IDF's pt.II

[J11]

Rebuilt the carbs, and earlier problem of starving at top end has gone away. Something was blocked somewhere!

NOW-- when cruising at constant speed, the 1/2 carb growls so loud, it's brain rattling. Every once in a while it'll backfire out the carb too.

If I give it gas, the growl goes away... if I let off, the growl goes away. If I'm constant, it growls. It'll stop for 10-15 seconds, but then it's back.

IDF 40
32 vent
135 main
200 air
f11 tube
52 idle
3 psi fuel
1.25 turns out at sea level.

Linkage is synced at idle, downrod geometry is similar on each carb...

RPM wanders a hair (surging/stumbling) at constant speed though, and that growling!

[philip912]

Sounds like you have a combination of a timing and carburetor setup.

What you have described on your carbs is a VW setup that does not work at all on the Porsche.

Here is the common setup for the Porsche:
30-32 venturi
130 main
190 mid
55 idle
F7 emulsion tube.

I suggest that you do the following:
1. Adjust the valves
2. Adjust the timing @ 3000RPM to 30-32 degrees
3. let the timing at idle fall where it may.
4. Then adjust the idle speed to 950RPM using the idle speed screws.
5. Next adjust the mixture screws to the "best lean" for each throat.

What type of distributor are you using?
If you have a 009 replace it.

Let me know how you you are progressing because I fought a similar problem with mine.

[philip912]

I forgot to ask the following:

1. What year is your car?
2. What is the engine size?
3. Are the Webers true Webers or are they Empi copies?
4. Do you have a digital advance timing light?

[J11]

Hi--

it's a 1967 with stock motor.
Bosch 050 w/ Petronix
Empi IDF

I think it was just too lean... I opened it up to 2 turns out, and popping & backfiring has stopped (it popped once today actually). It smells a little rich at idle, so I'm gonna try the 50 jets I have in a jar somewhere...

Timing is good-- set with a digi tach/light.

It's much better now, and I don't think I'm going to mess with them until I get an 031. The 050 & new in box Empis came with the car.

After the 050, I need to do Struts, then maybe some Spanish Webers... I'll bookmark this, and use your setup as a starting point for those-- I live at sea level, right next to the ocean. Thanks!

[philip912]

The Empi's that you have out of the box are setup for VW's. I went with the Empi's and quickly learned the hard way that these are junk. The emulsion tubes F11 are totaly wrong for the Porsche. To get the Empi to work properly I had to go to 2+ turns on the mixture screws which resulted in a too rich mixture that caused backfires on deceleration. After about 6 months of this nightmare I got a set of new Webers from Webers Direct, rejetted them and they run perfect from sea level to 8000 ft elevation.
The 050 is a decent distributor as is 031. I have had both but I finally selected the RS 0012 a new recurved distributor for the 912 produced by Benton Performance. What a difference! My Empi's are now back in the box where they belong.

[J11]

I've had this car just a few months...

Out of the box, those carbs had smaller vents & smaller jets. I got the bigger vents and a jet assortment with them too. PO never got to it. He had installed the carbs as purchased, then parked it, then I bought it.

He said he hadn't driven it & I believed him-- ran like crap! Although they looked new, filters and all, I opened them up & they were DIRTY! Floats were all over the place, etc. Still had some hiccups, so I went through them again. A little fiddling & much better now.

They're running well enough I can leave them alone & do other things first. I'll get to CB upgraded Spaniards later.

Kind of a relief as I need $truts

Care to share the rest of your set up? vents? jets? Thanks!

***edit*** oops! I just saw your set up above. DOH! Bookmarked!

carbs:


car:


at air-cooled BBQ

[philip912]

Great Looking car!! You can be proud of that find. Where are you located? I live in Hemet, CA 29 miles west of Palm Springs at 1800 ft elevation. I have all the elements 100+ degrees in the summer to 40 degrees in the winter. I go to all the club meetings in Orange county at sea level to 8000 ft at Lake Arrowhead.

I had a nightmare of a problem with the Empi's because the adjustments do not remain consistent. I took it to a Porsche Weber Guru and we put on the dyno and plotted the flows. The results indicated a change. The velocity stacks were also wrong. The popping thru the carbs (lean pop) even burned my K&N air filters. Lucky I didn't have a fire. When we richened the mixture to stop the popping it fouled the plugs and started backfiring on deceleration.

The new Webers solved the problem.

Why don't you join the 912 Registry. It is a fantastic club and the amount of knowledge and experience in this group is unlimited. I have owned my '68 since 1971 and I have learned more from this group in the last 4 years than anywhere else. I found them when I started on my total restoration in 2003.

[J11]

I'm up near Carpinteria. I'm familiar with your climate, having driven air-cooled VWs year round in Palm Desert. HOT!

You have me sold on new carbs sooner than later. They're still a little weird in the transition, and I have noticed the adjustments seem to wander...

I will join the 912 registry too. It's been on my short list for a couple of weeks now. I've been browsing the 912bbs as well.

I'll have a million questions, so talk to you soon

[Jaems]

J11, Another thing to get rid of are those stacks. They are only good for looks and if you are going to do SCCA racing. However for normal street driving and racing you do not want them. Your low and mid range acceleration up to about 5800rpms will be much better with out them. Anything over 6000-8000rpms the stacks will become useful.

If you have a good 031 it is the best distributor for the 912. The RSR0012 is just about as good. The RS didn't do as well with my setup as the 031. So I am really particle to the 031. Once you have the Webers and distributor sorted it out. You shouldn't have to mess with them for a long while. Just check the sync once in a while. I have almost 16000 KM since I finished with my set up. All I have had to do was just check them once a year. I have never had to readjust anything. However, I am using the Pertronix in the distributor along with the coil and CD box.

[philip912]

Hey Jaems,
Good to see you on the board! I agree with your assessment. I use the RSR0012 because my old 031 was shot. I converted to the Pertronix also and all my timing problems went away. When I purchased the new Webers they came with the typical VW setup including those stacks and a cheap fliter base. I replaced the filter assemblies with the Weber machined aluminum base #3377 from CB Performance Products. I replaced the velocity stacks with the shorter Weber stacks and K&N airfilters.

Cheers

[J11]

I appreciate all the info...

I have a set of those CB Aluminum bases, and when I went to put them on, the studs were a hair short-- just a hair. Removing the velocity stacks would actually be enough to make the lock nuts work!

No stacks + back to the CB bases. Check.

I do need to do struts before I replace the carbs. I have green ones (Bilstein?), which according to the 912 book I have weren't used on 912's, so I'm not 100% sure what inserts to get... and what related bushings I may need...

I should start another thread on that probably, and will when it's time to install. Can anyone confirm what to order though?

Thanks again.


***edit*** I'll start a new thread...

[Jaems]

They do not make the stock factory Bogi's anymore. So your choices are the Bilsteins or Konis inserts. I prefer the Konis. However, a lot of folks like the Bilsteins. It can be a matter of personal taste. The Konis should come with everything that you would need for the front struts. It has been a while. But I think that there is a special tool need for the installation of the front struts. The rear are a direct bolt in.

The struts will only make the car handle better. Carbs will make it run better. You will love it once you get everything sorted out.

[J11]

Ordered from CB yesterday:

***Edit***got a call back-- more is out of stock-- I'll update when it's sorted***edit***