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Timing Marker

jdeignan

Full Member
Joined
May 24, 2015
Messages
205
I have been trying to get to the bottom of my timing and AF ratio.
Backstory: When i bought the truck, the PO had rebuilt the engine, and it seems like he threw a bunch of extra parts together for everything else. Its got a serpentine pulley system, a huge electic fan, Edelbrock 1405, MSD 6AL ignition and the MSD 8479 Pro Billet distributor- nice, but I am pretty sure he never put a timing marker on the truck.

Issue: I’ve got idle vac at about 13-15inHg and a cam in there (unknown specs) that doesnt help. Cool lopey idle sound though.
It runs eye watering rich at idle and gas mileage is pretty poor.
I would like to fix that but I need to rule out a few things before I can blame Edelbrock. Let me know If I am off base:

1. Set timing. My radiator hose blocks the stock 302 marker at the 2oclock position. I brought it in to the shop because I was frustrated with it. The mech used this object at the 10 oclock position. https://ibb.co/g8xKj6
https://ibb.co/irRej6
Is that a timing marker? If so, how do i read it, because I dont see any markings on it for precision.
Regardless, he said he set the initial at 10.
So I threw ny timing light on there (vac advance unplugged), and read 16deg at 3k RPM. So I calculate 26deg total timing. Anyone else think it should be more?

2. Check floats and set to 5/16. Set idle to 700 and adjust idle screws for max vacuum.

3. Vac advance... I am going to switch to full manifold vac. Additionally, I just bought a vac advance (P28) that is all in at 8inHg. The canister installed is currently all in at 15inHg and with the low vacuum at idle, I dont want continuous changes in advance as the vac signal bounces from 13-15.

I figure if I dial in the correct timing, I can calibrate the carb. If it is still rich after all other variables are set, I can blame the carb and shop elsewhere.

Long read, but I look forward to hearing any advice yall have to offer.
 

centex77

Full Member
Joined
Oct 31, 2017
Messages
183
Timing marker can be placed just about anywhere you want it to be. Just make sure your timing marks are accurate. That’s more important than where you mark it. Sounds like you might have to bust out a dial and set timing the hard way before you can mark the damper.
 

Godwick

Sr. Member
Joined
May 14, 2011
Messages
407
Loc.
Santa Barbara, CA
Timing marker can be placed just about anywhere you want it to be. Just make sure your timing marks are accurate. That’s more important than where you mark it. Sounds like you might have to bust out a dial and set timing the hard way before you can mark the damper.
How does one "set timing the hard way?"

Sent from my Pixel 2 using Tapatalk
 

Apache Bronco

Jr. Member
Joined
Jun 14, 2012
Messages
70
Loc.
Roosevelt, AZ
Using a dial indicator in the spark plug hole to put #1 at tdc. The timing scale you use must have the marks spaced correctly for the diameter of the harmonic balancer. A very good idea, as harmonic balancers can slip, or the scale may be slightly off.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
I would say you have a late model 5.0 engine in there. Most likely that's why timing is read at the 10 oclock position. Irreguardless The first thing I would check as was said is your top dead center. Either verify that the current timing marks line up to that or create new ones that you can read.
Aside from that timing can be different on every engine. different cams ect. So initial timing can be trial and error you have to find out what works best for your engine. but generally something between 8-14 degrees works for most people.
As for your timing reading of 16 degrees at 3000 RPM well that's all it is 16 degrees. the 10 you trying to add in is already part of that. Multiple things could be happing with that low of reading either your TDC mark is not correct or your mechanical advance in the distributor is not advancing much due to heavy spring rates or other issue not allowing advance. You could be able to get a spring kit for the MSD and try to get all the advance in by 3000 rpm.
Most people try to have somewhere between 32-36 degrees total advance. So if you have 10 initial you want the mechanical advance to make up the rest. The MSD should have different settings to get different amounts of advance. Now this will all be different if you go with manifold vacuum for the advance as you will have to factor that in as well both initial and mechanical advance may need to be lowered.

Either way most of your issue is most likely incorrect timing as most carbs will adjust enough for a clean idle. if the timings off then your eyes will water.
 
OP
OP
jdeignan

jdeignan

Full Member
Joined
May 24, 2015
Messages
205
Yahtzee!
Turns out, the timing was way off.
With the help of a piston stop, I found TDC.

Can one of you check my procedure here?
1. Set at 0 TDC
2. Set rotor to fire #1
2.a. Unplug vac advance (all in at 15)
3. Rough start, sounds lean, but manageable.
4. Advance timing light to 10* and twist dizzy to realign marker. (This sets 10* initial)
4. a. Plug in advance
5. Set idle screws for max vacuum (got to a steady 16*)

This got me a 10* initial, 26* idle (with advance), and 39* at 3000rpm.
Ill be honest I cant remember if vac advance was hooked up for the 3k but will check tomorrow.
 

DirtDonk

Contributor
Bronco Guru
Joined
Nov 3, 2003
Messages
47,345
Sounds like your advance connected to full manifold vacuum then? While that works for some, most of us swear by (as opposed to "at") ported vacuum signal. So zero vacuum at idle and only kicks in once the throttle is advanced some.

Either will "work" and let an engine run, but the ported vacuum seems to give us more of the type of running we like with our engine setups.

Paul
 
OP
OP
jdeignan

jdeignan

Full Member
Joined
May 24, 2015
Messages
205
Sounds like your advance connected to full manifold vacuum then? While that works for some, most of us swear by (as opposed to "at") ported vacuum signal. So zero vacuum at idle and only kicks in once the throttle is advanced some.

Either will "work" and let an engine run, but the ported vacuum seems to give us more of the type of running we like with our engine setups.

Paul

Ah, the most prevalent argument on the internet! Ported vs Full!
I’m just experimenting. I had it ported before- seeing if it runs any better handling load.

That said, I will likely go back to ported cause of the 16inHg idle... Thats real close to 15inHg (when my advance kicks in) and Id rather have steady timing at idle than the advance on and off repeatedly.
 

broncnaz

Bronco Guru
Joined
May 22, 2003
Messages
24,341
Sounds like your vac advance was hooked up on your last test but you may want to check what the dist mechanical advance should be. I'm not sure on the MSD but there are usually different amounts that can be depending on how its setup. If I remember MSD usually uses different bushings so you may need to reaearch what bushings gives you what.
When using a ported vacuum source I don't really count the amount of vacuum advance as part of the total timing as it will be load dependent. But with manifold vacuum I think you have to count the vacuum amount as part of the total.
Either way sounds like your heading the right direction and are due for some road tests. See If you get any pinging. If none Id bump up the timing some more.
 
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