T/A470 Tuning Advice

[brbuilder]

MS73 - I'll have to check again on the transfer slots but I'm pretty sure they were square. I think my mechanical advance is about 25 so that puts me at about 45 total with 20 initial which is kind of high. Guess I'll have to mess with that some more. My main goal right now is to get it running well enough to pass emissions. Then maybe I can dial it in.

Ran better with the 61 jets. Not sure if I should keep jetting up to 63 or 65 or try a 6.5 or 7.5 PV or different discharge nozzle. Guess it will be a lot of trial and error.

 

[brbuilder]

Rusty - holds a little over 18 pretty steady on the vac gauge. Not rock steady but doesn't vary even a quarter point. I think I've got a 185 t-stat in there. Reads about 195 on the factory gauge. Been a while since I've checked it with an infrared temp gun shooting the t-stat housing. I think the factory gauge might be reading a little high. Plugs are a light tan slightly reddish color. If anything I would read the plugs as it's running a little lean.

 

[MS73HD302]

You got spot on with trial and error I read the plugs a lot while I'm getting mine dialed in and takes time and good consistent input. I'm no help on passing emissions

 

[brbuilder]

Passed Emissions!!!

Ran best with the following settings:

Timing at 12-14 btdc
Primary jets - 55
Power valve - 7.5
Discharge Nozzle - 28
Accelerator pump cam - orange
Idle - 750
Vacuum - 18.5

Runs good at light throttle but definitely needs a lot more carb tuning.

 

[Rustytruck]

does not Arizona worry about original smog equipment? are you running a stock air cleaner?
or do you just have to pass a sniffer test. no Dyno run?

 

[brbuilder]

Mine is a ‘69. Not much as far as original smog equipment. I have added a vent from the gas tank to a charcoal filer from a newer Ford Ranger PU and vented that to the open element air filter housing.

They put it on rollers, hook up hoses to the exhaust (I have dual exhaust), run it up to 33mph (needs to be between 30-35mph) and checked for a gas cap. They didn't test the cap just verified there was a gas cap. Never opened the hood. Took readings for HC and CO at idle and loaded (at 33mph).

 

[BUCKWILD]

Ohm check your wires, Ive had a lot bad out of the box with the same problems. Will cruse around ok but will not handle load, I went rounds with a 327 i built for a guy changed carb distributor coil and nothing checked the wires and ohm loading was stupid high

 

[brbuilder]

I'll check them. Thanks

 

[79INA69]

Just wanted to mention one more quirk about this carb and that is the check balls that are in the metering plates. These are one of the specific mods that make a T/A. When sitting for too long or with crappy CA gas these check valves will get stuck / gummed up. I believe there purpose is to prevent fuel transfer during extreme angles of operation. What you have to do is remove the metering plates and shake them up and down. If you hear rattling, your good. If you don't, they are stuck. This carb is harder to tune the transition from cruise to power because of these metering blocks. I also switched the power valve, longer duration cam with .031 squirters as well as jetting up to help the flat lean spot in my 670.

 

[brbuilder]

I think my plugs wires are good. Just an 8mm parts store “SuperMag” plug wire. They ohm'd out from just over 1000 up to 1380. However my coil wire might be an issue. It ohm'd at 7350.

 

[brbuilder]

I did blow out all the passages in the metering blocks with carb cleaner but did not shake them or listen for any rattling. Will have to do that.

Seems like my cruise mix is ok maybe a little lean. Plugs are ashen grey to light reddish brown. Checked them after my trip to emissions. My CO and HC numbers were on the higher side of the mid range allowed. I have a 7.5 PV and even when the vac drops below 7.5 it does not seem to be getting enough fuel. Wondering if changing the discharge nozzle will help. I've got a 28 in there now but have a 32, 35(originally in the carb), 37 and 40. Or try different accelerator pump cams? I also picked up an assortment of them. At what point do you start messing with the secondary diaphragm springs?

 

[79INA69]

Both T/A carbs I owned ended up with the lightest spring in them, silver I think. It is a very easy change if you haven't done it yet. I had an automatic trans in both cases. Obviously make one change at a time. They are good carbs out of the box and easier to mess with than a Q-jet.

 

[brbuilder]

I assume you are talking about the secondary springs. I tried the purple spring (mid range) it seemed better so went further and installed the white spring (lightest) and it seemed better yet. But still needs some more adjustments. I think it's still lean.

Agree with only changing one thing at a time. I'm also trying to keep notes of what I've done and my impression of the results, good or bad.