HOLLEY POWER VALVE TUNING- Everything You Need To Tune Your Power Valve | Holley Carb Secrets |
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- Опубликовано: 27 авг 2024
- Holley Power Valve and How to tune power valve along with so much more info. I've got my carb ls dialed in and I thought I'd show you how to set up one of the most viable items on your carb. On my carbureted ls I installed a vacuum gauge and an AFR gauge and went to town. Theres very little info when it comes to a holley carb and much less when you get into the PVCR, IAB, IFR etc. Tuning a holley carb is easy, once you know how all the systems operate. Hopefully this helps someone in the future looking to modify their holley 600 650 750 vacuum secondary or double pumper. Trying to catch up to the driveway engineer so lend me your power!
IVE BEEN TURNING WRENCHES FOR 50YRS, I GOTTA GIVE YA 2 THUMBS UP CAUSE THATS ALL I GOT, GREAT VIDEO
Thanks man, I appreciate it 👍
Great video. Yes once the power valve is tuned your engine will be a ton more driver friendly
Nice explanation of power valve function. I never use the rebuild kit 6.5 valve. I have 7.5, 8.5's for my SBC since my normal idle vacuum is at least 18 in hg. Right now I'm using the 7.5 and there's no bog on the way into the primary main jets. In winter I may use the 8.5. My 650 Holley is an old model from the 90's but it's never blown a power valve. thanks for the video info.
Thanks so much! Really appreciate it!
@@NightWrencher I enjoy your videos and have subscribed. Keep 'em coming.
👍 hope you stick around!
For me, it was imposible to ignore that happy face on your hand!! 🤣
>:(
You could possibly be right, 570-600 cfm maybe be better for your application. Dual planes usually allow you to go down on jet sizing, not sure which intake you are using but they provide a stronger signal. Holley has a carb sizing chart based on displacement and volumetric efficiency of the heads. Cylinders 7&8 tend to run leaner on LS engines so you maybe able to dial some timing out depending on your ignition controller. Your headed in the right direction with your videos. I run a primary metering block with adjustable PVRC jets on my turbo application, will work on NA motors too. Keep at the informative videos.
Thanks man, really appreciate it!
You're the man, appreciate your videos...
I appreciate it man 👍
I like your vidioes they are very imformative! I drag race and for the guys that are running a tall camshaft with lots of lift and duration you will have very little manifold vaccum at idle so low that you can not keep the engine running even by turning out the idle screws to richen the mixture, the fix is to use a 4.5 or less power valve to let more fuel into the idle circute so the engine will run! than adjust the idle jets and the curb idle. pull a few spark plugs and look at the color they tell the story of what is going on in the combustion chamber if they are black and wet you are running pig rich jet down 4 sizes and go from there untill you get a nice tan color. If you think your carborator is to big you can drop down six to seven sizes on the main jets to make the engine run good and lean, keep checking the spark plugsthis will save you from buying a new carburetor. there are a few good sparkplug reading vids out on utube check them out! hope this helps.
This is awesome man, thank you. I've very little knowledge of what to do in hard core racing situations. Most carbs I've tuned have been for mild or stock build, less than 500hp. I'm sure the wide band becomes fairly useless at idle with a huge cam! Thanks again!
@@NightWrencher you are right about the wide band! I have a small block ford 363ci that makes 550hp I run it at the track only, just headers on it no other pipes the collector is to close to the cylinder head so I can not use a wide band, but in other situations they are very good. most of your readers are probably not racers but when you move to a bigger cam to build more hp you run into the low vaccum problem but in all situations your spark plugs always let you know how lean or rich your engine is running.
I bought a nine fifty holley to go with a bigger cam that installed hoping it would be a good match with this new cam but it turns out it did not give me the extra power I was looking for and the engine was running way ritch on fuel, so I jetted down from #90 that came in the carb to start with both primary and secondary I worked my way down to #80s both sides, the carb came with a #4.5 power valve in it ( this is a full race carb) and with this change I got the adjustability back in the idle circute. The idle circuit and the power valve are two seperate ciruites but with low vaccum the power valve will open sooner allowing more fuel into the boosters so the engine will start. This saved me from buying a smaller carb I probably could have got by with an 800cfm carburator from the start. Now the engine starts and runs great and I saved some money! when you are making these changes and you run the engine at top end speed under a load listen for a( pulsating miss ) if this happens your engine is running too lean than you have to jet up on the secondary side probably two sizes to start with and keep checking those spark plugs. I hope this helps some one out!
@@randyjohnson1809 cool.
Most street Holleys come with a 6.5 pv.
I thought that if you want to pull in fuel quicker after the accelerater pump shot, you would go with a 7.5?
If an engine only makes let's say 12" of vacuum, a 9.5pv would open up really quickly right?
Right now my 381 Chev with a 650 speed demon, and a really big cam has a slight hesitation if I crack the throttle fast. What could it be?
I'm going to try a 35 then a 37 pump nozzle first, it has a 31 now.
If that doesn't do it, I'm going to try a 7.5pv then a 8.5pv.
Timing is 22* initial and 37* total, jets are 74 primary, 83 secondary, idle is around 800 rpms, transfer slots are pretty bang on too. It dynoed 511hp and 495tq.
Great info. I bought a Quick Fuel SS 750 AN and didn't pay too much attention to the power valve. I think i compensated for the valve opening too soon and dialed back my main jets to compensate. now the quality carb is acting wonky and just don't know where to go with adjusting. I have a 6.5 PV and about 11 inches of vacum at idle. Im going to set the jets back to factory and use the vacuum gauge like you said otherwise i feel i'm just guessing. I have an airfuel gauge already so this should get me there! Thanks for the info and keep up the good instruction!
Thanks man! Take your vacuum at cruise in high gear going about 65-70. Then put your foot down at close to half throttle and see where your vacuum drops to. Go at least 1 size above that number. Cruising at 65 should get your main jets dialed in with the wide band. If the engine goes too rich after the PV opens, youll need smaller PVCRs. If the carb goes lean, youll need bigger PVCRs. The opening point is just one tuning aspect, the second one is the size of the actual PVCRs.
This really makes sense to me now.Thanks nightwrencher.
Thank you sir, I hope it helps!
Great video. Single AFR reading are an average. Total fueling or total fuel area should be balanced. Primary jet + power valve = secondary jet. Hence the common jet spread. If not fueling distribution will be off but the AFR gauge will have you thinking everything is OK. Jet area charts will help to know total fueling.
Ive never heard it explained that way but it does makes sense! When I got my main jets dialed in, and then set up my power valve, I kept having to jet down my secondaries. Im running 65pri and 58 sec jetting with a .020 PVCR. I figure this is because the 650 I have on my LS right now is too big for the stock engine and it cant pull enough air in the upper RPMs. I tried blocking off my power valve and just jet up but the same thing happened but with less drivability. It really showed me how Carb sizing affects everything
Thank you for these videos. my mighty demon 850 comes with a 4.5 PV. At lite cruise, it’s grumpy. It seems it needs one closer to manifold vacuum. I wish you had a driving video to show how you figure it out with a afr gauge and vacuum gauge. I bought drill able fuel bleeds and Air bleeds and a dual wide band gauge. You are right it’s hard to find info. It’s miserable and I want to make it correct.
Hey man, looks like my comment didnt post. Setting up the PV is pretty easy if you already have the wide band. With the vacuum gauge hooked up find what your cruising vacuum is. Find a big hill and go up it slow and ease into the throttle, the AFR should start going lean, once it starts hesitating take note of the vacuum and then go up to the nearest number for your PV.
Excellent info thanx
Thanks a bunch! Much appreciated!
Thanks for the vid! helpful !!
Thanks so much! Much appreciated!
Wow, excellent explanation of the power valve I have two carb tune books and it could not tell me the powe valve was the circuit after the primary jets!!! Good work!!! How about vacuum secondaries would these take the place of the primary pv since they also work under load through vacuum decrease, I had to delete my primary pv on my quick fuel 580HR , has exact metering plates as holley?
Thanks you, I really appreciate it! The PV and the Secondaries operate independantly of each other, but what I notice is that the PVCRs on off the shelf carbs are drilled too big and force you to run a higher jet and a lower PV or itll dumo too much fuel. You can tune them independantly buy going up a steep hill at just enough throttle to open the PV but not enough to open the secondaries. Youll need an AFR gauge to do this correctly but if you dial it in, youll be able to clean up your cruise AFR and youll have a smoother transition. If not, keeping your jets up and blocking off the PV also works but youll be running rich at cruise. If youre racing, thats not a problem, but if its a cruiser, you really want to dial it in for driveability, good luck!
@@NightWrencher Yeah, I definitely have a afr guage, no way to tune it without one, Thanks!!! Keep it up!!
Good information. I've got several 600 cfm Holley carbs and they all seem to have wildly different PVCR sizes. I sold one of them so I can't measure but it ran really rich when the power valve opened under light to mid acceleration (10.5-11 AFR) so it's safe to assume that one was large. I have an 1850-5 Holley that has .042" PVCR and just acquired an 80145 Holley which is just a deluxe 1850 in center hung 4150 2 corner idle configuration, basically and it has .052" pvcr. I really want know what engine Holley thought a 600 cfm vac secondary electric choke was gonna run well with using 68/70 jets and a .052" PVCR because I have a pretty healthy running Ford 390 that sucks gas like it's already long gone out of style running 67/69 jets at 14.1 average cruise afr with the .042" PVCR that gets drowned down to 10.5-11 when the pvcr opens up LOL time to drill and tap that metering block tomorrow and reduce the size a little.
lol thats what goes through my mind when I go through out of the box carbs. Most of the time, the tune is way off but also different 600s have different tuning built in so maybe they need to publish the numbers so we know exactly what we're getting with each one.
@@NightWrencher yeah, I reduced the pvcr size to .034" on that 1850 and that's what it took to obtain a 12.5 average afr under high load with the power valve open with that 390.
Thats awesome, always good to see someone figure out their carb instead of giving up and going efi👍
@@NightWrencher Not only did I keep the carb I found a vintage aftermarket ball bearing dual point with vacuum advance breaker plate that fits in the stock distributor and rock that as well. Runs fantastic and I drive it everywhere problem free.
Very cool, I'm glad it worked out!
Vacuum should be taken foot on brake and in gear….then /2
Thats correct unless you have a manual transmission. In either case I would still go with the higher of the two.
I think you solved my problem. Trying to figure if my power valve or my accelerator pump needs to go UP> I have a 347, mild cam, pull 12-12.5 vacuum in gear idle. AFR reads about 12-5 to 13.5 idling. Cruise ( 14-14.5 at steady cruise) and if I hit the gas 1 inch I get a momentary lean stumble (AFR reads in the 16-17 range momentary before drops down and she goes like hell. I am afraid that persistent lean is going to damage my engine. My stock Holley power valve is a 6.5. The pump nozzle is a 31. Would you recommend I UP both or one at a time? should I go 7.5 or 8 on the power valve ? What about the nozzle? Thanks in advance...this is driving me nuts because the engine idle and runs AWESOME except for that split second stumble
Your cruise AFR is really lean, so youll need to compensate with both the accel pump and power valve. The way to tell which circuit you need to tune is how you create the problem. Sudden changes in air speed can't be tuned out with the PV. Extended lean conditions can't be tuned out with the accel pump. Sounds to me you need a much bigger pump shot to cover the lean spot. Order yourself a 50cc accel pump kit. It'll come with a black cam to extend the duration of the shot. If its too much fuel you can just change the cam and keep the same arm without a problem. You might also want to go up to a 35 squirter for more volume because it does go up 2-3 numbers and that lean misfire can really hurt something after a while. If you've got an extra 28 or 31 squirter you can drill it out to .040 and install the 50cc pump. I'm pretty sure that where your issue is. Lmk, hope it helps
@@NightWrencher Thanks !
@@NightWrencher one more question on the pump nozzle. I see they all sell in pairs. Does that mean I change the primary and secondary or just the primary ?
@@arcorob you can do both, but if your secondary squirter is working well, theres no need but you can check it after you swap the primary one Something else you should check is float height. If you got a glass sight plug raise the float level to 3/4 of the way up the sight plug, itll richen the curve a bit but itll allow your boosters to respond faster.
Thanks for the vid
Hope it helps you out!
Thanks for the video so if I understand right you are actually using your idle or main jets while cruising until you accelerate and your power valve opens ? I just swapped over to a 4 bbl from a 2bbl .
I have 66 main jets and 6.5 power valve and I'm way off in afr I am in the mid 12 on idle aft although that's just by screw setting it idles great but on acceleration it goes lean and in my off idle to mid range it's in the 15 16 range Wot is the same 16"s .
I'm thinking 68 from 66 main jets maybe 7.0 or 7.5 power valve then check wot it's a 600 street warrior with single feed I added a metering block in rear instead of plates .
Also set fuel level a little higher what do you think ?
Youre close on your tuneup but your off idle performance will be in the IFR. You'll need to drill that out a hair. WOT performance is largely controlled by the secondary jets, looks like at least 4 jet sizes higher in the rear. Get your AFR at 1/4 throttle in high gear dialed in to 13.5. Take your vacuum reading at that point and set you PV to 3/4 of that.
@@NightWrencher thanks 👍 the IFR are the holes in the metering block the ones on top of on the sides of the PV
@@NightWrencher yeah I see where they're drilling out the metering block and putting restrictors in there that's a little advanced for me right now but I know why they're doing it so that when you get to high speed your AFR doesn't go so lean so quickly because you're losing fuel in the float bowl so the smaller orifice in the emulsion tube high speed air bleeds keep it richer as you make the transmission at wide open throttle???lol
Not quite lol. The restriction limits how much fuel can pass through in the transition circuit. Kind of like a permanent jet. Yours is too small so all you need to do is drill it out a bit. Hardware stores still the tiny drill bits that you can use
@@NightWrencher do you recommend doing all the IFR restrictors slightly larger such as the one on the outside on the top of the car body as well front and rear the ones at the top of the metering block as well or just the ones that are right next to the power valve the two that are next to the power valve side by side
Looking at the vacuum gauge, when do I know when the power valve is opening up?.
When vacuum drops below the number on the PV, its open
What’s a good size to run on a Holley 500 ran on a 602 GM crate engine used for circle track racing ? 6.5? What’s a good accelerator pump size to use thanks ? I feel it’s a bit lean haven’t looked to see what a in it
Crate engine is turned at 6100 rpm. 460/490 lift cam.
If its dedicated a circle track racing car, I would actually take it off and jet up the primaries 4-6 sizes.
Where did you get that set of drill bits? I'm having trouble finding a good set like that for jets. Thanks
The things in the red box in the back ground are pin gauges used to measure orifices. For a drill bit set you could use something like this amzn.to/3PjvTUv along with a pin vice
I run a 570 street avenger and I’m going lean (up to 18 AFR)as the vacuum secondaries are opening with a 6.5 power valve and a black spring. I will try an 8.5 power valve and see if that helps.
I ran into a similar issue. After the secondarys open up my AFR would go back to the 12s. An 8.5pv fixed it
NightWrencher yeah there’s not many vids tuning vacuum secondaries. I run a 3000stall in my trans and as it gets to 3500rpm I need to check where my manifold vacuum is. There’s a lot happening between 3000-4000rpm.😄
What helped me out a ton was installing that vacuum gauge. I got 5 ft of vacuum hose for a few bucks and attached my $10 gauge to my dash. its a little ghetto but it gets the job done! Really helped dial in my carb and pin point my problems.
The 8.5 worked. But the 7.5 worked better. I think I’m a bit high with the secondary jets so I will play with them next👍.
Thats great! You might think your secondaries are too high, but chances are your PVCRs are too big.
Definitely going to ditch the rebuild kit power valve now 😅
Yeah that 6.5 wont do a lot of us any good.
I have a 650 Holley double pumper that we put a 750 base on and put a Proform main body on and we are using the adjustable metering blocks. This is a 4 corner idle carb. It is running rich at idle even after drilling small holes in the butterflies and putting 73s in the idle air bleeds. Where should I go from there? Car is a Chevy 383 with a Comp Cam 294 retro fit hydraulic roller.
Ok, so first, the 650 and 750 base plates are the same baseplate. Second, you should install the original metering blocks back on the carb and remove the adjustibles to verify if the rich condition is in the main body or the metering blocks. If you turn in your idle mixture screws, the engine should die. If it does not die, you have an internal leak from a blown power valve or installing the wrong metering block gaskets. Lastly you should NEVER drill your base plate UNLESS you have a radical cam that requires more air AND FUEL to idle. If you just need more idle, you could have opened your rear throttle blades a bit if you maxed out your transition in the front. One last thing to check is float level, if it is too high itll pull fuel through the boosters at idle.
@@NightWrencher the cam is pretty radical. The car will die if you turn the idle mixture screws all the way in. It has 4 corner idle mixture.
@@NightWrencher can you open up the rear blades like that if it is 4 corner. I thought those slots could not be over exposed either?
@@NightWrencher float level is just below the site hole.
If the engine will die from closing the screws, then you probably don't have a leak. I'm assuming you don't have an AFR gauge? How do you know its too rich? Low idle? Backfiring? Popping out exhaust?
Great video. Questions though lol! I have a 454 chevy motor . Was built for a blower setup . Motor has a huge cam has 8.1 compression and runs 8 inches of vacuum at idle . I just had some work done on the car becaise of tuning issues at a local shop and the shop put a 2.5 powervalve in. Now the car stalls under load if im not constantly giving it gas . Do you know what it could be ,or possibly a fix?
It has a 750 proform double pumper also
Do you javelin a Facebook page? I wanted to talk to you about a holley problem I'm having on my 66 chevelle
you can reach out to me on instagram if you need to chat!
Hey I have a sbf 347 6 spd 4.30 gears rpm air gap Afr heads etc. When I stomp on it it runs excellent until I go to shift second gear then it feels literally like I shut the key off by the time I’m in 2nd gear then it wakes back up and takes off. Occasional pop out the carb. I’ve been through timing numerous times. Forgot to mention it’s a Holley 4150 750 dp. Other than that it runs a little rich but it’s fine. A/f gauge flashes lean real quick when it happens. You definitely seem to know and been through carbs enough. I subd you any help would be great. I’m getting 14 inches of vacuum and there’s a 4.5 power valve. I haven’t touched the carb yet.
How much power do you think youre putting down to the wheels? On stick shift cars, shifting gears puts us in neutral as we let off the gas, bringing vacuum back up and then when we go to accelerate, the engine has to begin drawing fuel again and itll take a second or two to get it going again. Does the issue occur if you power shift the trans? Im gonna rule out jets and power valve because they should be all in by WOT. What is the AFR at the end of 1st gear?
Check your float level.
If you want to know how a power valve works and how to select, go to Holley.
You would assume that would be true but not quite 😂
Yeah, holley suggestion is always wrong in that one. Odd i agree
I didn't understand anything..... All I could do is stare at your hand !!!! You telling me not to makes me wanna stare more !
😭 im going to have to redo the whole video!