318 - Looking for "free" power (tuning!)

[MrJLR]

Ok....I have a 74' 318 in my 68' Barracuda.
It has a stock low compression bottom end, a Hughes Whiplash cam, home ported heads, Edelbrock 1406, Doug's headers and electronic ignition.
It starts and runs pretty good. ....I just feel that I could really get a lot more out of it with tuning.
I don't know much about the process. Do I tune the carb first, then the timing or the other way around?
Don't know crap about tuning carbs....but I listen and learn!
Timing is even more mysterious to me....

I have a good timing light and if I need a tool like a vacuum gauge or whatever I'm more than willing to get one....

I feel this could actually help a LOT of members here who, like me, are just knowledgeable to make it run, but not run its best!

So....where do I start?

Jeff

 

[Mattax]

Performance tuning a non-factory setup is a journey.
The process is iterative. You may have to go back over the same ground a few times as well as a lot tests with one change at time.

Start with timing curve. Initial, then idle and the shape. Just made a couple of recent posts about initial timing and shortening the advance with a chrysler distributor. Plot the entire timing curve.

Then adjust carbs idle mix. You may have to go back and forth with the initial timing and fuel mixtures a bit. Even with the Carterbrock, the throttle position at idle is important.
Then try your high speed cruise. That should be done with vacuum advance. If it revs and dies - its too lean to cruise. If it bucks or trailer hitches, its probably way too much timing.
For wide open throttle jetting, go to a 1/4 mile drag strip. Make a couple passes. Check the spark plugs and then try a little richer and a little leaner. See what jetting gets the best mph. If you hear pinging or the plugs show tiny specs of aluminum, take some timing out.

At minimum you'll need a notebook. Write everything down. As time goes on you'll come up with your own system that you find useful. I use paper notes, and transfer some stuff to computer spreadsheet later on. For example one sheet for the carb.

 

[Mattax]

Initial can be ballparked from here
Distributor starting point for a curve

If that suggests to start with a lot of timing, then you'll need less in the advance.
To get some idea of what works look at a factory curve, and then cut off the bottom; like shown here for a desmogged Chrysler 360
360 Tune Up

The Edelbrock Owners Manual is pretty good for tuning the various circuits.
But be aware that this illustration is misleading!

Part throttle acceleration is leaner than cruising until close to wide open throttle.
More about that here: How lean is too lean?

 

[DesertRat]

What he said + add a wideband AF meter to supplement the above advice.

 

[RustyRatRod]

You can change to 5/20 synthetic oil and that is also free horse power.

 

[MrJLR]

I found this video. ....kinda helps me get my head around timing.....




Jeff

 

[MileHighDart]

I found this video. ....kinda helps me get my head around timing.....




Jeff

Great video

 

[66jim]

Dump that open element air cleaner and install a cold air setup ducted to the front.
Electric fan(s) or at very least thermo clutch type.