Holley Help

Attention Holley tuners. I need some help. I took the front bowl off my Holley TA470 tday and found this,

not exactly, I took the jet out to see what size it was, 57. I expected to find a power valve with shoulders on it to make it easy to change. I don't know what size this, or even if it is changeable.
The 231 runs strong just off idle and even cruises good. The issue is when I turn uphill and naturally start to lean into the pedal a little more to maintain speed, it starts to splutter and miss. If I lean real hard into the pedal and open the 4 barrel, it will clear up and run like it should. It runs very well at WOT. I am thinking, jets are a little small or change power valve. I don't know how to get this one out, or what it is.
Anybody can help me??
Thanks in advance
Tim

 

I dont know anything about that carb but I think you are looking at the top of the PV. Its removed from the other side.

 

I don't know anything about it either. I'm just trying to learn. I ran out of time today. I had a date with my granddaughter.
Thanks

 

Get a book. Or at least read the Holley site. They have a tutorial on how to tune the power valve. If you don't have a air-fuel mixture gauge, you can tune the main jets by looking at the spark plugs. Both the pump shot and the power valve can be tuned to cure a stumble when opening the throttle. You also may need to adjust the float level so that the engine does not flood out on hills. This should not be a problem with the TA, which is supposed to be set up for off-angle operation, but it's something to check.

There aren't that many things to change ... partly why people like them.

They all run well at WOT, in my experience. Regardless of the tune.

 

I have fought and fought with my TA 470, & have improved this problem but never entirely eliminated it. Seems to be a problproblem with this particular carb. Very frustrating to me as I worked for a speed shop in the 80's and I've done literally hundreds of Holley carbs.
1st thing to try, smaller jets and a 65 PV.

 

I increased my PV size ,and my stumble went away . I think i'm at 8.5 right now idles at 18" of MANIFOLD vacuum so with a higher pv it will open sooner as vacuum drops , get a vacuum gage and drive around with it plumbed to the dash . My Olds runs a 850 duble pumper holley and my dauntless has a regular 390 carb that I fitted with truck avenger pieces.... you can mess with pump shot duration .squirter size but I would start with the pv …..summit has them $8

 

The power valve screws into the back of the metering block (the part the Jets screw into)....you just have to carefully pry it off the main body of the carb.

 

For reference on jets vs displacement a stock motorcraft 2bbl came with 47 jets to feed a 304 V8. That is probably lean by design in 1973 so Im going to try 49 on my rebuild.

I do not know if comparing 2bbl jets with 4bbl primary jets is a fair comparison, but it does seem like you have large jets for a 225.

 

Comparing Mototrcraft to holley Is apples and oranges.

 

Pretty sure they are sized the same way, ie 47 == 0.047" diam. orifice. Otherwise Doug is right - can't compare. Not interchangeable either.

 

The answer here is "it depends"
Google Holley jet size chart and you'll see what I mean.
Also, different carbs have different jetting requirements....venturi size, booster design and power enrichment circuit are all factors here. A two barrel Rochester, Holley, and Motorcraft might all use different size jets on the same engine.

 

Could be accelerator pump circuit - maybe plugged port to discharge nozzles. Accel pump curves can be tuned by the use of cams on the throttle shaft. You can tune your power valve by using a vacuum gauge to isolate the load at which your stumble occurs.

 

I'm still struggling with this Holley TA 470. I plumbed in a vacuum, and fuel gauge into the cab where I could watch it. I did have a vacuum leak at the base of the carb. Fixed. I was running a little low on fuel psi at 3-4, with a new Carter pump. Fixed. Now has an AC Delco pump, running at 5-7 psi. I changed the 2.5 PV to a 6.5, didn't seem to help it. I have tried a couple different throttle cams, no help. At idle I have 14-15 in of vacuum, and the engine starts missing at 2in or below on the vacuum gauge.
I called the Holley tech support and went through all this with the tech guy. When I had answered all his questions about my setup, he told me that this was a rock crawler carb, and not to expect it to do much better on the street.
Anybody got any ideas?
Thanks
Tim

 

I have struggled with similar problems with mine....and I've set up a LOT of Holley carbs. I have improved it some but basically, I've just learned to live with it.

 

Just my limited experience with both a Dauntless, and a Buick 215 V8. I went round and round trying to eliminate the dead spot right off idle with a Holly 470. I got it OK, but it still stumbled a bit. I never was happy. Wide open, the 470 was great.
I picked up a 390 and set it up with the same jetting as the 470, and the problem was solved. A good friend suggested the 390 as a better size for the small displacement engines, and the 470 was too big to get a good throttle response. The 390 (8007) fixed all my issues. Both were used carbs, but clean and in very good condition. I've since gotten two more 390s for different vehicles with these engines, and they all perform flawlessly.
-Donny

 

I've thought about going this route, but the TA470 works REALLY good off road
My problem is probably made worse by elevation...I live around 6000ft and regularly go on high elevation trails 10,000ft+

 

I swapped a TA470 on to a TBI 318 and it solved all my fuel problems lol

The grass is always greener somewhere.

 

The 390 likely has vacuum/fuel flow ports and venturi diameters tailored for better metering at low to medium throttle angles. This will provide better driveability for Jeep duty. Bigger isn't always better.