Alright, I've got a 74 350 with an XE262 cam and I followed Lars' instructions on recurving my distributor. I get my full advance in around 2800-3000 rpm.

My only problem is I only seem to get 14 degrees of mechanical advance, so to set my timing to 36* I have to set my initial to 22*. Is this too high? I set my initial to 18 just to be safe and took it out for a cruise, no problems that I can tell. So should I bump it all the way up to 22*?

Also I was wondering if 25 in of manifold vacuum is weird with an XE262, is there such thing as too much vacuum?

 

Sounds fine. If the engine idles smoothly with 22 initial, nothing wrong with that. I think I run 24 initial on my XE268 cammed 357. With 22 initial, you may consider whether to run manifold vacuum or ported vacuum to the vacuum advance, though. You may find that you will get smoother idle from the ported source since you already have a bit of timing at idle. Play with it and give the engine what it wants.

 

Thanks! I'll bump it up to 22* and see how it runs!

 

To much timing can cause detonation, not enough will rob power. If your not getting enough mech. ad. you need to adjust the curve. I'm sure Lars set you on the right track but you still don't have enough. Double check your springs and weights to make sure they're correct, if so then you may have to open the bushing slot to give you more travel so you can get all the advance you need. You can use a file or Dremal tool to do this.

 

I have the same cam and the initial timing on mine ended up at 22 also with 36 total per Lars. Been that way for 3 years with no problems

 

I was typing my first post at the same time as Lars, and was giving general advice assuming you MIGHT need more timing. Since he has experiance with the same cam, then definatly go with it.

 

Got my total timing at 36 degrees and it's running great!

 

not to long ago everyone was saying that 50+ total timing was the norm and i said that was crazy. now i see that the advice has changed to what i was saying, which was the 36 total. very curious

 

The total timing spec for a performance application has been 36 degrees since the advent of the small block in '55. I've never heard of anyone ever running 50 degrees total timing...that would never work. I hope nobody is doing that...

Total combined timing - full centrifugal plus full vacuum advance - can be 50 to 54 degrees. That's normal and okay. But you would never want to set total mechanical timing to 50.

 

Let see, you said that your distributor has 14 degrees of mechanical advance. Now is that advance that was observed on the distributor machine when is was recurved? OR, was that advance that you observed on the dampener while the engine was running? If on the engine while running, was the vacuum advance disconnected from the dist?

If on the dist. machine here is what I know.

Dist. advance when set on a maching is doubled in the engine. Cause the dist rotates at 1/2 engine speed.

So, 14 degrees of distributor advance becomes 28 when the engine is running. With the vacuum advance disconnected, you can put up to 8-10 degrees on the dampener. 28+10 = 38 degrees of advance.

Now for the vacuum advance. It should be connected to a source of manifold vacuum. That will provide extra advance for idling and part throttle driving. The advance at idle will be off your scale on the timing cover. If you have a timing tape on your balancer, you can read the actual total amount of advance while idling.

When you are motoring with a light throttle, you will have a bunch of advance in the engine. This is good for gas mileage. When you step on the throttle, the manifold vacuum will go to zero (or close) the vacuum advance goes away and the engine relys strictly on the mechanical advance. The engine at WOT will probably not tolerate more than 40-42 degrees before it starts to ping. Will have to listen for that.

So, now you know more than you asked but just wanted to give you an overview of how all that works so that you can adjust your timing to suit your engine and not do any damage.

If you put too much initial advance on the dampener, the engine will be hard to crank/start. You don't want that.

HTHs

Bob

 

Alright, here's what my set up is: I set my initial timing to 22* at idle with the vacuum advance disconnected and plugged. I have my distributor set with the springs and such so I get my full 14* of mechanical advance in around 3000 rpm. So, around 3000 rpm, I have 36* of initial+mechanical advance. Now with the vacuum advance: I am running my vacuum advance off of the ported source on the q-jet, so I get no advance at idle. At cruise, I get an extra 16* of advance. So, like Lars said, my total COMBINED timing is right around 52*.

I also must add that my engine has never felt stronger! I took my neighbor for a ride before I retimed it, then again after I timed it, he said the difference was like night and day. Thanks for the help guys!

 

Your setup is right on. Perfect. Leave it there and have fun with it.

 

Will do!