Alfa Romeo Owners Club of Australia Forum

Hi All,

I have tried and tried again to tune my engine with no success.

I feel like groundhog day every time I try.

Are there any mechanics that do home visits or any courses I can do on how to tune a carburettor engine?

I am also willing to pay someone to come and teach me whilst they tune my car.

The car has had some work done to the engine so I am wondering if this is making it more difficult.

Thanks

Joe

take it to benincas dyno
they know alfas back to front
the basics are once you think you have no leaks air or fuel
screw one of your idle (mixture)screws gently in ( clockwise ) and count the turns
once you have established that screw it out again to the same number
do the same to the other 3 so they are all the equal to the first one
You have established a base
start the engine with a higher than standard idle 1200rpm
get a piece of tube put one end in your ear the other near the opening of number 2
then compare to number 3
adjust the central balance screw ( on the throttle ) until they sound the same
now you have balanced carbs
now adjust each idle screw 1/4 turn anti clock wise to each one whilst running
did the idle go up or down
if it went up go again if it went down turn 1/4 turn the opposite way and then 1/4 again ( clockwise)you are now 1/4 turn clockwise from start
until you get the highest idle then turn them 1/4 turn Anticlockwise so that it doesnt run too lean
so play around equally until you find the best idle
then adjust you idle screw down to 800rpm
carbys 101
this assumes it was going originally

I have had success with a device called a colour tune. Google it they are made in England and are relatively cheap.  The idea behind it is you screw the device into the plug and when the colour turns blue the mixtures are correct.   Anyway google it to find out more.  Cheers. 


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Hi Joe
Check that it's not leaking at carburettor mounting blocks , ie; not split or damaged. If, OK adjust carburettors as previously described by Carlo above. A tool to balance carbs is available through e-bay, if the screwdriver, tube and sound method is not your cup of tea.   

I saw your previous posts are you sure you have 45mm carbs? 40mm original are best on this engine this could be a situation where you have he wrong pair fitted incorrectly jetted my advice would be to go back to stock carbs and have tuned properly and you'll have no dramas after that

Hi All,

Thanks so much for your feedback!

Carlo - I have no problem taking it to someone and I have heard good things about Beninca, I would just like to learn how to do it and I won't be able to learn if I take it there.

I have tried a few different methods with no success and I am not sure if there is something wrong with the timing or something else.

105greg - Thanks, I'll check that out.

Thanks Bonno - I'll re-check the gaskets etc.

Alfapride - Thanks for remembering. I think they are 40's, however, they have been rejetted or something.

Apparently the car has some PACE street cams and has been re-jetted with a electronic fuel pump.

Not quite sure how that effects tuning, however, I have never had it running smooth in 2 years!

Joe
Thanks for the acknowledgment  and would be of interest/helpful to forum members on the final outcome.

Cheers
bonno

It would be interesting to use a K type thermo couple with a suitable multimeter to measure the temperature of the exhaust runners near the head and see how much of an effect changing the idle mixture screws has on exhaust pipe runner temperatures.
Probably not as accurate as having sensors inside the pipe and directly measuring the gas temperatures and the changes would be slower to show as the pipes would have to heat up or cool down with the different gas temperatures as a result of mixture changes, but it should give some decent information about individual cylinder tuning.

Hi fellow Alfisti's
You can buy a unit for balancing multiple carburettors on e-bay for under $100AUD.  I am still not convinced that the use of carburettor balancer will fix the problem, ie; process of elimination of possible causes identified in the message thread.
Regards
bonno

No it may no entirely fix it
but you have to reduce the variables
once you have acheived this
then you adjust the idles as previously described
then if youi have misses around 2000 to 3000 we can fix this
tell me what jets emulsion idles are in it
what chokes and is it 40mm dellortos
then take the cam cover off and tell me whats the numbers on the cams
then we can tune it right

Wide band air/fuel ratio meters are well priced now, so I'd suggest getting 1, installing it and monitoring it during a test drive or 12.

Also make sure that the advance mechanism in the distributor is free to move and the ignition timing is correct.

Welcome to modifed carby cars............. Where, apparently, they are easy to tune, but you don't actually have the means or the huge selection of parts to actually tune them.
Or their ignition timing.

Hi Joe, I'm surprised nobody has suggested this yet.

First thing to do would be to do a compression and leak down test on the engine.

Could possibly have a burnt out valve, or even a broken piston or piston ring. Will make it impossible to tune if this happens to be the case.

Mick.

Hi fellow Alfistis
I think Joe has a lot of work to do, to establish the root cause of the tuning problem initially described. The difficulty I see is the lack of detail with what the car is doing at idle and whilst being driven, ie; rough idling, lack of power through the rev range, misfire, etc, etc. Sure the condition of engine should be the first thing of the fault finding process and all the others identified in the thread would then follow by the process of elimination. Like a former Prime Minister once quoted "Life wasn't meant to be easy".

cheers
bonno

Hi all, thanks for all the replies and feedback. I finally had some time to inspect the car and have some more info. Here is what I found:
Choke emultion 7482.3
Choke jet 80
Main emultion 7772.8
Main jet 145
Idle jet 55
Cams: Pace 2229
While I was checking things I noticed the top of the main and idle emulation tubes were very black which didn't seem normal. I will post some pictures. Thanks guys


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So how did you go with the comp test?

Quote from: Mick A on March 04, 2017, 09:57:09 PM
So how did you go with the comp test?

I wouldn't even know how to do that! The car needs to be running for that so I'm not sure how that will go


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Google how to do it. Engine just needs to be able to crank.

I am trying to help by giving the right advice to you and helping you diagnose a fault.

It's a process of elimination. You need to eliminate all possible causes.

A comp test should have been done before you even touched the carbies.

Cheers.

Joe
That black gunk definitely would be causing your car problems. Your carbs definitely need a complete strip and thorough clean and then tune and balance as described in an earlier thread PS : make sure there are no air leaks between carby and manifold.  Hopefully this might fix the problem.
bonno

Thanks for your reply Mick. I have just watched a video and the testing looks simple enough.

I just have a few questions

1. My car has an electric fuel pump. Does this need to be disconnected?

2. Do I need to remove the carbs or will air box removed be enough?

3. What compression is normal for the 2lr?

Thanks

Joe


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Quote from: bonno on March 04, 2017, 10:39:15 PM
Joe
That black gunk definitely would be causing your car problems. Your carbs definitely need a complete strip and thorough clean and then tune and balance as described in an earlier thread PS : make sure there are no air leaks between carby and manifold.  Hopefully this might fix the problem.
bonno

Thanks Bonno.

What would be causing the black deposits?

I did a "rebuild" on them recently using a rebuild kit from Thornbury Carbs.

I must have messed it up some how

Joe


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Comp test, you need one of these.
Take plugs out, screw in comp tester into cylinder 1, probably good to pull coil to distributor lead.  Crank engine for 10 sec until pressurised and record measurement.  Repeat on other cylinders, all should be same or close to each other.
In terms of tuning, I am having some issues of my own to figure out too.  Mainly misfire.

Thanks Neil.

Just to confirm - Do I still need to have the throttle all the way down?

Thanks

Joe

Joe
Check the fuel filter for signs of contamination  and or drain/flush  fuel tank.
bonno

Quote from: joestram on March 04, 2017, 11:00:28 PM
Thanks Neil.

Just to confirm - Do I still need to have the throttle all the way down?

Thanks

Joe

Yes, throttle should be fully open when doing compression test, and as advised, pull the main lead on distributor so engine does not fire.

Baz

Quote from: bazzbazz on March 05, 2017, 02:49:52 AM

Quote from: joestram on March 04, 2017, 11:00:28 PM
Thanks Neil.

Just to confirm - Do I still need to have the throttle all the way down?

Thanks

Joe

Yes, throttle should be fully open when doing compression test, and as advised, pull the main lead on distributor so engine does not fire.

Baz

Thanks Baz.

What do I do about the electric fuel pump? Obviously if I have my foot down the car will be pumping petrol into the carb/cylinder.
Will I flood the engine?

Joe


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It will be fine.

It doesn't work that way. Once the floats in the fuel chamber are up they will close the needle & seat valves. Fuel doesn't just pour into the engine. One pump of the throttle is one squirt of fuel into the combustion chamber from the pump jets. It will all be displaced out the exhaust valve as you perform the test.

All comp gauges are different so not all accurate, but what you are looking for is consistent readings from all cylinders. Hopefully you have somewhere around 175-200psi, that would be good from an old motor.

MICK.

Hi  Joe,
That black goo is a worry.  The Dellorto's air supply to the air correctors is unfiltered.  All that gunk may be restricting airflow through the idle and main air correctors.  This will make the carby run rich.  Very dificult to tune. 
Need to clean the idle and main air correctors as a priority.  Next job will be to ascertain how they got that dirty and prevent it from reoccurring. 
I prefer the Dellorto over the Weber, however the lack filtering to the air correctors in the DHLA carby is a pill.

Hi Everyone,

Firstly, I'd like to thank Neil for coming to explain and show me a thing or 2 about maintenance.

Neil was able to connect his compression tester and we found cylinder 1 & 2 had 220 and 3 & 4 had 200.

Neil also checked a few other things out and seems to think the issue might be isolated to the carbs.

When we started the test, fuel started to pour out of cylinder 1 & 2 trumpets so we disconnected the electric fuel pump.

All the spark plugs were black as well.

Thanks again everyone

Joe

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so you have a needl;e and seat issue
when you clean the stack can you tell
me what is the number on the air corrector thats the black end
cheers

Quote from: carlo rossi on March 06, 2017, 10:28:24 AM
so you have a needl;e and seat issue
when you clean the stack can you tell
me what is the number on the air corrector thats the black end
cheers

Hi Carlo,

The number on the air corrector is 210.

Thanks Carlo

Joe


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when you fix the needle and seat I think you are going to need larger mains
you have standard carb settings in a motor that has larger than normal cams
I need to find the specs on a 2229 pace cam
in fact I think someone has thrown on those carbs and took some other off
because its not a match you dont change cams and not jets
we will fix that

Thanks Carlo

for that autodelta cam  spec you will need 60 idles
and 155/158  mains

Thanks again Carlo.

Do I need to change the air correction as well, or will 210 be sufficient?

Thanks

Joe

not at this stage 210 is fine
we may look at a 180/190 later

Awesome - Thanks Carlo.

I've just ordered some 158 main jets, 60 idle jets, new spark plugs and leads.

Thanks again everyone!

I'll let you all know in 2 weeks (hopefully when they arrive) how the car is running!

Joe

 the 55 idles would have given you a real flat spot around 2500rpm
and then running hot and lean
probably should mention as sportiva says in needs 34 mm chokes
check what you have
if not order
ps tried this and it works great

Quote from: sportiva on March 07, 2017, 05:53:34 PM
This link is not Alfa specific it is about DHLA's and is very informative

http://www.s262612653.websitehome.co.uk/DVAndrews/dellorto.htm

Thanks for posting that Sportiva.

That's a really useful write up!!

Looking forward to receiving my new bits to test out all my new knowledge!!

Joe


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sportiva link is great to understand and is a great guide
but it is for a SOHC 2ltr with high lift cam .
so the alfa flows better down low being Twin cam hence the need for
larger idles also NOTE no 2ltr should have less than 34 chokes
Alfa cheated and put 32mm chokes in fact the carbs were straight off a 1750
motor
this is why performance between the 2 motors was marginal.
even their grp1 2 ltr cars (cheated)had 33mm chokes
it still said 32 for the scrutineers

Hi All,

I have just pulled the carbs off the car and realized they are DLHA40F.

For some reason I have been thinking they are 40H.

Not sure if that changes anything?

Also, Carlo has asked me about the choke size.

Is there a way to find the size without pulling them out?

I can't seem to find an inscription.

Thanks

they are really easy to pull out if the carby is off
pull the inner venturi out using three fingers it has a spring clip pressure
and the release the retaining nut on the side for the choke to slide out
or look in you might be able to see it on the bottom

Thanks Carlo. I can't believe I missed it!

I was was looking at the wrong part.

They say 32 on them.

Should I increase them as well?

Thanks

Joe

yes buy 4 X 34mm chokes
it makes a world of difference particularly
with that cam

Quote from: carlo rossi on March 13, 2017, 09:40:27 PM
yes buy 4 X 34mm chokes
it makes a world of difference particularly
with that cam

Thanks Carlo.
Just checked online...expensive little buggers!


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yeh but much cheaper than a new carburettor
Imagine those poor americans
they have to buy a new carby everytime!
they go by CFM very hit miss they have no idea what its doing
some say a 40mm dellorto is equivalent to around 250 cfm( means nothing really)
X 2 means a 2ltr with 500cfm! bigger than a 5.0ltr V8 stock!! so thats 125 cfm each 500cc
now back in the 70s the thing to do to your chev 350 or falcon 5.8 was to big valve the heads flow it and a cam extractors
and then a 750 double pumper Holley sits on top thats 94 cfm for each 720cc piston up from 74cfm
See how well the alfa flows, if the alfa was a 350 cubic inch behemoth it would need 180 cfm for each piston roughly double and this is a basically stock car!! and thats a 1450cfm Holley or what you call a Daytona race car CARB

I have to add thou a little known fact that in 1977 the fastest reasonably priced 2 doors
falcon 5.8 197 km/h  faster than your torana A9x 5.0ltr and  a charger( 4.3 6CYL) at 185kmh and the monaro 308( 5.0 ) at 176kmh
and the Alfetta gtv 194kmh some say it was faster but thats wheels magazine tested

Hi everyone - just an update - I've received my jets, however, can't track down a local rebuild kit.

I know I can buy them online, however, prefer to buy local.

I drove over to thornbury carbs last weekend and they were closed and have been trying to call all weekend and they seem closed as well.

I have tried a few other places from the yellow pages but seems like all those businesses are closed.

Where do others buy carb rebuild kits and gaskets from?

Is carby cleaner able to be shipped by post? I wouldn't have thought so?

Thanks

Joe


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YOu can buy carby cleaner from repco or super cheap auto. Kits might be available from some of the club sponsors or try the spare place in Adelaide if you want to buy local

Thanks for the reply Alfa Pride.

I will be calling them today :)

Give Bruno at Maranello a call, 9386 9650.

what have you got and what are you missing
you wont get the chokes in Australia i believe
dellorto.uk

have to say that auto italia was the perfect run to tune the car
2 jet changes on the way there
on the way back it flew and had a 5th gear drag with a 328 and a 308
level pegged
I think if they went back to 3rd or 4th I would have been a different story
but the moral of the story is a 2lt Nord with 40% more power is not a bad thing

Thanks everyone!

I have just purchased all my outstanding bits from the UK so hopefully they are delivered shortly and I can test it all out!

have the parts arrived?

surely the parts have arrived Joe?
how is it going

Sorry Carlo, I just saw these messages and your pm... the first order of chokes never left the UK so had to wait 30 days before lodging a complaint and then I purchased from a new seller...hopefully they are here in 2 weeks. Everything else has arrived and is ready for installation. Looking forward to bolting it all back together!


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whilst you are waiting take off the front cam cap on the inlet first
(one at atime)so you dont mix them up and check that cams are set to 105 deg
on inlet depending year of manufacture of the cap the degrees could be anywhere from 102 to 114deg
download the deg template from centreline to see what its set at
the exhaust can be at 108-104 the lower the gruntier down low
please note that from front of the engine the inlet for a lower figure goes clockwise (advance)
and the exhaust anticlockwise (retard)

Just finished reading this thread start to finish
...now keen to hear outcome!  We all started learning this way so keep it up. 

One thing I have seen in recent times is chokes with a poor radius on the front.  Presumably some inferior copy.  The fellow spent a few dyno sessions trying to work out why his high performance engine would not rev.  Changed echausts...tune..etc only to find a new set of chokes transformed it.  Closer inspection revealed a slightly shorter taper after initial rad.  Only thing I could think was that this was perhaps producing some flow separation past a certain flow point.

One other note would be that inlet trumpets length also has a material impact on power but you are a way off woring about that.  I note yours are quite short so more akin to top end rather than bottom end.

Hi everyone, I think I'm finally going to have some time this weekend. How do I take the chokes out? I can't figure it out!
All my parts have arrived now so I'm just going to reassemble the carbs with the new parts and hope for the best!!


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Hi Joe
Suggest that a possible youtube link may help in disassembly/assembly of your carburetors. Not much available on the net on the DHLA Dellortos except a "how to" guide, however 2 good Youtube videos on the DCOE webers maybe worth a look in particular part 2 @ 4 minute mark on removal of chokes.
Dellorto  How to guide
https://elthamracing.wordpress.com/how-to-rebuild-dellorto-sidedrafts/ 
Weber
Part 1
https://youtu.be/4dxO1TPWhlE
Part 2
https://youtu.be/9ta3cBkXXIA
Hope this helps
bonno

Hi Joe,
The choke or main venturi (depending on which school you went to) is held in place by the auxiliary venturi.  The auxiliary venturi has to come out first.  On the side of each barrel is a lock nutted grub screw - pretty well in line with the delivery nozzle.  A little bit upstream of the mid way point along the barrel  This grub screw is about 5mm in diameter and features a flat blade screwdriver slot.  The locknut must be loosend first.  Then the grub screw can be removed with a flat blade driver.  The grub screw features a pointed end.  This point engages a dimple machined into the outer wall of the auxiliary venturi.  Once the pointed end of the screw is clear of the dimple the auxiliary venturi can be pulled out.  Then the main venturi or choke can be pulled out with you finger.

When reversing the process DO NOT screw in the grub screw tightly.  It only needs to be very lightly nipped up.  The lock nut should then be done up firmly while preventing the grub screw from going in any deeper. A little dab of low strength loctite should be applied to the underneath of the locknut before tightening. 

Hi Bonno and Colin, thanks for the info!

My kids decided to have a lunchtime sleep today so I ducked outside to have a bit of a tinker.

I was able to locate the screw and Nut and removed them, however, the damn things still wouldn't come out!

I have posted a picture.

Am I missing anything?

I didn't want to apply too much force/pressure to avoid damage but wanted to double check I wasn't missing a screw that needed to be loosened.

Thanks again everyone!

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Hi Joe,
Try repeated applications of a good penetrant for a couple of days.  Leave the carbies standing upright as in your second photo.  Squirt some penetrant into the grub screw holes as well. 
Grab the wifes hairdryer and heat up from the outside just one barrel at a time.  We want the carby body to expand away from the auxiliary venturi.  If you apply heat for too long the auxiliary venturi will expand as much as the carby body.  We dont want that. 
The auxiliary venturi is a very close tolerance fit in the bore of the carby body.  I hope moisture hasn't got in there and started oxidation!

Sounds like Colin has had to do this several times in the past. I suggest that the possible cause for difficulty, is the tendency to over tighten the lock screw holding auxiliary venturi (refer to Part 2 video).

I don't think its possible to install the Dellorto auxiliary venturies arse about.  Locating tabs on the venturies are provided at about 1:30 on the l.h.s barrel and 10:30 on the r.h.s barrel.   These tabs locate in recesses provided in the carby air box / plenum mounting flange. 

I however don't recall these tabs being on every Dellorto I've played with.  if you put the auxiliary venturi in arse about and looked into the locating grub screw hole you wouldn't see the locating dimple. 

The Dellorto DHLA and Weber DCOE are both works of art and certainly not for the faint hearted or ham fisted!!

Thanks again for the replies Colin and Bonno.

Colin - what type of penetrant do you recommend? Will carby cleaner suffice or wd40?

I hope they aren't oxidised either!!

Joe


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As a Guru showed me, INOX is really really good.  Get some Joe.

Thanks Neil!!


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Hi Joe,

I've heard good reports about INOX, however never used it myself.  I usually use Penetrene (from Blackwoods) or a 50:50 cocktail of Acetone (from Bunnings) and auto transmission fluid / power steering fluid.  Its curious that Penetrene is the same colour, smell and consistency as the above brew!

CRC carby cleaner is great stuff but very aggressive.  Its usually my weapon of choice if brake cleaner isn't up to the job.  Both are great for cleaning but not as penetrants - they evaporate too quickly.

You may however need to spray carby cleaner onto the inner surface of the auxiliary venturi to cool / shrink it while heating / expanding the carby body with a hair dryer.  Don't let the carby cleaner come into contact with the rubber gaskets!

sorry guys been in italy
and i have to admit i havent been looking at my computer
but it seems you are in good hands
as they said clean clean and then clean
but it looks like it had a service of sorts
A truely amazing piece of work the dellorto /weber and solex
not to
upset anyone
so I recommend to  the start with  34mm chokes
158 ( 155 -160) mains 210 air corrector  f8 emulsion
and if you can accelerator jet 40 not overly important this one

Quote from: carlo rossi on July 11, 2017, 07:06:20 PM
sorry guys been in italy
and i have to admit i havent been looking at my computer
but it seems you are in good hands
as they said clean clean and then clean
but it looks like it had a service of sorts
A truely amazing piece of work the dellorto /weber and solex
not to
upset anyone
so I recommend to  the start with  34mm chokes
158 ( 155 -160) mains 210 air corrector  f8 emulsion
and if you can accelerator jet 40 not overly important this one

Will the Weber F8 emulsion tube actually link between a Dellorto air corrector and main jet and work?

no what I meant to say is 7772.8
but as the original sequence of 7772 is for all generally just the last number is quoted
sorry been in europe for last 5 weeks
hows it going Joe

well Joe its been 1, 1/2 years of tuning have you finished the tune up

Hi Everyone,

Sorry it has been a while since my last post.

I had some personal matters that took priority, however, now have time to get this thing started again.

The Chokes came though, however, I was never able to get the original ones out.

I replaced all the jets and tried to give the carbs a quick clean and replaced the O rings etc.

I have started to bolt the carbs back on and am finding that I have lost a few screws and nuts so I am on the hunt for these.

In the mean time, I have just moved house and I need to arrange the car to be moved so if anyone has a trailer please let me know - happy to pay for your time :)

I'll keep everyone posted on the tune

Joe

Happy New Year Joe
I am pretty sure a local fellow Alfisti  will be able to help with moving the Alfetta to the new location. If not, try your local tilt trailer guy who would be able to provide this service at a reasonable fee. With regards to the carburettors, the loss of some parts and the inability to remove chokes, may I suggest you get onto carby  specialist in Melbourne who will be able to service them off the vehicle (you remove and re-install then adjust). Provide details of the cams fitted to the vehicle as this will assist in jetting and choking (all covered in this thread so a copy of the post would assist).
cheers
bonno 

joe come to newcastle and we will setup the carbs for you  JUst the carbs dont put them on
im off until the 15th
between sportiva and myself we will get them sorted
or iof in melbourne post the beasts

Quote from: sportiva on January 01, 2018, 03:43:38 PM
I have parts for dellorto's tell me what you need or post a photo and I will check. Free if you pay the postage

Wow - that is very generous of you!!

I need the springs that help return the butterflies on each carb as my butterflies as closing very slowly.

I need a screw that matches up the throttle (this was lost under the decking) as well as 2 nuts that help attach the carbs to the block (again - under the decking)!

Let me know if you have these as well as any charges.

Thanks Sportiva