Starting my engine on a stand, issues arose Options

[malcolm2]

I have built a fresh 2.0 and borrowed a set of weber 40s to get her running, broken-in etc....

I bought a new single vacuum distributor with the flame thrower 3 module inside. Also bought the Petronix coil.

I built up oil pressure, then connected the gas lines, fuel pump, and coil. Tach and timing light too.

After a few tries, she started. As expected running very ruff. Back-firing thru the carbs.

I loosened the distributor and tried to make some adjustments. That seemed to help the back-firing a bit, but not totally. I got the idle timing to what looks like 7 btdc, but it is tuff to work everything without a helper.

I know next to nothing about these carbs, and about the same amount to tune them enough to bench run the engine, but I am looking into that. Any help would be appreciated on the carbs.

I got it idling, again, very ruff. So I wanted to do the cam break in, so I rev'd it up to about 3000 and held there. Maybe a minute and the revs dropped and I had to putz with the accelerator to keep her going. Again up to 3000, same thing revs dropped.

I have a note in to my distributor vendor about how this "rev limiter" on this module works.

So three things here. She is still running ruff, back-firing etc...and there is the high rev cut-off. Lastly the carbs, any quick checks or adjustments there? Any thoughts or suggestions?

[Mark Henry]

Do you have a snail sync tool? Sounds like a sync issue.
Bad linkage adjustment as well, the flat fours are super sensitive to sync issues.

What rev limiter? They cut off at high RPM and shouldn't cause an issue, but the bosch rotors have a resistor that can go bad. Just swap out a regular rotor.

[VaccaRabite]

First off:
(IMG:style_emoticons/default/thisthreadisworthlesswithoutpics.gif)

We need pic of your engine on the run in stand!

For the back firing you need to adjust the carbs and make sure they are drawing equal amounts of air. You need a tool to do this. Search for a carb snail. Its a gauge that you stick into the throat and it measures airflow. You want the airflow balanced between all the carbs.

You also want to be able to hold the engine at 2K rpm for 20 minutes to do the cam break in. And then 3K RPM to set ignition timing. For your run in stand - I put a cheap-o tach on mine, and also rigged a way to work the throttle. A tach is just 1 wire from the dizzy. And the throttle is also really easy. I just put some wire on the carb linkage, pull it to open the throttle to the RPM I want and clamped it off with a pair of vise-grips. field expedient and makes a lot of the tuning easier when you are working solo.

Zach

[malcolm2]

Do you have a snail sync tool? Sounds like a sync issue.
Bad linkage adjustment as well, the flat fours are super sensitive to sync issues.

What rev limiter?

I will see about getting the snail tool today.

The rev limiter is within the electronic module. appears to be adjustable. Wonder what it is adjusted to?

This came from the vendor: "If you are wondering, the Pertronix Flamethrower III module has a couple of advantages over the original Pertronix. First, the Flamethrower III module changes dwell as needed. It also senses when the key is on but the engine is not running, which used to burn out the original Pertronix! The Pertronix III is immune to this annoying problem! The Pertronix III has a digital rev limiter that you can set to the RPM that you feel is best! We believe these features are worth the additional money over the original version of the Pertronix module.

The Pertronix 3 SVDA Distributor, 12 VOLT is designed to run with a low impedance (0.32 ohm) coil for best operation"

[malcolm2]

I hear music in the back ground. You Tube may shut me down for no license. But for now.... Here is a vid of generating Oil Pressure. Finally something that did not cause me issues. (IMG:style_emoticons/default/piratenanner.gif)

Oil Pressure build up Video



https://www.youtube.com/watch?v=h2xtp-eEDQ0

[Mark Henry]

Do you have a snail sync tool? Sounds like a sync issue.
Bad linkage adjustment as well, the flat fours are super sensitive to sync issues.

What rev limiter?

I will see about getting the snail tool today.

THe rev limiter is within the electronic module. THis came from the vendor: "If you are wondering, the Pertronix Flamethrower III module has a couple of advantages over the original Pertronix. First, the Flamethrower III module changes dwell as needed. It also senses when the key is on but the engine is not running, which used to burn out the original Pertronix! The Pertronix III is immune to this annoying problem! The Pertronix III has a digital rev limiter that you can set to the RPM that you feel is best! We believe these features are worth the additional money over the original version of the Pertronix module.

The Pertronix 3 SVDA Distributor, 12 VOLT is designed to run with a low impedance (0.32 ohm) coil for best operation"

The rev limiter shouldn't be an issue if it's set correctly, pertronix either works or it doesn't.

[VaccaRabite]

I hear music in the back ground. You Tube may shut me down for no license. But for now.... Here is a vid of generating Oil Pressure. Finally something that did not cause me issues. (IMG:style_emoticons/default/piratenanner.gif)

Oil Pressure build up Video



https://www.youtube.com/watch?v=h2xtp-eEDQ0

Your video is marked private

Zach

[rhodyguy]

Depending on the idle speed adjustment screws to balance the carbs might only have the carbs balanced when the screws are on the stops. A worn sloppy linkage is not your friend. Increase the idle with ONE ISAS. The linkage will be in a natural state and the pulsing of the synchro tool will calm down. THEN use then synchronizing tool. Adjust the offending droplink. For timing, you can really increase the RPM and not have to try and sustain a stable idle with the pedal or hand operate the linkage. Makes the ordeal a one person task. The air bypass screws factor in as well. I would lightly seat them.

[malcolm2]

Your video is marked private

Zach

Thanks. I have marked Public.

[malcolm2]

Is this all there is to it? Just test or measure 1 barrel at a time either holding the RPMs steady or just idling?

[rhodyguy]

The number values on the tool are sort of irrelevant. You only have to have the reading be the same. The sealing portion on the bottom turns and exposes a hole. This is to help with the pulsing so the needle doesn't jump. Turning the idle up will help with the pulsing and no need to expose the hole.

[IronHillRestorations]

Here's my carb tuning procedure from a March 03 post:

Assumptions: the carbs have the optimum jet and venturi package (if you have an unknown engine/cam good luck on this one), the float level in the carbs is correct, the cams are correctly timed, the valves are properly adjusted, the ignition timing is dead on, you have the proper spark plugs for your engine, the linkage is good, the fuel is good, the engine is good.

Remember that the mixture and air bypass adjustment screws are precision needle valves, not head gaskets. Use your fingers to tighten them, not your fist.
Start and warm up the engine.
Make sure the two drop links for the throttle linkage are exactly the same length, and disconnected. You can use a 8mm thin ignition wrench to snap them off.
Turn the mixture screws all the way in and then 5 half turns out.
Turn the air bypass screws all the way in.
Turn the idle speed screws out til it just touches, and then in 3 half turns. (3 barrels I go 5 half turns)
Put on your hearing protection and start the car.
Use your STE and find the barrel that pulls the most. We'll call this one baseline.
Balance the barrel in the other carb that pulls the most with the idle speed screw. (if you have a Uni-syn, give it to someone you don't like and purchase a STE airflow meter)
Go back to the other carb, with the baseline barrel. You will have one all the way in, then use the air bypass screws and balance the other two barrels.
Go to the other carb and do the same thing.
Snug the jamb nuts on the air bypass screws.
All six barrels should pull the same amount of air at this point, if not repeat air adjustment procedure.
Snap the throttle linkage drop links back on the carbs. If the idle changes then you need to barely adjust the linkage mounts so snapping the drop links on, doesn't change the side to side idle balance.
Use the hand throttle or a vice grip and rag to lock the linkage between 1400 and 1800 rpm.
Start back at the baseline barrel and adjust the mixture screw in or out, to get the smoothest running and highest idle, then turn it in 1/4 turn.
Do the same with the five other mixture screws.
If you have to turn the mixture screws more than two turns either way (from baseline), you've got the wrong jets.
Recheck side to side and individual air balance, adjust as needed.
Road test the car.
If you get snapping and poping out the intake, it's generally a lean condition.
If you get heavy exhaust fumes, or pboofing out the exhaust it's probably too rich.
If you get a flat spot or popping out the intake at between 2800 and 3200 rpm, you probably need larger idle jets.

That's a rough, five minute draft of my carb tuning proceedure, hope it helps!

If it goes good it should take about 45 minutes, if not about three years.

PK

If it's running good but a little rich, you can turn each air bypass screw out to lean it out some, go a half turn out at a time and test drive. If you have good air balance, just make sure you turn all screws the same amount, and recheck the air flow at each barrel.

This was written 16 years ago before wide band O2 sensors were economical and easy to install, get one it will make your carb tuning much easier.

[IronHillRestorations]

I'll add that if your linkage moves at all when you put it back on, then you don't have the linkage correctly set up. Drop links have to be exactly the same length and both on the idle stop screw

[IronHillRestorations]

Where in Nashville are you? I'm coming through Friday on my way to east TN (Cleveland). If it's not too out of the way and my week doesn't go to hell, I might be able to stop by for a little bit.

[Superhawk996]

Assumptions: the carbs have the optimum jet and venturi package (if you have an unknown engine/cam good luck on this one), the float level in the carbs is correct, the cams are correctly timed, the valves are properly adjusted, the ignition timing is dead on, you have the proper spark plugs for your engine, the linkage is good, the fuel is good, the engine is good.

That rules out about 1/2 of the 914 engines in existence right there. (IMG:style_emoticons/default/lol-2.gif)

[Mark Henry]

Is this all there is to it? Just test or measure 1 barrel at a time either holding the RPMs steady or just idling?

I like how Amazon calls this "deluxe" seeing as it's the cheap Chinese copy. (IMG:style_emoticons/default/dry.gif)

The better one is the STE, made in Germany. About $20 more, mine's almost 30 years old.

[Superhawk996]

@mark henry

Curious if you have used a Uni-Syn. That's what I've always used and had great luck with that.

[malcolm2]

Where in Nashville are you? I'm coming through Friday on my way to east TN (Cleveland). If it's not too out of the way and my week doesn't go to hell, I might be able to stop by for a little bit.

East of town couple exits past the airport on I-40. Mount Juliet. You will probably head south (east) down 24 towards Chattanooga. But Cleveland can be reached taking 40 east most of the way. keep me posted.

Clark

[flyer86d]

Pull out each idle jet and make sure one is not clogged. Weber’s require clean fuel and very small particles will clog the idle jets. Also, Weber’s run about halfway thru the RPM range on the idle circuit. If it is rough at idle but smoth at full throttle, I’d look at the idle circuit.

Charlie

[thelogo]

Sorry but to encourage this is irresponsible

Theres a reason you should use a porsche mechinic (with the right tool's) for this kinda thing . unless you dont care if you accidentally melt down your engine prematurely.



( which you could very easily the way youre goin)



Then go ahead. (IMG:style_emoticons/default/sheeplove.gif)


Reminds me of my step dad who pryed the heads and intake off his cobra replica . so he could go for big power.

The old heads and carb made way more power as they were dialed in . then the new stuff. Which he didnt know how to tune and could never get dialed in properly.

Car just sits now. Weeping fuel . (IMG:style_emoticons/default/headbang.gif)


Im no mechanic beyond oil changes.
But i have a sobering sense of my limitations !!!