I put the engine back in my car on Saturday that I and a very great friend build. The engine set up:

74 2.0
Euro Mahle Pistons 8:1 set at 8.2:1
9550 RAT Cam with the whole Valve Train set up
Mallory Distributor Set up by Chris

I put 40 IDF Weber Carburators brand new
With 28 Ventures
Idle jets are 55
Molsifire 20C 115/F11

The Car ran strong smooth
Then I had a charging Problem and the Car started to ran worse and worse a lot of misfire. I fixed the Charging issue but I still runs worse and worse especially when you drive it longer then 15 min. I am think its the carbs but I blew out the jets after taking them out of the carbs. Still not better...

Any ideas?

Btw I am not looking for a discussion about a 9550 cam with carbs!

Fuel pump issues? If it ran strong and now does not it sounds fuel related. If not the carbs what's left? Pump, fuel, fuels lines Filter? Isolate and test each part. Report back. I'm sure someone else will help.

How bout run the carbs from a gas can. If it smooths out you know it's in the lines. If it still runs bad its in the carbs...

Also. Describe misfire better. Popping in the carbs? Backfire. Just a continuous sputtering motor?

Good luck.

Some Back fire mostly popping in the carbs (especially on the passenger side) lean?
Feels like its not running on all 4!

Also now it does not even start well

maybe your charging problem did something to the unilite? do you have a nother dizzy you can drop in to verify?

did you clean your tank for your brand spankin' new engine? mesh filter in the tank or a new fuel filter? avoid the little vw style. if the idle jets are plugged it's going to run poorly ALL of the time until you're off of the idle/progression circuits. the simplest test for plugged idle jets is the engine response when you gently close the idle air mixture screws (one at a time) on what you presume is the offending carb. what version of plug wires are you running? it's all pretty well spelled out in the Weber book from CBperformance. esp in the trouble shooting guide. stick a flow meter on the front barrels of each carb on a warm engine at idle. if the readings are different your linkage is off or you could have a vacuum leak in the induction system. so many variables with carbs...hard to diagnose with limited data.

what is a Molisfire 20C? the 115s are your main jets yes?

I think he meant emulsion tubes. Those should be F11s for pretty much ANY Type 4 engine, right Kevin? I don't know what 20Cs are. 115s are small - that's what I had which was causing my hesitation/stumble from the idle circuit to main. But like you said, there are a number of variables to cover first before even approaching the jets. I think it sounds a lot like fuel filter/pump related. But I'll echo everyone else's sentiments... we need more info about the setup and the problem.

Do you have a points replacement system of any sort?

My suggestion is to change to 32mm vents, 50 idles, 125 mains and see what happens.

Mallory Unilite

Reason I ask is if the idle jets aren't plugged I had a Unilite module fail in just that way. You can see it with a timing light as an unsteady timing at a fixed rpm. Worth looking at and easy to fix. I started running the Mallory widget that protects the module myself.

-Aaron

I think the Mallory just quits altogether if the optical module fails.

I say fouled plugs? or maybe clogs somewhere in your carbs.

There are numerous places IDFs can clog on you, like anywhere from the main
stacks to the AF control screws and not just the idle jets themselves.

John

That is one fail mode, but I have experienced the mode I described first hand - in my car.

I did not know they could partially fail.

I went out to start my car one day and it would crank fine but no fire.

On a whim I switched out the optical module and it was back in business.

Went right inside and ordered the circuit guard module and never had a problem again.

I still bet the OP's carbs are clogged somewhere because that is such a common
problem with IDFs.

John

You know, my car is starting sort of similar kind of symptoms. Runs great until it gets good and hot and then starts some stumbling crap. Mild, but it's just not quite as strong or smooth at that point. The last time I had it out and hot, the tach started bouncing (beyond normal 914 tach bounce) 1k rpm swing from 4k to 3k, like a drop. I've been wondering if my Mallory is all right...

Sounds like the problem... Carbs simply can't be ran out of the box these days.

That's my thought too.


The only time I've ever experienced that was when the coil clamp was loose and the coil negative was grounding to the engine tin. But this could also happen if the Mallory stops triggering intermittently.

If you have a Mallory coil, try swapping it out for a stock or Bosch Blue coil. We've noticed problems with some coils when they get hot.

Apparently this thread doesn't need to be named Urgent since the OP hasn't responded.

He's busy working on the car!

I was working on the car all day! And it was urgent because I plant to move to California this morning with the car but now I will leave tomorrow morning....

I tried everything you guys recommended and thank you all for your help !!!!

It turned out to be the new Webers... The holding Nut for the needle pump came loose, so the Float where stocked at empty but the pump was cramped close so the right side was starving for fuel !

Now the engine is running AWSOME! I love the 9550! Best cam I drove ever Jake!

Good to hear. Sorry, you didn't mention the reason why it was urgent. Glad you fixed it!

The who what where?

Glad you fixed it!

John

needle valve seat came loose, contributing to a sticking float, which starved the carb for fuel.
makes sense if it was never tightened properly at the factory.

It does seem that new carbs, whether Weber or Empi, need to be rebuilt before installation.
I've seen float level settings way off more than once, among other problems.
Same is true for Mallory distributors. They have numerous possible problems which must be resolved up front to avoid performance issues.

yes. im sure they're not built in lab like conditions...

You hit the nail on the head Chris and I'm glad I got the distributor from you!

You said 50 idle jets... The idle jet adjustment screws are pretty far out,
It seems like 60 would run easier but that is just a speculation from a guy just starting to scratch the carburetor surface!