holley rebuild help needed.

[mrmustangman357]

I rebuilt a holley 600 a while back and it ran like *****. idle screws didn't work, even though the blades were in the idle slot, at WOT it backfired like crazy. I took it apart, holley told me to check the power valve since it may be incorrectly sized for my combo, how the heck do I identify this power valve?

also, is this the proper orientation for the secondary metering plate (it is a 4160)? :

if anyone has a good linky that shows what factory stuff like gaskets originally came with the carb, that would be extremely helpful. Im starting to second-guess myself when it comes to things like the throttle body gasket and secondary gasket

 

[PUNISHER RACING]

that is a 6.5 pv ..............600 what dp or 3310

 

[mrmustangman357]

its an 80457. 600 cfm universal. has the single inlet and side hung floats

 

[D.Hearne]

Ditto, 6.5 PV. Make sure the gasket behind it is correctly centered. And for the metering plate gaskets, make sure to use the correct ones, kits come with multiple gaskets for different applications. I compare the old ones as I take it apart and pick out the correct ones for the assembly.This prevents gaskets blocking passages(a metering gasket on backwards will block certain passages too) You also have to verify all the tiny passages are clear of dirt and debris, I soak the parts in carb cleaner for a day, then using spray carb cleaner, spray thru all passages (use eye protection) and then follow with compressed air.

 

[PUNISHER RACING]

little bit about the motor combo, and what was done to carb (jetting)

 

[10secgoal]

Do you know what your vacuum was at idle. Holley is thinking the number might be too small. If you idle vacuum around the same PV sizing, it could open or flutter at idle shooting the AFR thru the roof. The idle mixture screws wouldn't be much help if it was acting up.

 

[mrmustangman357]

here is the combo:
351W
9.8:1 compression
twisted wedge heads
.530 roller cam 230 duration
performer rpm air gap manifold


I'm eventually going to a demon, but I can put this 600 on until I feel like upgrading. It pulls between 11-14" at idle depending on initial timing selection.

So, to identify the power valve, I read the two numbers clockwise from that wierd letter? How do I identify if it is blown on the bench without a $80 proform power valve tester? I have a vacuum pump if i can use it somewhere. . . . I checked my other 4160 and it has the secondary metering block gasketed as shown

 

[PUNISHER RACING]

that carb is way too small first off, do you have anything else to play with? You are getting that backfire at WOT because of a lean pop. Skip the Demon and buy a 700 dp Holley. To check your PV place the front side(side with #'s) to your lips and inhale the other side of valve should pull shut and stay that way. Or of you have a brake bleeder you can use it to. Just attach a 3/8 hose to it and pump it till PV closes and watch gauge to make sure it maintains pressure. That carb can get you by in a pinch but is really less than ideal for that combo!!!!

 

[10secgoal]

The carb not being an ideal size for the motor won't cause a lean pop. A carb size identifies the CFM it moves, not the amount of gas it's moving. A 600 can flow just as much gas as a 750. Although a lean spot could be adjusted out by the pump shot and float level. If either is wrong, it could pop on any motor.
When you get it running again, get a vacuum reading in 3rd gear at WOT. That reading will give you a better idea of whether it's too small or not. If it's pull 6in og vacuum, then the pv can close also making it pop.

 

[mrmustangman357]

thanks. didnt think of it being too high a restriction at wot to cause the popping. I checked the pv on my vacuum tester and it took 9.5" to fully seat the needle (as indicated by me tapping on it and increasing vacuuum until the noise stopped). In contrast, my other 6.5" power valves fully seated at 7.5". My gauge may be off, but the power valve in the 600 seats after more vacuum is introduced. I will swap it out for the lower running ones and see what happens. when I ran the carb on my motor previously (before swapping to the ugg edelbrock), at wot regardless of rpm my motor did the backfire thing. I figured its not because i was outflowing the carb, it was because something was F'ed up in my secondaries. When i tore it apart, i found the secondary metering plate directly attached to the blue nonstick gasket. the insructions say to use the cork (shown in original post), then a metal plate, then the blue gasket. I don't have a metal plate? when i put it back together, i will include the cork gasket as well, but the only difference i see with that is that it covers a center hole. WTF?


\maybe this is why so many folks jump over to edelbrock, but dammit i need the tuning potential of a holley!

 

[D.Hearne]

That popping might also be the distributor not advancing far enough. Check that out too. I'd bet on that being the cause if it was doing it also with the E'brock carb. That 600 would be a great daily driver carb for the motor as well, once you've got the problem solved. You could always buy a larger carb for the strip and swap em as needed.

 

[mrmustangman357]

That popping might also be the distributor not advancing far enough. Check that out too. I'd bet on that being the cause if it was doing it also with the E'brock carb. That 600 would be a great daily driver carb for the motor as well, once you've got the problem solved. You could always buy a larger carb for the strip and swap em as needed.

the edelbrock solved it, but it has a little lean spot at cruise I could not adjust out. it showed up on by wideband o2 gauge

 

[Fast63]

did you try changing metering rods and springs to get rid of the lean spot?