48 IDA transition jetting suggestions

[stealth67vw]

So my 67 bug has been returned to semi daily driver status and I have a lean transition stumble between 1800-2800 rpm. Specs are 78 x 94 2165cc, 5.352" Eagle H-beams, Heads Up ported 42 x 37.5 044s with a large wedge/d type port, Engle FK-45 with CB 1.4s, Berg 1 3/4" merged heater box with A1 2 1/2" Renn Kafer muffler, 9.4:1 CR, MSD 6AL with 010 distributor, Pertronix module and NGK D7EA plugs gapped at .045. The carbs are new Spanish IDAs with 40mm vents, 160 mains, 190 airs, 55 F10 idles with 120 holders, F2 emulsion tubes. 3rd progression hole has been drilled, float bowls and fuel inlets opened up and fuel pressure from my Mallory Comp 70 4070LP pump is 4psi. Engine idles nicely at 800-900 rpm without loading up.

The stumble was less noticeable with 60 idles but was pig rich, you could smell it was rich, sitting and idling. AFR was around 11:1 using my AEM UEGO wideband gauge. With 55 idles the AFR is 12.0-12.3:1. When it transitions into the stumble the AFRs go lean past 17:1 until it gets thru it and holds steady at 13.2-13.4:1 to 7,000 plus. If I stomp on at every stoplight I don't even notice the stumble, but I can't cruise around WOT all the time for legal reasons (LOL) and it smacks the 7400 rev limiter fairly quick.

I've read in the past of people changing out the idle jet holders for 100, 110 or 115s. Alfa1750 on Ebay has them in increments of 5 from 40-200. What would you IDA experts suggest?

http://www.ebay.com/itm/290658737433?_trksid=p5197.c0.m619

[Dano382]

I just switched idle holders from a 120 to 100 and it pulls longer on the idle jet and doesn't lean out on the transition like it did before. It made a huge difference. Try a 110 and a 100 and see what it likes. Before, it didn't matter what size idle jet I had, it would lean out fast right before transition and have a slight stumble.       

[John Palmer]

You give all kinds of information, but fail to mention what the initial, and total timing are set at?  You need "at least" 10 degrees of initial advance, even 12 degrees would be OK as long as you do not exceed 31-32 degrees total mechanical advance.  Yes, retarded timing will cause a "off idle" stumble.

[stealth67vw]

30 degrees total, 10 degrees at 900rpm idle. I'm also using Chevron 92 octane with no ethanol (Yep, you can get that here in Oregon).

A couple people have suggested going from the 190 airs to 210s or 220s and bumping the mains up to 165s-170s to get the mains to come in earlier.

[John Palmer]

30 degrees total, 10 degrees at 900rpm idle. I'm also using Chevron 92 octane with no ethanol (Yep, you can get that here in Oregon).

A couple people have suggested going from the 190 airs to 210s or 220s and bumping the mains up to 165s-170s to get the mains to come in earlier.

I hesitate to try and tune your engine on the internet, but he's some ideas.  I'm assuming we are talking sea level?

I like to try the easy things first, they are quick, and cheap.  Crank some more timing into it.  Try a couple of more degrees of timing, up it to 12 degrees initial, and 32 total is not that much.  It will either "get better" off idle, or not change anything.

It's been more than 10 years ago, but we never got our IDA's (with a 44mm venturi in a 2110cc motor) to run on anything smaller than a 60 idle jet.  On 55's it would just pop and sputter just "off idle", remember the idle circuit is still working as the main circuit comes in for midrange.  

We run 60 F10 idles, 120 idle airs.  

Your 160 mains also "seem to me" to be really small, a 175 to 180 main is more in the middle.  

We run 185 to 195 mains, with a 200 air jet, and F11 tubes at sea level (in a 2386cc motor).

I don't know how you could bend a small D7EA plug open to .045" gap, with out the ground electrode being bent open like a "V"?  Opening the plug that wide does nothing.

How much do those "sock covers" richen it up?  Have you tried it without?

Good luck, sometimes the little thing are the most frustrating to find.  

[stealth67vw]

This so far has just been my baseline jetting, I only have about 50 miles on the engine so far. The plug gap is what MSD suggests for my 9.4:1 compression and I'm at 1000 feet elevation. I have run with and without the screens and noticed no difference just as Shawn Geers claims.

Thanks for your help.

[Tony Wilkie]

hey John, I love the internet builds   
Stealth, just let us know what you finally ended up with 

tw

[Bruce]

I just switched idle holders from a 120 to 100 and it pulls longer on the idle jet and doesn't lean out on the transition like it did before.  

I recall talking to Doug Berg about this many years ago.  He said the idle jet holder is much like the main air corrector jet, but for the idle cct.  Richen it up by going smaller, adds fuel to the top end of the idle range.
In 2000, I drove down the whole left coast on 48s and used a 100 idle jet holder.  I found that right at cruising speed, the mixture would start to load up causing rough running.  If I came to a bit of a hill, the load would increase and I'd be out of the idle cct.  Down hill did the same, moved me out of the rich zone.
Since then, I learned better would be to use a 110.  I know a lot of guys are using a 115 to provide a very small enrichment in the transition.
You have to consider that you have the 3rd progression hole too.  That adds richness, so if someone is giving you advice on their setup, and they don't also have the 3rd hole, it's not as relevant.

[Dano382]

I just switched idle holders from a 120 to 100 and it pulls longer on the idle jet and doesn't lean out on the transition like it did before.  

I recall talking to Doug Berg about this many years ago.  He said the idle jet holder is much like the main air corrector jet, but for the idle cct.  Richen it up by going smaller, adds fuel to the top end of the idle range.
In 2000, I drove down the whole left coast on 48s and used a 100 idle jet holder.  I found that right at cruising speed, the mixture would start to load up causing rough running.  If I came to a bit of a hill, the load would increase and I'd be out of the idle cct.  Down hill did the same, moved me out of the rich zone.
Since then, I learned better would be to use a 110.  I know a lot of guys are using a 115 to provide a very small enrichment in the transition.
You have to consider that you have the 3rd progression hole too.  That adds richness, so if someone is giving you advice on their setup, and they don't also have the 3rd hole, it's not as relevant.

I have 3 progression holes and have done alot of test and tune with A/F meter. I went from a 70/120 idle set up to a 65/120 and just that little change in idle jet size caused it to lean out into the 17's on the idle to main transition. I have tried everything from a 190-220 main air change and still same issue. I talked with jack at jaycee and he said a smaller idle air would carry the idle jet a little longer into the transition. It fixed the issue. I havent tried a smaller idle jet as of yet but should be able to go 60 without any issues. I can't see why people dont spend a few bucks on jets and try different setups and see what the motor likes. yes every motor is different, yes timing has alot to do with it but, from what he described sounds like a smaller idle air will help.  Doesn't hurt to try.

[John Palmer]

This so far has just been my baseline jetting, I only have about 50 miles on the engine so far. The plug gap is what MSD suggests for my 9.4:1 compression and I'm at 1000 feet elevation. I have run with and without the screens and noticed no difference just as Shawn Geers claims.

Thanks for your help.

John, In my past life, I once "missed a N.O.S. tune-up", and I burnt the ground electrodes almost completely off the end of the NGK plugs. 

Funny thing.........Our MSD 6AL ignition "never missed a beat", the engine ran and idled perfect.  I think you could TIG weld with an MSD ignition.  MSD builds ignition systems, not spark plugs, they are just giving you general "generic" guidelines for a V-8 type engine.   Most old school V-8 engines normally run .035" plug gaps. 

An NGK D7EA (or the like heat ranges) have a short ground strap that is very distorted at anything past .035". 

Just my experience.
John 

[Sarge]

How many washers under those NGK's, Mr. P??   I like the 115/60 idle jet stack for my rig... the carbs have the third progression hole, 40mm vents, f11tubes and 200/160 jetting.

[Taylor]

Could it be that the f2 coupled with a low float level is causing your lean condition?   The "step," as the Weber book calls it,  in the emulsion tube controls when the mains start coming on. An f2 has a high step when compared to say an f7 ( I don't have an f11 to compare,) so the mains come in later. That "step" is also controlled by float level. A low float level with  f2s bring the mains in late.

[stealth67vw]

The floats are at 10mm right now. Looking back through my chicken scratch notes, I gapped the plugs to .040" not .045". When it stops raining, I'm gonna try the F11 e tubes, 200 airs and try the plugs gapped at .035 one part at a time since I have these already. If I don't improve to my liking, I'm gonna try some 115 idle airs.

Thanks for all the help guys.

[John Palmer]

How many washers under those NGK's, Mr. P??   I like the 115/60 idle jet stack for my rig... the carbs have the third progression hole, 40mm vents, f11tubes and 200/160 jetting.

Sarge, I lost count, but they are cheaper when "bought by the dozen"!  LOL

[Jim Ratto]

I use 110 air idle holder w/ 60 John and my opinion is your flat spot will get worse with F11 in place of F2
you might try F4s
My car despised F11s, HUGE lean gap, even with 105 air idles/60 fuels

I agree you need lots of initial adv. Try a locked yet?  

BTW I found a plug which is way more forgiving when tuning, a pronounced improvement in off idle repsonse, NGK Iridium version of your D7EA. If you want some let me know.

[DKK Ted]

This so far has just been my baseline jetting, I only have about 50 miles on the engine so far. The plug gap is what MSD suggests for my 9.4:1 compression and I'm at 1000 feet elevation. I have run with and without the screens and noticed no difference just as Shawn Geers claims.

Thanks for your help.

John, In my past life, I once "missed a N.O.S. tune-up", and I burnt the ground electrodes almost completely off the end of the NGK plugs. 

Funny thing.........Our MSD 6AL ignition "never missed a beat", the engine ran and idled perfect.  I think you could TIG weld with an MSD ignition.  MSD builds ignition systems, not spark plugs, they are just giving you general "generic" guidelines for a V-8 type engine.   Most old school V-8 engines normally run .035" plug gaps. 

An NGK D7EA (or the like heat ranges) have a short ground strap that is very distorted at anything past .035". 

Just my experience.
John 

Ever used the e3 plugs? They have a e3-36, that compares to the NGK D7EA. Bought a set to try, still need to install them, also runing the MSD 6AL set-up.

Ted

[John Palmer]

This so far has just been my baseline jetting, I only have about 50 miles on the engine so far. The plug gap is what MSD suggests for my 9.4:1 compression and I'm at 1000 feet elevation. I have run with and without the screens and noticed no difference just as Shawn Geers claims.

Thanks for your help.

John, In my past life, I once "missed a N.O.S. tune-up", and I burnt the ground electrodes almost completely off the end of the NGK plugs. 

Funny thing.........Our MSD 6AL ignition "never missed a beat", the engine ran and idled perfect.  I think you could TIG weld with an MSD ignition.  MSD builds ignition systems, not spark plugs, they are just giving you general "generic" guidelines for a V-8 type engine.   Most old school V-8 engines normally run .035" plug gaps. 

An NGK D7EA (or the like heat ranges) have a short ground strap that is very distorted at anything past .035". 

Just my experience.
John 

Ever used the e3 plugs? They have a e3-36, that compares to the NGK D7EA. Bought a set to try, still need to install them, also runing the MSD 6AL set-up.

Ted

Ted, I guess I'm just "too old, or too stubborn" to understand how a spark plug "with two extra ground electrodes" could produce any more power than a standard plug like the NGK D7EA, or in our case the colder NGK D8EA plug because we run N.O.S..  Maybe if we were running a high percentage of nitromenthane fuel and were having problems keeping the fire lit.  But the MSD 6AL system has tons of extra spark to jump the air gap and fire the plug on a standard single ground strap plug.  Call me a skeptic, but I'm not a guy that buys into all of the marketing programs.  Maybe you can enlighten me?  But I want to see "back to back" dyno runs, and ET/MPH slips that clearly "show a measureable" performance increase over a normal quality plug.  Besides, the E3's are not cheap compared to the NGK plugs.  We currently only run a small N.O.S. HP shot, and we have a box full of "little blue pills" if more power is needed.  LOL

[DKK Ted]

I hear ya John, thats why I got a set of them to try, $25 for the 4 at O'Rileys Auto. Running the D8EA now, have a set of D7EA's to run also to compair, ya there is alot of hype on these e3's. couldn't hurt to try I guess, I'll see what happens and post my results later.

Ted

[stealth67vw]

Finally got back to playing with the jetting and I'm getting close. So far I bumped the mains to 170s and airs to 200s. It still stumbled. I then tried 110 idle air holders with 60 idles and it fixed the stumble, but idle AFRs are rich and the 1800-2800 range AFRs are about 14:1. AFRs above 3000 go rich to about 12.2-12.4:1. Next I'm going to try 210 and 220 airs and maybe 175 mains. Right now it runs smoother than my fuel injected Nissan pickup but still needs more fine tuning to make me happy.

Just to be clear I'm not using the AFR gauge to tune the engine, but more to see what's happening with the changes I make.

[Jim Ratto]

12.2 -12.4 isn't rich for your motor

[Jim Ratto]

John you might look for an emulsion tube with fewer holes in the "upper portion" of the tube than the F2 has. I don't have my book with me but if you're still in need I have a chart of tube type/code and Weber part number. PM me if you are interested.

Jim