Stumble @WOT

[texas69bee]

Get it hooked up to the other port and leave it. The carb ships from the factory with the idle screws at 1.5 turns. Adjust until A/F to 13.5 Adjust timing 34-36 deg. Check your timing with advance hooked up as well to make sure your not pulling to much advance and causing it to lean out. I tried that other port as well and the backfiring did mess up my power valve. Also check your plugs.

 

[oldbee]

Ok I listened more than once to the videos & it sounds like ur not transitioning to the main fuel circuit, probably feels much worse in person. PV not kicking in or not enuf timing. Ur getting rpm's from the acc pump shot & then dieing out from not enuf.

 

[texas69bee]

Ok I listened more than once to the videos & it sounds like ur not transitioning to the main fuel circuit, probably feels much worse in person. PV not kicking in or not enuf timing. Ur getting rpm's from the acc pump shot & then dieing out from not enuf.

X2 on the valve and make sure it’s the right size.

 

[rebootej]

Ok I listened more than once to the videos & it sounds like ur not transitioning to the main fuel circuit, probably feels much worse in person. PV not kicking in or not enuf timing. Ur getting rpm's from the acc pump shot & then dieing out from not enuf.

Yes it feels awful in person. Okay ill switch the line and check the PV and I've also been wanting to add more timing back in. Will the power valve obviously be bad by looking at it?

Sounds to me like a tight converter and high (highway) gears... Don't think that qualifies as a stumble. Your engine actually sounds pretty good.

I do want/need to change the rear end gears eventually but the car didn't used to do this so something changed.

 

[rebootej]

Update.. brought my initial timing up to 15-16 degrees BTDC. Reduced the amount of vacuum advance to about 5 degrees at idle and hooked it up to the manifold vacuum. Also reduced the mechanical advance a bit because previously my total advance had been about 38 degrees and i had pinging/detonation issues. Not sure exactly how much mechanical advance i have in there now, ill be ordering a dial back timing light after this, id been borrowing one perviously.

Road test, car is running aloooot better. The lean spike bog is still there a little but not as noticeable for sure. Wondering if it wants more? Im still going to open up the carb tomorrow night and check that power valve.

 

[oldbee]

No pinging yet? Crank in some more.

 

[texas69bee]

https://forums.holley.com/entry.php?430-Holley-Power-Valve-Tuning

 

[rebootej]

Okay so update. Changed the power valve to a 7.5 so it opens a little sooner. Not sure if the old one was bad or not but after i replaced it the car did run leaner so maybe it was leaking a little? Also cracked open the secondaries a little with the set screw. Car is running alot better! still leaning out a little but not as bad as it was definitely more drivable. Going to try and dial a little more vacuum timing in and maybe some initial timing as well?

 

[oldbee]

My guess would be more initial. Leave the vacuum alone. I would never try cracking open the secondaries open from what factory setting is.

 

[rebootej]

My guess would be more initial. Leave the vacuum alone. I would never try cracking open the secondaries open from what factory setting is.

Okay. Ill give it more I was just really far into my transfer slot on the primary side

I tried it because i watched a video on one of the holly videos about it.

Also found this interesting but will keep playing with timing for now
https://www.holley.com/blog/post/carb_class_5_basic_carb_tuning_tips/

Once you get the main jetting where you want it, it will probably be too lean for full throttle, full power runs. That’s where the power valve circuit comes in. There is one more adjustment left after you establish the correct power valve opening point. The screw-in power valve channel restrictors act as jets for the power valve circuit. So, if your vehicle is surging or coughing through the carb (popping) at wide-open throttle, you can richen it up with larger restrictors. Zach says that .005” change in size will be a noticeable difference. Most QFT™ carbs come from the factory with .043”-.048” power valve channel restrictions. If the main jets feel right and the engine is too rich under full throttle, then you can also reduce the size of the channel restrictions.

 

[rebootej]

Im a teacher and the Car Club advisor. The kids talked me in to running my car at the track this weekend. First time ever doing this.

First time ever doing this. Car ran great in the quarter with WOT. But did have some lean issues after leaving. Still have some issues to hunt down but pretty happy with how the car is running.. Just wish it was faster...!

 

[texas69bee]

Good to hear, congrats on the progress.