Engine missing at high rpm HELP!!!

[clubracr]

My 914 E production is experiencing a miss above 4500 rpm. It doesn't seem to have hurt my lap times and I actually ran my fastest lap ever with this happening(probably was totally flogging car out of frustration). It happened between sessions with no notice. Shut car off running great and next time out it started. I have checked valve clearance, installed new 009 distr, valve springs look ok, timing is ok(but willing to hear reccomendations),intake and carb gaskets new-Dellorto 40s,dwell is right, bought MSD but not installed yet, bought elec. ignition but not installed yet. This condition causes the engine to sputter from 4500-7000 rpm. I have to short shift or wait longer for the engine to wind up. It is consistent and does not go away. Plugs like new. I heard about something on the carbs that plugs up but don't remember the specifics. Any suggestions would be greatly appreciated. Thanks!!!

[Joe Bob]

You are running "E" Production in SCCA with a 009 dizzy? You are a better man than I...the 050 would be my first choice, unless the Porsche haters at SCCA won't let you...

As to your missing, check the fuel filter.

[clubracr]

Will give the 050 a shot. Fuel filter only has 6 races on it and is the 12" long aluminum "nascar" type but it's worth a shot replacing the element. Thanks. Anyone got an 050 for sale reasonable?

[Ian Cubus]

Sounds like you have a fuel delivery problem somewhere. As already mentioned check your pump and fuel filter. Once that's ruled out check your jets (idles and mains) to make sure you don't have any trash in them. There are also screens located in the carbs where the fuel lines enter. What kind of pump are you running? Are the float bowls running out of fuel? What size motor and jets do you have? These are the questions that come in my mind. I am running carbs on just about everything I own so I am somewhat familiar with some of the headaches. Let us know what you find cause I am curious. Thanks, Ian

[clubracr]

This is my first 914 and my race car and also my first car with carbs. that said, how do I know if my float bowls are running out of fuel. I assume the carbs have the factory size jets in them. I'm going to order carb kits and shop that job out. I'm using an electric Holley fuel pump. If I disconnect the line at the "T" I have plenty of fuel. Thanks for all of the advice!!

[JP Noonan]

From what I've heard plugs only show what is going on at the time the motor is shut down. Since the problem is consistant, try getting it to miss than shut the motor off at that moment, then read the plugs to see what the mixture is doing during the miss. I would do it at the lowest RPM possible, I don't know whether shutting a motor down at 7000 is a good idea or not.

Somewhere in my foggy memory is an article out of a VW magazine that talked about a missing from the 009 weights spinning and hitting the inside walls of the housing. Anyone else remember? It had something to do with the Brazilian made Bosch dizzy. If it says "Bosch" but not "Germany" it is Brazilian. I've also been told that the 009 is for low RPM stationary VW motors, like generators.

[mufflerbearing]

first thing I would check is the points run a dollar bill through them check the gap but probably not because of your new distributor, but it's worth a shot

[turbo2.0]

I had a similar problem. Like the previous posters indicated, try and sort out the ignition first. The 009 and the 050 can deliver the same top end hp, but the 050 has a wider advance curve, allowing more retarding at static. Spin the motor up until it starts to miss, hold it there for a few seconds or more, kill the ignition and put in the clutch at the same time and coast down. If the plugs are wet or partially fouled, it's the ignition. If they are clean, it's probably your high speed circuit in the carbs. This works better with new plugs. Check float bowl levels, floats, (the dells usually don't have float problems like the webers), and then check the mains and the AIR CORRECTION JETS. If the motor is leaning out at full throttle/high rpm, it's probably a float level or air correction problem. I would definitely spend time looking at all of the ignition before I started messing with the carbs though. Carrbs usually don't just go bad all of the sudded like ignition will, unless it's a fuel delivery problem like they said. Points, dwell, timing (with a light, at 3500 rpm,) plugs, and wires. If theres a problem with the mechanicals inside the distributor, it will show up with the timing light. A 009 has to be set farther advanced static than a 050 in order to achieve the same total advance, and thats what we measure with a centrifugal advance distributor, total advance, not static.

[Joe Bob]

Panorama Magazine, Pelican and the local VW aftermarket shop should have the 050 available...$50 new.

[This message has been edited by mikez (edited 01-09-2000).]

[John Rogers]

If the car is used just for racing, there may be water in the gas tank since the car sits more than it is driven. I have the same trouble with mine. Use a coup[le of cans of water eliminator. I would install the MSD unit and electronic ignition and stay with the 009 since all you care about is toital advance unually and I run about 36 to 38 degrees total with 103 octane VP gas. When was the last time you rebuilt the carbs? I would do them every winter if I lived in a climate that got really cold, So Cal doesn't have this problem. I rebuilt both Webers recently and they had some white vaseline like goop inside the float bowls and the air tubes and there was some corrosion. Even race gas will let stuff build up.

[turbo2.0]

They sell stuff to keep gasoline from forming varnish. I can't think of the name right now, but I use it in my Waverunners during the winter. The problem with most gasoline is that it is produced using a catalytic cracking process, where a large, heavy molecule is "broken" and reformed into a useful gasoline blend stock. (can you rell I've spent way too much time in a refinery)? After a while, the reformed molecule tends to revert through oxidation back to it's more stable configuration. The result is a waxy varnish, and a reduction in octane. In warm weather you can loose an octane point a week. This happens slower in cold. On a street engine it's probably not a big deal, but on a race car it is. Of course, I'm sure no one here lets old gas sit in a tank for very long. One other point, most water eliminators are alcohol based, some are mostly methanol. Some alcohols are bad for older rubber o-rings, and I have heard that some even attack magnesium. Just something to get the conversation going...

[Alpine]

I think the general consensus on the Rennlist mailing list was that the 009 distributor is poop.

Alpine

[turbo2.0]

For normal to high performance street driving, the 009 is not that great. The lack of a wide centrifugal advance curve just means that it has to be set at a much more advanced static setting. This may hurt starting, idling, and/or low end performance a little. The 050 has more total advance capability. That's it. Other than that they are nearly identical. For all out racing where the engine is usually at high rpm, the 009 will work as well as a 050. Neither one works as well as the stockers on a 914, IF you have a decent vacuum signal to work the vacuum advance, although they are a lot less expensive. NOTE: this is just my opinion, and I'm sure that there are others who disagree.

[MJHanna]

Check to make sure your carbs are in sync. If they are out, they can cut out. I know this is basic but you have to have a baseline.

[JP Noonan]

Just a random thought, what about iceing? Could that do it?

[scott matre]

I don't think that your problem is with fuel delivery per-se. if you were running out of gas in the carbs, your engine would cut off and on. I think that you are either having ignition probs, or running too lean. Diagnosis. if it misses in neutral, and/or 1st gear also it is ignition. If it only happens in the higher gears it is lean. suggest you run high speed to cause the miss, then turn off the engine while it is still floored. THEN do a plug check. Rule here is white is not right, richen it up. I fought just these probs with Mikuni's on a GT-4 car every time the weather changed. which reminds me. The weather is cooler now, more 02, means leaner mixture. BECAREFUL - lean means overheated heads/burned valves

[PeteD]

With Dellortos I would first check the fuel pressure. I suggest having about 7psi going into a regulator near the carbs with an output of 3psi. This should ensure good fuel delivery.

Secondly, if you are running well at idle and mid-range, this means you have your idle circuit set-up (jetted) correctly. But at full throttle, the majority of the fuel flows through your main jets. I found that I needed a bigger air jet to run smooth at high rpms. The emulsion tube (of which there are 8 different ones available), which holds the main jet at it's end, is a real neat thing to mess with when tuning, but it is kinda confusing. They ship with a #3, but for racing another emulsion tube might prove better. If you don't have a copy of Tomlinson's Dellorto book, get one and read it over and over. Eventually it will all make sense.

But, all that said, I am with the others who say make sure your spark is good first. (You might have floating points, cross firing, cables too close to metal, etc).