Hello,
I have a tuning question for all those out there that have mastered (or survived) the art of Weber 44 IDF tuning. Background: engine is 2270 Type IV based with 78.5mm stroke and 96mm bore, ported and massaged 2.0 heads with dual springs, Raby Cam (9500) setup engine to run 9.6:1 compression. I'm running the factory distributor with points replacment timed at 34 degrees at 3500rpm.
I'm currently running the following jets in my 44IDFs:
Air Correction : 2.0
Emulsion Tubes: F-11
Main Jets: 1.50
Pump Jets: 0.50
Idle Jets 0.60
Venturi 36mm
I started with 52, then 55 then finally 60 idle jets, the smaller ones were too lean and didn't have response on the mixture adjustments. With the 60's I'm able to tune about about 1 turn out. My problem is the engine just seems a little flat form about 2000rpm until about 4-4500rpm where it really wakes up. I'f I'm at 3000rpm and floor the throttle it simply doesn't pull any harder, just more noise. But like I said if builds to around 4K...you can feel the power kick in.
I know I need the 60s to get a good idle with my setup, but what's a good suggestion for the 2000-4000 range? I think it's running lean in this range as I've hear an occassional "pop" and miss when open the throttle too much in this range.
Suggestions?
Full Version: Another Weber Tuning Question
I have a similar engine that was pretty happy with about those same jets.
I am pretty sure the max advance you want to run is 28 degrees.
That is what Jake always recommended IIRC, maybe he will chime in.
John
Can't help you with the carbs. I run EFI...
You're in the right place!
I'll retard the timing to 28 degrees tonight and see if that helps. Drove to work today and held at 3000rpm was getting occassional carb pops....
Solved - the saga.
I tried retarding the timing to 28 but had another problem in that with my stock distributor this gave such a low speed idle that I had to crank the throttle stops. This in turn then open the throttle plates off idle range into the transistion circuits....and in the end, this didn't fix my rough running between 2-4000 rpm issue.
So I moved distributor back to 34 degrees (I don't have a detonation issue), cranked the throttle stops out to lower the idle back to 800rpm...and that's when I noticed it.
My sync meter is one of th snail types and in the process of sync-ing the carbs again i noticed a rattle inside the meter. I took the sync meter over ot the bench and looked inside with a flashlight and noticed that the brass weight that goes on the "needle" had came loose and was rattling around inside. I was so very lucky this weight hadn't fallen out and been sucked into my engine. I took the meter apart and re-installed the weight (with some super glue). Before I was getting high readings on the meter in the "7ish" range and consistent from side to side and after the repair it was in the "3ish" range with a big difference between the banks.
After sync'ing with the repaired meter and resetting the mixtures, it runs tremendously better. I still have a "flat" spot but from what I've read, this seems kind of normal, and something I plan to experiment with accelerator pump settings. What's gone are the pops and misses from un-sync'd carbs.
Just wanted to share with everyone that sometimes the problem is not where you think it is. If I hadn't noticed my meter was broken, I would have been chasing my tail forever.
I tried retarding the timing to 28 but had another problem in that with my stock distributor this gave such a low speed idle that I had to crank the throttle stops. This in turn then open the throttle plates off idle range into the transistion circuits....and in the end, this didn't fix my rough running between 2-4000 rpm issue.
So I moved distributor back to 34 degrees (I don't have a detonation issue), cranked the throttle stops out to lower the idle back to 800rpm...and that's when I noticed it.
My sync meter is one of th snail types and in the process of sync-ing the carbs again i noticed a rattle inside the meter. I took the sync meter over ot the bench and looked inside with a flashlight and noticed that the brass weight that goes on the "needle" had came loose and was rattling around inside. I was so very lucky this weight hadn't fallen out and been sucked into my engine. I took the meter apart and re-installed the weight (with some super glue). Before I was getting high readings on the meter in the "7ish" range and consistent from side to side and after the repair it was in the "3ish" range with a big difference between the banks.
After sync'ing with the repaired meter and resetting the mixtures, it runs tremendously better. I still have a "flat" spot but from what I've read, this seems kind of normal, and something I plan to experiment with accelerator pump settings. What's gone are the pops and misses from un-sync'd carbs.
Just wanted to share with everyone that sometimes the problem is not where you think it is. If I hadn't noticed my meter was broken, I would have been chasing my tail forever.
Nice work. I want a 2.3 TIV! 
I thought I would follow up on my posting to let everyone know how it turned out....final jetting ,
Idle 65
Main 140
Correction 200
36mm venturi
Here are some key notes/ hard lessons I found:
1. Do not assume your carbs are preset/adjusted, my floats where way off and my small idle bypass screws were not bottomed out resulting in different flows per cylinders. Setting floats and bottoming out bypass screws helped tremendously. Also found some factory “crap” in the fuel bowls.
2. For the hex-bar linkage - make sure there's no side to side play in the hex-rod...screw the ball ends out to minimize the side to side play but still allow for smooth and full rotation. Side to side play moves the throttle arms making syncing a problem (nightmare). Don’t assume the rod will “center”. Really creates inconsistent idles, etc.
3. When syncing the carbs...start the process with one carb having the linkage tight and using the throttle stop screw with the other carb having the linkage unlocked (adjustable) and the throttle stop screw backed out. This will help you a ton, it's a bit of pain but puts the sync in the throttle linkage and not the carb throttle stops. Once I had the throttle linkage adjusted to get the carbs sync'd I then tightened the lock nuts up on the carb linkage rod. I also then adjusted the one throttle stop screw back in just to the point of contact and verified that I had a sync at idle. This way you can get a precise idle sync and linkage sync throughout the range. This eliminated carb "popping" anywhere in my throttle range.
4. Start jetting from bottom up with Idle, mains then air correction. I found a good thread on here that had great advice that if your idle mixture is more than 1-1/2 to 2 turns out from bottom then the jets are too lean. With 50 and 55 idles, my mixture screws had no effect at all. With 60s the peak adjustment point (+1/2 turn) ended up being about 2 1/2 out. I also had a horrible stumble flat spot off idle. When going to 65's my final adjustment is about 1 turn out but more importantly, no more stumble/flat spot.
5. For mains I found another thread on there that advised of starting rich and moving lean until dialed in....great advise. With 150’s I had a noticible flooding condition that would clear out nearing the top end, moving to 145s was still too rich with the engine have a “surging” . However with 140s they give a good strong pull off idle until about 4500 then you can feel the air corrections starting to lean it out a bit and the car pulling even a bit harder. I might be able to get more power with 135s but she's running so sweet and staying cool as is.
6. When jetting, don't change more than one type of jet at a time and remember start at idle and work your way up the throttle position/rpm. The jets overlap so much you have to start with right idle and go from there.
All in all it was a learning process to get this engine dialed in, but now that it's running great, it's all worth it. My 2270 pulls really hard and the car is night and day compared to the original 2.0.
Idle 65
Main 140
Correction 200
36mm venturi
Here are some key notes/ hard lessons I found:
1. Do not assume your carbs are preset/adjusted, my floats where way off and my small idle bypass screws were not bottomed out resulting in different flows per cylinders. Setting floats and bottoming out bypass screws helped tremendously. Also found some factory “crap” in the fuel bowls.
2. For the hex-bar linkage - make sure there's no side to side play in the hex-rod...screw the ball ends out to minimize the side to side play but still allow for smooth and full rotation. Side to side play moves the throttle arms making syncing a problem (nightmare). Don’t assume the rod will “center”. Really creates inconsistent idles, etc.
3. When syncing the carbs...start the process with one carb having the linkage tight and using the throttle stop screw with the other carb having the linkage unlocked (adjustable) and the throttle stop screw backed out. This will help you a ton, it's a bit of pain but puts the sync in the throttle linkage and not the carb throttle stops. Once I had the throttle linkage adjusted to get the carbs sync'd I then tightened the lock nuts up on the carb linkage rod. I also then adjusted the one throttle stop screw back in just to the point of contact and verified that I had a sync at idle. This way you can get a precise idle sync and linkage sync throughout the range. This eliminated carb "popping" anywhere in my throttle range.
4. Start jetting from bottom up with Idle, mains then air correction. I found a good thread on here that had great advice that if your idle mixture is more than 1-1/2 to 2 turns out from bottom then the jets are too lean. With 50 and 55 idles, my mixture screws had no effect at all. With 60s the peak adjustment point (+1/2 turn) ended up being about 2 1/2 out. I also had a horrible stumble flat spot off idle. When going to 65's my final adjustment is about 1 turn out but more importantly, no more stumble/flat spot.
5. For mains I found another thread on there that advised of starting rich and moving lean until dialed in....great advise. With 150’s I had a noticible flooding condition that would clear out nearing the top end, moving to 145s was still too rich with the engine have a “surging” . However with 140s they give a good strong pull off idle until about 4500 then you can feel the air corrections starting to lean it out a bit and the car pulling even a bit harder. I might be able to get more power with 135s but she's running so sweet and staying cool as is.
6. When jetting, don't change more than one type of jet at a time and remember start at idle and work your way up the throttle position/rpm. The jets overlap so much you have to start with right idle and go from there.
All in all it was a learning process to get this engine dialed in, but now that it's running great, it's all worth it. My 2270 pulls really hard and the car is night and day compared to the original 2.0.
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