How hard to change a Holley Power Valve? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

TIMSPEED · 04-27-2003, 12:09 AM

Well, since I had a HUGE backfire through my carb a while back, I'm thinkin I destroyed the power valve in my Holley 4160. How hard would it be to put a new one in? I see summit has them for like $8...thanks!

BigRed · 04-28-2003, 12:35 PM

Ask this question in the Engine & Drivetrain forum and you'll get a good response. I just bought a new book on rebuilding/modifying/tuning Holleys. I recommend you do the same. It's full of good information. Once I find out the answer to your question, I'll let you know.

TIMSPEED · 04-28-2003, 12:43 PM

Thanks Scott! Yeah, I think I will buy that book...but I'm not much into carb cars...just gotta get this RUNNING.

LOHRTBT · 04-28-2003, 01:13 PM

I was gonna replace mine ....but from what i hear they dont go bad very often....but it might fix your prob.

**Captkaos** · 04-28-2003, 02:18 PM

You have to pull the bowl/s off to replace it.
Before you do, what makes you think you blew it? It is running rich now?

TIMSPEED · 04-28-2003, 03:56 PM

Quote:

Originally posted by Captkaos
You have to pull the bowl/s off to replace it.
Before you do, what makes you think you blew it? It is running rich now?

Well..I'm not puffing black smoke, so I think it's running TOO lean...but if I was running THAT lean, wouldn't my headers glow at night? It has a HUGE stumble when you go from light throttle to medium/heavy throttle, or from no throttle to light throttle. Holley said on my carb, it comes set to be REALLY lean #62 Jets, and they said to go to #64 jets and that'll fix my problem...

BigRed · 04-28-2003, 04:02 PM

Well, jets are easy to replace, so I'd definitely try that first! If I was to replace my Power Valve, I'd go ahead and do a full rebuild while I was at it.

TIMSPEED · 04-28-2003, 04:24 PM

Quote:

Originally posted by BigRed
Well, jets are easy to replace, so I'd definitely try that first!

That's exactly what holley said was my problem. I have #62 Primary Jet's stock, and he said I need #64's...so, how do I change Primary jets? (Or are jets, jet's? Like, is there a difference between primary and main jets? Cuz I can't find Primary Jet's at Summit)

BigRed · 04-28-2003, 04:49 PM

From what I've seen, the jets are the same. On the top of each bowl there is a nut with a flat-head screw in the middle of it. Basically, you just hold the nut with a wrench while unscrewing the screw. Then the nut will come right off. The threaded portion that the screw went down into is your jet. You screw that out and I think it's that easy. However, I haven't done this on a running carb. I have adjusted my floats via the nut and screw, but haven't actually changed the jets. I did pull the jets out of a carb I have sitting in my garage (same model as mine - 4160).

**Captkaos** · 04-28-2003, 04:50 PM

A blown powervalve (fuel enrichment) will cause the motor to run rich all the time as it will be dumping gas all the time because there is no vacuum to keep it closed.

Jets are the same secondary vs primary for a Holley. You will still have to remove the bowl to get to the metering block to remove/change the jets. Based on your symptoms I would say your powervalve is ok. Most Holleys now come with "blow out" protection in them now. Not sure about the 4160, but... I would try rejetting it. I would also recommend setting the idle and mixtures with a vacuum guage.

Where is your base timing set? How much vacuum advance are you running? I would say start at about 10 degrees mechanical advance and work your way from there.

TIMSPEED · 04-28-2003, 04:51 PM

Quote:

Originally posted by BigRed
I did pull the jets out of a carb I have sitting in my garage (same model as mine - 4160).

OK...and how did you do it?

BigRed · 04-28-2003, 04:55 PM

CaptKaos, why do you have to remove the bowls to change the jets? It looks like you could replace them just by unthreading them up from the bowl. Just curious. Haven't gotten to that chapter yet.

TIMSPEED · 04-28-2003, 04:59 PM

Quote:

Based on your symptoms I would say your powervalve is ok. Most Holleys now come with "blow out" protection in them now. Not sure about the 4160, but... I would try rejetting it. I would also recommend setting the idle and mixtures with a vacuum guage.

My friends dad did this, and he said when he turned the idle mixture screws all the way in (LEAN) it didn't die, so he said I must be leaking fuel somewhere. But when I E-mailed holley, they said that I need to up my primary jet's to #64 instead of #62, because I'm running too lean.

Quote:

Where is your base timing set? How much vacuum advance are you running? I would say start at about 10 degrees mechanical advance and work your way from there.

Again, my friends dad set my base timing @ 14º, and in drive, he measured about 19"hg of vacuum. Originally, I had my distributor hooked up to full vacuum, instead of ported vacuum, so my ignition was already fully advanced I imagine @ idle, I guess I'll take my carb apart today and put in the new jets...

TIMSPEED · 04-28-2003, 05:00 PM

Scott, Look at this picture ~>4160 Exploded View
#118 are the primary jets...they're inside the fuel bowl.

**Captkaos** · 04-28-2003, 05:53 PM

Quote:

Originally posted by TIMSPEED
Again, my friends dad set my base timing @ 14º, and in drive, he measured about 19"hg of vacuum. Originally, I had my distributor hooked up to full vacuum, instead of ported vacuum, so my ignition was already fully advanced I imagine @ idle, I guess I'll take my carb apart today and put in the new jets...

When setting your base timing, disconnect the vacuum advance hose (plug it off). Try rejetting it and see what it does. It sounds like you are leaning out at tip in, so rejetting should help.

TIMSPEED · 04-28-2003, 06:05 PM

i'm on my way to get jets now! Hopefully this works!
To change jets, I just pull the bolts out of the fuel bowl and then pull it off and change the jet then put it back on right? Thanks guys!
BTW: What should my base timing be at? 8º?

BigRed · 04-29-2003, 08:37 AM

Quote:

Originally posted by TIMSPEED
Scott, Look at this picture ~>4160 Exploded View
#118 are the primary jets...they're inside the fuel bowl.

I stand corrected.

Hey, I stand there alot!

**Captkaos** · 04-29-2003, 02:39 PM

Quote:

Originally posted by TIMSPEED
i'm on my way to get jets now! Hopefully this works!
To change jets, I just pull the bolts out of the fuel bowl and then pull it off and change the jet then put it back on right? Thanks guys!
BTW: What should my base timing be at? 8º?

That is a good starting point, you will just have to see what the motor likes. From the video, it looks like the problem is gone.

TIMSPEED · 04-29-2003, 02:42 PM

Quote:

Originally posted by Captkaos
From the video, it looks like the problem is gone.

You'd think huh?! But this morning, on the way to work, it was kinda stumbling...but it was like a hit and miss thing. Mighta been cuz it wasn't fully warmed up...who knows. I didn't set the fuel bowl yesterday before I made that video.

I got some more tuning and burnouts to do today.

Tracy Focht · 04-29-2003, 05:50 PM

The top nut on top of the fuel bowl is the needle/seat, and adjust the float level.

Change the jets:

Grab a small spray paint can lid, and pull one of the bottom bowl screws. Gas will drain out. be sure to have a couple rags handy to soak up excess gas.

Pull other three bolts, and carefully pull the front bowl off. Then there will be a matering plate as well, that will need to be pulled off. Be careful not to rip any gaskets. Then you will see two jets and the powervalve. The powervalve will have a 6 and a 5 on the other side if it's a 6.5 powervalve. 5 and a 5 is a 5.5 and so on.

Why you have it off, you might as well replace it, and jet up at least two sizes. But, I think your problem is the pump squirter is too loose, and i would adjust that first.

If you had a blown powervalve, you'd be running really, really fat at idle and puffing black smoke and gas fouling plugs.

But to setup the proper way on PV, is to get a vacuum gaige and see what your idle vacuum is.

Good luck!

04-28-2003, 12:35 PM	#2
BigRed Registered User Join Date: Jun 2002 Location: DFW, TX Posts: 1,680	Ask this question in the Engine & Drivetrain forum and you'll get a good response. I just bought a new book on rebuilding/modifying/tuning Holleys. I recommend you do the same. It's full of good information. Once I find out the answer to your question, I'll let you know. __________________ Scott Shelbourne

04-28-2003, 12:43 PM	#3
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	Thanks Scott! Yeah, I think I will buy that book...but I'm not much into carb cars...just gotta get this RUNNING. __________________ I have a few cars... See Them Here

04-28-2003, 01:13 PM	#4
LOHRTBT BeWarE tHe eViL CrAnkTOe! Join Date: Oct 2002 Location: Yukon, OK Posts: 3,605	I was gonna replace mine ....but from what i hear they dont go bad very often....but it might fix your prob. __________________ ~Dave~ You can call me Mike, Mike Oxlong - 1986 Chevy SWB - Stock for now - *1986 Chevy Custom SWB* *Stolen 6/26/05* - 1985 Chevy SWB SOLD - 1999 T/A Some mods www.cardomain.com/id/ramairdave AIM Screenname - Jester84

04-28-2003, 02:18 PM	#5
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	You have to pull the bowl/s off to replace it. Before you do, what makes you think you blew it? It is running rich now? __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

04-28-2003, 04:02 PM	#7
BigRed Registered User Join Date: Jun 2002 Location: DFW, TX Posts: 1,680	Well, jets are easy to replace, so I'd definitely try that first! If I was to replace my Power Valve, I'd go ahead and do a full rebuild while I was at it. __________________ Scott Shelbourne

04-27-2003, 12:09 AM	#1
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	How hard to change a Holley Power Valve? Well, since I had a HUGE backfire through my carb a while back, I'm thinkin I destroyed the power valve in my Holley 4160. How hard would it be to put a new one in? I see summit has them for like $8...thanks! __________________ I have a few cars... See Them Here

04-28-2003, 04:49 PM	#9
BigRed Registered User Join Date: Jun 2002 Location: DFW, TX Posts: 1,680	From what I've seen, the jets are the same. On the top of each bowl there is a nut with a flat-head screw in the middle of it. Basically, you just hold the nut with a wrench while unscrewing the screw. Then the nut will come right off. The threaded portion that the screw went down into is your jet. You screw that out and I think it's that easy. However, I haven't done this on a running carb. I have adjusted my floats via the nut and screw, but haven't actually changed the jets. I did pull the jets out of a carb I have sitting in my garage (same model as mine - 4160). __________________ Scott Shelbourne

04-28-2003, 04:50 PM	#10
Captkaos www.73-87chevytrucks.com Join Date: Dec 1999 Location: Birmingham, AL Posts: 6,935	A blown powervalve (fuel enrichment) will cause the motor to run rich all the time as it will be dumping gas all the time because there is no vacuum to keep it closed. Jets are the same secondary vs primary for a Holley. You will still have to remove the bowl to get to the metering block to remove/change the jets. Based on your symptoms I would say your powervalve is ok. Most Holleys now come with "blow out" protection in them now. Not sure about the 4160, but... I would try rejetting it. I would also recommend setting the idle and mixtures with a vacuum guage. Where is your base timing set? How much vacuum advance are you running? I would say start at about 10 degrees mechanical advance and work your way from there. __________________ Chris Lucas 1973 Chevy C-10 1978 GMC Jimmy (2WD) - SOLD 1987 R10 twin turbo LS 1991 R3500 SRW CrewCab 1985 K5 diesel swapped project 1989 K5 2WD conversion w/ Vette susp Project Captkaos Customs 73-87chevytrucks.com

04-28-2003, 04:55 PM	#12
BigRed Registered User Join Date: Jun 2002 Location: DFW, TX Posts: 1,680	CaptKaos, why do you have to remove the bowls to change the jets? It looks like you could replace them just by unthreading them up from the bowl. Just curious. Haven't gotten to that chapter yet. __________________ Scott Shelbourne

04-28-2003, 05:00 PM	#14
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	Scott, Look at this picture ~>4160 Exploded View #118 are the primary jets...they're inside the fuel bowl. __________________ I have a few cars... See Them Here

04-28-2003, 06:05 PM	#16
TIMSPEED Join Date: Jan 2003 Location: Modesto, CA Posts: 1,321	i'm on my way to get jets now! Hopefully this works! To change jets, I just pull the bolts out of the fuel bowl and then pull it off and change the jet then put it back on right? Thanks guys! BTW: What should my base timing be at? 8º? __________________ I have a few cars... See Them Here

04-29-2003, 05:50 PM	#20
Tracy Focht Registered User Join Date: Dec 1999 Location: Stillwater, OK 74075 Posts: 2,936	The top nut on top of the fuel bowl is the needle/seat, and adjust the float level. Change the jets: Grab a small spray paint can lid, and pull one of the bottom bowl screws. Gas will drain out. be sure to have a couple rags handy to soak up excess gas. Pull other three bolts, and carefully pull the front bowl off. Then there will be a matering plate as well, that will need to be pulled off. Be careful not to rip any gaskets. Then you will see two jets and the powervalve. The powervalve will have a 6 and a 5 on the other side if it's a 6.5 powervalve. 5 and a 5 is a 5.5 and so on. Why you have it off, you might as well replace it, and jet up at least two sizes. But, I think your problem is the pump squirter is too loose, and i would adjust that first. If you had a blown powervalve, you'd be running really, really fat at idle and puffing black smoke and gas fouling plugs. But to setup the proper way on PV, is to get a vacuum gaige and see what your idle vacuum is. Good luck!



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