This is something for you to try to get more pep when you first hit the gas. First of all read it through until you understand what I did. I switched over from FI to a center mount progressive two barrel carb but this would work with any carb configuration. I had the stock distributor with vacuum advance and retard. I hooked up the vacuum retard to ported vacuum on the carb. What this does it retards the timing at idle. I then timed the engine with the vacuum hooked up to factory specs. The engine idles as it should at around TDC. As I start to accelerate from a stop the vacuum drops and the retard in the distributor releases giving me a little timing advance and the engine takes off with more pep. This advance works until the engine catches up and vacuum increases causing the distributor to retard to stock timing. Now the mechanical advance works for the rest of the acceleration. If I am cruising in a higher gear and give it gas the distributor again advances when the retard losses vacuum when the pedal is pushed giving the car mare advance again until the engine increases vacuum where it then retards to factory timing. At cruise speeds. the distributor mechanically advances to 27 degrees and runs there until again acceleration causes the vacuum to drop and momentarily advances the timing. The car has very noticeably better take off from a stop and accelerates quicker at speed. try it.

I've also noticed that the car runs better when it's still a little cold. No stumbling. Has anyone tried this?

Be sure and check your total advance. Its been too long since I worked on a -4 to remember exactly what the timing curve looked like. But, if I understand what you've done correctly, you are getting more advance at low speed acceleration which will make it peppier but you might also be getting excessive advance at high rpm WOT acceleration that could lead to pre-ignition. Check your total advance at 4000 rpm with the vacuum line disconnected.

Agreed, 28 (27) degrees BTDC total advance is the most you want with carbs. IIRC 3500rpm.

Been there done that. The timing advances to 27 degrees at 3200rpm. If the pedal is floored at cruising speed it will momentarily advance it further but for so short of a time it will cause no problems. I stated this in the original post. Had you read it entirely you would have seen it.

Okay...Yeah....but like the majority here we have a very low opinion of the single Weber, to practically all peeps it's a huge downgrade.
I doubt if many members read past the third sentence of your original post. Once they saw "I switched over from FI to a center mount progressive two barrel carb...." they likely hit the back button. If you have had good luck with your progressive then cool and good for you as you're one of the very few, just don't expect any converts here.
If you had questions or a tuning write up on the dual IDF webers or dells (or stock and aftermarket EFI) you would have more action on this thread.

Not trying to be a dick, just telling you the truth.

The title of this post should have been an indicator that it didn't apply to you. That's great that you love your FI. It seems the only reason you clicked on it was to talk trash on Carburetion and to spread your negativity. I am a mechanic with over 50 years of experience and I'm here to try and help others. I found this little trick through trial and it works.Hopefully it will help someone. Why are you in this thread other that being a dick?

Someone got their panties in a bunch ...



Many of us here have been down the road with of carburetors (including the guy you are trying to call out above).

Just because you don't like their answers doesn't mean they don't know what they're talking about.

Vaccum advance should be ported vaccum. Retard should be manifold vacuum.

But what do I know.

@pcdarks
Your mistake was how you titled the thread. You referred to "all you carburated folks" when most of the 914s converted to carbs are multiple carbs not single. So "all" is incorrect and draws in unwanted attention to your tip. No need to get sensitive and dismissive when you caused the misunderstanding to begin with.

I have carbs, dual weber IDA triples.

This will work with ALL carb configurations as stated in the third sentence of my original post. Try it see if you can feel a difference.

Also though, I believe you may be misunderstanding how/when vacuum is occurring in your intake.

First "Ported Vacuum" if that is what you attached your retard canister to, is above the throttle plate so it produces low vacuum at idle and increases when you open the throttle so this would not be retarding the timing at idle. If your timing is retarding at idle you most likely are connected to manifold vacuum.

BUT

Secondly, in either case (ported or manifold vacuum) engine vacuum only drops under load so just sitting there revving your engine to check the timing will still be retarding the timing via vacuum. The manifold vacuum is only going to drop if there is a load on the engine (revving in neutral does not produce a load), at which point you will see more advance than what you set it to.

It sounds like all you have done is over advance your timing.

If you want to achieve similar results in a safer manner you could get a programable distributor to dial in more advance though the low and midrange while still maintaining a safe max advance. Alternatively you could try connecting the advance side of the distributor to actual ported vacuum (if one exists on that carb) which would add advance off idle but then pull it back under load so you dont detonate your engine however if you set your timing properly in that case with no vacuum lines connected it may leave you over advanced at idle (depends on the mechanical advance curve in the distributor you are running).

I didn't say this before, as this tread has all the markings of a shit show and I'd rather not.... but it won't work for all carb configurations as many high performance carbs guys here run non-vacuum advance (mechanical) dizzys.
I have the three carb engines, I have the two T4 that have mechanical Mallorys and my /6 engine has a PMS twin plug mechanical dizzy.

Only now am I changing my 914/6 conversion to FI, the main reason is I need another intake/ignition system for my next 914/6 project.

KELTY360 is correct, your title is misleading, really you need to suck it up or you won't be making any friends here and if you're serious about the 914 you will need help here from time to time.
I'm an engine builder, I've been into building VW 's over 30 years, and into the 914 for 20 years...I still get things wrong about these cars all the time, but I suck it up, learn and move on.

Assuming you are not actually verifying your timing while flooring it driving down the road... So what is happening here is the the minor load on your engine from accelerating it up to speed is enough to drop some vacuum and you lose the retard/timing over advances but once the RPM has stabilized it comes back down to 27. The problem is these are not the conditions you drive under and when you are actually under load while driving this is happening all the time.

Take a drive WOT up a long, steep grade on a hot day and report back...
PS. I have some spare motors sitting in my garage when you do.

Your timing is over advanced.




Advancing timing can help with cold idle, its actually a feature that they have built into Megasquirt for that reason (and im sure other injection systems) only with Megasquirt it dials back the advance once the engine is warm so you dont damage your engine by running to much advance all the time.




Come on Mark, dont be so harsh!

Ill help out anyone regardless of whatever differing beliefs they may hold about life, the universe, and everything.... and carbs. Just as long as they don't piss me off, and to date only one person on this board has managed to relieve themselves of me ever offering my input on their threads again. And lets be honest at this point with all the information out there on the shortcomings of the single carb setup on these cars anyone who still swears by them I just view as sort of having a religious belief, and I learned a long time ago not to get into arguments over peoples beliefs. Personally never been a fan of praying the the controlled fuel leak on top of my motor is delivering something near the optimal amount of fuel as i drive down the road. Me, I'm an engineer, I like data, that's why I run a system that can log it all!

More than happy to share findings from that data if it helps get people on the right track!




To your point though, I could see a car with dual carbs and a hot cam having an absolute trash vacuum signal that would throw the timing all over the place so yeah... probably wouldn't want to do something like that in that case... or at all, given the only thing going on here is over advanced timing.

I went from mechanical advance, to vacuum advance distributor on an old chevy v8 years ago. It helped a lot for street driving. Less stink at idle, more part throttle power, better mpg. I see why they added vacuum advance to the distributor design back in the day. Just my $.02...

Adds a little more pep.

Just goes to show ya that belief systems are relative to the observer.

Someone says pep and someone says overadvanced timing.

Timing is relative ......and pep and overadvanced timing are entangled.

Starting to sound like Veeks now.

I'll rest my physics belief system and move on.

Right up until the rapid unscheduled de-tangling

But if he likes how it runs tuned that way than cool, who am I to say how to tune your engine. Im just saying his max advance under load is more than the 27 degrees he set it at unloaded and to much advance under load can have its downsides.

When I was much younger I one time mistook the 27 degree mark on my fan for meaning 0 and timed it using an adjustable light set at 27. Off idle response was amazing!!!

and now i know what to call those crackling sounds it was making...

PEP!!!!

I just sold my pep for a hundred bucks, I consider myself lucky

Keep the PEP up James..... I knew you'd get that.

So the pistons and valves become detangled and go straight to the......Bad Place.

Gonna start calling you St. James if you continue to keep up the PEP.


Speaking of PEP and self defracation...I used to think that the lyrics to "Sweet Emotion" by Aerosmith was "Suntan Lotion". That was before college of course.

I've wondered if and what would happen if one used two of the progressives on a 914? Dual progressive carbs?

It's already been done with smaller ICT carbs. It works but isn't good for performance. The pulses on one side of the engine are out of sync so one cylinder tends to run rich and the other lean.

Why stop there?

Use 4 of them, mount each as close to the head as possible and add a central air box they all suck air from.

That way, each carb kinda acts like an injector spraying straight onto the intake valve. And they'll do it progressively!

I found my new intake manafold!

On a big enough engine, that design would work better then all four lined up along the crank. Might actually be nice for a around town daily driver. After it was tuned lol

These look pretty Peppy.....how bout four of these?


Click to view attachment

How about these???

Click to view attachment

2 per side, pointed inward. Make an common filter/airbox for them.


Clay