Passing Time

harmonic balancer should be right on . It is new and the marks lined up with timing mark on front cover when installed.

A. When timing using vacume and running WAO uphill and adjusting to ping/no-ping, the tiiming light shows about 30 BTC static with about 20 ft/lb manifold vacume.

B. When timing about 16 BTC, engine will idle and run smoothly at 700 curb rpm but will serioulsy cut out with any load or acceleration near idle speed.

C. If I compromise and run at about 18-20 BTC static 35-40 total timing, vacume is a smooth 17 -18 @ 700. Theengine does not cut-out (die) under low rpm load, but does have a flat spot that is easier to drive around.

Engine is 65 casting 289 with XE256H comp cam that I just put in. Intake and carb are the original cast and autolite 2100, that I reinstalled to break the build in because I knew that they were reliable.

Questions:
1. I realize that 30 BTC is waaaay to advanced to run, but what makes the engine run better, including idle, road speed, and accleration at this timing if it is so wrong?
2. Is there anyway to tune out the flat spot that I get with low rpm acceleration?
3. Why at 16BTC, which is nominal, does the engine simply not run worth a chevy?
4. Suggestions on where I run it based on the above.

No need to make fun ofthe cast stock intake, exhaust, and 2V carb unless these are what are not meshing with the new cam and higher compression (160-170).
It is a work in progress and I am upgrading one step at a time.

Thanks in advance, Brad.

Haywired

I have the same setup as you exceptI have a 570 VS holley on a cast Ford manifold.
Had the same issues as you with base timing and total advance.
Got in touch with Comp and they gave me the specs to set the timing at 6 BTDC, had to readjust everything to get it to idle properly.

It runs much better now with this setting and a total of 36 degrees at 2800 RPM than it ever did at 30 degrees base.

I have a solid 15 inches of vacuum a 750 rpm now, and excellent off idle response with no flat spots or bogs.

Cam was installed striaght up on the marks

Comp also stated that the 256 has more duration and over lap than a stock 289 cam so it will run a lower vacuum at idle

Hope that helps

Starfury

It sounds like something's wrong with your advance. If the engine runs without pinging uphill at 30* initial, your mechanical advance isn't functioning properly.

Set the initial at 12* or so with the vacuum advance disconnected. Rev the engine to 3k and check the advance at that point, then report back.

Passing Time

So... set it at 6 BTC and then re-adjust everything from there.

That seems so far off base from where I am, I was thinking that it was running pretty good at 18-20 except for the low end loading, but I'll go from your experience and their advise and give it a try this weekend.

Thanks for your input. After I try this and compare to where I am (nothing to lose from trying), I'll post back with results.

Brad.

Passing Time

I know that at 16 static, total runs 30+.
The scale on the balance stops at 30. So, it I was guessing I would guess 32 total.
The advance is nearly new.

Stepman

I'm with star on this one. Make it easy and unplug vacuum. Set you timing at 10 (round number) and make sure it advances at higher (3k) rpms. Also make sure vacuum is hooked to right port. If you are starting off at 20-30 degree, you should have a hell of a ping.

If you're only getting what ,15 degrees advance....maybe the two are working against each other.

Passing Time

OK
Timed to 10 static.
advances to 20 at 900 rpm when vacume advance reattached at idle. Vacume 16 @900
Total timing approx 33 at 3000. (scale stops at 30)

Runs much better now. Still has very mild flat spot, but very good throttle reponse and a nice exhaust note at idle speed andon the road.
I'm going to try 6 BTC as suggested above and compare.

Questions.

Should I be getting nearly 10 advance at idle speed?

Am I getting enough total advance?


Thanks for the help so far she's starting to sound pretty good.

69FECoupe

At idle, there should be no change in timing when youconnect the vacuum advance. It sounds to me like you are connecting it to the wrong port. The port should have no vacuum at idle.

imnotmy77stang

FYI if your balancer only goes to 30 you can buy timing tape from MSD for like 10 bucks or less.

Starfury

Vacuum hose is definitely connected to the wrong port. It's possible to set the engine to run off full manifold vacuum, but I don't recommend it for most people. Find the ported vacuum port and hook the hose up to that.

Also, recheck the total timing with the vacuum advance disconnected. You're trying to check the function of the mechanical advance alone.