427/425 Engine Problem

[John L.]

Re: 427/425 Engine Problem

Rich - if I remember correctly, the power valve supplies additional fuel at low vacuum. It he is still using ported vacuum, it is going to be very low so the power valve will supply enough fuel to keep it running ok. When the car warms up and he has the engine running at a higher rpm, the PV will not supply the extra fuel and maybe starve the engine. Could be that he has had the wrong PV both times or the engine is not producing sufficient vacuum.

[Chris H.]

Re: 427/425 Engine Problem

Rich, the stumbling started after the car had been driven for about 10 minutes and the shielding was not installed. And yes, the 207 was a typo.

[Richard M.]

Re: 427/425 Engine Problem

John, I think Walter needs to do more diagnosis to determine if the power valve is suspect. I don't want to discount it as a possibility, but since he's had 2 different carburetors involved, it appears the odds of having 2 bad PO's is not that common. However, I'd be the first to admit 2 of "anything" going bad or "DOA" is not to be overlooked. I've had these types of oddities before. Quite head-shaking.

Chris, I had a similar issue and when we tested the failing coil using a IR gun when we suspected it had failed, I was surprised how high the temperature was. In one case it was over 250* F. Engine coolant temperature was normalized at 180* F. It's cumbersome to test, swap, and retest coils in a 427 with shielding. The design makes it hard to R&R. If you happen to do more actual coil testing, it would be another data point to know what the actual coil temperature is when it fails with a IR gun reading.

Walter, We've had more examples of other users experiences and we still are eager to hear from you after more testing. These things certainly take time to analyze so when you get back to testing let us know the results. Again, it seems this is the 3rd or 4th similar experience I've been reading about lately, and since many of us have had similar issues I'm very interested to know the outcome.

Rich

[Walter R.]

Re: 427/425 Engine Problem

I will post when I have findings. I have corresponded with Jeff at DC and I am going to rule out fuel first and than go to ignition. I haven't been able to research further in last few days. We are going to rule out vapor locking first as suggested by Richard. If that not the culprit I will install 3rd. carb that I have and change fuel pump if necessary even though my fuel pressure checked OK. Fuel pump not expensive and I will have new pump.

[Chris H.]

Re: 427/425 Engine Problem

Rich, interesting you should mention temperature. When I removed the bad coil, it was hot to the touch, even 30 minutes after engine shut down. The TI coil when I pulled it was warm, but certainly not as hot as the bad coil.

[Richard M.]

Re: 427/425 Engine Problem

I will post when I have findings. I have corresponded with Jeff at DC and I am going to rule out fuel first and than go to ignition. I haven't been able to research further in last few days. We are going to rule out vapor locking first as suggested by Richard. If that not the culprit I will install 3rd. carb that I have and change fuel pump if necessary even though my fuel pressure checked OK. Fuel pump not expensive and I will have new pump.

Walter, When the problem shows up, if you immediately test for and have fuel at the accelerator pump nozzles with proper flow, ie not vapor lock, I would then test ignition for spark. I'd have a timing light handy and clamp the inductive pickup right at the coil wire. Crank engine and see if you have spark. This could be tested withing a minute or two of the failed condition while everything is still hot.

I would definitely do this before swapping in a 3rd carburetor.

Rich, interesting you should mention temperature. When I removed the bad coil, it was hot to the touch, even 30 minutes after engine shut down. The TI coil when I pulled it was warm, but certainly not as hot as the bad coil.

Chris, Coils normally run hot, even hot enough that you can't hold on. However, I have never seen a maximum operating temperature spec for any coil. Failures I've encountered were over 250F, on 2 coils up to 280* F.

Rich

[Walter R.]

Re: 427/425 Engine Problem

I am happy to report that I have solved issue. I decided to rule out fuel first and knew the carburetor was not the issue. I removed in line plastic fuel filter that had been installed between fuel line before fuel pump. The short rubber hose (3-4") from filter to fuel pump was bent a bit and the filter was dirty. When looking in the hose you could see there would be some restriction in fuel flow from the bend. After installing new filter and hose drove the car with no problems. I did not declare problem solved until I drove out a few more times duplicating conditions. Engine has never run better after additional trips. The hose could have bent more when it warmed up further reducing fuel flow as well as other conditions created when engine warms. After dealing with the problem for 10 months this was an early Christmas present.

[Ara G.]

Re: 427/425 Engine Problem

I am happy to report that I have solved issue. I decided to rule out fuel first and knew the carburetor was not the issue. I removed in line plastic fuel filter that had been installed between fuel line before fuel pump. The short rubber hose (3-4") from filter to fuel pump was bent a bit and the filter was dirty. When looking in the hose you could see there would be some restriction in fuel flow from the bend. After installing new filter and hose drove the car with no problems. I did not declare problem solved until I drove out a few more times duplicating conditions. Engine has never run better after additional trips. The hose could have bent more when it warmed up further reducing fuel flow as well as other conditions created when engine warms. After dealing with the problem for 10 months this was an early Christmas present.

and my good friend Mark Lincoln wins the prize.......Glad you figured out your issues Walter.....Enjoy the car...ARA

[Mark L.]

Re: 427/425 Engine Problem

Thanks Ara. Glad that Walter found the problem. Best wishes to you and your family for a great holiday season. See you in January!

[Ara G.]

Re: 427/425 Engine Problem

Thanks Mark, and the same to you and yours.....See you in January. Glad Walter found the problem as well....ARA

[Leif A.]

Re: 427/425 Engine Problem

Walter,
I'm glad to hear you found the problem. But, correct me if I'm wrong...haven't you just set yourself up for future problems?? You say you re-installed a fuel filter BEFORE the fuel pump. If memory serves, I don't believe there was ever meant to be a fuel filter BEFORE the fuel pump. The filter in an of itself will create a fuel flow problem to the fuel pump. AFTER the pump I understand but I don't believe BEFORE the pump.
Merry Christmas and I wasn't yelling

[Richard M.]

Re: 427/425 Engine Problem

Nothing like finding the smoking gun. Congrats Walter.

But, yes, as Leif says, it's not a good idea to have a fuel filter BEFORE the fuel pump, should always be after the pump.

Rich

[Walter R.]

Re: 427/425 Engine Problem

I will take your advice and remove filter.

[Walter R.]

Re: 427/425 Engine Problem

I was premature in declaring problem solved. Issue still occurring. I took car to an expert and he will fix and I wiil report findings. What is the correct volt range that we should have at distributor and coil while the engine is running?

[Walter R.]

Re: 427/425 Engine Problem

As everyone can see this issue has been difficult to diagnose. We thought we had problem solved several times only to discover it wasn't. Adding to my issue whenever my engine would stall my battery was weak even though battery checked out OK. Found faulty voltage regulator was culprit and replaced. We determined my coil was getting hot after running for a period and replaced. After driving car for a few miles and returning to shop we thought the problem was solved. While car sat idling the problem surfaced and we were back to the same issue. We were convinced that the coil heating up was our problem. My mechanic put a volt meter at the pink ignition wire where it attaches to the white resistor wire in the TI harness with a reading of 12V with ignition on. We tested the other end of the resistor wire that attaches to the coil and got the same reading. This did not make sense as we should have a voltage drop at the coil side. I bought a resistor from NAPA and attached the pink ignition wire to one side of the resistor and the white resistor wire to the other side. We got a reading of 6V at the coil with ignition on. I drove the car for several miles returned to the shop and let the car idle. The engine continued to run great and the coil remained warm but not hot. Does anyone have any ideas what is occurring. Can you have a faulty resistor wire?