FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: Hotrodjohn71 on January 30, 2026, 11:50:46 AM
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I realize i have other threads going on the forum for which i am very grateful for the input, but if you would bear with me. I will open this can of worms.
Please walk me through and help me undetstand the process for setting timing on an FE engine before ported vacuum became the norm.
May I share a bit of my personal experience in this area. I restored a '67 326 Firebird for my wife. My goal was originality. When it came to the engine, it was factory setup with manifold vacuum advance and had a 2GC Rochester (no port for advance), and a steel tube going from the original distributor vacuum cannister straight to manifold vacuum.
I had never setup an engine to run of manifold vacuum nor had it been a consideration, but i realized i needed to either look for a similar Rochester with the port for vacuum advance (which there are a few) or proceeded with restoring the exhisting process.
I went on a forum and threw out my question and as you probably can surmise, I got strong arguments for and against manifold vacuum advance. I did alot of research at the time about the theorey of high advance at idle and the combustion process and the cooler temps and all the pros and cons of both (much of which I have forgotten).
In the midst of all of that, a member reached out to me with a process for setup of timing that I never heard of but I decided to try it. I have had my wifes Firebird tuned this way for years now and it runs like a top. It has never knocked or pinged. Runs cool always fires right up and has great power (for a 2bbl 326).
Here is a cut * paste of the procedure shared with me:
"Hi John.
Set the initial timing with VA disconnected. If the engine is stock, high compression, 6-8* is good. If it has a cam, or is low comp [ 7.5-9:5:1 CR ], I would increase the initial timing to about 10-12*. Make sure you use an adj VA unit such as the Crane. Adjust the Allen screw fully CW [ softest setting ] as a starting point.
The TOTAL amount of VA that is added is governed by the travel of the actuator. This is adjustable with the Crane unit using the notched plate.
The timing at idle can be anything from 30 to 55* [ yup, 55* for really radical combos ]. Note that until 1968 when we got the useless PVA for emission reasons, Pontiacs left showroom floors idling with 26*, 6* init + 20* MVA. So increasing a few degrees to 30ish is still conservative.
To determine the reqd timing at idle: Disconnect VA for this test. Chock wheels, warm up engine, put into gear if auto, engine idling. Loosen dist clamp & SLOWLY turn dist CW [ advances timing ]. Rpm increases. Keep going CW until max rpm/smoothest idle is obtained; toggle dist to make sure you have highest rpm.
Now check timing. You may need a timing tape on the dampener. Do not be surprised if it is well above 30*.
Whatever it is, that is the 'sweet spot' for your engine. The adj VA units can add about 30*. Use any combination of init + MVA to attain the reqd idle timing.
Once you have dialled in idle timing, idle mixture & speed can be reset.
There is some on PY who don't like MVA. One person, who gets the Prima Donna treatment, & uses all sort of exaggeration & idiotic lies to discredit it's use. One of his favourite sayings, & I saw it this week, is 'timing clear off the scale'. The only timing scale I am aware of is the two full revolutions of a 4 stroke engine, which is 720*. If idle timing was 36*, that represents 5% of the total available. 5% of ANYTHING is hardly 'clear off the scale'. PM anytime.
Cheers.
Not sure how far we got. But you have the sweet spot, which is the total vac adv that gets applied. Now for the RATE adjustment, in case I didn't give that to you. This gets done after the sweet spot is done & engine is idling with this.
Turn the Allen Key [ AK ], 3/32", fully CW. This the softest spring setting.
Engine idling, in gear if auto, turn AK 2 turns CCW & re-check timing. Keep going 2 turns CCW, & checking timing each time. At some point timing will probably become unsteady or drop. At this point, go back 3 turns CW. Job done!
Your reference to max advance. I presume you mean init + centri + VA. That is usually 45-55*, but can be over 60* with a big cam & low comp ratio.
Hope this helps, feel free to PM.
Cheers."
Now I would like to know what the process was for the early Ford FE motors that Ford used before ported vacuum became the norm
I would like to compare it to this proces listed above which works well but I want to also gain some more good knowledge.
Thank you
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Edit
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I have a customer and friend with a GTO, the correct carb would have been manifold vacuum, but the carb he had was ported. Common challenge in early Q-jets being different. So thanks for sharing your success
We cammed the Goat, set it up like a Ford with ported, dialed in the curve and it runs great.
This will be in line with some of your other questions.
- If your desire is a more radical low vacuum cam for the 390, then you may have a benefit of getting better idle with manifold vacuum
- If you have a more streetable cam, you may get some gas mileage benefit with ported
In the end though, as a reference, I have never had to use manifold vacuum, even on engines exceeding 600 HP in a streetable configuration.
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My advice is to use whatever advice you receive as guidelines. Then go play with your timing until you get it the way you like according to your particular preferences, engine configuration, and driving style.
You’re right about folks getting passionate about their opinions on timing. I’ve found some ideas from those passionate people don’t work well for me. In my particular scenario I like full manifold though I can understand scenarios where folks want ported or none.