setting timing

[BRAD ARTHUR]

I've read all kinds of threads on timing, but here’s some more questions.
First off I am running a 1405 edel. Carb, edel. Cam,edel. Intake, stock exh manifolds, z&m hei, all this on a 304. With about 1500 miles on a overhaul.
I’ve been getting it to run good but not its best. While tunning it in still I’ve bounced between carb tunning and setting, timing initial ,mech vaccum.
I’ve read these motors run well from 3*-15*int.,w/34*-38*total. Advance. My question when setting timing and installing a distributor rotate eng in the direction it runs till #1 is at TDC on compression stroke. Timing mark on harmonic balancer should be at TDC, then instal distributor w/ rotor pointing at#1 .
1-(when leading edge of rotor contacts edge of #1 or center of rotor to center of#1?) Will it run @tdc, then adj timing.
2-will it make a difference if you are off 1 tooth or will you be able to adjust that with rotating the housing?
3 - is there a way to verify you are on the exact right tooth for the dist.
I am using a dialed timing light, before I had this I used a standard light. And was @ 55* total advance 12 int. And it ran good with no pinging. When I back ofF to 36 total runs good but not like it should.
I am trying to optimize performance and playing with mechanical springs and total timing, but think I’m off a tooth or something causing it to run best @55 *total.
I also changed accel pump nozzle from #28-#43.
I get a slight hesitation, from idle to take off in gear almost a hick up or stumble, but goes away when let off.

I also thought of running a CTO switch for the vac. Adv. Is it worth it? Which one?

Hope this all makes sense, sorry for the long post. I’ve been trying different things and can't get it. What’s everyone else running? Any comments or suggestions would help thanks.

[BRAD ARTHUR]

i reread my message and i wasn't to clear on my questions, it was getting late last night. here are my basic questions:

1) can you be off one tooth on distr. drive- and will it make a difference / or should you be able to adjust with rotating the distr. housing after you've stabbed the distr.?
2) when initial stabbing of distr., how can you be certain you are on the exact right drive tooth? set piston @tdc, harmonic balancer should be @or near tdc on scale- or where it was when you set the cam/ crank timing via timing chain tdc. could be off if your balancer has slipped through the rubber.-and stab the distr. son the rotor is @ center -center of #1 in the cap/ or leading edge of rotor to trailing edge of #1?
3)with aftermarket cam, carb, intake should i still be between 5-12* btdc initial- 34-36*total
4) would i see much of any benefit running a cto switch for vaccum advance

hopefully its clear as mud now?

[jeepsr4ever]

Yup clear as mud.... :?:

Actually it doesnt matter where you put your dizzy as long as the rotor is facing the #1 cylinder plug wire...remember 18436572 firing order clockwise and go from there. Most guys will make the number one plug face the front but in reality it doesnt matter where on the cap it faces only that it is timed right using a timing light on the harmonic balancer...that help?

[BRAD ARTHUR]

my #1 on the cap is @the backside of the cap but i have the correct firing order c.w..

at tdc on the crank balancer, the rotor needs to be centered on #1 of the cap?
would it matter if you are off 1 tooth or should you be able to adjust it out?

right now it runs best @36* initial advance, doesn't seem right, back it down to 36* total advance@3000rpm's and loose power ???????

i rotated the disrt. 2 teeth c.w. and restabbed the distr. still runs best at high initial timing, i've also been playing with the springs &wieghts of the mechanical. my wieght bushings were wore on the bottom lip- compared to the new bushings in the adv. kit.

any base #'s of initial, mechanical, or vaccum. would help. or why 36* initial adv. is running the best. how many turns out for the vaccum adv. screw?

[tufcj]

What distributor and ignition system are you running, first of all?

Moving a tooth will only affect the position of the distributor relative to the engine block. It won't change timing because once you move a tooth you then have to rotate the cap the same amount to get it to run again.

Your total timing is a combination of initial, vacuum and mechanical. You should set your initial (at idle, vacuum disconnected and plugged) somewhere between 6 and 10 degrees BTDC.

If you're seeing 55 degrees total, and initial is set at 10, that means the combo of mechanical and vacuum is bringing in another 45 degrees. I don't think a factory distributor will advance that far. You can leave vacuum disconnected while you rev it to see what the total mechanical is (total - initial w/vacuum disconnected), that will let you know how much vacuum advance it gets.

Most aftermarket distributors have stops that can be moved to limit mechanical, and some have a set screw (inside the vacuum hole) to limit vacuum.

Your vacuum should also be attached to a PORTED vacuum source. This is usually somewhere toward the top of the carb. Ported vacuum is OFF at idle and increases as the throttle is opened. Manifold vacuum for vacuum advance won't give the right signal.

Last, if your harmonic balancer is old or high mileage, I've seen the outer ring slip as the rubber deteriorates. Be sure that the mark for TDC is lined up when the piston is truly at TDC.

Just some things that come to mind.

Bob
tufcj

[BRAD ARTHUR]

hey thanks for the info, that was what i was thinking but wanted to be sure.

[BRAD ARTHUR]

and what kind of vaccum reading should i be seeing at idle. can i read this off the carbs manifold vaccum port? left side on the 1405.

and iam running a z&m hei disrtibutor, coil in cap.

[tufcj]

The ported vacuum (where the advance should be attached) will read "0" at idle, and increase as engine RPM increases.

Manifold vacuum will should read somewhere between 12 and 20 at idle, it will drop if you "blip" the throttle, and will read about the same at a no load steady run. The problem with manifold vacuum is it drops as load increases (like driving uphill in high gear or towing). That will reduce timing when you need it most.

[dimension4]

I'm having the same problem as Brad here; I have to set my initial timing to 36* to get a decent idle. I'm leaving off vac. advance, when I connect it it will backfire out the carb and header and then die. I have an edelbrock torker manifold and 650 carb. I am pulling 15" of Hg at idle.