The Cal-look Lounge

Hi

I have a 1915 With this setup: Engle 110, Stock rockers, 10:1 compression ratio, pertronix ignition. The heads are CB 044 with 40 and 35 mm valves, ported.

The engine is run in JeeRacing's dyno, and ran well. As far as I remember it dynoed approx 130 hp without belt with a merged header.

The problem is that the spark plugs on one side is fouling after a couple of hour oof driving in normal traffic. The carbs are chinese IDF 48 with 36mm venturis. 55 idle jets and 125 main jets. The spark plugs are NGK B6ES. The carb float height is spot on, (and triple checked). The needle vaves are checked (and working).

Any ideas? I have tried another ignition system (009 + Bosch coil) without success. I have run through the carbs several times. I have run out of ideas.....

BR

Jens Kristian

Have you tried to swap the carbs over to see if the fouling changes sides?

No. The engine is in a bus, and it is very difficult to swap carbs. By the way, the carbs are responding as normal to adjustments in the idle screws.

Do you know your fuel pressure? Pressure adjuster is at least quite easy bolt-on -thing to try.

Other thing that comes to mind is the temperature of the fuel on carb bowl that could cause problems - but that usually manifests as poor start after running hot for a while.

If the carbs themselves are hard to change - you seem to have taken the carb tops off for float and needle valves check. If the problem is still somehow related to needle valves or floats, could you try to swap only carb lids?

Fuel pressure is controlled by Filter King fuel pressure regulator. http://espimages.biz/2386/I/179/52/FPR004.JPG It is supposed to have a factory setting of 3 psi, which should be OK. I'm using a standard type mechanical fuel pump. I have not tried to swap carb lids.

Take a pic of your plugs so we can take a look.
Have you tried a hotter plug as a test? Smaller numbers are hotter with NGK so try a 5 and see what happens.
Also, your plugs are standard type and not BP, with the P standing for projected electrode.
Projected electrodes are better for resisting fouling.  ;)

I went from spark plug 8 (which was clealy too cold) to spark plug 6. Did not help. Can try BP4ES and see what happens...

Sure. When you pull the plugs try to get a pic of the fouled ones vs. the good ones on the other side. That would be interesting to see.

Do the Chinese Idf copies have the choke circuits, sometimes extra fuel can leak through them on Webers, plugging the  choke circuits would stop any potential route for excess fuel.

How can I plug the choke circuits?

There are several ways to plug the circuit
Tap a thread and use a screw to firmly hold the moving parts of the choke mechanism closed.

Tap and use a plug to block the gallery.

Use JB Weld to block the gallery. I did this , it works fine but I am not sure how long JB Weld stands up to fuel.

Also if you don't already have them , fit heat insulating spacers under the carbs, IDF's can spill fuel caused by heat soak after shutdown , this can result in a carb fire.

What is the lambda telling you while driving in the "fouling" range?

-BB-

I have Empi 44s. They eliminated the choke circuits on these, I imagine your Chinese 48s are the same.

The lambda is a bit rich. But it is a Vintage Speed exhaust, With a strange placement of the lambda, so I do not trust it too much.

What is a bit rich if I may ask? I tuned my 1915 with Vintage Speed exhaust perfectly well with 48 IDF`s, lambda and IR temp. Is it enough air entering the engine compartment on the side that is fouling? And does anything change when/if you have the engine lid open? And if you use a IR temp meter, is there any major difference in the exhaust temperature from side to the other side? If you do not have a IR meter you can borrow mine or bring the bus to the garage.

How cool would it not be with asymmetrical jetting  :)

-BB

Wow, was that a typo or do you really have 125 main jets?

The 44IDF comes stock with 135 mains and the 48IDF with 150 mains.

Having run both on my 1915 engines of different combinations, I always ended up at a jet size over, so 140 if it was a 44IDF and 155 if a 48IDF.

44IDF's come standard with 36mm vents and the 48IDF come standard with 40mm vents.

If you are running a 48IDF with 36mm vents and 125mains it has to be way too lean.

Greg

Hi

I have tried 40 and 36 vents in the IDF 48s
Ran 145 main jets With 40 vents (on the dyno) and 125 main jets with 36 vents (used lambda in the car). Anyway, I do not think that too small main jets cause the fouling problem.......

BR

JK

have you measured what's your actual fuel pressure?

1. measure voltage @ 1.5 terminal of your coil with key on. You might find it's 10V or less. Before I went to CD ignition in my car in 1994, I wired up a Hella 40amp relay so the coil was getting full, clean 12V.
2. try NGK iridium plugs, I believe you can get your configuration and heat range in iridium, the part number will end in -"EIX". Be careful about going to a hotter plug. If you aren't fixing the issue, but masking it, by going to a hotter plug, if what ever the root cause is someday fixed, you're going to have an issue you won't want.
3. check valve lash
4. I don't think it's a fueling issue. If it was, you'd be having tuning issues more often than just after hours of being stuck in traffic. Excess fuel pressure makes a Weber car an absolute nightmare to drive at steady state. I mean pure misery. The car will hunt and bumble along until you ring its neck and stand on the gas. If it runs good otherwise, except under conditions you described, I think it's an ignition / voltage issue. I'd even measure voltage @ 1.5 on  coil AFTER driving it in traffic and it begins to act up.

Good luck

Jim R.

Sorry- one more thing. Air filter(s)- clean, correct dimensions, able to pull air in..? Velocity stacks aren't too tall, and jammed up against air filter lid? good luck

I normally run 5's in stock engines (factory original) and 6 for higher compression engines like my 9.5:1 1776. I have 7's in the turbo.

chinese carbs eh  ::)

Thanks for the help.

Valve lash is checked. I am beginning to believe that it is not purely engine related. It might be that the engine does not get enough air. The car it sits in only have "rib air intake" on one side. The fouling happens on the other side. The fouling happens after long drives at cruise speed. The enging compatment get hot as a result of limited air intake and the vintage speed exhaust. On Shorter rides it goes like champ. It idles smoothly. It behaved nicely in the dyno. So it might be related to lack of air, or electical issues (too low voltage as you point out)

Take a longer drive without engine lid, or racket it up, so the engine gets all the air it needs.


After that, if the fouling is due to lack of air, maybe get some duckting from under the car to the engine bay?

MAX 2.5 psi on idf (china 2.2 psi )
China needle valve is crap (buy Italy manufactured)
/// Micke

What type of fuel pressure gauge do you use to check pressure to the tenths of a pound? Mine is 0-15 I think and hard to read those low values. :-\

No, I get you, I agree, I would think 125mains would be way too lean...

So can I ask what your Air correction jets are?

Cheers,

Greg

Too small air inlet to the engine bay might indeed be the problem! It also could explain why your unusually small main jets compared to aux venturis still somehow work.

My older beetle had two of the air inlet louvers taped shut from under the outer grill by previous owner. Probably to save dual carbs from getting wet when left to the rain. My ET got whopping 0,6 sec better (to 15.2) on quarter mile just by removing engine lid - top rpm's were much better.

Would it if the engine doesn’t get any air?

Deck lid standoffs to the rescue!  ::)

Well every engine I've ever tuned in, which is a lot of "1915's" should never have to run anything less than a 135main jet in a 44IDF and nothing less than a 155main jet in a 48IDF.
Of course this means that the air is available in the usual way, if it can't get ANY air, then it can't run at all...

 Greg; I modified your post to make it easier for everyone to read cronologically.



What I ment was that an engine running in an enviroment with less available air, should need a smaller fuel jet?

The bus it is in only have ribbed vents on one side, so if the seal between engine and car is tight, the enigne will maybe have less available air to suck in => hence the small fuel jet.

Right, well in that case I agree completely, it's simply how it works...

From the morning to the afternoon at the same racetrack I end up changing jets, all due to the changing air during the day and elevation. You probably have heard of Mt Panorama Bathurst in Australia.

So on a 1915 engine revving to 8000rpm, and 48IDF's I change from a 160main jet in the morning (lots of cold air) to a 155main jet in the afternoon (warmer air)...

It's just the 125mains that I have a problem with, in 30yrs of playing with Webers on VW engines, I've never had anything with the size carburettors and venturies that Jens has that would need to run with such small main jets... If they were 40IDF's with 28mm venturies I'd understand.

So what are all your jets Jens? and what was the A/F ratio on the dyno that ended up with this jetting?

Cheers,

Greg

They are 36mm vents.

AFAIK the engine has only been in an engine dyno, not dynoed in the car.

Oh its a splitty. You gotta do the 70's thing and slap the old side scoops and add some stickers to them...

https://bringatrailer.com/wp-content/uploads/2014/07/1967_Volkswagen_Bus_21_Window_Deluxe_For_Sale_resize.jpg

I'll ask what all the jets are over again.

BTW I'm just trying to help.. as I love tuning Webers in, I have done it on VW's for 30+ years.

I'm just not near you or in your country, so I rely on some data to be able to help.

Cheers,

Greg

Hi apprecciate all the help.

The engine sat in a car belonging to a friend of mine. It is now taken out of the car. I will revert to you when I get the chance of looking at the rest of the jets. I do not think the problem is related to "air choking" anymore, as the car was driven with the lid open the last time the plugs fouled. So it must be related to the carbs or ignition. But I still cannot understand how too small main jets can foul the plugs.... This has to be related to idle jets, idle screw adjustment, floats or needle valves. Or heat related problems in the carbs (boiling gasoline or needle valves getting stuck when they get hot?). Or ignition related. The prblem is that every time the plugs fouled, the engine had been driven for quite some time (30-90 minutes). So it is difficult to sort these things without mounted the engine in a car.

Try and get pics of the plugs for us please.  ???

Maybe the jets have been previously drilled larger than the size they were stamped.

Sorry, I didn't ask earlier, but how many turns out are your mixture screws (running IDF's, correct).
And probably doesn't matter with your current issue, but have you experimented with the idle-air-bleed adjustment (if you are running IDF) to see if you can improve and clean up the issue?

Good luck nailing this down. I hate my own problems like this.

Jim

These kind of problems are frustrating for sure. I have a permanent AF gauge on my car which I've found very helpful for not only tuning, but as an indicator when shit happens unexpectedly, like a hose falling off alerting me and letting me know like a 'check engine' light.
With the prices falling for AF gauge packages, would it be smart to have one to help nail down these issues as they arise? Or would it just add confusion.

You may have just answered my questions on this Jim, I stopped drilling and or soldering up jets for this reason, got expensive to buy new sets, must have $1000 in the kit over the years, but at least I know exactly what I am dealing with at all times.

Also, to Martins point, I have a permanent Innovate meter in the racecar, and a CB one in the streetcar, no guessing and a real world dyno at your fingertips for the exact place and driving/weather environment you are in. Invaluable.

I too would like to know what the answer is eventually, the only time I was constantly fouling plugs in my engine was with a very large cam and the wrong heat range of spark plug, it would drown the spark and leave me hesitating all over the place, the only cure at the racetrack was to take the car out the gate and run it through the gears on the road (race car was driven to the track)... I would then attempt to get to the start line without constantly starting the car.

Talk about a hassle!
Please check back in when you have some more info, I'm know I'm not the only one interested in what you find.

Cheers,

Greg