I just purchased a 67 F-bird with HEI installed. Runs great but at cruise speed, light thottle, I have a rattle which I believe to be spark knock. I am using premium fuel. Anyone have any thoughts?
Also: I'd like input on the following.
1. On a stock 326 2V, will the initial timing of 6 degrees remain the same?
2. Can i use the same type plugs and what would the plug gap be?
Welcome! The first step would to make sure it's spark knock. One way I can think of to check is to retard your timing a little and see if the sound changes....
Try disconnecting the vacuum advance to the distributor.It might be pulling in to much timing during cruse. (HEI's some time have a lot of advance built in.)
As stated disconnect and plug the vacuum advance and if the rattle goes away you have spark knock. If this is the case, it's just a matter of getting an adjustable can and setting it for less timing.
As for your other questions:
1) Depends. Are your heads original? Closed chambers tend to like more timing, so the factory distributors have a bigger curve. If you are runnig an HEI with older heads you need to make sure the total timing is the same. So compared to points you will have more initial timing. This will probably be okay as the engine will probably like more initial.
2) Type of plug will depend on the heads and the ignition. You need to verify your head codes, so you have the correct plug thread and length. For HEI, try a colder plug than with points and set the gap to 0.045". This could actually be part of your problem.
3) See point 1. This will depend mostly on which heads you have. Find your codes and verify on www.wallaceracing.com You need to know your compression ratio and whether they are open or closed chamber style.
Eng including the heads were rebuilt to original specs with harden value seats, according to the previous owner. Other than the HEI and a one wire alternater car is correct. Plug are what the manufacture recommends and gapped .040. Inital timing = 10 degrees BTDC.
I will try diconnecting the vacuum and go for a test drive as soon as the weather breaks and the cars off the blocks.
