I have a 4777 on my mild 360 340 cam and headers and alum dual plane intake. had 68 jets in front and a unknown (no markings?)power valve. Just running a little rich and wondering what everyone would suggest as a good starting point for jets and power valve. i have 74,67,64, jets and a 3.5 power valve. I live in the Fortworth TX area now so I'm not sure what the altitude is here but I'm sure its not to high. With the price of gas I'd like to run as lean as I can without hurting the motor. I left my vacuum guage behind so I guess I'll have to get another one of those. any sugestions?
holley 650 jets
- Thread starter mod5v
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Believe you can find a chart of specs for all holley carbs through the holley tech pages. I've used it in the past to get my carbs setup stock...
68 in front sounds about right to me and actually may be a little lean. The stock pv i believe is 6.5 but yours shouldn't make much difference except not open as soon as the 6.5.
74 up front is too much and 64 is not enough.. prob need to stay around the 68-70 range is my guess - may as well replace the pv with a good quality 6.5
68 in front sounds about right to me and actually may be a little lean. The stock pv i believe is 6.5 but yours shouldn't make much difference except not open as soon as the 6.5.
74 up front is too much and 64 is not enough.. prob need to stay around the 68-70 range is my guess - may as well replace the pv with a good quality 6.5
You need the vacuum gauge. For the power valve, go with one 2hg below your vacuum reading at idle - 8.5hg at idle = 6.5 power valve. As far as jets go that is something you need to determine through making a series of runs. The best starting point is the size the carb came with from Holley. Most 4777's came with 67's in the primary. At least one came with 71's. The thing to remember is that you should not change the primary jets from stock unless you also change the secondary jets or metering plate. The difference between them (usually about 8 sizes) is there to keep the primaries and secondaries balanced by making up for the flow through the power valve. If you do not keep this difference you can cause bogging on transition and other performance issues.
ramcharger
Dismember
Here's the link for the Holley Numerical listings: http://www.holley.com/data/TechService/Technical/Carb Numerical Listing.pdf
2shelbys is right, the 4777 came with 71's and the 4777-1, -2 and -3 all had 67's from the factory. Drop it down to 66's and see if it runs like crap. If it does, go up to the 67's. You may end up right back where you started but what the hell, it's a good learning experience. Get one of the "blue" re-usable float bowl gaskets while you're at it. You'll know why when you're done.
2shelbys is right, the 4777 came with 71's and the 4777-1, -2 and -3 all had 67's from the factory. Drop it down to 66's and see if it runs like crap. If it does, go up to the 67's. You may end up right back where you started but what the hell, it's a good learning experience. Get one of the "blue" re-usable float bowl gaskets while you're at it. You'll know why when you're done.
Thrasher
YoungestMemberUALocal7
I don't mean to hijaack your thread, but I have a holley 670 double pumper on my 360... cam is a 262/272 420/442 and I have an air gap intake. I'm guessing I need smaller jets on my carb? Seems like it's running very rich :sad2:
Get one of the "blue" re-usable float bowl gaskets while you're at it. You'll know why when you're done.
Good advice.
I already have the "other" no stick gaskets in it and so far so good but I do know what you mean. I have a set of 67's here and just picked up a new vacuum guage so later today I'll check it out. I'll pull the rear bowl off and check those jets just to see whats in there. So I'm getting the impresion that everyone feels that 64's in the front are to small?
Too add...
If your car is an auto, make sure you are taking the idle vacuum reading in gear. The park or neutral idle readings won't get you were you need to go when selecting a PV using the -2 method. For 4 speed cars, I like to cut the idle vacuum in half to select a PV.
I also agree that the holley jetting to start with is usually pretty close. Start there and work your way to proper jetting. If the car is surging at cruise, usually that means it's lean. If you can get an Air/Fuel meter, that would help as well.
If your car is an auto, make sure you are taking the idle vacuum reading in gear. The park or neutral idle readings won't get you were you need to go when selecting a PV using the -2 method. For 4 speed cars, I like to cut the idle vacuum in half to select a PV.
I also agree that the holley jetting to start with is usually pretty close. Start there and work your way to proper jetting. If the car is surging at cruise, usually that means it's lean. If you can get an Air/Fuel meter, that would help as well.
It's a 4 sp car and I just pulled the rears out and they are 78's. The list # on the carb is 4777-4 {11} with 2065 under the list#. I'm sure these aren't original jets because i got it used although in very clean condition.
So from what I've read on here it likely had 67's front and 75"s rear and maybe a 6.5 PV when it was new. I'll get as close to that asI can with what I have and get it running and check the vacuum at idle to get a PV rating and the drive it and see what it runs like. It will be a while before I can get a wide band O,2 sensor.
So from what I've read on here it likely had 67's front and 75"s rear and maybe a 6.5 PV when it was new. I'll get as close to that asI can with what I have and get it running and check the vacuum at idle to get a PV rating and the drive it and see what it runs like. It will be a while before I can get a wide band O,2 sensor.
I would love to have one too but man they are expensive.
So right now I have 64's front 3.5 PV and 74's in the rear. I adjusted the idle with the vacuum guage and at 800rpm I have 15hg vacuum. I have a 7.5 PV so it sounds like I should put that in. Am I correct in understanding that the PV opens and enriches the fuel when the vacuum drops below its rating? I have read other places that you want a power valve# that is aprox half your idle vacuum. That would make the 7.5 I have ideal. If its actually 2hg below idle I would need one at 13hg i'm not sure I've seen one that high.
Try it with a 67-74 split and the 7.5 pv.
My mild 340 was lean surging with 65 mains.
My mild 340 was lean surging with 65 mains.
Well the 64's worked but if I idled for more than 5 minutes the temp started to go up. So as I had to take the car to work I put the 67's in with a 6.5 power valve. It runs good and has just a slight surge a 70mph or 2850rpm I think that the timing is just a bit advanced as I'm running the vacuum advance to try and get a liittle better milage. I have a 28 mile ride to work so at 13mpg anything that helps is good. I have some 66"s now so will try them and check the total advance soon. I have my damper marked a 30* so I can check total advance with a standard lite.
ramcharger
Dismember
The mains really should not affect your idle mixture at all.
dgc333
Well-Known Member
Didn't know Holley made a 670 Double Pumper. I have a 670 Street Avenger which is a vacuum secondary carb on my 360 with an XE268 cam. It likes the stock 65 primary and 68 secondary jets and either the long yellow or purple spring in the vacuum pot.
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