If the power valve he was previously running had an opening vac point higher than his actual manifold vac at idle, the valve would have been open, unneccesarily enrichening the idle mix. The correct choice of pv should mean it stays closed at idle (or just block it), thus not affecting idle mix. I'm guessing this was the case based on Jason's comment. Devon
Andy- let me preface this by saying that I'm no Holley expert. And I consider Holley tuning a "black art" so to speak! Most of my knowledge came the hard way. I do plan on playing 20 questions with my carb guy on Monday. But from what Ive read, a power valve block off will make for an extrememly rich low idle condition. For a drag car with a 1500 rpm idle that does a 1/4 mile at a time, that may not be an issue. Maybe one of the Holley gurus can explain to us what applications a plug is for. I dont see a use for it myself other than for drag use only. But with the carb set up that way (PV block off), it seemed to idle fine in neutral (1000 rpm), but die out in drive. From sitting in the driver seat, it died out slowly. It felt like someone was pouring fuel down the carb, drowning it out. I playing with the secondary butterfly adjustments, mixture screws etc to no avail. PV's keep the mixture lean, until the vacuum drops to below the rating of the valve. Once below the vacuum rating, the PV richens up the mixure. For example, a blown PV will make the idle extremely rich. So, my theory was to remove the plug and install a 3.5 PV in the secondaries. And it seemed to work. Im sure someone else can explain this better than me. I think 2.5 PV's all around would of been better with the vacuum as it is, but im not messing with it again. What I should of done was to put it on my 5 gas analyser before and after just to see the HC difference So, the final setup is 84 jets and a 3.5 in the primaries 85 jets and 3.5 in the secondaries Mixture screws turned out 2 turns on all 4 corners. 5" of vacuum in neutral ( I didnt check in drive) The car now idles in gear at 700 with a 308S cam. :beer
Jason, Glad to hear you got it worked out. I don't know what AED does to their carbs, but I have no PV in the back, and a 4.5 up front. Jetting is 80/92. It idles very nicely and even returned over 13 MPG on a trip to and from Marcus Dairy.
Chris,Jason did remove the power valve,he removed the rear plug and replaced it with a power valve. Thanks
Chris, It would seem like removing the rear PV and installing a plug, in conjunction with rear jet extensions and rear jetting 8-10 over "stock" would be done to eliminate a lean-bog condition on hard launches. The cause is the rear PV and jets being "uncovered" with fuel. How else can you combat this on a Holley? After thinking about it a little more, I don't see how plugging the rear PV could ever effect the idle mixture, unless the PV is blown.
Should have had no effect. I'm guessing something else was up, maybe a leaking metering block gasket that got fixed when it was put back together. Devon
The carb thats on my car is basically a "put together" carb from Allstate. In other words, Allstate built my carb from parts as per my specification. I do remember telling them I was very interested in straight line performance and was willing to give up some driveability. In hindsight, that may not have been the best thing to have told them. I do tend to drive the car on the street occasionally (when its not holding down the garage floor) The carb has aftermarket red anodized metering blocks. I did notice they installed jet extensions in the rear when I had it apart. You guys have me wondering now if removing the plug and installing the PV corrected the problem or not. Its a possibility that I fixed it without knowing it as Devon suggested. While I hesitate to start fiddling with it again, I feel compelled to re install the plug and the #92 jets just to see if the problem re-appears. I tend to belive that the secondary side was loading up. Maybe if Im bored I'll screw with it again. Here's the link to Allstates website. They are very good. They did an excellent job restoring my 7040246 Q-Jet. They do cad plating and re coloring. It looked almost too good to run gas though....almost:grin: http://www.allcarbs.com/index.html
Hey Jason, If you want, you can install my AED 1000 HO carb and drive around with it for awhile. See if you notice a difference. I'm not using it right now, but will in the future I'm sure. Let me know.
Not an out of the box 1000HP, but similar. AED builds there own carbs from Holley parts. It does have a 4 corner idle. Take a look here. It is the 1000HO http://www.aedperformance.com/HO.htm Here are the specs: http://www.v8buick.com/attachment.php?attachmentid=87174&d=1169934555 Some Pictures: http://www.v8buick.com/attachment.php?attachmentid=87080&d=1169854507 http://www.v8buick.com/attachment.php?attachmentid=87117&d=1169899894 http://www.v8buick.com/attachment.php?attachmentid=87082&d=1169854507 Jason had his engine dyno'd with my carburetor.
I decided to check the innards of my 1000 HP carb a week or 2 ago, because of this thread. I had purchased it used and the owner said it had stock jetting as the bowls had never been off. What I found was 78 front and 82 rear jets, rear jet extensions and 6.5 PV's in the front and rear. The front had a 30cc pump and 35 discharge nozzle, and the rear had a 50cc pump and 35 squirter. So much for being stock. What I did was jet up to 84/92 (retained the jet extensions), lowered the front PV to a 3.5 and plugged the rear. I added a 50cc front accelerator pump kit with the brown cam installed in the #2 position. What this accomplished was a significantly better idle (TA510 cam) -- it will now idle in gear, hot restarts are much better, and it has much better throttle response. There is no adverse part-throttle driveability w/o a secondary power valve. Along with JW's billet fuel pump, -8 line and RobbMc's 1/2" sender, I feel much more confident about getting enough fuel to the engine this year at the track. :Comp:
Hi Guys I am having a problem with my HP 1000 it won't idle in park much under 1000 rpms and it makes your eyes water like crazy,could it be a blown power vavle.i turned the idle screws to one turn out and it did help with the richness .if i try to adjust the idle down under it dies .thanks for the help.:beers2:
