It turns out it was the seal/rubber ring at the top of the distributor shaft. It was bulging out too much. We took it out… went in perfectly.
So, we put the OLD one on (from the previous distributor) and it fit right in.
YAY
Then, we went to put the spark plug wires on… and they DID NOT FIT!
Why?
Because this HEI distributor has MALE connectors.
We ordered some from the local store and within hours they had it for us.
Got them on and everything hooked up. Did an advance curve test and she seemed best at 14 degrees at idle and 30 degrees at 3,500 rpm.
Took her out and she ran really well. Still a TOUCH of knocking and pinging up around 3,000 rpm going uphill.
So we knocked her down to 12 degrees at idle. It was WORSE.
So, we tried 16 degrees at idle. Not as bad… but worse than 14.
We settled on 14 degrees and she’s running really well.
I’m going to call Blue Print Engines on Monday and tell them what happened.
They sold us the distributor understanding that we had knocking and pinging. Maybe there’s something we’re missing.
The problem isn’t fixed by replacing one working distributor with another working distributor. What you are going to have to do is adjust the curve to your car. See if Blueprint sells springs for the new distributor.
First off I want to thank you for taking us along for the ride. Speaking for myself, I want to fix this problem. It’s stuff like this that can burn up enthusiasm faster than gunpowder. I want you and your son to have a victory and a sense of accomplishment. To feel good about it, and have a happy ending.
Why is this so hard? The original stock engine ignition and carburetor were dialed in by engineers with time and resources we don’t have. They were able to set parameters that would work across literally millions of cars in a multitude of climate elevation and uses. When an engine is modified, the stock parameters may no longer apply. We become the development engineers. For most folks this takes you to the very edge of our knowledge, and most likely well beyond.
So that’s where we are at: looking over the edge, learning new things. The best way to do that is to carefully change one variable at a time. One must be disciplined and patient.
Looking at this problem we have several factors to consider. First is ignition timing, and that means the curve in two parts, mechanical and vacuum. Next is fuel. The carb senses load by monitoring vacuum at full throttle under load vacuum should be close to zero and the carb putting out a rich mixture. Finally there is cylinder temperature, more specifically the heat range of the plugs. There are many more factors such as combustion chamber shape and cam shaft specs but we aren’t able to easily change those variables. In any case it is doubtful that those parameters are so radical that we need to go down that path.
Thanks so much for the help and encouragement, Bill. Really appreciate it.
And thank you everyone elsel!
Answering some questions here.
We tried vacuum advance for a bit… she didn’t like it.
Blue Print, the makers of the engine and the people who sold us the NEW distributor, said to NOT use vacuum advance.
So, it’s not been hooked up.
She is spinning tires. Really moving great. Sounds great. So I’m happy about that.
I haven’t taken her on the highway yet. We just changed the oil… so maybe later today.
As for the jets, I believe we put in the .101s (she had .098s in her before)
Metering rods are 7035s and used to be 7547s
Springs are 7 inches HG
Quick hi-jack of that thread - I have to work on the timing on my car very soon, but one thing I was wondering… What precautions should one take before working in a distributor ? I HATE (and i cannot emphasize that enough) getting shocked so i’ve been a big chicken so far. Only yesterday was I brave enough to open the cap
Is there a safe way to ground the coil to ensure there’s no residual charge in it ?
Ssava,
You are definitely experiencing “light load pinging”. The dyno testing that your company did was more than likely done for maximum performance. Under full load, my guess is that during the dyno test they blow right through your problem on the way to max HP. Not uncommon for engine dyno testers. So what do we do about it?
First I would quiz the Blueprint guys. Did they use long tube headers? What carb did they use? How is it set up? This will help a bunch. I see you are running stock exhaust manifolds.
If your car was in my shop I would carefully map your advance curve with a timing light. Using the idle stop screw I would increase rpm in 100 increments until you reach “all in” or max advance. You may need to actually open the throttle by hand to reach all in. This of course is not with a load on the engine, so actual throttle opening will be far less to achieve. But it will give you and idea of how quick your centrifugal advance comes in and how much total.
That said you look like you have enriched the primary side of your 600 CFM Edelbrock. The step to .101 on the jest size was a large step up. Not sure what you mean by metering rod sizes of 7035 and 7547. the factory set rod size is 1459. I see you picked number 18 on the Edelbrock chart which would give you the .101 jet and using the stock 1459 metering rod. The factory Step up spring in your carb is for 7 inches of vacuum or higher to hold the metering rod down into the main jet. There is a kit:
that contains an 8 HG spring that and will allow the rod to move up quicker and allow more fuel under part throttle. That will be your next step. The metering rod and spring work similar to a power valve in a Holley carb. A 8.5 Holley power valve comes in very early and is used in many of their performance carbs. A stock carb would usually come with a 6.5 Holley power valve.
Did you purchase the 1487 Calibration Kit? If you did, the 1449 Metering rod ((070 x 037) will enrichen the part throttle opening mix a bit more. Number 19 on your chart.
As you don’t have a dyno this is basic seat of the pants tuning. Also remember that summer and winter weather can affect light load pinging. Hot weather is the worst and a stable cooling system is a must.
If the above enrichening does not remove this light load pinging then get back with Blueprint and aske them to “slow” down the advance in your dizzy or ask them how to do it. It would be very simple with an MSD dizzy that you once had. Keep us posted as we all learn from your journey!!
Take a pic of your dizzy with the cap off. I can tell by the rotor which centrifugal system you more than likely have
Robert Campbell is taking you to the right place. It would also be very helpful to know the vacuum reading when you are getting pre-ignition as that can help identify the spring you need for the step up of the rods. You would extend the hose on your vacuum gauge so you can have it inside the car with you during testing.
That is a different problem than you said before. So under full acceleration you get pinging? If so we have another problem. I thought you said under light acceleration up a hill!
No. My apologies.
BEFORE the new distributor… yes. We had that problem.
But with the new HEI distributor it seems it’s only when I put my foot in it.
I’ve driven her a bit more and took her into Nashville. Was on the highway for a good 30 minutes doing 85. No problems.
Getting on highway. No problems.
Hills. No problems.
It’s only when I get the gas pedal down to about 50% depressed. Right about the time when the secondaries open up. Sometimes before. Sometimes after.
She has TONS of power otherwise and honestly… I’d NEVER need to worry about it because I don’t drive her hard.
But my son and I want to know what’s wrong so we can fix it. Even though it doesn’t affect my daily driving.
