I bought a timing light to check my timing. It has the advance and retard buttons and will go all the way to 90 degrees advance. I made sure the lead is on number 1. Wow what a shock no timing mark. At first I thought it was wore off but I found the slot so I thought how is the running so good and it out off this bad. Well when I advance my light 90 degrees there is my mark. It’s on about 12 or 14 degrees initial timing ( I guess) so now my question. Why is the mark 90 degrees out? Do I just find TDC and make a new mark? This is the 454.

Guess today is the day for feeling stupid. Just figured out there is upper and lower timing brackets. If you use the lower one the light has to be on plug wire number 5. Ok so now with the vacuum advance unhooked and plugged my timing is less than 0 by a few degrees.

Don’t feel unique or stupid. You found it quickly.

I often am stymied by things and they get tangled up in all the other channels rolling in my mind. Often I go to bed and my mind quiets some of those other channels or challenges that were taking up my bandwidth. I’ll wake up with the answer in the middle of the night.

That is why I have a pencil, pencil not pen because a pencil always works upside down or any direction. And a pad of paper. Often wake in the morning and have to decipher the answer. Wife has learned not to ask why I’m moving around in the middle of the night. I try to stay as close to sleep as possible during all this. No lights.

You beat me to the answer! With all the belts and brackets on the front of the engine, the top marks are sometimes not easy to see. Bottom marks work great on plug #5.

As for timing, with vacuum line plugged the factory timing was 0 to 4 degrees BTDC. This was consistent with EPA regs of the day. If you want best performance, set the timing as far advanced as can be without knocking, usually 8-12 degrees BTDC. Also, be sure the vacuum hose for the advance goes right from carb base to the distributor advance. Some had valves, etc to delay spark advance. With the distributor cap off, if you apply suction to the advance hose you should see the arm inside distributor moving.

While you are at it, check to see that centrifugal advance is working. With vacuum line disconnected, you should see the timing advance when the engine speed increases, usually around 15 degrees. If not, check the weights in the distributor. They often are rusty and stuck.

With timing properly advanced, you should get better acceleration, throttle response and fuel mileage.

Consider yourself lucky Paul, my 71 on a 70 chassis does not have the lower timing do-dad! Still have not figured out how to time this engine, no way to get near the mark with the engine running. Did it by ear for now.

Got a chance to finally drive the Barth yesterday through the mountains of Rockcastle county and I couldn't be happier with the way it runs. ( almost ) I drove about an hour up and down the mountains and only had three small backfires at random times but I have a new issue. Now when I am barely pressing the gas I get a slight miss. The carb still has the plugs pressed in for the adjustments, I was hoping I could get by with leaving them in but its looking like I will need to take them out. I think tomorrow after work I will adjust my APT and see if that will fix it. Thanks everyone for the reply's!!

a slight miss?

things that I have seen or speculated on at times:
- the paint on the engine has aged out, and condensation causes rust, and the "fresh" spark plugs get a rust colored stain on the ceramic. perhaps that's a path for energy to be lost.
- idle mixture screws? you are just slightly hitting the gas, so the throttle plates will open and you might not have transitioned to the mid range circuit of the carb, and are just relying on the idle circuit.
- somewhere along the lines I installed a variable advance can for the distributor, from Crane cams, I think it was intended to better control the spark advance in conjuction with lighter advance springs on the advance weights.
- make sure all the plugs and wires are in good shape

Matt

Every time one of my Barth 454's did a backfire or stutter when it accelerated the problem was fuel delivery! Check the filter even if brand new! Most times it took about an hour running to make play time, the longer it ran the more often it would backfire or stutter!! If it was shut off even for a short time might start the process time all over.