Vintage Mustang Forums banner

1 - 5 of 5 Posts

·
Registered
Joined
·
1,018 Posts
Discussion Starter #1
After I break in on my 289 build, have a few questions about fine tuning the 289.

For the break in, I believe I have the carbuerator basically set with the mixture screws 2 turns out, will set the points at .017, and timing at 10 degrees.

After the break in period, what do you start with 1st to optimise output of the 289? 1) tune carb mixture screws (in then out until the engine start to stumble and screw back in just a touch for a smooth idle 2) set dwell and then 3) set timing? Where does vacuum pressure come in? What sequence should be followed?

In addition, few newbie to tuning questions. Setting dwell, I read that you disconnect the vacuum advance on the distributor and cap it. 4) What do you cap? The vacuum line to the distributor or the distributer vaccum port or both? I just purchased a timing light/dwell meter/dial timing light. 5) Using the dial timing light, if I want to set the timing at 6 degrees, I set the timing light at 6 degrees and watch for the zero on the harmonic balancer set beside the timing pointer? 6) WIth a 289 hipo style build (flat tappet hipo cam, Autolite 4100, Stealth intake, HiPo exhaust, and distributor set to Boss 302 specs), what should timing be set at, 6 degrees?
 

·
Registered
Joined
·
3,245 Posts
You look like you’ve already got a pretty good game plan. Rule of thumb for idle screws is 1 ½ turns out. Your sequence of things looks fine. Regarding setting the engine with vacuum, I’ve never done that and don’t think you need to either. People will disagree with me on this, but I’m old school, I guess. Cap the hose that you pull off the distributor, you don’t need to cap the distributor itself. Yes, you are correct with the operation of the timing light. Or you can just leave the timing light on 0 and check the timing marks on your balancer for your desired timing. Speaking of, you’ll want to set it at 12* BTDC, 6* was used on the tamer engines.
 

·
Spammer Hammer
Joined
·
9,777 Posts
It’s going to like more timing than that...guaranteed. You’ll probably find it’s really happy around 12BTDC. Remove hose from distributor and plug the hose. Set the idle mixture screws wherever they produce maximum intake manifold vacuum.
 

·
Registered
Joined
·
952 Posts
If you have a vacuum gauge, then I'd use it along with the timing light. Just for a double check, I'd disconnect vacuum from the distributor (as mentioned above). Watch the vacuum as you adjust the idle jets in/out slowly. If the vacuum increases, stop adjusting at the highest value. Then set your timing with the light and do the same thing by turning the distributor a little at a time. At the highest vacuum reading check the timing with your light. I usually drop back just a shade from max vacuum.
 

·
Registered
Joined
·
854 Posts
Just to add, go with 1/8 steps on the screws and wait a bit until it settles. I also back off a bit if I reached max vacuum.
I personally think there is nothing wrong to use a vacuum gauge. You can see and learn a lot, especially if you are not an expert in tuning an engine. Experienced guys see, feel, hear if the engine is happy or not. Make sure you connect to full manifold vacuum.

You might have to repeat this step once or twice until you are happy with the result. Nothing wrong with it. Shut off the engine and start again at 1 1/2 turns out.

Good luck and post your results :)
 
1 - 5 of 5 Posts
Top