Holley question - Page 2

nhramnl · 04-03-2017, 07:28 AM

I was told decades ago to remove the power valves on Holley carbs being used for all-out drag racing and simply jet the carb up 3 or 4 jet sizes. The rationale I was given (and it seems to make sense) is that power valves are devices that provide part throttle enrichment (i.e. they open when you depress the accelerator and vacuum drops to their approximate opening point), and drag race engines spend the entire run at WOT.

Eman · 04-03-2017, 09:21 AM

The picking a power valve method of idling in drive makes no sense. The PV has no part in idling, so why idle in drive to pick a PV? If your PV is opening or effected by idle vacum something is wrong. Wrong PV could close at WOT if vacum rises. Not worth having a PV in a race engine.

SSDiv6 · 04-03-2017, 11:22 AM

Quote:

Originally Posted by Rod Greene

It seems that guys either love the LM2 or hate it. I posted this same question on another website and they can't say enough good things about Innovate. Makes it difficult to decide. The Daytona is a bunch more money and I had never heard of them until now. Maybe I should just buy a Racepack and make it portable.
Keep the suggestions coming guys.

Rod, I suggested the Daytona Sensors because you stated you wanted a good unit to use in the future in other projects.

Therefore, if cost is the issue, I would recommend the NGK unit. It works great and very affordable.

I can assure you there are many that have been disappointed with the LM-2 units due to issues and not being reliable.

GallopinGhost · 04-03-2017, 01:01 PM

My problem with the LM-2 was with rpm. It would not display, record, or playback anything over 2K rpm. I tried multiple work arounds as per their tech support. After a year of playing around with it, I accepted the fact it didn't work as advertised. AFR displays ok.

Myron Piatek · 04-03-2017, 01:06 PM

The amount of jet change needed when blocking off the power valve is determined by the PVCR (power valve channel restriction) - the 2 little holes under the power valve in the metering body. That can be as high as 10. But I never used the formula.

As for using the vacuum reading "at idle, in gear", it's just a reference to make sure that the power valve you start with isn't opening at idle, in gear. If the reading is 7" of vacuum, you'll need a power valve below that to avoid a constant over-rich condition - i.e.: 6.5, 5.5, etc.). It's simply an on/off switch. But as mentioned, it's often eliminated in a race application with success. It's more important in a street application that spends more time idling.

04-03-2017, 07:28 AM	#11
nhramnl Senior Member Join Date: Feb 2010 Posts: 507 Likes: 8 Liked 358 Times in 83 Posts	Re: Holley question I was told decades ago to remove the power valves on Holley carbs being used for all-out drag racing and simply jet the carb up 3 or 4 jet sizes. The rationale I was given (and it seems to make sense) is that power valves are devices that provide part throttle enrichment (i.e. they open when you depress the accelerator and vacuum drops to their approximate opening point), and drag race engines spend the entire run at WOT.

04-03-2017, 09:21 AM	#12
Eman Member Join Date: May 2014 Location: E TN Posts: 468 Likes: 16 Liked 133 Times in 76 Posts	Re: Holley question The picking a power valve method of idling in drive makes no sense. The PV has no part in idling, so why idle in drive to pick a PV? If your PV is opening or effected by idle vacum something is wrong. Wrong PV could close at WOT if vacum rises. Not worth having a PV in a race engine.

04-03-2017, 01:01 PM	#14
GallopinGhost Member Join Date: Jun 2010 Location: VA Posts: 230 Likes: 23 Liked 21 Times in 13 Posts	Re: Holley question My problem with the LM-2 was with rpm. It would not display, record, or playback anything over 2K rpm. I tried multiple work arounds as per their tech support. After a year of playing around with it, I accepted the fact it didn't work as advertised. AFR displays ok. __________________ Brian Carpenter Stock 1358

04-03-2017, 01:06 PM	#15
Myron Piatek VIP Member Join Date: Nov 2001 Location: Florida Posts: 1,542 Likes: 34 Liked 138 Times in 51 Posts	Re: Holley question The amount of jet change needed when blocking off the power valve is determined by the PVCR (power valve channel restriction) - the 2 little holes under the power valve in the metering body. That can be as high as 10. But I never used the formula. As for using the vacuum reading "at idle, in gear", it's just a reference to make sure that the power valve you start with isn't opening at idle, in gear. If the reading is 7" of vacuum, you'll need a power valve below that to avoid a constant over-rich condition - i.e.: 6.5, 5.5, etc.). It's simply an on/off switch. But as mentioned, it's often eliminated in a race application with success. It's more important in a street application that spends more time idling. __________________ LOCOMOTION Racing