Carb throat balance when tuning now a rebuild saga !, those with Zenith carbs can learn from my bad fortune ? Options

[porschetub]

Doing a tune on my Zeniths ,cant find an exact rpm range and done a ton of research ;
Bruce Anderson mentioned 1800 in his book,
Factory says 1000 in the gary.suggate site factory manual,
Haynes manual tells us 1000.
So far I have tuned throats @ idle ,1000rpm ,1400 and 1800 on hand throttle and strangely I get the same balance any way ?.
Now thinking its not an issue but would appreciate feedback from 6yl guys with carbs,TIA,cheers

[IronHillRestorations]

You tune the mixture at 1800. Idle speed should be 950 or so, but some engines will idle better a little higher.

If you are asking about the number on a syncrometer, that’s an arbitrary number, you just want all barrels to have the same number, there’s no specific value you should get.

[rhodyguy]

Like Perry said. Turning the idle up settles the needle down and delivers a constant reading.

[nditiz1]

It's not an issue to tune them at idle. You want to make sure they are close. If 1 is bouncing between 5.25 and 5.75 your middle ground is 5.5 make sure the other 6 are around there too. If one is bouncing around 5.3 and 5.8, that's close enough.

The main think is getting the linkage set once they are all relatively balanced. Checking at different RPMs to ensure both open and close as one through the range. Also, you want to make sure you are getting to WOT. So many carbs have be tuned without ever checking and people wonder why their car is under powered.

[porschetub]

Thanks for all the replies and sorry for the delay, I can get them very close but critical to have idle screws even for normal idle and upping engine speed for balancing .
Spent a lot of time dialing the length of the drop links and have replaced many worn out ball cups ,strangely nearly all RH thread ones were worn out ? .
When I first rebuilt these before I fitted the 2.2T motor I noticed both side cam rollers had seized @ some stage and there were area's on the rollers that had flat spotted and there was a lot of wear on the throttle cams which I have since replaced.
Both the carbs were in very poor condition,I had no history when I bought this engine but the seller on behalf of the owner did say that "it ran like shit" this turned out to be a blessing as I knocked the price down and it turned out just to be the carbs and I had bought a strong engine.
Working on more carb repairs as our crap fuel has buggered several parts just waiting to hear back from alfa 1750 on ebay,will update ,cheers.

[Retroracer]

Thanks for all the replies and sorry for the delay, I can get them very close but critical to have idle screws even for normal idle and upping engine speed for balancing .
Spent a lot of time dialing the length of the drop links and have replaced many worn out ball cups ,strangely nearly all RH thread ones were worn out ? .
When I first rebuilt these before I fitted the 2.2T motor I noticed both side cam rollers had seized @ some stage and there were area's on the rollers that had flat spotted and there was a lot of wear on the throttle cams which I have since replaced.
Both the carbs were in very poor condition,I had no history when I bought this engine but the seller on behalf of the owner did say that "it ran like shit" this turned out to be a blessing as I knocked the price down and it turned out just to be the carbs and I had bought a strong engine.
Working on more carb repairs as our crap fuel has buggered several parts just waiting to hear back from alfa 1750 on ebay,will update ,cheers.

I usually increase the idle to 1200rpm or so for tuning, as it smooths out the pulsing of the readout. I have the overrun correction circuit disabled, as I suspect most do. As you point out, once achieved, the balance is pretty consistent across a range of RPM (which is of course the goal!)

The accel pump cam rollers on my TIN40s (when I got them) had their bearings crumbling; so they would have flat spotted if I'd used them as is. Getting replacements seemed impossible at the time, so I modified some from McMaster-Carr ones to fit, which was tedious. If Alfa1750 has these available that would be good to know for sure.

My carbs have been gone through recently - twice - as I foolishly let them stand over winter without flushing or draining them; and the the Ethanol based fuel wreaked havoc on the entire fuel system! Weeks later: new stainless fuel lines, new fuel pump, new fuel regulator - which leaked once plumbed in, so waiting on a replacement from PMB. The car's summer was spent up on jack stands; annoying...

On a positive note, to help alleviate future embuggerance, a couple of local places here in Oregon, USA do sell Ethanol-free gasoline. That'll be the main fuel choice once I get everything running again.

- Tony

[porschetub]

Thanks for the reply Tony,my carbs are euro spec so no overun system which appears to be a blessing as this system is rather hard to dial in if fitted and to delete requires other work.
I repaired my rollers and they work a lot better ,alfa1750 now sells these but as whole assemblies but not when I was sorting mine .
I made the same mistake as you did with fuel so I will run my carbs out of fuel then drain whats left in the bowls via the main jets,strange thing is the RH side carb has the degraded parts from the old fuel other side not so ,all my pump discharge noozles orings are now leaking and the mixture screw ones the same,they just fell apart when I screwed them out.
Fuel hose to each carb were in " soon to fail mode " 2 quality brands used 1 was hard and starting to crack and the other was like mush ,all rubber hoses changed for Gates 50 psi carb hose.
Looks like I will order 2 complete base rebuilt kits and take an offer to use a mates ultrasonic cleaner...I don't want to be doing this again as its a right PITA to get the carbs on and off.
Thanks for the input from all keep it up,cheers.

[porschetub]

Thanks for the reply Tony,my carbs are euro spec so no overun system which appears to be a blessing as this system is rather hard to dial in if fitted and to delete requires other work.
I repaired my rollers and they work a lot better ,alfa1750 now sells these but as whole assemblies but not when I was sorting mine .
I made the same mistake as you did with fuel so I will run my carbs out of fuel then drain whats left in the bowls via the main jets,strange thing is the RH side carb has the degraded parts from the old fuel other side not so ,all my pump discharge noozles orings are now leaking and the mixture screw ones the same,they just fell apart when I screwed them out.
Fuel hose to each carb were in " soon to fail mode " 2 quality brands used 1 was hard and starting to crack and the other was like mush ,all rubber hoses changed for Gates 50 psi carb hose.
Looks like I will order 2 complete base rebuilt kits and take an offer to use a mates ultrasonic cleaner...I don't want to be doing this again as its a right PITA to get the carbs on and off.
Thanks for the input from all keep it up,cheers.

Checked all the float levels with my PMO gauge (which I finally found ) and all levels exactly even in the middle of the two lower marks as per Zenith setting so happy with that but knew they were ok but good to check.
Can't run the engine anymore as have to many leaks from bad seals ,RH is now leaking fuel and fouling plugs due to leaking pump noozles.
Kinda pissed me of because I had it running real nice for a short time until this,any way when my kits arrive it will be fine,cheers.

[porschetub]

Currently working in the engine bay doing a tidy up of all the things I didn't do because I was in a hurry to get the car on the road after conversion , good time to do this until my carb kits arrive besides.
Didn't go with alfa1750 this time as service not what it used to be ,pissed me off really as I have spent a lot of money with them in the past , I could have ordered direct from them in Italy but VAT killed the price.
After much researching suppliers I came up with oldtimer07110 out of Germany on ebay and found they had a better range of kits from basic reseal to total rebuild @ much sharper prices for parts and made in Italy anyway.
Alfa1750 came in @ $205nzd shipped and oldtimer came in @ $142 for a lesser kit so it wasn't hard to choose a supplier (IMG:style_emoticons/default/dry.gif) .
Kits came in quickly from Germany and good quality so have been stripping LH carb and now close to getting it cleaned ,its a long involved job as many of the gallery plugs and bowl check valves were very tight ,somewhat dreading the RH carb as it had minor water damage (not from the fuel tank ) but a little moisture causes havoc with alloy and brass parts .

Due to start RH carb soon but plan to run the fuel tank dry and pump out all the varnished fuel before that ,other than than very little rubbish in the fuel bowls I think due to a second filter in the enginebay ? ,will report further and make this a " vergasser fixen ' thread (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/biggrin.gif) as it may help others,cheers.

[rgalla9146]

Be certain your timing is correct, advance is working freely through full range and
returns to idle reliably.

[porschetub]

Be certain your timing is correct, advance is working freely through full range and
returns to idle reliably.

Thanks for the comment ,had just done that before the RH carb started leaking ,timing was out a small amount (retarded) @ 6000 rpm ,adjusted the idle speed as necessary .
All this was made easier after having my tacho repaired with new driver board more accurate and no more erratic needle movement which it had before failing completely some time back.

[porschetub]

Be certain your timing is correct, advance is working freely through full range and
returns to idle reliably.

Thanks for the comment ,had just done that before the RH carb started leaking ,timing was out a small amount (retarded) @ 6000 rpm ,adjusted the idle speed as necessary .
All this was made easier after having my tacho repaired with new driver board more accurate and no more erratic needle movement which it had before failing completely some time back.

Got the LH carb fully stripped ,and have stripped the RH side down till I can remove it from the inlet manifold then full strip down.
Pumped out the fuel from tank using fuel pump ,blocked LH feed and pumped out using RH side carb delivery ,was surprised @ what came out, first litre or so was yellow stale crap (smell ) and the next lot was clean fuel with a light red tinge to it as it should be.
No real mystery here as the car has been sitting so bad fuel settles @ the bottom of the tank ,good news is no water,rust or other crap so happy ,fuel pipe banjo filters were clean so my forward ( @ pump ) and enginebay filters are doing there job.
Striped back paint on air cleaner base ,epoxy high zinc primer baked on and enamel paint for durability.

[Dion]

Well done Dean, will be like new! Glad you found another vendor. I may need a few new parts for my Zeniths they’re boxed up currently. I need to prep for winter storage soon. Will run tank dry like you did. Maybe i should run another filter pre pump (IMG:style_emoticons/default/idea.gif) .
Keep at it mate!

[porschetub]

Well done Dean, will be like new! Glad you found another vendor. I may need a few new parts for my Zeniths they’re boxed up currently. I need to prep for winter storage soon. Will run tank dry like you did. Maybe i should run another filter pre pump (IMG:style_emoticons/default/idea.gif) .
Keep at it mate!

Thanks mate ,dropped carb parts off today and should be ready in a day or so then the long assembly job begins .
Pleased to know this guy as he has a great rep as a tuner of Porsche 911's and has owned 2 short wheelbase cars in the past including an "S'' , he is a clever guy and real easy to talk to with a wealth of knowledge on anything with 2 wheels also.
Yes Dion I think a secondary fitter has worked for me and certainly can't cause any problems besides I believe others have done this to good result .
Some lessons learnt here and will change how things are done ,TBO don't want to do this again (IMG:style_emoticons/default/sad.gif) ,cheers.

[porschetub]

Well done Dean, will be like new! Glad you found another vendor. I may need a few new parts for my Zeniths they’re boxed up currently. I need to prep for winter storage soon. Will run tank dry like you did. Maybe i should run another filter pre pump (IMG:style_emoticons/default/idea.gif) .
Keep at it mate!

Thanks mate ,dropped carb parts off today and should be ready in a day or so then the long assembly job begins .
Pleased to know this guy as he has a great rep as a tuner of Porsche 911's and has owned 2 short wheelbase cars in the past including an "S'' , he is a clever guy and real easy to talk to with a wealth of knowledge on anything with 2 wheels also.
Yes Dion I think a secondary fitter has worked for me and certainly can't cause any problems besides I believe others have done this to good result .
Some lessons learnt here and will change how things are done ,TBO don't want to do this again (IMG:style_emoticons/default/sad.gif) ,cheers.

Some research and a few small jobs till my clean parts come in .
Checked on the fuel we get in my country and the only fuel I continue to run is our regular low octane fuel as it only has 10% ethanol and don't expect an issue with my engine as the 2.2T is low compression @ 8.6 to 1 , the shelf life would be better than the higher grade fuel has more ethanol to boost the octane ,but all suppliers indicate 6 months shelf life max .
My fuel was older and the addition of fresh fuel never mixed due to not driving it .
Been sorting my last bad ball cup joint on the rear bellcrank to grossbar lever ,jeez remember why I didn't replace it back then, cup was seized on the ball so had cut it off ,not easy (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif) ,but now sorted .
Carb parts not ready yet as the main bodies found to be much dirtier internally than first thought...worth the wait for a second bath IMO.

[porschetub]

Well appears my carb rebuild is a slippery slope with all the (IMG:style_emoticons/default/stromberg.gif) rapidly sliding down to me (IMG:style_emoticons/default/headbang.gif) .
Carb clean wasn't what I was told and due to the solvent used I got a fair amount of surface corrosion on metal parts so suspect it had a strong salt content !!!.
This result has caused a reclean of most parts due to scale formation, pissed off factor is high in the scale which I don't need.
Then just to add further drama one fuel pump noozle was leaking in the carb body after doing pump test, pulled it and found a hairline crack above the groove for the sealing ring
not able to repair !!.
Really hope my WTB gets a response as not sure where to head then as a bit screwed @ the moment (IMG:style_emoticons/default/sad.gif) .
Cheers.

[porschetub]

Well appears my carb rebuild is a slippery slope with all the (IMG:style_emoticons/default/stromberg.gif) rapidly sliding down to me (IMG:style_emoticons/default/headbang.gif) .
Carb clean wasn't what I was told and due to the solvent used I got a fair amount of surface corrosion on metal parts so suspect it had a strong salt content !!!.
This result has caused a reclean of most parts due to scale formation, pissed off factor is high in the scale which I don't need.
Then just to add further drama one fuel pump noozle was leaking in the carb body after doing pump test, pulled it and found a hairline crack above the groove for the sealing ring
not able to repair !! , another PO legacy (IMG:style_emoticons/default/chair.gif) .
Really hope my WTB gets a response as not sure where to head then as a bit screwed @ the moment (IMG:style_emoticons/default/sad.gif) .
Cheers.

Lh side carb now done and all settings checked , reset pump delivery as was out a touch also found one cam roller adjuster was bent ? ,can't imagine how as it was hard to straighten , fuel delivery checked and within spec .
Same on Rh carb but a bit more to sort , have repaired pump discharge noozle and we have even leak free fuel supply now so really happy,checked tip in throttle and found one butterfly not equal to others, my fault as I replaced damaged spindle and coupler on the original rebuild ,made adjustment and all transition ports now lined up.

Cheers.

[porschetub]

Both carbs back on after checking for delivery with full fuel bowls ,hoping the weather holds and I can put some fuel in and check for leaks under system pressure .
Did some checks on the old fuel and found no water content ,so it is now lawn mower fuel
cause the B&S motor not too fussed on octane remaining (IMG:style_emoticons/default/biggrin.gif) ,otherwise I would have been worried where the water came from but have confirmed source as suspected.
Prime carbs with pump and no leaks tried to start and only firing on a few plugs , pull the Bosch ones and find 3 dead ,replaced with new NGK's and started first cranks of starter, high idle but found bellcrank rod too short so pull that off for the mean while .
Will recheck timing as I screwed with that (IMG:style_emoticons/default/headbang.gif) (IMG:style_emoticons/default/headbang.gif) and balance idle and throats on them tomorrow ,early indications are good @ this stage even with basic timing but no point in going further until that is spot on .
Cheers.

[porschetub]

No luck today ,used to tune these carbs easily but not in this case anymore ,no response from tip in throttle ( idle ) or air bleeds so can't get the timing spot on ,timing isn't the issue but leaking mixture screws are, most I removed had air past leaking the 'o 'rings so OD is too small.
The air bleed screws weren't working as the idle screws were already doing that in spades (IMG:style_emoticons/default/sad.gif) , have more "o"rings that were in the kit perhaps they are the right ones so may have fitted the wrong ones but being so small they are almost impossible to measure them or compare with the old ones as they were toast .
These are the worst to fit due to how they go on ,you need to be super careful as they pass on to the mounting thread then into a recess then into the correct groove ,they can't be too large otherwise the spring won't go on.
Will update as I hopefully move forward but after some measurement not 100% sure this will sort it ? my gut feeling on my vacuum loss is it maybe something else any suggestions would be a huge help , TIA and (IMG:style_emoticons/default/beer.gif) .

[porschetub]

No luck today ,used to tune these carbs easily but not in this case anymore ,no response from tip in throttle ( idle ) or air bleeds so can't get the timing spot on ,timing isn't the issue but leaking mixture screws are, most I removed had air past leaking the 'o 'rings so OD is too small.
The air bleed screws weren't working as the idle screws were already doing that in spades (IMG:style_emoticons/default/sad.gif) , have more "o"rings that were in the kit perhaps they are the right ones so may have fitted the wrong ones but being so small they are almost impossible to measure them or compare with the old ones as they were toast .
These are the worst to fit due to how they go on ,you need to be super careful as they pass on to the mounting thread then into a recess then into the correct groove ,they can't be too large otherwise the spring won't go on.
Will update as I hopefully move forward but after some measurement not 100% sure this will sort it ? my gut feeling on my vacuum loss is it maybe something else any suggestions would be a huge help , TIA and (IMG:style_emoticons/default/beer.gif) .