Attempted to tune SU Carburetors but still backfiring on intake

[gundee]

Can you specify which pictures you need and from where exactly? Do you want pictures of the cam with the valve cover off??

 

He specified the photos for you to take in post #53.

A photo with the valve cover off and the crank pulley timing marker set to zero would be nice as well.

[jalexquijano]

I highly doubt it's a valve problem... and your mechanics tale of having to adjust the one valve to .013" never did make any sense at all. That's a wild goose chase IMHO.

 

It's going to be either a fuel or ignition problem that is affected by heat. What is the temperature gauge reading when in Traffic and the problem occurs? More likely fuel. Having to pull the choke lever on when it gets hot indicates engine is running out of fuel. Could very well be vapor lock.

 

Can you take a few clear pictures of your engine. I want to see a few things. Some good shots of the carburation and fuel lines and fuel filter would be very helpful. Take a few general pictures of ignition system and wiring as well.

 

BTW... do you have the factory heat shield in place under the carbs?

 

Edit: You need to find a different mechanic IMHO. Your Porsche " expert " has some strange ideas or you are not understanding him. Either way, these are simple engines and any decent mechanic should have it running like a top by now.

CHickenman,

 

Please apologize for not sending these pictures earlier. I believe the Heat Shield is under the carbs as you can see from one of the pics hereby attached.  Also my car has an electric fuel pump installed near the gas tank and is measuring 4psi! Do you think vapor lock could be the problem? I have a Champion 3 row radiator and an electric fan that turns on when the ac is engaged!

Edited December 22, 2015 by jalexquijano

[jalexquijano]

He specified the photos for you to take in post #53.

A photo with the valve cover off and the crank pulley timing marker set to zero would be nice as well.

 

Okay here are the additional pictures including the engine with the valve cover off and the airtex 8012s electric fuel pump which is pumping 4psi!! Mechanic insists the compression is good. He adjusted the exhaust valve on cylinder 4 back to .010. The rpm drop in said cylinder is not that noticeable as in the other 5 cylinders when you pull the spark plug wire off. Is this okay?

[Jarvo2]

Ok, so you have air, you have fuel, how about spark?

 

Several follow up questions:

 

1) Are you running points or electronic ignition?

2) Have you upgraded your voltage regulator to an internally regulated alternator & voltage regulator bypass?

3) What octane fuel/gas do you use?  

4) How loose is your distributor shaft / rotor?

[siteunseen]

Looking at that fuel filter makes me think you have some rust somewhere. The tank probably. Do you run a filter right after the tank?

[gundee]

Ok, so you have air, you have fuel, how about spark?

 

Several follow up questions:

 

1) Are you running points or electronic ignition?

2) Have you upgraded your voltage regulator to an internally regulated alternator & voltage regulator bypass?

3) What octane fuel/gas do you use?  

4) How loose is your distributor shaft / rotor?

 

1. He is running a Pertronix set up in his distributor.

2. He has the internal regulated alternator upgrade per photos.

[Jarvo2]

1. He is running a Pertronix set up in his distributor.

2. He has the internal regulated alternator upgrade per photos.

 

Must be that hot cam that he's running then.

[jalexquijano]

Must be that hot cam that he's running then.

 

Replies to questions:

 

1. I have a pertronix 1761 distributor with a 3.0 0hms pertronix coil with new cap and rotor!

 

2. I am using NGK BP6ES spark plugs gapped at .031

 

3. i have a Bosch 60 amp internally regulated alternator.

 

4. i use 95 octane fuel

 

5. the distributor shaft is not loose!

 

6. My cam is a 274F Schneider cam:

 

http://schneidercams.com/274FL6.aspx

Edited December 23, 2015 by jalexquijano

[gundee]

The spark plug gap per the factory service manual says .031 to .035.

Pertronix says you can add .005 on top of that if you wish, using their coil.

Some really don't notice that much difference. 

I have my Pertronix set at .035 plug gap. 

 

That particular camshaft is actually their lowest grind. No problems there.

May want to advance the cam gear to hole number 2 if not already.

[jalexquijano]

Mechanic tested the car this morning on heavy traffic after changing the fan clutch (NIssan OEM Fan clutch) and Water Pump (Paraut) Japanese Brand. He had also adjusted all the valves to .010. Once in traffic the temperature started to rise and the idle became rough tending to stall. He is now trying to sort this issue. Im glad this happened to him while testing as i am not paying a single dime until this issue is solved.

 

I am really getting frustrasted! As i am in the middle of a crossroads with no solution to this overheat, rough idle and stalling.

 

Isnt this a Vapor Lock issue even though i have an Airtex Electric Fuel Pump installed near the gas tank?

Edited December 24, 2015 by jalexquijano

[Patcon]

How hot is it there in traffic?

[jalexquijano]

33 degrees Celsius; humidity is very high at about 80 percent!!!