jetting my IDAs

[67worshipper]

ive just installed new plugs and done the one blast up the road to get a base setting for my plugs, and theyre black.its def. spluttering at sort of light throttle or cruising speed but if you put your foot down it clears and your off.if you give it the beans then theres a big plume of smoke, so shes rich for sure.gonna check the timing but im looking for base figures on the IDAs.the motor is a 2276 fk8 37.5 and 42 mm valves 8.5to1 cr 48idas on tall manifolds. the venturi size is 37.would like to get it roughly right before rolling road and also to learn abit about setting them up.thanks in advance barry.

[Jim Ratto]

ive just installed new plugs and done the one blast up the road to get a base setting for my plugs, and theyre black.its def. spluttering at sort of light throttle or cruising speed but if you put your foot down it clears and your off.if you give it the beans then theres a big plume of smoke, so shes rich for sure.gonna check the timing but im looking for base figures on the IDAs.the motor is a 2276 fk8 37.5 and 42 mm valves 8.5to1 cr 48idas on tall manifolds. the venturi size is 37.would like to get it roughly right before rolling road and also to learn abit about setting them up.thanks in advance barry.

set timing 30BTDC total

I'd guess @ 155 main, 60F10/120air idle, 180 air corrector and F2 or F7 or F11 tubes should run good to start. Float level is CRITICAL!!! Mixture screws should give a nice hard idle 3/4 out from bottom.... less than that you need leaner idle jet, more than that you need richer idle jet.

Sounds like your problem is main and idle jet are both trying to overcompensate in lower rpm/mid for each other.

[67worshipper]

thanks jim. is there an xray diagram of the IDA carb on any forums so i can see what im looking at?

[Torgeir Schibevaag]

http://www.carburetion.com/diags/48IDAdiaginfo.asp

Here`s one

[67worshipper]

ive just installed new plugs and done the one blast up the road to get a base setting for my plugs, and theyre black.its def. spluttering at sort of light throttle or cruising speed but if you put your foot down it clears and your off.if you give it the beans then theres a big plume of smoke, so shes rich for sure.gonna check the timing but im looking for base figures on the IDAs.the motor is a 2276 fk8 37.5 and 42 mm valves 8.5to1 cr 48idas on tall manifolds. the venturi size is 37.would like to get it roughly right before rolling road and also to learn abit about setting them up.thanks in advance barry.

set timing 30BTDC total

I'd guess @ 155 main, 60F10/120air idle, 180 air corrector and F2 or F7 or F11 tubes should run good to start. Float level is CRITICAL!!! Mixture screws should give a nice hard idle 3/4 out from bottom.... less than that you need leaner idle jet, more than that you need richer idle jet. when you say mixture screw 3/4 out from the bottom is that 3 quarters of a turn or 3 to 4 turns out ?

Sounds like your problem is main and idle jet are both trying to overcompensate in lower rpm/mid for each other.

[Jim Ratto]

three quarters of a turn from (lightly) seated.

[Harry/FDK]

Thanks, i'm gonna need this too!

Barry, pls keep us posted !

[dirk zeyen]

hi barry,

it could be the needle valve, if there is a sealing problem it's raining fuel in your carbs...
start your electric fuelpump without runing your engine, look inside the carbs if they are dry.

dirk zeyen

[67worshipper]

Thanks, i'm gonna need this too!

Barry, pls keep us posted !

going to strip carbs at the weekend so will post as soon as i know what ive got inside.

[JS]

http://www.carburetion.com/diags/48IDAdiaginfo.asp

Here`s one

Ah, my Windows background for quite some time. Know your carbs! 

[67worshipper]

very informative diagrams

[67worshipper]

right ive taken the jet holders out and ive got the following F11 emulsion tubes,165 main jet,180 air corrector.60F10 idle and 120 on the jet holder.ive not looked at the mixture screws yet but looking at what jim said its pretty much bang on apart from the 165 main instead of the 155. any questions?

[Jim Ratto]

right ive taken the jet holders out and ive got the following F11 emulsion tubes,165 main jet,180 air corrector.60F10 idle and 120 on the jet holder.ive not looked at the mixture screws yet but looking at what jim said its pretty much bang on apart from the 165 main instead of the 155. any questions?

Your problem, upon first impression is that your main jet is too large and it is trying to come into circuit too soon, causing your flubbering. It happens when guys run wrong idle air jet too (holder).
Try a 150 or 155
Make sure fuel press is no higher than 3.5psi and floats are per Weber specifications

[67worshipper]

ive just checked the mixture screws and they were wound out alot.I then wound them right the way in being careful that they only just touched the base.I then wound them out 3/4 of a turn and started the engine.It didnt like it a great deal so switched off and wound the screws out another 1/2 a turn each.Once the engine had warmed abit i took it for a drive up the block.What a difference! theres still abit of a fluff in the middle but nowhere near as bad and it can be driven without being on/off the throttle.I think now i will try 150 or 155 main so the mixture screws can be turned back in a little.Rule of the thumb is venturi size X 4 so 37 X 4 is 148 probably 150 then? on the right track?

[67worshipper]

pulled the car out today and checked the timing.that was out by 8 degrees so adjusted to 30 max BTDC at 3000 rpm +. running nice and strong now especially at idle and revs strong without plumes of black smoke upon revving.going to change the main jets for 150s or 155s so i can wind in the mixture screws back in a little.should i buy both lots or just go for one set?

[Martin Greaves]

What you could do is buy a jet drill and gauge kit and then look out on ebay for jets. There is always 2nd hand packs of smaller size jets on there then you just ream them out to the size you want.

[dangerous]

This has already been mentioned
but YOU MUST check your fuel pressure and float level
BEFORE you start playing with jetting.

Pressure that is too high will effect the fuel level even if the float is set correctly.

Some people like to run between 1.5 and 2 psi.

[67worshipper]

i will check this as well dangerous.going to fit a pressure gauge inline by the regulator.can the pressure be checked without a gauge? whats the procedure for the float level check?

[The Ideaman]

http://www.piercemanifolds.com/Float_Level_2.htm

This should help some.  Berg sells a tool for this.  http://www.geneberg.com/product_info.php?products_id=973

[Jim Ratto]

That tool set from Bergs is somewhat useful, but not 100%.
You can set the floats without it too. Just need a piece of small diam. vac hose (silicone works nicely) and a vernier caliper.
I actually prefer using the hose and calipers over the Berg tools. Much less cumbersome.

Check any old Haynes Weber repair manual, it has all the specs and the easiest method I know of. 

[67worshipper]

right then ive replaced the 165 mains for 155s well ive tried 150s as well and they feel pretty good too.the problem ive got is at steady cruising.in the transition period it feels fine but at steady 50 to 60 mphish it feels like its holding back.sort of on offish if that makes sense.any ideas? ive not synced the carbs yet will this need doing and also in the weber manual ive read about the air by-pass screws but i dont know if that applys to idas or idfs any ideas?

[Jim Ratto]

right then ive replaced the 165 mains for 155s well ive tried 150s as well and they feel pretty good too.the problem ive got is at steady cruising.in the transition period it feels fine but at steady 50 to 60 mphish it feels like its holding back.sort of on offish if that makes sense.any ideas? ive not synced the carbs yet will this need doing and also in the weber manual ive read about the air by-pass screws but i dont know if that applys to idas or idfs any ideas?

"holding back" could be a fuel delivery issue, or floats set incorrectly.

IDAs don't have air bypass screws. Idle speed at carb arm and mixtures centered with each butterfly, opposite of fuel inlet.

[Jim Ratto]

right then ive replaced the 165 mains for 155s well ive tried 150s as well and they feel pretty good too.the problem ive got is at steady cruising.in the transition period it feels fine but at steady 50 to 60 mphish it feels like its holding back.sort of on offish if that makes sense.any ideas? ive not synced the carbs yet will this need doing and also in the weber manual ive read about the air by-pass screws but i dont know if that applys to idas or idfs any ideas?

PS.... the carbs being synchronized is one of the first steps, absolutely a MUST. Not only should they pull same volume of air at idle, but open at same time, and get to full throttle at same exact time. Get this worked out before you change anything else on carbs, i.e. jets, mixture settings, etc.
Just for good measure follow these steps

1. make sure heads are torqued
2. make sure valve lash is set (0.00" with chromoly p/r, .005" with aluminum, both COLD)
3. make sure fresh plugs and contact points if applicable
4. make sure contact point gap is set .016"
5. make sure total advance is set to what your engine likes (30BTDC you mentioned)
6. make sure intakes are sealed at heads and carburetor and make sure air horns are sealed if applicable
7. make sure fuel filter is clean and fuel pressure is set correctly
8. make sure float level is exact (see Haynes manual)
9. warm engine up to at least 150F oil temp
10. make sure carbs pull same volume of air at idle speed of 900-1100rpm
11. mixtures screws should be 3/4 turn out from seated for strong, smooth idle on all cylinders
12. check linkage for rate of opening, both carbs should snap open exactly same time and close completely
13. check carb pulling same amount of air still after closing? If not find out why
14. check carbs for pulling same volume @ 2500rpm? If not check why
15. now you can make jetting decisions.

[67worshipper]

thanks jim.going to get it set up very soon and i will let everyone know the outcome.

[Jim Ratto]

thanks jim.going to get it set up very soon and i will let everyone know the outcome.

  go get 'em!

[Harry/FDK]

Barry, any progress ?

[OC1967vw]

That tool set from Bergs is somewhat useful, but not 100%.
You can set the floats without it too. Just need a piece of small diam. vac hose (silicone works nicely) and a vernier caliper.
I actually prefer using the hose and calipers over the Berg tools. Much less cumbersome.

Check any old Haynes Weber repair manual, it has all the specs and the easiest method I know of. 

Berg tool is a direct copy of the original Weber tool for adjusting float levels in 48IDAs. I have both