And your gonna love the price of the two stage Power Valves!
NOT!Spendy little gizmos...
Report back on how it works!
CJ
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| Author: | rock [ Tue Jan 20, 2009 12:57 pm ] |
| Post subject: | CJ, ya might saved me from myself |
CJ, Very timely response and good info from you, you saved me from myself! I knew that rule incorrectly...I had been told the PV should be HALF the running vac. Mine is about 15, so was looking to put the 6.5 in since I don't have a 7.5. I use a 270 cam, Holley 8007 with secondary metering block with 54 jet, primary at 51, 2500 stall convertor from Midwest, and a 3.91 all in a '64 truck. I am now using a slant six bell 727 (from a fellow forum member!), but ran an 833OD for a while. I idle in P at about 1,000 at 18 - 19 inches, and in D at 600 at 15. If I kick it of course it goes to zero, but feathering open to pass someone it goes to 5 to 8 inches. I had in a 10.5 at one time and got terrible mileage and that slight touch of bog, so went down. What you are saying makes sense, going up to 12, 12.5 would allow some fuel in during the transition phase. Man, I am gonna do that! I have never used a two stage PV, but was even toying with that. Hey, Northern, see what thosee 8007's getcha into? I love it but if you want to bolt and go, look at the Eddy 500. Oh I see typed the wrong Holley number last post...I have an old L 9694, a 450 cfm not a 9696 in case someone was wondering what is that! rock '64d100 |
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| Author: | ceej [ Tue Jan 20, 2009 2:16 pm ] |
| Post subject: | |
And your gonna love the price of the two stage Power Valves! NOT!Spendy little gizmos... Report back on how it works! CJ |
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| Author: | wjajr [ Tue Jan 20, 2009 2:18 pm ] |
| Post subject: | |
I'm just getting up to speed with Holley, mine is an 8007, and I was puzzled as to power valve selection when I found this info on Holley Tech page: http://www.holley.com/data/TechService/Technical/power_valves.pdf [quote]POWER ENRICHMENT SYSTEM The power enrichment system supplies additional fuel to the main system during heavy load or full power situations. Holley carburetors utilize a vacuum operated power enrichment system and a selection of power valves is available to “time†this system’s operation to your specific needs. Each Holley power valve is stamped with a number to indicate the vacuum opening point. For example, the number “65†indicates that the power valve will open when the engine vacuum drops to 6.5" or below. An accurate vacuum gauge, such as Holley P/N 26-501, should be used when determining the correct power valve to use. A competition or race engine which has a long duration high overlap camshaft will have low manifold vacuum at idle speeds. If the vehicle has a manual transmission, take the vacuum reading with the engine thoroughly warmed up and at idle. If the vehicle is equipped with an automatic transmission, take the vacuum reading with the engine thoroughly warmed up and idling in gear. In either case, the power valve selected should be 1/2 the intake manifold vacuum reading taken. EXAMPLE: 13†Hg vacuum reading divided by 2 = 6.5 power valve. If your reading divided by 2 lands on an even number you should select the next lowest power valve. EXAMPLE: 8†Hg vacuum reading divided by 2 = 4 power valve. Since there is no #4 power valve you should use a 3.5.[/quote] |
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| Author: | ceej [ Tue Jan 20, 2009 2:28 pm ] |
| Post subject: | |
Major Oops!!  I've never been able to run my slants with less than a 9.5 PV though. My idle vacuum tends to be in the 19" range, so that explains why. Wonder where I got the -2"? Thanks for catching that wjajr . Hope Rock reads it! With his cam selection, the vacuum is understandably much lower. CJ |
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| Author: | emsvitil [ Tue Jan 20, 2009 3:19 pm ] |
| Post subject: | |
I think the power valve selection forumula that Holley states is more for V8's (or more cuin/lb or car) as they'll have a higher vacuum reading under light cruise. With a slant, I'd select a power valve that won't operate unless you're accelerating. So the selection would be based on the lowest vacuum you usually see under cruise conditions (slight uphill, for worst case). That way you only get power enrichment when you're accelerating, or are more in the throttle for hills....... |
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| Author: | ceej [ Tue Jan 20, 2009 3:59 pm ] |
| Post subject: | |
Yeah, I'm thinking the 2" under cruise was the minimum you needed to keep out of the power valve under light acceleration. Something like that. I run 19" idle vac in gear, but around 15 or 16" at cruise. That makes more sense for the application. Since our engines are so small for these big carbs, our vacuum goes shallow much too quickly as we open up the throttle, so we end up with low velocity, and need enrichment sooner than a larger engine. I still think the two stage pv would be a good experiment for a street car. My understanding is that it doesn't flow as much fuel as the standard even when vaccuum is at the shallow setpoint, and flows less fuel still at the deep vac setpoint. I read somewhere on the Holley site that the two stage was not suitable for performance applications. That, once again, might not be true for our application. --Street/Strip Car-- as opposed to a purpose race car. CJ |
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| Author: | wjajr [ Tue Jan 20, 2009 4:42 pm ] |
| Post subject: | |
emsvitil: Quote: I think the power valve selection formula that Holley states is more for V8's (or more cu. in./lb or car) as they'll have a higher vacuum reading under light cruise .An air pump is an air pump, doesn't mater if it has 4-6-8-12 cylinders. Cam and compression and exhaust mostly determine vacuum. An eight, because of its larger displacement, requires a less radical cam to make adequate power, hence higher vacuum than a six or four of smaller displacement trying to make the same power with a hot cam. I found this page: HOW TO SELECT THE RIGHT CARBURETOR SIZE of interest. You will see it is based on air flow and RPM. Nerds click here On the Holley Tech Page there is an informative video covering power valves roll film , and a carburetor sizing & type calculator. Run your engine specs on it, as it walks you through a tutorial. Rock to Ceej: Quote: I have never used a two stage PV, but was even toying with that.
Two Stage Power Valve APPLICATION GUIDELINES:here |
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| Author: | SV162 [ Tue Jan 20, 2009 5:39 pm ] |
| Post subject: | |
This may shock some of you but I run a 4.5 power valve in my 8007. I don't have any bog/ flat spot/ hesitation issues at all. My idle vac in gear is 9". I used the Holley method of choosing the PV by halving the vac reading at idle. Initially I was using a 6.5 because I used my vac reading in N which is 14". Then I found out that this was wrong and I should be using the in gear vac reading. Going to the 4.5 made no difference to how the car drives but has slightly improved fuel economy. I'm using 57 primary jets, 59 secondarys (plate), short yellow spring, 25 shooter and stock pump cam in postion 1. |
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| Author: | DusterIdiot [ Tue Jan 20, 2009 6:18 pm ] |
| Post subject: | Dump another log on the... |
Holley's PV method is up for scrutiny by some of the carb guys in the field...halving the vacc reading in gear is good for a race car... street driven cars are supposed to run under the 2" under rule like Ceej stated (it keeps the power valve from opening on light acceleration, and keeps it economical when you are passing normally not like Midi....)  Just Kidding Neil...no really...The two stage power valve uses holes instead of picture windows for fuel metering and will starve out most big or thirsty engines. I run a 2 stage in my 8007 occasionally and ran one in the Hollet 450 cfm to see if I could save a bit of $$$ using it... the 8007 uses a 10.5/5.5 PV which works fairly well on street manners and the small carb it dials in pretty well, but would dump it in favor of a 10.5 picture window special if going to the track... the Holley 450 I ended up using a 12.5/5.5 (I think that's what it was...CRS setting in now..LOL)... and it did fine, manners were OK I swapped out for a 9.5 standard PV and noticed no difference in mileage or power... One item that people forget to factor into the 'carb' equation is the VE of the engine... a 90% VE engine will have different demands than the 70% grocery getting OEM wheezer... (of course the Hpak crowd has to look at that 'window' where the ram tuning can artifically cause the VE to increase.. ) Something to think about, -D.Idiot |
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| Author: | wjajr [ Tue Jan 20, 2009 6:29 pm ] |
| Post subject: | |
SV162: Quote: This may shock some of you but I run a 4.5 power valve in my 8007. I don't have any bog/ flat spot/ hesitation issues at all. My idle vac in gear is 9".
Ditto SV162, I removed a 6.5 that came with the rebuild kit after digging out this imbedded 'tuning info' at Holley, and popped in a 3.5 PV. (Vacuum in gear 8 Hg/2=4 an even number, rounded down to 3.5) I have to wait until spring comes to test drive her. |
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| Author: | 73NorthernDuster [ Wed Jan 28, 2009 1:40 pm ] |
| Post subject: | Found one |
Ok guys I picked up a Holley 8007 carb off of ebag...Looks to be in good shape but I will be rebuilding it to suit my engine and to learn how it works. Iam looking for suggestions on which rebuild kit to buy. Should I get a holley kit, or is there another companies kit that is of equal or better quality. Should I get a regular kit or is the trick kit worth the extra money (will it have the parts I would need for using it on a slant?). Here is a link to it. Hope the price was reasonable. It's about average for the one's that have come up on ebay in the last couple of months. And any other suggestions on parts you might think I need after looking at the pic would be appreciated http://tinyurl.com/c6hny9 Thanks Brent |
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| Author: | Joshie225 [ Wed Jan 28, 2009 1:58 pm ] |
| Post subject: | |
The Holley renew kit is what I would buy for overhaul. I'd also get a quick change vacuum secondary cover and spring kit. Maybe even the 4150 conversion to get a metering block for the secondary side instead of the metering plate. The carb looks fairly clean and the price was good, but it's an older model. You can tell it's old by the slot head float bowl screws. |
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| Author: | rock [ Wed Jan 28, 2009 4:23 pm ] |
| Post subject: | Northern, What Joshie said, and |
Northern, I buy a used one and figure to rebuild it out of the hat..then I know what I have. Joshie and DI told me the same thing they are telling you and I never regretted getting the $100 worth of stuff all at one time...you will like a secondary metering block, you will love the quick change spring kit, and don't screw around, get Holley parts. You don't need cams yet for it but you may want them later. If old enough your carb is going to need teh little backfire power valve blowout protection kit that goes under its throttle plate. Right now Carquest has a good stripping chemical and you ought to get a gallon of it in my opinion, to dunk metal parts into. Whwn you put it back together I suggests spraying the gaskets with PAM fro9m the kitchen or spray silicone, because you will taking it apart a few times to get the jets right. Use a tad of vaseline on the ends of the fuel tube between the fuel bowls, because you want to be easily able to pull out that tube and put it back in a few times.. If the carb is on your car and you want to remove the bowls while on the car, a small fuel collector like a plastic pan 4" x 6" by 3/4 " deep will hold the bowlful that will come out when you undo a bottom bolt first. I haven't found clear bowl sight plugs worth the cost, btw. Get Urich's or Emanuel's book and read them until you understand what the carb is doing, and match their pics to your carb. take your pics too and make sketches, particularly of how the little red lever goes and how things on the exterior of the carb fit...inside is easy to remember. It's a lot of fun! rock '64d100 |
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