meter at idle?alfadave wrote:Got diverted in January!
But have now got back on the sud.
The Air flow meter is a great little item, and easy to use.
The colourtune was a bit difficult to see in bright sunlight, but got a blue flame ok.
Seems to be running fine.....so its MoT time soon.
As the car was first registered on 01.02.1980 this is its last official MoT required. But lead us not into temptation ! I think I'll continue to have MoT tests......or at least what they used to call pre MoT's
Thanks sprint88qv......your twin carb set up check list is spot on.
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Re: Twin carbs
I think mine were between 2.75 and 2.9 kg/h, which seemed to align with the workshop manual tolerance.
Re: Twin carbs
Would that figure be the same for webber and dellorto 36 and 40?Sprint88qv wrote:I think mine were between 2.75 and 2.9 kg/h, which seemed to align with the workshop manual tolerance.
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Re: Twin carbs
I would have thought they’d be there or there abouts for each engine configuration, as the cams, valves, inlet/exhaust flow, piston compression etc., would have been a common design for a set carb. Perhaps 36’s would draw slightly less based on the Venturi being slightly smaller, so a tiny bit less volume of air can be pulled in the same time period?!
Mine are dellorto 40’s on a standard 1.7 8v engine.
Mine are dellorto 40’s on a standard 1.7 8v engine.
Re: Twin carbs
Thanks sprint88qv
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Re: Twin carbs
My simple brain tries to think of it as the bigger carbs (Venturi/jets) allow you to get more air/fuel mixture into the engine to make a bigger bang and therefore more power. However, it depends on the engine set up attached to those carbs that determine how effective those bigger carbs are. A piston engine is really like a pump, so if the pump system (piston/valve/inlet port/camshaft profile) attached to that carb doesn’t have the right amount of suck for that carb set up, then it won’t give the optimum performance.
Everyone remembers those days of the old Escort boy racers that would fit huge Weber 45 dcoe’s to their 1.1 engine and then be surprised when it would run like a dog and have no power.
At the end of the day you need to have the right engine and carb configuration to get the right amount of suck and air/fuel combination to give the optimum power.
That’s my simple thinking though, I’m sure others have done good thoughts.
Everyone remembers those days of the old Escort boy racers that would fit huge Weber 45 dcoe’s to their 1.1 engine and then be surprised when it would run like a dog and have no power.
At the end of the day you need to have the right engine and carb configuration to get the right amount of suck and air/fuel combination to give the optimum power.
That’s my simple thinking though, I’m sure others have done good thoughts.
Re: Twin carbs
Air speed is more important than volume which is why over sized carbs run rough . Small carbs will have a high air speed over jets so pull more fuel and mix better where a large carb will have a slower air flow do pull less fuel .large carbs for top end power small for bottom end grunt so it’s slways a compromise. I have a old two stoke dirt bike i use for enduros and after trying three different size carbs ended up with a smaller one than standard that makes jus as much top end but lower end is so much smoother it pulls up most hills on tick over .
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Re: Twin carbs
You’re absolutely right, the Venturi effect.
Good to experiment and above all, learn.
Good to experiment and above all, learn.
Re: Twin carbs
I got approx 3.5-4.0 kg/h on all 4.
The scale is quite small, and difficult to read accurately.
Can't see anything in Haynes re air flow?
The scale is quite small, and difficult to read accurately.
Can't see anything in Haynes re air flow?
Re: Twin carbs
I would have thought that for engines of the the same size the air flow would be the same at the same engine speed?
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Re: Twin carbs
I’d agree. Although mine is 1.7 with 40’s and I think Dave’s is 1.5 with 36’s.
I’ll double check my numbers though.
I’ll double check my numbers though.