[mk e]

Originally Posted by ferraripilot

Running rich all over. No question the engine is sucking more from the carbs requiring I dial back the jetting. I have ordered some size 50 idles, 130 mains and I'll go from there.

Well just plug in your laptop and......oh that's right you have jets


It sounds like you have a nice set up

[bretm]

Originally Posted by mk e

Well just plug in your laptop and......oh that's right you have jets
...

If I had jets my car would be running already for almost a year!

[ferraripilot]

I put some miles on the engine over the weekend. Still breaking in the engine so I haven't opened anything up. I can drive it around in 2nd or 3rd gear easily enough. What a fantastic engine though. Incredibly flexible yet I can tell if I really open it up I could spin the rubber of the wheels. Power wise it feels very similar to a '87 Porsche 911 turbo without the lag of course.


Hoping the 36mm chokes show up today. Here's what I'm thinking will happen. The 36mm chokes will decrease the signal to the carbureter causing there to be less 'sucking' through the carb meaning I won't be running as rich with my idle jets and main jets. What's going on with the 32mm chokes is the engine has soooo much vacuum that it's sucking fuel in like crazy and these little stock jets are even too much for most situations. 36mm should clear that up by decreasing the signal. I love carbs, they're such simple creatures.



And of course this will all come off the car once I inject it probably next winter. Really really looking forward to that, Mark

[mk e]

There is just no replace for displacement

[ferraripilot]

Tried 36mm chokes yesterday. No measureable difference in throttle response or torque. I'm going to have to work this out on a dyno. Splitting hairs here so it seems.

[Kaos Andy]

A little of topic,
Can anyone tell me what direction a 348 engine spins. I am thinking of fitting one to my E30 BMW convertible. Has anyone done anything like this?
Thanks
Andy

[ferraripilot]

Originally Posted by Kaos Andy

A little of topic,
Can anyone tell me what direction a 348 engine spins. I am thinking of fitting one to my E30 BMW convertible. Has anyone done anything like this?
Thanks
Andy

That would be a big job! Start a thread on it when you get going. 348 engines spin anti-clockwise when looking at the flywheel

[ferraripilot]

I dialed in the idle last night. Still rich with 55s, waiting for the other jets to come in. All the carbs are balanced and it runs very smooth now. Ignition timing really wants a ton of timing in by around 2500 rpm, about 29-30 degrees. I suspect 'all in' total ignition timing will be in the neighborhood of 36 degrees by around 5500-6k rpm. The dyno will know :O

[ferraripilot]

Not going to drive it until I have the mixture under control. Rich rich rich even with stock 3.0L jetting. it's a good bet that the engine is getting a good bit more airflow.

[ferraripilot]

Still waiting for the jets to show up......... Mark, no comments from you about injection and a laptop either! Not at least until I have mine setup, then you can make fun of carbs and all their lame-ness until the cows come home. But at least for now, these carbs are about as useful as a chocolate teapot.

[mk e]

Originally Posted by ferraripilot

Still waiting for the jets to show up......... Mark, no comments from you about injection and a laptop either! Not at least until I have mine setup, then you can make fun of carbs and all their lame-ness until the cows come home. But at least for now, these carbs are about as useful as a chocolate teapot.

No comments from me, I don't actually dis-like carbs anywhere as much as I pretend to.

I haven't had a set of weber jets in my hands in maybe 20 years so I don't recall exactly how they look, but with other jetting my favorite "roughing it in" technique was to just solder the big jets shut and then re-drill to the new size. Then when I was close I'd order real jets.

The other option is order the smallest size they make and start drilling up...but that means you'll be lean which is less than ideal but live-able if you watch the mixture and keep the load down until the mixture is looking good.

[tpdipower]

May I suggest a few things.
First, if the throttle plate are open too far, they will expose the first progression hole causing excess fuel to flow. Make sure your air bleeds are closed off.
What is the reading on your flow meter? I know on my 512BB with cams it is reading about 5 to 5.5 .Any higher than that it you will have a rich condition. I am also running 55 but I just changed to 60 to eliminate a flat spot and slight lean condition ( also checked on the dyno)
Also check the ratio of fuel to air on the idle circuit.
You can use the bypass air bleeds to add more air.
The last resort is to drill the throttle plates. a 0.025 hole will be enough.

Call Michael at Pierce manifolds. Now there is someone who know the webers.
very reasonable, very knowledgeable, great company.
I sent my 40 IFC3 to them, gave them the info on my motor, they flowed them and built them.

[ferraripilot]

Originally Posted by tpdipower

May I suggest a few things.
First, if the throttle plate are open too far, they will expose the first progression hole causing excess fuel to flow. Make sure your air bleeds are closed off.
What is the reading on your flow meter? I know on my 512BB with cams it is reading about 5 to 5.5 .Any higher than that it you will have a rich condition. I am also running 55 but I just changed to 60 to eliminate a flat spot and slight lean condition ( also checked on the dyno)
Also check the ratio of fuel to air on the idle circuit.
You can use the bypass air bleeds to add more air.
The last resort is to drill the throttle plates. a 0.025 hole will be enough.

Call Michael at Pierce manifolds. Now there is someone who know the webers.
very reasonable, very knowledgeable, great company.
I sent my 40 IFC3 to them, gave them the info on my motor, they flowed them and built them.

I know the direction I need to go in and know exactly where I'm rich and lien on these things, it's just a matter of waiting for parts to arrive now. I'm reading exactly 5 on the flow meter and have the throttle plate open not even half a turn. It idles very nice right now, just very rich (11:1) so I need to bring it down a bit. Progression until the mains kick in is also very rich as it's still on the idle circuit. The mains kick in and it is a little more lean but not much. The only range it's close to be right in is above 5k rpm, but I have yet to push the motor beyond about that range so I can't deduce a whole lot yet. I'm going to probably dump the F36 emulsion tubes as they tend to lean out at the upper end yet remain fat in the mid range. F24 tubes will remain rich at the top end yet run a bit more lean mid range. I'm currently using 140 mains and 220 air correctors so I figure I will try 130 mains with 200 air correctors and see how that works out when logging with the wide band sensor.

I will report back once this is going.....

[bretm]

Originally Posted by ferraripilot

I know the direction I need to go in... just very rich (11:1)....

How do you know the air/fuel mixture and where you're rich vs. lean? Do you have a fuel ratio meter in the exhaust?

I've seen them advertised in Summit Racing, etc. but never tried one myself. Just wondering how well they work as it sounds like you have the process down to a science.

[ferraripilot]

Originally Posted by bretm

How do you know the air/fuel mixture and where you're rich vs. lean? Do you have a fuel ratio meter in the exhaust?

I've seen them advertised in Summit Racing, etc. but never tried one myself. Just wondering how well they work as it sounds like you have the process down to a science.

I have an Innovate LM-1 wideband meter. The O2 sensor is a bit upstream on the exhaust pipe and is very very accurate. I can datalog long drives to really get an idea of what the a/f ratio is doing during cruise, accel, decel, idle etc. This would be impossible without one!

[bretm]

Originally Posted by ferraripilot

I have an Innovate LM-1 wideband meter. The O2 sensor is a bit upstream on the exhaust pipe and is very very accurate. I can datalog long drives to really get an idea of what the a/f ratio is doing during cruise, accel, decel, idle etc. This would be impossible without one!

Just looked it up. That is too darn cool. I used to have a Jeep Wrangler that I swapped a Weber carb onto (along with a better head, Crane Cam, GM DEI ignition, etc.). Wish I had something like the LM-1 at the time!

Now you've got me thinking that tuning a 2-stroke Dell'Orto carb on a shifter kart would be easier with an a/f meter... Time to do some research.

[mk e]

Originally Posted by bretm

Now you've got me thinking that tuning a 2-stroke Dell'Orto carb on a shifter kart would be easier with an a/f meter... Time to do some research.

Bret, I 'm not so sure an O2 sensor will work on a 2 stroke with a tuned pipe because by design you have unburden fuel and air in that pipe?

And on a race motor what it the "correct" mixture? Maybe if you get the mixture on a dyno then use the O2 sensor to help day to day weather elevation type tuning but if you measured the conditions when you were on the dyno it should be just check the current conditions and do some pretty simple math to get back to optimal??

[tpdipower]

1/2 may be too much.
The motor is needing more air to run, due to the overbore and stoke. The cams will also change the signal to the carbs. All of these will add the confuse the carbs. Cylinder pressure has been increased considerably and so has the signal too the carbs.

Are the cams installed straight -up or retarded a couple of degrees?

You may try and close the throttle plate and adjust the air bleed/bypass screws.

Check you static timing, you may also need some more initial timing after the throttle plate settings.

Then clean up plugs and try an different heat range (hotter). Don't go too wide on the gap.

When you are happy with the overall tune, then use a colder plug.

[ferraripilot]

Originally Posted by tpdipower

1/2 may be too much.
The motor is needing more air to run, due to the overbore and stoke. The cams will also change the signal to the carbs. All of these will add the confuse the carbs. Cylinder pressure has been increased considerably and so has the signal too the carbs.

Are the cams installed straight -up or retarded a couple of degrees?

You may try and close the throttle plate and adjust the air bleed/bypass screws.

Check you static timing, you may also need some more initial timing after the throttle plate settings.

Then clean up plugs and try an different heat range (hotter). Don't go too wide on the gap.

When you are happy with the overall tune, then use a colder plug.

Kind thanks for the tips. Mind you these are much hotter cams than stock cams, but I am maintaining a tight LSA as I know these Ferrari motors run well like this. Intake is 104 and exhaust is 108. Initial timing is 10 degrees. I believe the idle screw isn't even half a turn, maybe somewhere between 1/3 and 1/2 turn.

I will certainly keep everyone updated. Still waiting for my new jets.......

[ferraripilot]

Interesting revelation this morning after a bit of driving and tuning last night. I made the 55 idles work and the car is idling about 13.8:1. The rings must have seated or something between last night and today because the wideband is showing the engine very lean during cruise at 15:1+ while on the main circuit jets. Lots of lean misfire too during the transition. Very interesting as it was never doing this before. So, I have F36 tubes, 140 mains, 200 a/c in right now. I am going to just swap to F24 tubes and keep the same jets and see how that changes things. The pump jets squirt a ton of fuel in and temporarily bring the mixture down to 10.8:1 so I'm thinking about moving to the next size smaller pump jets just in the name of keeping uniformity when I really hit the gas pedal. I know F24s really fatten up the mixture a good bit so we'll see how much we get. Might need to bump the mains a bit further even.