heard this one yet????

[stevenfromtexas]

Originally Posted by Steeveedee

I would try spraying something inert from underneath that could enter the alleged leak. Maybe nitrogen?

yes sir, that is one spot i did not try (under the intake). that's first on my list tomorrow.....

[Missourimark]

Does this still have points ? If not are still running the ballast resistor ? Have seen HEI and other systems that eliminate the point system with a ballast resistor still in the line , they don’t run well that way . It takes 12 volts to make them work .With that air cleaner you have on it’s probably a normal carb sound you are hearing. I don’t think its a vacuume leak, or you should of found it by now.

[stevenfromtexas]

Originally Posted by VWNate1

I'm subscribed as I'm keen to hear the final solution With 10 degrees initial advance (must be zero vacuum to the dizzy @ idle !) you should be getting 21" of vacuum steady as a rock if not more at hot idle .

....errrrr......actually, i can't get it above 17"'s of vacuum. i hope i don't have other issue going on being as you mentioned the 21''......

[stevenfromtexas]

Originally Posted by Missourimark

Does this still have points ? If not are still running the ballast resistor ? Have seen HEI and other systems that eliminate the point system with a ballast resistor still in the line , they don’t run well that way . It takes 12 volts to make them work .With that air cleaner you have on it’s probably a normal carb sound you are hearing. I don’t think its a vacuume leak, or you should of found it by now.

no sir, i have the petronix ignition. no more points or resistor.

ok, i couldn't remember if i would hear that "sucking" noise when i drove it 20 years ago. if thats the case, ill live with it......the one thing that is bugging me is the sputtering at a quarter throttle in all 3 gears. can't really cruise through town in any gear when it bucks and jerks with just a little pedal


thank you all for your help!!!! sorry to be a pest!!!!

[Missourimark]

17 pounds of vac is good , is there a ballast resistor on the firewall ?

[stevenfromtexas]

maybe we could all meet in a central location and discuss all of the issues we have with our pickups.......

wait...isnt that called a "car show".......

[stevenfromtexas]

Originally Posted by Missourimark

17 pounds of vac is good , is there a ballast resistor on the firewall ?

no sir, all new wiring. AAW harness. no more resistor

[Missourimark]

I guess you need to go back the basics , do a compression test , do your plug readings at the same time . When you put the timing light on it does it fluctuate when reving the motor ? That would tell you that the vac advance is working on the dist. Something I like doing is using a infrared temp gun on the exhaust where it ports out the head , a cooler temp would indicate a missfire. Is the Petronix up to snuff ? Don’t know how to test it, maybe some will chime in.

[VWNate1]

These rigs didn't use ballast resistors ~ they used a calibrated resistance wire from the ignition switch to the hot side of the coil . this wire was yellow .

Pertronix is good, can I assume it at one time ran fine with the Ignitor system in it ? .

Don't apologize for asking for help ! that's what this forum is for .

[stevenfromtexas]

Originally Posted by Missourimark

I guess you need to go back the basics , do a compression test , do your plug readings at the same time . When you put the timing light on it does it fluctuate when reving the motor ? That would tell you that the vac advance is working on the dist. Something I like doing is using a infrared temp gun on the exhaust where it ports out the head , a cooler temp would indicate a missfire. Is the Petronix up to snuff ? Don’t know how to test it, maybe some will chime in.

yes sir, it does advance with rpms petronix is a couple years old. installed when i built the engine. i read through here and saw a few guys liked it. my thought was that i wanted the same look as stock, with he coil and all. AND.....my ability to tinker with points es no bueno

[stevenfromtexas]

we are getting closer!!!!

after checking for "squirt" with the accelerator last night i noticed, it wasn't. so i got another pump with seals on it already. hated to buy a whole new kit for just the acc. stuff. any who....its running MUCH better...however there is still a little sputter (at quarter throttle) although way better than it has been.

new question......

explain or direct me where to read about this adjustment

this was a reman carb from a few years ago when i built the engine. the original was in my opinion farther "gone" than my minimal tech skills could have done. bought the one i have now. i honestly can not remember if the old one had this adjustment or not.

it sits up a little and when i push on it i get some good squirt-age . obviously it has to do with the acc. pump. just curious if some adjusting in this area will totally solve my herky-jerky with quarter throttle.

it is getting much better though

[Steeveedee]

I'm going to guess it's a bowl vent valve, but I haven't seen it on an exploded view except on a Holley. In any event, the next thing I would do is move the throttle to 1/4 open, and hold it there until the squirt stops. Then give it a little more throttle and see how that squirt works. If you don't get much fuel squirting, there is something in the accelerator pump circuit that ain't right. If I had to guess, I'd say the piston seal, but that's obviously new. Next culprit might be that the bore is worn. To check that, you'd have to take it apart, again, though. At this rate, you'll soon be able to do it in your sleep.

It is entirely possible that your vacuum advance is not working. If you are cruising at 1/4 throttle, the vacuum advance will help with throttle tip-in, but if not, it can lag some. Do you have a hand-held vacuum pump that you can check to see if the advance works and doesn't leak down? You can hook it to live engine vacuum to verify that it works, but that won't tell you if it leaks.

[VWNate1]

Yes, that's the float bowl valve and is separate from the accelerator pump .

Sometimes the lip of the accel. pump plunger rubber gets caught during installation and flips up, reducing the ability to pump much fuel .

[firedemon]

only getting 17 inches of vacume did you try to adjust the distributor or just the carb ? sometimes the distributor will give you a few more inches of vacume and adjusting the distributor with the vacume guage will help you find your motors happy place timing wise . tons of videos on you tube that can explain way better than I can type

[VWNate1]

Yes, this is possible, they taught it @ the GM factory training I took close to 50 years ago :

Warm up the engine fully then set the idle to about 700RPM . connect the vacuum gauge to the direct manifold vacuum port and watch it closely as you s l o w l y advance the distributor ~ as you advance the timing the gauge's needle will rise, eventually it will begin to twitch, stop and ease it back until you get the highest steady vacuum, snug down the dizzy's clamp and take it for a test drive, radio off, windows closed ~ when you get it to 35 ~ 40 MPH in top gear on a flat and level road, depress the foot feed to the floor and listen for knock or ping noises ~ if none, you're good to go .

If you hear even a -slight- ping or knock, stop and using the timing light, back the timing off -ONE- degree, snug the dizzy and try it again .

The idea is to give the engine all the advance it'll take without any ping .

This is called the "Throttle Ping Test" and is how old GM i6 engines were properly tuned before the $tealerships decided that test drives were a waste of time . actually they just wanted us to work harder and faster, no matter if the Customer didn't get the high quality works they'd payed for .

Give this a try, you'll prolly like the result .

I hope you knew to open the spark plug gaps to at least .040" after in stalling the Pertronix Ignitor ? .

[stevenfromtexas]

Originally Posted by Steeveedee

I'm going to guess it's a bowl vent valve, but I haven't seen it on an exploded view except on a Holley. In any event, the next thing I would do is move the throttle to 1/4 open, and hold it there until the squirt stops. Then give it a little more throttle and see how that squirt works. If you don't get much fuel squirting, there is something in the accelerator pump circuit that ain't right. If I had to guess, I'd say the piston seal, but that's obviously new. Next culprit might be that the bore is worn. To check that, you'd have to take it apart, again, though. At this rate, you'll soon be able to do it in your sleep.

It is entirely possible that your vacuum advance is not working. If you are cruising at 1/4 throttle, the vacuum advance will help with throttle tip-in, but if not, it can lag some. Do you have a hand-held vacuum pump that you can check to see if the advance works and doesn't leak down? You can hook it to live engine vacuum to verify that it works, but that won't tell you if it leaks.

ill try the 1/4 throttle you mentioned at the first......
the advance works with suction. also when i disconnect it to check the timing then reconnect, it sucks my hose on the canister and the engine "advances".....

[stevenfromtexas]

Originally Posted by firedemon

only getting 17 inches of vacume did you try to adjust the distributor or just the carb ? sometimes the distributor will give you a few more inches of vacume and adjusting the distributor with the vacume guage will help you find your motors happy place timing wise . tons of videos on you tube that can explain way better than I can type

i redid the vacuum test this morning. i was taking the reading from the carburetor port. i re-read these post and i guess i missed the "manifold" port for vacuum test. I have a steady 20''of vacuum there.
i'll do all of your test again in the morning. assuming 20'' of vacuum is the correct amount, or do i go as high as possible???

[VWNate1]

You have the vacuum advance hose connected to the WRONG carby port ~ at idle, the *MUST* be no vacuum signal ! .

Experiment until you fine the port that gives vacuum the *instant* the throttle is opened, you'll need to re time the idle advance but I'm betting you're going to love how it runs after you fix this common problem .

[stevenfromtexas]

Originally Posted by VWNate1

I hope you knew to open the spark plug gaps to at least .040" after in stalling the Pertronix Ignitor ? .

thank you for this. i've put over 100 miles driving it around a 5 mile loop after doing the little tweaks seeing what works and what doesn't......

yes sir, i actually have them a little more than that. i read some older post that mentioned even more than that of a gap. mine are at .055 right now. you reckon i should move the down to .040?

[stevenfromtexas]

Originally Posted by VWNate1

You have the vacuum advance hose connected to the WRONG carby port ~ at idle, the *MUST* be no vacuum signal ! .

Experiment until you fine the port that gives vacuum the *instant* the throttle is opened, you'll need to re time the idle advance but I'm betting you're going to love how it runs after you fix this common problem .

i am really confused now.....i only have 1 port. this is the same one when i took it apart.

[VWNate1]

20" is very good for an old engine .

You can power tune it using the vacuum gauge but if it pings, knocks or diesels when you shut it off hot, back the timing off one degree at a time until it doesn't, this is very important as knock/ping is deadly to your engine .

If you take the time to learn and do all this, you'll be richly rewarded with a rig that starts easily hot or cold, runs far stronger than you'd ever imagined and, you can impress your buddies and make beer $ by doing these same basic steps on their rigs, even the V8 ones .

[VWNate1]

The distributor vacuum advance port is on the inside of the carby facing the rocker box where you'll often burn your fingers trying to re attach the rotten and loose fitting hose .

It gets NO vacuum until the throttle is opened, even a tiny bit .

GM made millions and millions of these carbys and some had three + vacuum ports .

Maybe a picture of yours would help ? .

No, DO NOT close those spark plug gaps ! .

When HEI was first introduced the recommended gaps were .065" ! .

My '69's engine burns a LOT of oil so I'm running the 1977 250 i6 HEI GM dist. and .070" plug gags, it runs so sweetly and strongly it's amazing ~ no oil smoke either as it gets fully burned ~ you can smell burned oil when standing behind my truck but not see any smoke .

Leave the plugs be for now, it sounds like you're closing in on any problems .

[stevenfromtexas]

...
goes the distributer from here.

[Steeveedee]

.055" plug gap is pretty big if you are still using the stock coil. I'd close them down to no more than .040" as VWNate suggested. Too big a gap with the stock coil can also cause performance issues. There is no amplification with the Pertronix ignition; it is just a more reliable switch than breaker points.

Make these changes one at a time so that you can trace down the actual culprit! If you don't, the next time something crops up, you'll be looking at what you did and wondering which one actually was the solution...and doing them all again until it's fixed.

[Steeveedee]

Originally Posted by stevenfromtexas

...
goes the distributer from here.

That port is above the throttle plate, so should have no vacuum at idle- it is "ported spark"- the correct place for your vacuum advance to be hooked into.