Webers the right way!

[JCoop]

Tuning time...

OK maybe all you experts can help me before I run a big stack of bills for parts. First thing I did was set the fuel pump pressure to a tick over 3 psi.

I've synched the carbs decently in that the meter shows an even 4.5 - 5 equally on the 4 inner barrels at around 800 RPM. I followed the procedure as shown on Richard's DVD. The idle mixture is good and a bit fat at just a hair more than a half turn out on all 8 jets. She idles quite smoothly, a few lean spits when cold but disappears when warmed up, and when I stand on the throttle, she jumps like a scalded cat, much like the immediate reponse on my CL600's injection. Nice power with a seat-of the-pants increase of maybe 10-15 horses. Revs smoothly and pulls strongly all the way up to 6000. The problem is at cruise or a steady rev at around 2500-3200 RPM. She gurgles and pops and misfires until I gun it again. Unfortunately, this is where I cruise generally, 2800-3200 RPMs in 5th and doing 70-80 mph. I decided to change all plugs (Motorcraft ACSF 32C) and a new MSD blaster 2 coil as I wanted to carry a spare anyway. I also checked and reset the timing to 10 deg. advance at idle and 21 deg. max without the vacuum connected. with the vacuum hooked up, that setting read 13 deg at idle and around 41 at 3000. That made the car idle even smoother and acceleration seemed to improve; however, the stumble and popping, misfire persists at the transition points 2800-3200 RPM. Almost seems like it's starving for fuel. Now in reading the several tuning articles, it seems like the emulsion tube is the culprit. Currently installed is an F7. Should I get a F9? Could it be too much advance as well?

 

[Jac Mac]

Hi ,
Before you mess with those weber's sort out that ignition curve. You say that with the vacuum adv disconnected & blocked that you have 10deg initial @ idle & 21deg?? total???
My suggestion would be disconnect the vacuum adv, have the distributor recurved with 12deg in the distributor. This with 10deg initial will give you a total of 34deg at the crank (10+12+12=34) . Run the motor up to 4000 rpm+ and verify that you have that ( 34 deg btdc ) with a timing light. Now without the vac adv hooked up try a test drive. Hopefully thing's should be a lot better. You could try just advancing the timing up to 34deg with the dizzy as is but if the info you have provided is correct that would give 23deg initial which may be a bit tough on the starter. If all is now OK all you need is someone in your area to sort out the vac adv side for you. Personally I would leave it disconnected but your emission rules may preclude this. Good Luck.
Jac Mac

 

[JCoop]

Good advice...I'll do that today. At $24 each, those emulsion tubes are a bit stiff to experiment with. Thanks.

 

[JCoop]

Jac,

I retimed the ignition yesterday with MY timing light (I had been fiddling with a friend's at the shop). I checked it with the vac. connected. it was too much so I backed off and now getting 34 deg. at 3500. Idle is at 12-14. Misfiring and popping is still there. I fiddled with the idle jets

(I've posted my woes in the CAV forum.)

 

[Jac Mac]

Hi, I think you have misread the suggestion- The 34deg is WITHOUT the Vacuum advance connected. Leave the Vacuum advance DISCONNECTED until you get on top of this problem. ( I am concerned as to where you are sourcing the vacuum from- ie throttle plate or manifold runner, but that can wait until this problem is sorted) Just plug the line with a golf tee or similar object. Let us know if that help's.
Do the CV Attachment bolts have a close tolerance shank between the threadend and bolt head to act as an alignment dowel, Most hi-perf CV's that I have looked at use these to carry the torque loading's.
Somewhere in the archives I have the jetting etc for a 306hp shelby, I will try & find it for you guy,s although each motor has its own specific needs!
Regards Jac Mac

 

[JCoop]

Hi, I think you have misread the suggestion- The 34deg is WITHOUT the Vacuum advance connected. Leave the Vacuum advance DISCONNECTED until you get on top of this problem. ( I am concerned as to where you are sourcing the vacuum from- ie throttle plate or manifold runner, but that can wait until this problem is sorted) Just plug the line with a golf tee or similar object. Let us know if that help's....
Regards Jac Mac

Jac Mac, you 'da man!
I used one of my rare Lacoste golf tees to plug the vacuum and retimed the dizzy to 34max @3500. This also yielded 14@idle. I also backed out the mixture screws to a full turn. Started up fine. Took a test drive, SMOOTH AS SILK on a steady rising throttle all the way to 6000 in 3rd! I can't believe that made such a difference. Idle is down but steady at 500. I'll bring it up to 800 and check the synch.
The vac takeoff by the way, was set up by Ian and onto one each of the pair of extensions he rigged up, going to an equalizing box. The power brake servo also takes off from there.
So I guess I'll just leave the vacuum off as my car is emission-exempt.

 

[Jac Mac]

Hi J,
Good to hear, Sounds like you have been using full manifold vac which is wrong. You must use a vac source from the area around the throttle butterfly for dizzy vac adv. Im not even sure where this is on an IDA, it may be an undrilled casting boss in this area. Emission factors aside the only benefit vac adv will give you is perhaps 1 or 2 mpg under highway cruise conditions ( As you are using Lacoste tee's as blank plug's this probably wont worry you TOO much. LOL).
Your IGN curve may need to be further optimised yet as the numbers I have given you are"safe" for most application's, but should allow you to sort the jetting out. ( Might pay to keep Ian advised on your findings to help others if they dont read it here)
Regards Jac Mac

 

[JCoop]

Well, so far, it's singing the Weber song. Awesome, seamless power; so I'm not touching anything...until next week.

I had some residual water that contaminated the oil during the manifold swap, and I am running some 10W40 flush in there before I switch back to synthetic 15W50. At that time, I'll do a plug check and double check the synch. I'm a happy camper right now.

Maybe when you get the time and inclination, you can explain why full manifold vac will not work for dizzy advance?

Cheers!

 

[Jac Mac]

Hi J,
If you use full manifold vac to your dizzy advance unit you will have a lot of vac advance added at idle, slightly less at part throttle/cruise/low load conditions, and none at Hi-load/WOT position. This is what was happening in your situation, when you ran the RPM up to 3500 under no load with the vac hooked up the the high manifold vac pulled the whole 18/20deg of advance in to add to your initial 10+12deg and gave you a total around40/42deg. But out on the road under load @3500rpm the vac dropped away and you only had 21deg adv total( 16deg retarded).
The correct place to take the dizzy vac from is (READ CAREFULLY) :Just above the closed throttle butterfly on the half that moves back into the barrel of the carb on opening.
With the vac taken at this point the adv unit will see little or no vac @ idle, some as you crack the throttle to pull away under low load or normal driving conditions, and high vac under light throttle cruise low load/ or descending hills with the throttle slightly open.
Now having said all this I cannot see any provision for this in any photo,s of IDA's that I have and to be truly effective all 8 carb bores would to be linked into a common point before connecting to the dizzy, as the pulsing that takes place in an IR setup will kill the signal to some degree.
That old saying: When in doubt -leave it out applies here. Look's like you will have to buy a new golf tee!!!
Now here are the IDA setting's I have, They were from a BOSS 302 that made 498hp @ Falconer& Dunn in the early 70's so may be a bit big for some of you guy's.

MAINS-170, CHOKES-45, AIR CORR-130, EMULSION-F7, PUMP JETS-50, IDLE-70/F16. IGN/Timing -19deg initial/42deg total. RPM range used 5000/7800. Compression Ratio woud have been around 12.5/13 to 1.
Regards Jac Mac

 

[Keith]

13:1! Phew, those were the days....rockonsmile

 

[Chris Coote]

Re your inquiry on jetting I am running the following my 48IDAs
Emulsions F7
37 chokes
165 mains
145 airs
F7 emulsions
50 pumps
65 F10 idles
120 air correctors
Hope this helps Cheers

 

[JCoop]

Re your inquiry on jetting I am running the following my 48IDAs
Emulsions F7
37 chokes
165 mains
145 airs
F7 emulsions
50 pumps
65 F10 idles
120 air correctors
Hope this helps Cheers

Thanks! I haven't looked at the E tubes yet so I don't quite know what mains and correctors are in there yet. so far, the 60 idles are working great; wtill a little burble at the transition 2800-3000 RPM. I'll fiddle with the mains this weekend.