Interesting Weber jetting

[JCoop]

Originally Posted by ENTDOC

Ray, keep in mind we are using 40's on stroked 427's, not that they might not work for you on the 302. What emulsion tubes are you running? chuck

F7s, Chuck.
Part of my problem is, I think, the restrictive filters I installed. I'm installing new plugs today and run the car without them and see.

Thanks for the link, Hans.

[Gun Doc]

I ordered my parts from Top-End Performance (http://www.racetep.com/)…Good prices quick delivery and great customer service.

Gun Doc

[ENTDOC]

you may be right on the filters Ray, perhaps 40's will overcome them.

[JCoop]

Originally Posted by ENTDOC

you may be right on the filters Ray, perhaps 40's will overcome them.

And it's confirmed! I just installed a set of 40mm chokes and the motor feels like a totally new machine. It was a fairly easy swap except now I know to be very careful when pulling the squirters out not to lose the O rings The set I got from Vee Dub Parts were beautifully machined pieces, a far cry from the original 37mm cast ones originally in there. They slipped right in, nice 'n shiny.
I just drove a mile home from the shop; not even far enough to warm up the oil but without touching anything else, the idle is smoother, no spitting, sneezing or coughing coming off idle, and a quick blip of the throttle and she just jumped without any hesitation or transitional hiccups. Yey! I gotta give her a workout tomorrow!

[ENTDOC]

let me know how it all works out as I am about to finish the CAV upgrade with Ians shifter, IDA's and sound deadening.

[Eljaro]

And it's confirmed! I just installed a set of 40mm chokes and the motor feels like a totally new machine. It was a fairly easy swap except now I know to be very careful when pulling the squirters out not to lose the O rings The set I got from Vee Dub Parts were beautifully machined pieces, a far cry from the original 37mm cast ones originally in there. They slipped right in, nice 'n shiny.
I just drove a mile home from the shop; not even far enough to warm up the oil but without touching anything else, the idle is smoother, no spitting, sneezing or coughing coming off idle, and a quick blip of the throttle and she just jumped without any hesitation or transitional hiccups. Yey! I gotta give her a workout tomorrow!

Well, glad to hear that the 40mm Venturis work well on a 302 also.
Dont know how come the word spread that the 37mm were the chokes to use for everyday driving.
Maybe for the layman in anything mechanic it is best to leave the webers as they come, but for anyone wanting to tinker around it is fun and definitely brings driving improvement. Doesn't it ?
I bet once you try larger chokes you get the real Weber feeling.

[dlampe]

I have 2 sets 45mm chokes. I wonder if that is just to much? I think I might give them a try this winter. It really isn't that hard to switch them out. My mill is a 380 with Yates heads that really breath well. Any idea how this could effect my jetting? I am currently running 40's.

[Rick Parker]

dlampe

You have PM

[Jac Mac]

Originally Posted by Eljaro

Well, glad to hear that the 40mm Venturis work well on a 302 also.
Dont know how come the word spread that the 37mm were the chokes to use for everyday driving.
Maybe for the layman in anything mechanic it is best to leave the webers as they come, but for anyone wanting to tinker around it is fun and definitely brings driving improvement. Doesn't it ?
I bet once you try larger chokes you get the real Weber feeling.

600cc(292ci) per cyl----38mm for Hi Perf Road---41mm for competition
650cc(318ci)-----------40mm-------------------42mm
700cc(342ci)-----------40mm-------------------43mm
750cc(366ci)-----------42mm-------------------44mm
800cc(390ci)-----------42mm-------------------45mm
850cc(415ci)-----------42mm-------------------45mm

Starter main jet size is approx choke size x 4 ( eg 45mm choke = 180 main)
On IDA Air Corr should be about 40/50 less than jet for comp- perhaps 30/40 less for road. Use Air & Emulsion to tune for each individual engines characteristics- Once you get more than 10 away from that starter size of the main jet you are chasing Fairies!

Jac Mac

[BERNIE]

Originally Posted by Eljaro

CalMetal

I used F7 tubes and modified them with a very thin sleeve (0.5mm wall thickness) with 4 holes to partially or totally cover up the bottom holes to see what happened. So I kept doing mods to the sleeve and the emulsion tube until what I had as a result looked exactly like the F14 tube..
But my F7 tube is not a perfect F14 , because the 8 middle holes drilled at an angle are not 100% covered. There is a gap between the sleeve and the smaller diamater part of the tube where these holes end inside the well.
I also had to drill the 4 aditional holes at the top, where the F7 tube has only 4 but the F14 has 8 holes.
With this arrangement I was able to get rid of the bog and the lean condition, according to the OS2 sensor and the gage. Then I went about to reduce the main jet to the point where on full load at 6000 rpm the AFR would stay stable and not go up..
After that the car ran fantastic, I would say perfect. Plugs are tan now, whereas before they were black as a coal mine and no main jet would correct that because smaller jets would lean out at WOT and that is a no-no.
I have ordered a set of F14 tubes and once I have them I will try them out. If I am too rich at the transition I can drill some holes where the F7 has the angled ones and correct for that.

Installed F14 and tested on dyno,very good on bottom and picked 20HP,problem at the top is too lean with 100 air corrector,what is solution to modified the top with addditional holes or what?

[Eljaro]

Hi Bernie,

before massaging the emulsion tube I would try a smaller air corrector jet. The smallest is a 0.80mm size. You should try that first.
You can also try a slightly larger main jet if that is not enough.

Modifying the F14 emulsion would imply drilling the inside well of the tube with a 3mm drill to a depth of 30mm and drilling 1mm lateral holes at about 28mm from the top. It would be a matter of drilling first one, then two and up to four holes and testing each time. The center hole can be plugged with a 3mm brass plug any time again and the tube would be back to original again.


I am glad to hear that my personal feeling about the good response of the F14 tubes has been confirmed on a dyno.
I am still putting my new engine together and have 8 42mm Venturis waiting to be installed. Will see how they work.

[BERNIE]

Originally Posted by Eljaro

Hi Bernie,

before massaging the emulsion tube I would try a smaller air corrector jet. The smallest is a 0.80mm size. You should try that first.
You can also try a slightly larger main jet if that is not enough.

Modifying the F14 emulsion would imply drilling the inside well of the tube with a 3mm drill to a depth of 30mm and drilling 1mm lateral holes at about 28mm from the top. It would be a matter of drilling first one, then two and up to four holes and testing each time. The center hole can be plugged with a 3mm brass plug any time again and the tube would be back to original again.


I am glad to hear that my personal feeling about the good response of the F14 tubes has been confirmed on a dyno.
I am still putting my new engine together and have 8 42mm Venturis waiting to be installed. Will see how they work.

Thank you,how do you expect to improve richness with one mm hole from 100 jet (difficult to get 080 air jet!!!).another question have tested F2,F5,F7,F9,F11,F14,F16 on dyno seems F2 not too bad,F14 really much better but too much leaner at the top,but not yet F15 what do tou think about?,

Regards,

Bernie

[Eljaro]

if you can not get .80 air jets you can take some of the larger air jets you have laying around, drill them larger on a lathe, make yourself brass plugs, plug them up and drill them new with a .80mm drill.You can also plug them with tin solder and drill them again to .80mm.
Do you have the dyno sheet on how the curve looks like with the F14 tube?
I do not know what the F15 will do. But from what you say right now the F14 is the best combination with only the lean top end to be taken care of. The only way to correct that now is with the air jet.Try the smaller air jet before doing anything else.
If you can get a smaller drill than .80, say 0.50 I would try that too. You can always keep enlarging the hole if you overshoot on top end richness.

[BERNIE]

Originally Posted by Eljaro

if you can not get .80 air jets you can take some of the larger air jets you have laying around, drill them larger on a lathe, make yourself brass plugs, plug them up and drill them new with a .80mm drill.You can also plug them with tin solder and drill them again to .80mm.
Do you have the dyno sheet on how the curve looks like with the F14 tube?
I do not know what the F15 will do. But from what you say right now the F14 is the best combination with only the lean top end to be taken care of. The only way to correct that now is with the air jet.Try the smaller air jet before doing anything else.
If you can get a smaller drill than .80, say 0.50 I would try that too. You can always keep enlarging the hole if you overshoot on top end richness.

Will try first with modify air jet and start at 0.50 and up and up to get perfect air/fuel ratio around 12/8,13.2.all around.
Dyno sheet shows around 15/20 more HP between 3200/4600 ,during dyno session between F14 and F16 ,(engine is a full race 289 for historic racing)

[Snakebit]

Bernie, are you running 40mm chokes on the 289? I have a 331 small block with 185 AFR heads 60 idle jets, 1.10 holders, f5 emulsion tubes, 155 mains and 190 airs. Running 37mm chokes. Plugs are black and is running rich. just ordered a set of 40mm chokes from VEE DUB parts.

[BERNIE]

Originally Posted by Snakebit

Bernie, are you running 40mm chokes on the 289? I have a 331 small block with 185 AFR heads 60 idle jets, 1.10 holders, f5 emulsion tubes, 155 mains and 190 airs. Running 37mm chokes. Plugs are black and is running rich. just ordered a set of 40mm chokes from VEE DUB parts.

42 choke,190 air is too lean try 155/ 160 air and 120 holder,probably better with 40mm choke

[Eljaro]

Finally I got my engine back together again, this time it's a KC 482 Pond Alum.block with hydraulic roller lifters. Well, the engine does run very well and does not leak (yet).
My old weber setup was now no good any more, and my self made emulsion tubes ran horrible.
So I got back to tuning.
First thing I noticed, now that the engine runns hotter because it is so new, is that the pump jet dumps gasoline into the the carb when the hot engine is turned off. All my efforts to keep the carbs cool have not brought any improvement.
I noticed that the gasoline in the accel.pump circuit starts to boil and spills out of the only orifice it has , which is the pump jet. This happens only with the 0 pump spill. I used th 0.50 pump spill, which got away with that, because the gasoline can flow back into the bowl when expanding.
Since the 0.50 pump spill produces a slight flat spot, I have ordered 0.35 pump spill valves which I hope will work better and get away with the slight hesitation on acceleration and prevent fuel spilling into the carbs when engine is off.
I used the newly ordered F14 tubes, which seem to work fine, but the top end is lean now with 120 air correction jet. I tried 100 air correctors and that is now much better, but I have ordered 0.85 air correction jets because that is what I think will work best.Main jet is 140 now, and idle jet is 70 with a 100 holder.
Next weekend I will get back to tuning with the new parts ordered. Will se how it works out.

[jimf]

I have watched this thread with great interest as a while ago I bought a weber 48 ida conversion set up for my 393 W stroker. I plan to install it soon. Before I do install it, I am changing the 37 mm chokes to 40mm right away as this engine is built to breath. One thing I am curious about is when you change to larger chokes would you not also have to change the auxiliary venturis to a larger size. I have seen no mention of doing anything with the axiliary's. Although there is not a great selection of auxiliary's there is one size larger (5.0) than what is in there right now(4.5), just wondering if anyone has changed any of these and what the results where.

[Hans-Olof Blom]

Eljaro,

This is very interesting. I have a 482 engine that I plan to put a Weber 48 IDA set-up on.

What cam are you using?

What chokes are you using?

[rokndad]

Sr. Eljaro,

I have the same question Hans made about cam, duration, lift, Lobe Separation. I want to consider Webers for my car and am watching your very expert "dialing-in" with great interest. Thanks for all your hard work.