I am kitting a holley carb and the old power valves have no numbers on them. What would be a good starting point? Carb is a 4150, stock from a 375 horse 396 or 425 horse 427 and it is on a pretty stock 350. Too much carb, I know but it's not mine and I just need to get it running halfway decent. I got the master rebuild kit and it has a variety of power valves. Also the old inlet valves have no numbers on them and there are about 5-6 sets in the kit so it would be nice to know which ones of them to use too. thanks.
The numbers have moved from the edge to the face and can be read at 3 oclock and 5oclock, you want a 65 the needle and seat will have number on the flat spot at the top in the threads, i use the 110, your kit should at least have a 100 if it don't have the 110
I'd start with a 6.5 power valve. I usually end up at an 8.5 or 10.5, but I tend to jet my stuff pretty lean so I want it to come in soon. Inlet valves? Needles and seats? Jets? Devin
Same power valve front and rear? Yes, needle and seats. The new ones are marker with letters. The old ones have no markings. I looked all over the old ones with a magnifying glass and there are no numbers, maybe it was rebuilt with a cheapie kit once.
Most kits come with a 6.5 or a 65 depending on who made the power valve. It is a good starting point for a car that carries about 13-14" of vacumm. Now get it together and fire that bigger up, get your car running and tunned, check the vacumm. If you are pulling a ton more vacumm than that or a ton less at idle you will need to change the power valve, but 6.5 is the most common power valve used.
If it has a 4 corner idle circuite then the secondaries would have a different power valve unless it has locked secondaries in which case the secondaries would open at the same rate as the primaries. In order to determin which power valve to use on the secondary idle circuite you need to know the normal vacumm when the secondaries are ready to come open. You would normally check that under load. If the kit comes with two power valves it is going to be the larger of the two I believe, for a starting place.
Vacuum secondarys with no idle circuits on the rear. The kit came with about 10 power valves. This car will make a few Sunday drives and go back in the shed, maybe for 5 more years, so I'm not concerned with getting it perfect, just want it to run halfway decent and not load up or fall on it's face.
Only gets on power valve. You only run a power valve on an idle circuite. You are running a stockish 350 a 6.5 or 65 depending on who made the power valves. You are talking about needls and seats when you call them inlet valves correct? You use the biggest ones for alcohol and the smallest ones for gas if that helps. It won't make as much difference on a stock ebngine as it would on a built alcohol that has a high fuel demand. If your needle is too big it is just going to fill the bowl faster.
That's for race cars... He plans on driving it on the street... Number 84 jets on a stock 350???... Are you insane???...
Holley says 1/2 the vacuum reading at idle for a power valve, but most carbs come with a 65. If you have a lumpy cam you might drop back to a 45 until you check your vacuum reading. I really can't remember any vacuum secondary carbs with power valves in the secondaries. If it does have a secondary power valve, I might consider plugging it and bumping the jets 6/8 sizes.
Larry, I am not in his carb and he could certainly have one that I haven't seen yet but the only Holleys that I have ever seen with a second power valve were ones with a 4 corner idle circuite, I have had a lot of Holleys apart over the years. I am going to have to say that you are correct in this statement. I would like to know what kit he has that came with lots of extra parts so I can get one.
This factory LS-6 Holley 780 carb came with vacuum secondaries and a secondary metering block with a power valve.. Don't know what power valves came with it... I think I threw the old ones out..
Benno, Holley sells a "Trick Kit" with different gaskets, needle/seats, power valves in it. But believe me, none of that stuff is thrown in there for free.
Now that would be a real******* to set up and I guess I haven't run onto one. If you changed springs you would have to change power valves. I guess once you get it set it would be OK. Well damn the luck, every time I set one up that is a little on the wild side I have to chase power valves.
Kit was a buck and a half locally, found one on line for 97 plus 10 shipping. The secondary metering block looks like it has provisions for idle mixture but the holes are blind and there's no threads in them. I ran the numbers, it has a GM part number and a list number. It is the original carb for a 1969 375 horse 396 or 425 horse 427. Probably an over the counter replacement since it has a 1597 for a date (159th day of 1977) The kit came with 3.5s, several 6.5, one 8.5, one 10.5 and 3 with some small, mostly unreadable numbers around the outside edge of the diaphragm side. I checked them with a vac pump and they started moving around 5 in and were all in at about 10.
Those kits with a silly amount of stuff, like the stock boy went from bin to bin grabbing a little of this and some of that....it even comes with an****ortment of pump cams. Like Larry said, it ain't cheap.
Here is a link to a Holley Tech Bulletin on power valves. http://fasthotrods.com/index.php/technical-information/doc_download/38-powervalves
I'm having Holly problems. I have a 400 SB with Brodex heads and cam. My car makes 6lbs vacuum. I live at 7200 feet above sea level. When I bought the car it had a 750 double pumper. Would get about 100 mi on a set of plugs. I installed a 600 Holly and Holly recommended a #2 power valve. I'm still flooding, Pretty sure I have a 64 jet. I thought I was getting close, but now I again have fouled plugs. I've been as low as a 56 jet, but lost power. I just read where someone plugged the power valve, maybe I don't need a power valve. Here in the mountains you only get 60% of the air as you do at sea level. If someone has a thought, it would be greatly appreciated. Thanks John
Thats true, this one has 1000 miles, but who is to say that you can't get a bad one. I will check it tomorrow. I keep thinking the very low vacuum is causing me problems with this carb. I'm ordering a vacuum pump so my power brakes will work. my brakes are*****py too.
my 460 motor with an older holley 780,duel feed, single pump, vacuum sec, only primary idle adjusters and two power valves i think it has 3310 stamped on it, but i dont remember if there is a letter after that#. any way I have a lumpy cam and if I take a vacuum reading on the carb where the distributor vacuum line goes I get 4", if I take a reading under the front of the carb I get 15" so where you are getting your reading will make a diff in pv's I havent sorted mine out yet as it will idle fine(with a lumpy cam 545 lift/284 in/296 ex) but just above idle as I add throttle it will stumble. in fact i noticed tonight while driving at 40 mph (2.80 gears) it felt like it was misfiring and I could hold the throttle in a spot that it would continue to stumble above that point it would go ...I believe there is an 85 pv in the rear and a 65 in the front. I am going to check plugs and get a pvs around 75 and try that
The vacuum advance line should be hooked in front of the carb... Where you got the 14-15" vac readings... Always shoot for the highest vacuum readings...
why bother with them, richen 2 steps, and put a power valve block in and now when she backfires....it wont kill another pv.
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