T/A470 Tuning Advice

[brbuilder]

I thought this would be easy. Get a 3 day tag, get the emissions test, get my plates and be cruising around Chandler, Az. Got the 3-day tag, took it for a ride in the neighborhood and that was the end of easy. Ran great in the garage and on the street at extremely light throttle up to about 2000-2200 rpm. Give it a little more throttle and it falls flat. A major bog, Not a hesitation and it comes back, just nothing. Let off and it will hold about 1500-2000rpm.

It's a ‘69 302 with performer 289 intake, T/A 470 carb, Cardone electronic distributor, GM 4-pin HEI module, motorcraft TFI coil, resistor wire bypassed, new 8mm wires, Bosh platinum plugs, long tube headers, dual exhaust. I bought the carb used quite some time ago. Previously replaced the needle and seat. Had a small leak at the accelerator pump diaphragm. Replaced that and checked the jets. They were 50's. Stock is 57 so changed them to 57's. Small improvement. Readjusted the idle mixture screws using a vac gauge. Timing was at about 10. Advanced to 18 btdc. Small improvement. I think I've got the accelerator pump lever arm adjusted correctly. Carb has the orange accelerator cam lobe in the number 1 hole.

Don't know if it's a carb issue, ignition issue or something else. Any thoughts, suggestions, comments welcomed and appreciated.

 

[DirtDonk]

Still could be either lean on fuel or something amiss with the advance, but checking for at least the advance is pretty straightforward.

What about the PCV valve and other potential vacuum leak areas? Usually a small vacuum leak lets itself be known at idle, but a big one like for the PCV hose or power brake booster hose can really mess up acceleration.

But getting back to the jetting for a moment, your headers and dual exhaust alone will usually dictate richer main jets and more squirter. Is your orange a higher value, or less? Maybe more squirter and a little more jet?

Paul

 

[DirtDonk]

And back to the carb itself, since even Holley says that the larger TA is the appropriate one for our V8's, that would point even more to the jetting I would think. There was a large number of discussions about this when the TA first came out. For us, the 470 seemed perfect and fit with Holley's long standing recommendations. But that flew in the face of what they were recommending where the 470 was for smaller six-cylinder engines and the 670(?) was the one for us.

Double check with them, and ask them what they think the jetting should be if you decide to stick with the smaller carb. Still seems like the best size to me, but make sure to include the exhaust setup in your discussion.

paul

 

[brbuilder]

Have hydroboost brake so no vacuum leak there. The PCV valve and hose are new so I don't think there is a vac leak there but the PCV valve itself does not fit super tight in the grommet in the valve cover. Should this be a tight seal at the PCV valve to grommet to valve cover?

I think the orange accelerator cam lobe is in the middle range.

Bought this carb a long time ago and thought 470cfm would be great for a basically stockish 302. Wasn't planning running up into the 5000-6000rpm range much if at all.

I just have an on old SUN timing light, not a dial back type light. Just increasing the rpms and watching the timing marks it is advancing. Not sure how I would check for vacuum advance vs mechanical advance.

Squirter/discharge nozzle is a 35 which is the stock size. (middle of sizes 25-52) Guess I'll see if I can pick up a different nozzle. From what I've read the lower numbers number nozzles deliver the pump shot over a longer duration and the higher number nozzles deliver the pump shot much quicker. Not sure what would work best on mine.

Thanks for the input.

 

[DirtDonk]

Yes the PCV should be a snug fit, but no I seriously doubt it could cause the problem. Most of them are fairly loose after all these years anyway. And that everybody suffers that kind of a bug.
All extra vacuum ports in the carburetor are plugged presumably, but here again if not you know pretty quickly even at idle.

For the advance you don't need a dial back light. They're just nice to have.
If the advance continues in a linear fashion and smoothly without bouncing around a lot than the mechanical advance is probably OK. You can check vacuum advance in a basic manner by disconnecting it and reconnecting it to see what's going on. One thing related to that that can cause this problem sometimes is using for manifold vacuum for the advance rather than vacuum.
If you used an always open port you can swap the hose over to the ported hose fitting and see how that works. It's the one that will have no vacuum at idle.

 

[brbuilder]

The timing seemed to advance smoothly to a point and maxed out. I need to add some highlights to my timing marks to see them better. (Curses of getting older) I've got my distributor vac advance connected to the ported vacuum nipple on the carb, passenger side, high up on the metering block.

I've ordered several larger primary jets that I'll try today. Nobody seems to stock these parts in my area. There was a place in Tucson called Don's Hot Rod Shop that had anything you needed. I haven't found a place like that here in the SE Phoenix area.

Thanks

 

[Rustytruck]

on a regular Holley 600 for the small block ford liked the black cam the best for me. other profiles were too lazy.

 

[brbuilder]

I'll probably pick up the cam assortment pack for fine tuning but now my issue is around 2000rpm. It accelerates ok up to about 2000rpm and then doesn't want to take any more throttle after that. I think I had the float level too low. Readjusted to have fuel spill out of the site plug if you rock the vehicle. Might have to try different jets again now that the float level is I think correct.

 

[sanndmann3]

If I recall correctly, I had very similar issues with my Holley T/A back 10 years ago. Had it offroad on the dunes and hit a drop off and pounded hard. Ran similar to what brbuilder described after that. Figured I dislodged a piece of dirt or something so I x-rayed the metering blocks and found the following...

 

[sanndmann3]

What are the list numbers stamped in the top of the metering block?

 

[73azbronco]

Might think about getting it emission tested anyway. Let them tell you what they see on the analyzer. Your next one to pass won't cost anything. BTW, I had to detune three times to get it to pass when I had a 351 with older 4100, ran like crap when it passed, readjusted after passing but runs great again.

 

[brbuilder]

I'll get the numbers off the metering block this morning.

I'll mess with it a little more this weekend. Maybe get it a little better. Hopefully it will run well enough to make it to emissions. I'm thinking a smaller squirter might help but don't know if I can find one locally. I've checked the #5 plug (easy to get to) and it's looks good. The porcelain is a very light tan/grey/slightly reddish color. You can tell the ground strap was hotter from the tip/end and back about 1/2 to 3/4 towards the housing. If only driving it a few blocks can tell anything.

Do you know if they have you run it in gear on the rollers and up to what rpm/speed?

 

[brbuilder]

The number on the metering block is 12313.
Guessing you had to replace the metering block or is there access to that area of the block?

 

[sanndmann3]

You might give Holley tech line a call. there was a silent recall many years back. They sent me new metering blocks to replace the defective ones. had same part number with a -1 after the 5 digit number...
don't know if they are still doing that or not...or if it is even your problem but worth a call...

 

[brbuilder]

Ok thanks.

 

[Rustytruck]

for your emissions test make sure you truck is rumnning hot like a 195 thermostat do not advance the timing more that the factory ford setting. make sure your idle is set high. hook up a vacuum gauge and make sure the needle is dead steady at idle speed. this is extremely inmortant in addition too actual tune up settings for emissions.

 

[MS73HD302]

Mine did this from too much pump shot. Bandaided with the pink cam till smaller squirted came in. Plugs look good just fat when hammering the throttle Also the check valve under the squirter could not be seated completely giving a momentary lean spot. I tried opposite ends of the cam specs would almost die with blue cam and would buck HARD... pink cam chirping tires 1st and 2cnd. I've got 4.11s with 31s so pretty good mechanical advance in turn needing less shot.

 

[brbuilder]

Rustytruck - is that emissions testing in CA or AZ. I don't remember them ever checking timing down in Tucson. I think they put it on the rollers and sniff the exhaust and at idle and 50mph? I hope what you describe is not the procedure here in the PHX area or I've got more work to do.

MS73 - I wish mine was just a momentary lean spot but mine falls flat on it's face. Went back to basics last night - set fuel pressure to 6psi, set float level to just below the site widow/plug, set timing to where it sounded best (20btdc too high?) and stock 57 jets. Ran better so upped jets to 61. Ran better. Now I can run it up to 3000rpm before it falls on it's face. Holley tech suggested 7.5 power valve and/or upping squirter from 35 to 37 or 39. Are you running a TA470? What size jets, squirter and PV?

Thanks

 

[MS73HD302]

I've got the standard 1850-2 vacuum secondaries 600cfm and run 62F 68R jets to get a light soot on the plugs 28 size squirter 6.5 PV
20 degrees is a lot of initial... I run 10 degrees and timed vacuum port for the dizzy.
Are you transfer slots set to a square?

 

[Rustytruck]

Rustytruck - is that emissions testing in CA or AZ. I don't remember them ever checking timing down in Tucson. I think they put it on the rollers and sniff the exhaust and at idle and 50mph? I hope what you describe is not the procedure here in the PHX area or I've got more work to do.

MS73 - I wish mine was just a momentary lean spot but mine falls flat on it's face. Went back to basics last night - set fuel pressure to 6psi, set float level to just below the site widow/plug, set timing to where it sounded best (20btdc too high?) and stock 57 jets. Ran better so upped jets to 61. Ran better. Now I can run it up to 3000rpm before it falls on it's face. Holley tech suggested 7.5 power valve and/or upping squirter from 35 to 37 or 39. Are you running a TA470? What size jets, squirter and PV?

Thanks

Thats emissions in California the the process of reducing emissions are the same. less timing reduces NOX and Higher temperature and idle promotes clean burn. without having a wide ban to tune from your only indication of how the engine is running is a vacuum gauge, if the needle is steady you have no miss fires and the mixture screws are equal on both sides any hiccups and it will show on the vacuum needle. any vacuum leaks will promote a lean miss fire which will show up on the vacuum gauge.