Well, after many years being away from Carbs, and learning Robert Bosch's systems on my own personnel vehicles, I am now taking what I learned about basic carb principles, to tuning Holleys for drag racing, and reading the two different books I bought on Webers, I would like to ask all of you kind folks what Carb Synchrometer is your personnel favorite? I see the Uni-Syn and another named Synchrometer TYPE SK from Redline Inc. The latter is much more exspensive than the uni-syn. An ex-F1 mechanic here in town says Uni-Syn. Are there others, and has anyone used this Redline product? Thanks.

I have the both. The SK is a lot nicer. The unisyn is hard to use because the little ball is hard to watch, and also the reading depends on the angle of the vertical tube.

Dunno if it's the same thing, but the tool I got from aircooled.net is easier to use than the older uni-syn.

Carb Sync tool

It's the one on the left, looks like a hair dryer.

That's the SK type. Works great.

I use the syncrometer.....the hair dryer.
Bog simple to use, but it must be used properly...that is to say in the proper sequence.

When You get to the point of using the tning, lemmeno and I'll give you the drill that I use.

I luv carbs.

J P,

I've been working with my Synchrometer fin-tuning the MFI on my engine. Been at it since last week, driving every day, tweeking this and that every second or third day.

I would love to know what your routine is for accurately using the synchrometer.

Michel Richard

Ok Thanks for the tips, I will look for the Redline Type, I figured it would be better using the cost=value theroy, but I wanted to ask. Thanks for the tips, I have the 40 IDA's on a 3.0 liter six. I has some popping thru the exhaust at idle (mixture?), and hesitation off idle that I thougt could be not enough fuel from the accelerator pumps, I will experiment with new pump diaphrams and squirter size after I learn the sync process. JP, I will contact you on the drill, I really prefer hands on training compared to reading. I mix both, to learn as much as I can. The method has always helped fix the airplanes....you have to respect someone who knows what they are doing. I always listen to the guys who have done it, and have the facts. The sound of this car is fantastic, with the carbs breathing in, the fan and the exhaust, it has the note of what I have always thought a sports car should sound like. I love carbs too. I still have allot of reading to do, but I am beginning to understand the Webers operation like I did the Holley on my Big Block Chevy Race Car.

FWIW, here's my sequence. It will be interesting to see how it's different from JP's. I'm assuming you're starting completely from scratch.

First, don't even start doing this until the valves are adjusted and the ignition timing is correct.

Start the engine and get it fully warmed up. Drive the car some.

Disconnect the linkage completely. Starting with one carb, loosen the locknuts on the air bypass screws, and turn them both in until they're lightly bottomed. Using the meter, turn out the lower reading of the two until it matches the one that's fully closed. The idea is to have the least amount of air possible going through the bypass. Repeat the procedure on the other carb. If you can't get them even front to back, then remove the bypass screws and make sure they're not all buggered up.

Using only one throat per carb (I usually use the rear ones), adjust the throttle stop screws until the carbs are matched to each other, and the engine is idling at your target speed (I shoot for around 900rpm).

Double check that all four throats read the same. If you have a mismatch front to back, go through the whole procedure again.

Reconnect the linkage, making sure it doesn't preload the throttles any. The engine speed should be the same after you reconnect it. Blip the throttle a couple of times, and check for sync again.

This gets the sync right at idle, and as long as there's not a big difference in the lengths and angles of the two sides of the linkage, they should stay in sync all the way to full throttle. It's hard to check sync much above idle, as the meter just pegs. Try to get the two linkage arms spaced the same distance apart from a vertical line drawn through the throttle spindle on each carb, or they'll open at different rates.

Michel: Been a long time since I tole you any lies.

I've never dealt with MFI (no lie), but the routine *should be* about the same.

Disconnect the down link to the drivers side linkage.

The drill is :end to end, side to side.

With the motor running around 1500-2000 rpms, check all holes. Select the most flow on one side (I do the pass side first) and bring the other 2 holes(on a 6), on that side only, up to that reading.
The books are pretty clear on how to do this, so I'll not go into this. I'll also pass on the fuel metering screws...except to say, do this first.
If you've done the fuel metering screw screws properly, the air bleed screw's adjustments should be minimal.

Do the same on the driver side....ignoring the pass side readings, for the moment.
Now you have end to end.

Using the idle adjust screw (the one that opens/closes the butterflies)on the driver side, adjust as required to bring the flow on both sides
even.

Loosen the double ball down link lock nuts. This goodie will expand or contract as you turn the shaft.
Adjust it to reconnect the linkage (this gets you close). Back off the idle screw on the drivers side....take a reading on them....expand or contract the down link as needed to make the reading the same as on the pass side. Tighten the lock nuts....Bingo, side to side. I let the whole linkage "rest" on the pass side idle screw.
Back it off to bring the idle down to spec, making sure there is clearance on the drivers side idle screw.

On my car, the throttle pedal vs pushing the linkage by hand make for different readings on the side to side thingy so check both ways. If there is a difference....use the throttle pedal and adjust to that.

As you can tell, this can take *some* screwing around, but IMO, most carb running problems
(assuming all else is well) are syncronization caused.
I set mine (as well as I could) about 2 years ago and haven't touched it since....I do check, however.

I proly left out somethin' out, but I'm tired of typin'.

On MFI the idle adjust screws don't move the butterflies, they open air passages around them.
Don't mess with the butterfly stops unless you have a lot of time on your hands, it is better to leave them alone unless something is grossly wrong.

The stuff about adjusting the linkages does apply. I used to pop off linkages and watch to see if the airflow changed. If it changes when you pop one off, the linkage was adjusted incorrectly.

martin, jp's method is beautiful in it's simplicity. my experience is with 4s but the same mechanical methods should apply. it found that trying to adjust both the idle screws, one would push off stop and throw off the flow rates. using the pass side rod to match the drivers side will save you a lot of grief. the book from C.B. performance adresses the 40 IDA too. the air bypass screws are adjusted after you are all done with the syncro. but they need to be set the same before you even warm up the car. the one on the left at aircooled is what i own.

kevin

One thing I forgot. Make sure the engine is warm.
Even a lousy running engine will warm up

MArtin:
As I recall, Dunkle had some warpage problems resulting in a vacuum leak at the base of #5. (carb to manifold). Should be a shim in there. I had one at the same place.

The idle adjustment screws I am refering would be more accurately described as idle stop screws, one per side, NOT the mixture screws, 3 per side...or 2 on a 4 banger.

JP, sounds like you know this car very well! I am glad to hear it, thanks for all the info, I will use it, and learn from it as well. Is this warpage something that needs correction, and if so what is the fix, parts or machine work? Thanks again.

I dunno, it was 3-4 years ago that we talked about it. He said he fixed it with a shim/gasket thingy & RTV. I don't know much about the car. Just that little tidbit.

I know CCLINSOLDHISSIX was having some ....ah...clogged jets or fouled plugs....I never really got into it...he solt it too quick

I was gonna take it for an AX pass, but he was having "issues".....nuthin major.....the throttle cable was sticky...way stickey and it wasn't runnin' on 6.
Gave him a couple of ideas......poof, it was gone.

That car's got potential, me thinks.

I have improved the throttle linkage, I took out some of the slack and lubed the ball/socket connections. Its a little better. I will replace the throttle cable soon. I have heard there is a complete cable system from someone. Gets rid of the mechanical bellcrank completely. It runs great after you pass through the off idle circuit, but the hesitation/popping is very obvious. Right after that is when you better be holding on to something, as it is pulling like a drag car, it screams, and it makes me grin. Wife won't ride in it, says it's to fast. Makes me laugh. I will not disappoint with this car, I will do it right.

and



........sounds awfully like a blocked idle jet &/or idle circuit (assuming no manifold leaks). I have 46IDA's on a 3.2 and the damn things block up just to spite you if you just look at them funny in the morning.

Heh, my wife won't get into mine except to help bleed the brakes....."it's noisey & stinky & hard to get in/out of"....about perfect, me thinks.

Popping/hesitation is usually lean condition.
IMO, if you're mixture screws are open more than 3 turns, the idle jets are too small.

I run 60s on my 2.7 and they are set at about 1.75 turns open.
For a otherwise stock 3.0, B Anderson recommends 34 mm venturi, f3 tubes, 160 mains and 175 air correction jets. 60 to 65 idles.
I run his 2.7 hot rod setup and it seems spot on.

Get an MSD 6AL and hi vibration coil. NGK BP6 or 7 ES plugs gapped at bout .045......great for "burn thru". I think Craig already put the good plug wires on.

Are you a night owl also? I do second shift at the lazy B.

I don't have the book handy JP. What size venturis are you running? Carbs are 40's?

And I use the STE

I got used to using the unisyn but I also got very good at tuning them by ear with a length of hose, it's amazing how close you can get them with the hose I would initially set them with the unisyn then fine tune by ear.

Get the STE sycrometer. Unisyns restrict airflow and make carb adjustments difficult.

If I might add some Weber tuning advice.

Wear earplugs or sound muffs, as you'll probably get some back firing until everything is adjusted perfectly.

To correctly adjust the air bypass screws; start with them screwed all the way in, find the barrel that is drawing the most, and adjust the others to (on that carb) to balance air flow. This is why you want the STE syncrometer and not a Unisyn.

I've got to run now, but I'll post my tuning proceedure later.

PK

I do not have any of that info, other than the carbs are 40's. I have not taken anything apart just yet, I wanted learn more before I do anything. I just won a Uni-syn on e-bay, and am bidding on the Redline type as well. I got the Uni for $20 new in the box. I'll know on the other in another day. I will just buy one if I don't win this one. John Dunkel might know the info on the carbs. He told me that it has clogging issues on the idle's.

JP, as far as shifts, you wouldn't believe how it is where I work, I have no set shift, no days off, vacation, benifits, etc. My Boss says Christmas is just another day. If there is a plane on the ground, no matter how long, I am there. The Aviation buisness has little concern for those who make it happen. My record so far is a 23 hour day, at work. That makes for a real interesting drive home after work. Soon as my Wife finishes her Degree, I am done fixing jets...I will try my luck at an education. They say you are never to old. Not sure if I agree. But I will try. I have tried to break into the automotive scene, at least they are off on Sunday's, and don't work to late into the night.

Ayup, 40s with 34 mm venturi.

I get clogged jets occasionally. When I put the thing together, I made the mistake of trying to seal a questionable fitting with teflon tape..down stream of the filter..bout every 6 mos or so, I get a little bird's nest in an idle jet to remind me that I'm a dumb shit.

Continual jet clogging should be dealt with. It is not normal. A good filter close to the carbs....clean out everything down stream of the filter...including the carbs. Good winter project.

I had not actually looked at the ID info on the carbs for exact letters/numbers until now, my carbs are 40 IDTP 3C . What makes these different than say just a 40 IDA 3C ?

Mercury gages rock. You can monitor both sides at the same time. BUT - be very careful. Mercury can be a PITA if not handled with care.

That makes them stock 914/6 carbs (40 IDTP 3C) as opposed to 911 units (40 IDA 3C). Not mutch real difference actually. Not sure of the details. Seems like there was a post regarding that very thing in the last couple of months.

I have spent most of this day reading about these carbs, I found that the factory manuals shows 40 IDT P1 3C1, or 40 IDT P1 3C. These are 40 IDTP 3C. I am still trying to find the exact differences.

J P,

Thanks. I must say I thought you had ben refering to a particular method of using the synchrometer itself. I just stick it on the throttle opening and read. Guess you do the same.

Adjustment of the MFI appears to be slightly different than carbs. I did have to start from scratch, and adjust the throttle stops, then the individual linkagages etc . . . Quite a bit of work.

I still have a couple of issues to work out, but it's coming along.

I sometimes have pretty heavy smoking at idle. which looks like oil, and it goes away as soon as I give it a little throttle. Engine was rebuilt not long ago and the stem seals should be OK. Is there anything else that can cause this ?

Michel

Martin,
Here's the link to the thread we had recently dealing with some similar questions.

http://www.914world.com/bbs2/index.php?act...f=2&t=13373&hl=

Carl

I just checked the Haynes Weber manual and they list the original equipment Weber carbs for various cars. For Porsche 2.0 sixes there are six different carb numbers listed, all beginning with 40 IDT, with diferent jet and venturi combos. I think Weber used the number variations to designate these different combos.