Weber 40 IDF Fine Tune---Help?

MAB · 07-17-2003, 05:36 AM

I just recently installed a set of 40 IDF's on my 68 porsche 912, with weber intakes (not a conversion kit) and empi air cleaners. The engine is newly rebuilt--all of it. With the new carbs, it runs so much better, but I'm having difficulty fine-tuning them. As the car gets hotter, the idle continues to climb up and up to the point of when I get to a light, the car is pushing 1800 rpm's (but like I said, it has to get hot after driving for a while.) It also seems to have intermittent dead-spots, sometimes off the line or after about 3000 rpm's if you hit the gas, it fades out or almost dies, then kicks in.

Is there anyone in the Orange County, CA area that can assist in adjusting properly? I've followed the basic weber adjustment info and I've taken it to a few places, but they only balance the carbs with their balance tools, and then play with the screws and send me on my way. Who's the pro who can set them up right in my area?

Thanks,

Mike

craign · craign's Garage

You might want to post a message on the SoCal 912 board

www.bay912.org

look for the link to them on the left side of the page. have you used the weber tuning procedure on the PCA 912 site??

http://912sig.pca.org/Weberadj.pdf

Craig

adot · 07-17-2003, 12:49 PM

Hey Mike

the car is pushing 1800 rpm's .

Sounds like a dizzy problem to me.

Not the new carbs

Brett

C. Clark · C. Clark's Garage

I had a similar problem, I pulled my 050 and re-installed the old 009 and bingo, the idle problem went away.
Chas.
69/912

912s · 07-19-2003, 03:54 AM

Does the idle slow after you set for a brief period or does it stay at 1800?

MAB · 07-20-2003, 06:32 AM

Sorry for the delay-
the idle goes up and down. After driving for a while, it just won't drop back down to an acceptable level at a stop. Usually doesn't hold at 1800, but more like 1400. if I put it in gear, it will drop to 900, but I have to kick it down when its warm. On the nice cool days, it never walks up like that. The stuttering, (flat spots) are there, either way. Could be timing, I'll give that a try.

Ace912 · 07-27-2003, 10:22 AM

Mike,
I got the same problem, I cant figure it out, Please let me know if you find anything out.

Regards,
Andy.

Sweetheart912 · 07-27-2003, 06:56 PM

Hi Mike. I just did a Weber conversion on my 69 this weekend. I posted a 3 part "how to" just a while ago. Maybe something there can help you sort it out. It sounds like your throttle rods and weber arms are not set right to give you full throttle opening & proper idle return. Depending on the displacement of your new engine, you also sound like you are running way too lean. What distibutor are you running? See my post on distributors. Hope the posts help out. Let me know. George

Sweetheart912 · 07-27-2003, 07:33 PM

Hi again Mike- I forgot something. You should also check the long metal, 2 arm accelerator arm throttle rod/bar that runs behind the fan shroud. Your 2 carb throttle rods hook to this bar. If loose, the bar slops around when you dump & release the accelerator pedal, sometimes binding up. Even if all the 2 front & 1 bell crank rear rods are aligned with great karma, you will always be a tad off on the carb throttle and have all sort of false demons appearing. You can fix this by removing the male ball part of the socket at the back left or right of the shroud and adding a small washer(s) where needed until laterally tight but still loose enough to move up & down freely. Put some good hi temp grease on these balls before reassembly. Sounds like hokum but the happy point can be reached with a little fussing. It is an OFTEN overlooked but simple fix. Hope this helps. Good luck, George