Modified A will not run at higher RPM

It ran great until he removed and replaced the manifolds. Distributor advance was not changed. I already suggested that he talk to FSI but that is about long term survival of the motor not his current problem. A Brierley head is 7:1, I have 2 of them.
 
I have a gauge attached to the outlet side of the regulator to set pump pressure. ChatGPT suggests hat possible problems could be a plugged filter, restricted fuel line, or blocked tank vent.
- Weak pump output or low voltage at the pump.
- A restriction or malfunction in the regulator.
The best way to separate pump trouble from regulator trouble is to measure pressure before the regulator while watching the existing outlet gauge. If inlet pressure also collapses, look upstream. If inlet pressure remains healthy while outlet pressure falls, suspect the regulator. I will put a pressure gauge on the inlet side and see if it drops.
 
Re: Modified A will not Calihute

Badpuppy said:
Point bounce?
Click to expand...
The FSI is electronic - no points. It sounds like he has one oh their centrifugal advance ones. The FSI is sensitive to how it's wired and needs a good ground to assure it works right.
 
The 2 gauges will not show you anything useful unless you remote mount them inside the cockpit so that you can see them when the engine is actually acting up. If the problem does not start until approx 1/2 throttle then what the gauges show without load is meaningless. You need to do the most basic of flow tests. Disconnect the line between the tank and the filter (if you have a filter before the pump) and check for good flow (all the tests with tank cap removed). Disconnect the line between filter and pump and check for flow. Disconnect the line between pump and regulator and check for flow (pump running). Test between regulator and fuel block (pump running). Road test with cap removed or loosened. People are throwing out an unending stream of ideas here but I think that it is time for some actual testing on your part (and a call to FSI with possibly a timing change although I seriously doubt that timing is your problem) to try and narrow the possibilities.
 
It might help us if you could give a full list of which parts were removed and replaced/upgraded as part of the 12V conversion. You described it as though only the manifolds were removed, but a 12V conversion with an electronic distributor would require you to replace most of the electrical components in the car.
 
You never mentioned what your initial ignition advance is set at. How are you setting the initial static timing?

Yea, it will advance 28 degrees but your total advance is very much affected by the initial setting. Put timing marks on the pulley so you can accuratey know your timing.

Also, if you painted things, make sure your distributor body has a good ground- run a ground wire from the distributor to a know good ground on the block.
 
What fuel pump are you using? Did you change that out when you switched to 12V? Also I have had poor luck with Spectre (round dial) fuel pressure regulators. I recommend Holley low pressure regulators with an added liquid filled pressure gauge.
 
Are both carbs on a log type manifold? If so try a progressive carb linkage, play with how much the second carb opens, you may only need a touch more gas at higher speed.

Calihute calihute calihute calihute calihute....sounds like a horse cantering by to me,

same way a train went linginalong liningalong, but a tram went managadom managadom over the rail joints. Just reliving my childhood here.
 
If it ran great last year your first suspects should be things that you changed. (Or junk that came loose and went into a jet when you removed the fuel line.)

I would concentrate on things that you changed, not things that are the same as when it ran good last year. Things that you changed include grounding of the engine, you have to scrape through that paint. I have three ground wires on my A engine because of past lousy experiences with bad grounds being the simple explanation of mysterious problems.

It wouldn't hurt to use a voltmeter to measure the voltage from ground to every point that should have 12 to 14 volts when the engine is running. You could have a high resistance connection that is just good enough to feed the coil at low RPMs. The majority of electrical problems are bad connections between good parts.
 
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