Thread: 350 running rich

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Thanks for the help guys!! Here's a pic of the vacuum gauge I'm using.

I'll definitely watch the videos linked, thank you!!

I'm plugging in right at the very bottom of the front of the carb just above the gasket. There's 2 ports, I'm using the left one for the vacuum advance, and the one right next to it for the vacuum gauge.

I'll have him order a 4.5 PV and some smaller jets. I probably won't get an opportunity to work on it again until next weekend, I'll post my results.

I should add that when he got the truck he said it ran great, but it started running poorly so he called me to work on it. He didn't drive it much, maybe 30 or 40 miles before it started acting up. He tried to get more information on the motor specs, but unfortunately had no luck. Since I've been working on it, it hasn't run good at all. When we took it for a ride, it would misfire horribly when getting on it at all. If you just put around with it, it seems to go alright, but as soon as you put anything into it it sputters and misfires something terrible. He said that one of the previous owners had raced it and ran race gas in it.

The carb is manual secondary, and I believe it does have a second power valve in it. I have taken the secondary half apart yet, so I don't know for sure. I tried to find some identifying numbers on it so I could see what CFM it is, but there's no numbers stamped in the usual spot on the choke tower.

Thanks again for all your help!!

Here's the only numbers I could find on it. It's hard to see them, but they're 6508065. Maybe the 650 portion is saying it's 650 CFM? Nothing really comes up when doing a search on those numbers.

You're using ported vacuum, unplug your vacuum advance and plug the gauge in there.
https://documents.holley.com/199r11202.pdf
https://documents.holley.com/199r10014rev1.pdf

The PV (power valve/enrichment valve), if its diaphragm and gasket are sealing (verified by installing new one), will not add fuel to the idle circuit even if opened as it feeds fuel through the venturi boosters and operates off venturi vacuum, manifold vacuum only controls when it opens.

The carb is idling way too rich, the idle circuit is not fed by the jets in this carb design. While jetting is absolutely going to need adjustments, IMHO, first up should be getting the idle circuit under control.

The OP just gave us a clue that he did not buy this carb new or he would know more about it. It is possible the carb has been fiddled with by others and the idle feed restrictor may need changing.
https://www.musclecardiy.com/perform...bration-guide/

JMHO, Once we get the idle/transition circuit under control we can move on to further tuning the carb.

Originally Posted by 36 sedan

You're using ported vacuum, unplug your vacuum advance and plug the gauge in there.
https://documents.holley.com/199r11202.pdf
https://documents.holley.com/199r10014rev1.pdf

Just to be clear, I'm currently using the port that I have circled in red, would that be the correct one? Or should I use the one that I have the vacuum advance plugged into, which is the one directly to the left of the one I circled?

Also.in the last picture - above the ground wire, between the three threaded holes is a vacuum port. It is used to open / close the secondaries, on a vacuum secondary carb. Next time you run this motor, verify that it isn't pulling air in through there!

Originally Posted by 34_40

Also.in the last picture - above the ground wire, between the three threaded holes is a vacuum port. It is used to open / close the secondaries, on a vacuum secondary carb. Next time you run this motor, verify that it isn't pulling air in through there!

I will definitely check that out, thank you for the tip!! Should there be a plug screwed in it?

Your original picture of your motor shows a double pump carb (mechanical secondaries).
To confirm which port is manifold, put your finger over each one at a time while the motor is running, the one that pulls on your finger at idle is manifold.

Originally Posted by 36 sedan

Your original picture of your motor shows a double pump carb (mechanical secondaries).
To confirm which port is manifold, put your finger over each one at a time while the motor is running, the one that pulls on your finger at idle is manifold.

Sorry, I just used that pic to show the location of the ports. The ones on the carb I'm working on are in the same place, but sticking straight out instead of angled like the pic I referenced. The vacuum advance line was plugged into the right one when I started, is that not the correct place for it on this carb? Could I t off on the brake vacuum to test the vacuum?

Originally Posted by DennyW

I see now. You have your vacuum gauge on a ported port. That's why it only shows " vacuum on the gauge.
You have to find a full vacuum port for the vacuum gauge.


Attachment 72684


Attachment 72685


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If you are running the normal Chevy Style where it uses full vacuum at idle, then you have to use the right port depending on your setup...


Descent video...

Quick Fuel Technology Carb Install and Tuning Walkthrough- RODDING REVOLUTIONS ISSUE #1
https://www.youtube.com/watch?v=70hhpX2tfsE

The 3rd pic you posted is where I should be plugging in the vacuum advance then, correct? Right now that port has a plug over it.

Just put your finger over each port one at a time, the one that pulls on your finger at idle is manifold vacuum, hook the gauge to that one.

However, using the wrong vacuum port is not the cause of your problem. You were able to close the mixture screws completely without killing the motor. Normally I would say you have a vacuum leak, however, I think you are getting fuel from the transition circuit possibly because your throttle stop is adjusted to high and why I suggested dropping your Idle speed to 700rpm. With your altitude the mixture screws will probably need to be less than a 1/2 turn out (open) on all 4 corners.

Lowering the idle speed will also let you check initial timing without any mechanical advance starting to effect it, I suspect your initial timing my be a little low. Also, always check and set timing with vacuum advance disconnected. And, be sure to check total timing if you change initial timing.

And, when adjusting mixture screws go slow, make small changes and wait for vacuum to catch up.

Originally Posted by JD323

Sorry, I just used that pic to show the location of the ports.

The picture you posted in post #8 sure looks like the same motor/carb as in your video? The rear (second) accelerator pump on the secondaries makes me think it is a double pump carb.

But, be that as it may, we are not there yet...

Originally Posted by 36 sedan

The picture you posted in post #8 sure looks like the same motor/carb as in your video? The rear (second) accelerator pump on the secondaries makes me think it is a double pump carb.

But, be that as it may, we are not there yet...

Yes, same motor, I was referring to the pic of the bottom of the carb I posted with the circled port. Sorry about the confusion! Yes, the carb is a double pumper.

https://www.holley.com/products/fuel...parts/BR-67212

he has only drivin it 30-40 miles??????? previous owner ran RACE gas in it???????? now high altitude????????

Race gas and street gas are terribly different-------he needs to completely drain the system and then put gas from a trade mark name company back in it-------and always fill up at the same place-----------the differance of street and race gas is so different that its qqqqqqqqqqqqqqqqqqq!!!!!!!!!!!!!!!!!!!!!!

Originally Posted by jerry clayton

he has only drivin it 30-40 miles??????? previous owner ran RACE gas in it???????? now high altitude????????

Race gas and street gas are terribly different-------he needs to completely drain the system and then put gas from a trade mark name company back in it-------and always fill up at the same place-----------the differance of street and race gas is so different that its qqqqqqqqqqqqqqqqqqq!!!!!!!!!!!!!!!!!!!!!!

Jerry, I don't see where he raced or ran race fuel???
Am I missing it??