TheSamba.com :: View topic - 412 CB Performance Carb Conversion / Exhaust Gasket Info

Sat Sep 12, 2009 7:20 pm

Hey everyone - I'm in the process of swapping an injection system out of my dad's 412 2dr but have run into a snag. The fuel pump is not running - it appears to be controlled by a relay under the dash. The electrical diagram I reviewed shows the relay is controlled by the injection ECU. I can bypass the relay and run the pump full-time, however is there any threat of flooding the carbs? What's the easiest way to get the pump running if the ECU has been removed during the carb swap?

Also, I'm putting on a header and dual exhaust. I bought the kit from a guy who had it for his van but never installed it. I need to find exhaust gaskets. Any suggestion on a company that sells gaskets? T4 parts seem to be a little more difficult to come by...

Thanks

Sun Sep 13, 2009 10:45 am

You can't use a high pressure FI pump on carbs.

Sun Sep 13, 2009 1:05 pm

I purchased a fuel regulator to drop the pressure to the recommended 3.5psi. The main concern is getting the fuel pump to run. The wire diagram shows power to the pump coming into a relay under the dash that is controlled by the ECU. The other wire controlled by the relay seems to go back to the ECU, maybe some type of confirmation that the relay is closed. Not sure - the diagrams are in German. I can piece some things together from the van diagrams (similar nomenclature) but still can't get the whole picture. Looks like my best choice is to wire the pump direct to the fuse panel to a slot that receives power only when the ignition switch is on.

Sun Sep 13, 2009 2:45 pm

Trying to drop pressure from 30-60# down to 3.5# is asking for failed pump or regulator, if it will even work at all.

You also will want to wire up a kill switch or other interruptor for ANY electric pump (even the right one you will soon buy) so you don't pump gas all over you in an accident. The EFI system stopped the pump when the engine quits.

Sat Oct 09, 2010 10:31 am

Hey man, I am really stumped. I bought a 1971 411 for my kid and the FI had be converted to a single carb. I have pieces of the FI, but not the total system. A modified intake was put in place, and the carb that was placed on the VW 411 is a Rochester BC type one-barrel model 7007200; the same one used on a 53 Chevy Bel Air 6 cylinder. Due to budget issues I have been trying to tweak the issues out and see if I can get a daily runner for my son out of the deal. After rebuilding the carb with a kit from Napa, I did finally get the car running, but I have some big idle issues and top end power issues. Here are the issues:

1. Idle surges up and down (low to moderately high. I installed a Facet Possible EFP3 electronic fuel pump. Around $40. The engine runs but surge idles as mentioned above. Also as mentioned, the top end speed is only around 50 MPH with a pretty long time to build up to that speed. The PSI delivery on the installed fuel pump is around 2.5, but the specs state 1.5 - 4 PSI. I also tried installing a Spectre dial fuel pressure regulator to keep at around 3.5, but that just prevented the car from running altogether, so I pulled it off.
2. Based on what I have read, the Rochester carb installed has a manual fuel pressure PSI at 8 and 130 GPH flow for a 1953 Chevy Bel Air. The engine that this carb was matched with was a 6 cylinder Chevy engine for the 1953-56 Bel Air, a much bigger engine that the VW 411 1.7 L.

So, here are some questions:

1. Do I need to up the fuel pressure to account for the 8 PSI and 130 GPH that the carb is set up for on a 6 cylinder Chevy Bel Air engine? Can it be the pressure at 2.5 PSI is too low for the carb?
2. Will the 8 PSI and 130 GPH be too much for the 1.7 L engine?
3. Should I scrap the whole thing and try to find a carb that would match the project and pray for the funds to accomplish the deed? Really like to keep the cheap if at all possible?

Any help or insight would be great!

Thanks!

RJH

Sat Oct 09, 2010 11:25 am

3 lbs is correct for dual Solex's on a 1600 Type 3 squareback. It will do 75 mph in 1/2 mile. Pull your distributor and clean/check that your advance is functioning. Mine has 5-7 degrees initial advance static timing with 30 degrees total advance at 3000 rpm. You need a timing/dwell/tachometer multi meter to tune it with! You also Need a 411/412 Manual from www.books4cars.com ?

Sun Oct 10, 2010 7:39 pm

I cleaned and checked the advance on the distributor and it appears to be working fine. The only thing now is that there appers to be even more of a huge flat spot now on acceleration than before cleaning and adjusting the advance on the distributor.

Still have the idle surges up and down and still have very low accelerastion and top speed still at 50, but now big flat spot.

Wow, what a project. Think I should scrap the old Rochester and get a webber for the carb converted 411?

Sun Oct 10, 2010 10:47 pm

i say find the F.I. stuff and put it back on
It also ads proper HP

Mon Oct 11, 2010 5:50 am

x2 or find a Bus engine that has dual Solex carburetors.

Mon Oct 11, 2010 7:48 am

there is a guy in canada
when he gets back into the country he has Tons of F.I. parts and T4 parts
including 2 pairs of 40 solexes...ill let you know when he gets aoled of me again

Mon Oct 11, 2010 9:16 am

What specs are you using for your timing? The timing needs to be set to the required spec for the distributor you are running and not necessarily the original specs for the engine. If you have a dual vacuum distributor the specs for that distributor depend on both vacuum cans working correctly, otherwise the timing will be way off. You can set the timing for most any distributor at 28-30° BTDC at 3500+ rpms with the hoses off.

You are in uncharted territory dealing with a Rochester carb, have no idea what it would really take to get one running.

Tue Oct 12, 2010 10:43 am

Thanks for all of the replies and yes, I would love the contact info for the canadian gentleman. I'll see if tweaking the timing helps and will report back.

Thanks again!