[Stuckinda60s]

Total timing should be set with vacuum disconnected and plugged. Fifty* total timing at cruise with vacuum advance hooked up isn't unusual, particularly with low compression. The first thing for you to do is get an adjustable vacuum advance such as Mallory sells. Determine what total timing is at what rpm and then you can adjust the vacuum can for best cruise without surge.

What is the engine code? What is the date code on the heads and do the heads have screw-in studs?

You can get detonation with low compression, depending on circumstances. .

[360Rocket]

If anyone here is learning "How to tune 101" at my expense I have cut and pasted why I need vacuum advance as these guys are helping me with:

Now connect the vacuum advance from the carburetor to the distributor and read the timing on the harmonic balancer while revving the engine to 2,800 rpm. This number will now be greater than 34 degrees with the addition of the vacuum advance. Let’s say it now reads 49 degrees, which would mean the vacuum advance is worth another 15 degrees. These are typical numbers.

First, let’s look at the mechanical advance portion of the timing—the 34 degrees total. This is determined by the weights and springs spinning around inside the distributor. This establishes the amount of timing the engine will see at wide open throttle (WOT). As you are probably aware, at part throttle the engine will create a certain amount of vacuum in the intake manifold. This is because the throttle is mostly closed and the engine is pulling against this restriction. Because the throttle is mostly closed, very little air is moving into the cylinders. So at light cruise, such as running down the highway, the engine is making much less power than it would at this same rpm at WOT.

With less air and fuel in each cylinder, the air-fuel mixture is not as densely packed compared to WOT. This less-dense mixture requires more ignition timing to complete the combustion because it takes longer to complete the combustion process. So we need a way to increase the amount of timing based on the load on the engine. This is how vacuum advance works. At part throttle, high manifold vacuum moves the diaphragm in the vacuum advance canister on the distributor to add more timing. But at WOT, the vacuum drops to near zero and vacuum advance is removed and the total timing then is established by the initial plus the mechanical advance.

So there are significant advantages to retaining the vacuum advance on your distributor.

[Murf]

Originally Posted by Stuckinda60s

Total timing should be set with vacuum disconnected and plugged. Fifty* total timing at cruise with vacuum advance hooked up isn't unusual, particularly with low compression. The first thing for you to do is get an adjustable vacuum advance such as Mallory sells. Determine what total timing is at what rpm and then you can adjust the vacuum can for best cruise without surge.

What is the engine code? What is the date code on the heads and do the heads have screw-in studs?

You can get detonation with low compression, depending on circumstances. .

Well, that's what I tried to say. Sorry if I was confusing. I've been told I have that effect on people.

Murf

Sent from my Z936L using Tapatalk

[Stuckinda60s]

Originally Posted by Murf

Well, that's what I tried to say. Sorry if I was confusing. I've been told I have that effect on people.

Murf

Sent from my Z936L using Tapatalk

No problem, you didn't do too badly. I didn't see your posting because I had started mine and left the computer while I did some things. I came back not knowing you had posted in the interim and finished my post. When I posted I saw yours and considered removing mine, but I figured that mine might serve to make yours a little clearer while adding some detail. Not trying to step on your post.

We still need to know Rocket Man's engine code.

[360Rocket]

Originally Posted by Murf

Well, that's what I tried to say. Sorry if I was confusing. I've been told I have that effect on people.

Murf

Sent from my Z936L using Tapatalk

I think you did great Murf, you can never get too much input. Lemme go see if I can spot that code. It looks like a "YC" It has 455 on the bottom side of the block..

Stuck....I actually slipped in engine size in post #12...lol.

[Stuckinda60s]

Originally Posted by 360Rocket

I think you did great Murf, you can never get too much input. Lemme go see if I can spot that code. It looks like a "YC" It has 455 on the bottom side of the block..

Stuck....I actually slipped in engine size in post #12...lol.

Yeah, I had seen that you posted the engine size, but I've also seen more than my share of 350's represented as 455's That includes one that a forum member recently posted about that he had bought as a 455 and driven for some time before he found out the truth.

But, that wasn't the issue. If we knew the engine code, we could, as you've seen from NeighborsComplaint, determine what initial timing is supposed to be.