rear power valve or not?

[Firebird454]

If you cut 1.5 60' should you block off the rear power valve and jet up on a car that is drivien on the street quite a bit?

[n2o4myfix]

depends on what your trying to do and your set up, to make any significant changes to your 60' measured by tenths and not hundredths, use nitrous.:hyper:

[Firebird454]

not trying to 60' any better. I was just wondering about the effects of uncovering the powervalve under hard acceleration

[1fastdeuce]

I never ran one in the rear. I know jet extension help when you get to that point.

[Firebird454]

I never ran one in the rear. I know jet extension help when you get to that point.

I've heard to many different numbers as to how much you jet up. What would you recomend?

[1fastdeuce]

I've heard to many different numbers as to how much you jet up. What would you recomend?8-10 sizes.

[1fastdeuce]

depends on what your trying to do and your set up, to make any significant changes to your 60' measured by tenths and not hundredths, use nitrous.:hyper:Exactly. A 150 hit is good for dropping a 1.50 60 down to 1.30's:biggrinsa

[Firebird454]

Exactly. A 150 hit is good for dropping a 1.50 60 down to 1.30's:biggrinsa

I wish. That will have to wait until next year. :)

[BLUE66]

Yes generally jet up 8 sizes, block power valve and get some jet extensions for the rear too. Or put the juice to it!
Are you sure you are not spinning???

[70Maverick]

I run front and rear p/v's in my dommy and have pulled 1.28 60's. You may be suprised to find out the Pro Stock guys are all running p/v's too.:D but they all have sheetmetal Tunnel Rams..... Mostly street car? Leave it in there. Just make sure you have the right #.

[Slow Ride]

I have a power valve in the rear. I had to get jet extensions. Everyone kept asking me why I was off the gas when I pulled the front tires off the ground. Problem was solved with jet extensions. I usually pull 1.48 to 1.52 60' times with just a bit of air under the front tires.

[1fastdeuce]

If you have a carb built by Pro Systems for street use, Patrick only puts a PV in the front. I would have to think Pro Stocks have the carbs sitting sideways so they wouldn't be affected.

[70Maverick]

If you have a carb built by Pro Systems for street use, Patrick only puts a PV in the front. I would have to think Pro Stocks have the carbs sitting sideways so they wouldn't be affected.

Yeah, i hear ya. You would think it would pull fuel away from it under acceleration, but it works, and I'm just doing what i'm told! Lol!

[BLUE66]

There is really no need for a p/v in the rear unless for some odd reason you cruise with the secondary blades open past the transiton slot. I can't imagine where that could even happen. They will alow a little smoother transition at that point as you roll in to the throttle, other than that under hard accell the p/v is open anyway.
Either way can be tuned to work. Just depends on the setup.
I prefer not to have one, one less thing to go wrong. Keep it simple, = less headaches, and more fun.

[Firebird454]

I have what was a brand new 870 street avenger. Before ever taking it to the track I plugged the powervalve and upped jets by 8 sizes and used jet extensions. Over the winter I had the choke taken off, the secondary checkball removed, some what look like 1/8" holes were drilled in the throttle blades, and rear jets were jetted up another 4 sizes. It was tuned with an a/f guage on an engine stand, but was lean at an idle and rich at WOT. The mixture screws were actually turned out 3.5 turns. It worked fine just driving around, but when I took it to the track I had some problems. First the engine would die after the burnout and would take alot of cranking to restart. Then the launch was terrible seemed to stumble and the car surged going down the track. I slowed down from 6.8's @101 to a best of 7.1 @98on my first run, every run after seemed to get worse. By the end of the day it was going 7.4 @94. So I am filling the holes, putting the check ball in and putting stock jetting in hopes of curing what ever went wrong.

[BLUE66]

Sounds like your fuel level in the bowls is not correct. That stuff should not affected how it runs like you are describing.

[70Maverick]

The lean at idle condition is from the 1/8" holes in the throttle blades, really no reason for them unless your cam is so radical that you have to crank up the idle speed so high that your into the transfer slot. But blocking them obviously won't do anything for your WOT issues. What is the secondary check ball? Is this a vacuum secondary carb? Never heard of one. Sounds like your just too rich on the secondary side to me. Just pull out the motor and bring it to the dyno! Lol!

[70Maverick]

Sounds like your fuel level in the bowls is not correct. That stuff should not affected how it runs like you are describing.

Very possible to Brian. Could be starving itself down track, or it's pig rich!

[1fastdeuce]

I would say it's too rich. I would check what was said above. Also, what is the fuel pressure doing at wot?

[Firebird454]

I did check the float levels at the track, even lowered the rear a tick, but it didnt help. They looked right on. I don't have fuel pressure guage in the car its one of those on the fuel log. I did think about that though. I do have a brand new holley black pump I could put on. The carb is a vaccuum secondary the check ball goes in the diaphranm housing.

[Firebird454]

My cam isnt that wild, it idled fine with out the holes

[BLUE66]

Try a different carb and see what happens?

[Firebird454]

Try a different carb and see what happens?

I put an old decrepid 3310 I had laying around and again it seems fine on the street. Next time at the track I will try to bring a few to try. I have a friend with an 850 dble pumper he isnt using at the moment and I have another friend with another 870 street avenger he might let me try out for comparsion. hopefully mine put back to stock will at least ran like it did last year.

[BLUE66]

I have an 850 here you could try too if you want.

[Firebird454]

I have an 850 here you could try too if you want.

That would be great. Thankyou.

[Jim]

Did you mess with the timing at all? If it's too retarded it will do what your describing too.

[Firebird454]

I did play with timing, because I was thinking that too, but nothing helped. I just got the carb back, but no luck. It starts better, but it is just getting way to much fuel. I have it back to stock, but I'm getting about 3 mpg, and runs rough until I rev it up a bit. It just feels like its not burning all the fuel. Floats are adjusted fuel pressure is set at 7. car runs fine and gets about 8/9 mpg with the 3310. I guess I will just have to use that this year, until I can afford another new carb. I'm thinking of the chokeless 830 race carb. I just wont have $700 for a new prosystems or equivilent.

[B.G.]

I guess I will just have to use that this year, until I can afford another new carb. I'm thinking of the chokeless 830 race carb. I just wont have $700 for a new prosystems or equivilent.

Before you burn $$ on another carb.... Call the alburetor-Al Golueke 920-336-6763 He's the Mr. Miyagi of holleys. He'll only answer after 5:30 during the week-and saturdays all day. Tell him what your buddy did to it, and let him do his thing. $ well spent

Or, if you really want to throw that old thing away, I'll give you scrap price for it:jumpy:

[Firebird454]

Before you burn $$ on another carb.... Call the alburetor-Al Golueke 920-336-6763 He's the Mr. Miyagi of holleys. He'll only answer after 5:30 during the week-and saturdays all day. Tell him what your buddy did to it, and let him do his thing. $ well spent

Or, if you really want to throw that old thing away, I'll give you scrap price for it:jumpy:

I'm going to try some new needle and seats, and a new rear float(the one I have is old has and been on several different carbs). Not sure that will do anything, the floats seem to adjust, but they are the only things not new on it at this point.lol. I just would hate to have to run that 3310. Its runs good, but makes noticeably less power.

[1fastdeuce]

Was the base plate ever unbolted from the main body? If the screws weren't put back were they were taken out of, if will dump fuel directly into the intake.

[70Maverick]

Needle and seat, and floats will do nothing for ya if the carb is not dumping fuel out the vent tubes or the boosters. You need to put a double pumper on there, and get rid of the vac. secondary carb!

[B.G.]

You need to put a double pumper on there, and get rid of the vac. secondary carb!

He's right, that 3310 is junk too....I will also give you scrap price for that as well. I'll even come and pick them up from you..:jumpy:

Do you have any more junk carbs? Gather them all up so i only have to make 1 trip. thanks

[396BBC]

Deuce u mean it matters which bolt came out of which hole? Meaning if u take a bolt out of a hole that bolt has to go back into same hole or just make sure all 6 have a bolt in them?

[Firebird454]

He's right, that 3310 is junk too....I will also give you scrap price for that as well. I'll even come and pick them up from you..:jumpy:

Do you have any more junk carbs? Gather them all up so i only have to make 1 trip. thanks

I'll eventually get the 870 to work right, the 3310 I'll hold on to, it has served me well over the years as a carb I can throw on any motor in a pinch, besides I like this particular one, it has the secondary metering block. Shane I will ask next time I see him if he took off the base plate.

[1fastdeuce]

Deuce u mean it matters which bolt came out of which hole? Meaning if u take a bolt out of a hole that bolt has to go back into same hole or just make sure all 6 have a bolt in them?

Just make sure all the screws are in. Every carb I saw has 8 holes but only 6 screws. If I remember correctly, 2 of the holes are through holes and will leak fuel. The screws should be 3 across the front and 3 across the back. The side holes are left open.

[Firebird454]

Needle and seat, and floats will do nothing for ya if the carb is not dumping fuel out the vent tubes or the boosters. You need to put a double pumper on there, and get rid of the vac. secondary carb!

I see Summit has the race 830 dbl pumper for $460

[1fastdeuce]

If it's the one I'm thinking of, it's not good for street driving. It has a 1:1 linkage.

[1fastdeuce]

If you do decide to buy a new carb, you should check with Blue66. He is local and a sponsor of this site.

[n2o4myfix]

I see Summit has the race 830 dbl pumper for $460
My buddy has one of those, it also has the holes in the butterflies, its been a strugle getting it to respond with any changes we did to it, we ended up getting a new base plate (getting rid of the 1:1 butterfly movement and butterfly holes) and converting it back to more of a street carb. It was a headache.
If you do decide to buy a new carb, you should check with Blue66. He is local and a sponsor of this site.

X2

[Firebird454]

If you do decide to buy a new carb, you should check with Blue66. He is local and a sponsor of this site.

Definetly will buy from him first if I can swing a new one.

[n2o4myfix]

I have what was a brand new 870 street avenger. Before ever taking it to the track I plugged the powervalve and upped jets by 8 sizes and used jet extensions. Over the winter I had the choke taken off, the secondary checkball removed, some what look like 1/8" holes were drilled in the throttle blades, and rear jets were jetted up another 4 sizes. It was tuned with an a/f guage on an engine stand, but was lean at an idle and rich at WOT. The mixture screws were actually turned out 3.5 turns. It worked fine just driving around, but when I took it to the track I had some problems. First the engine would die after the burnout and would take alot of cranking to restart. Then the launch was terrible seemed to stumble and the car surged going down the track. I slowed down from 6.8's @101 to a best of 7.1 @98on my first run, every run after seemed to get worse. By the end of the day it was going 7.4 @94. So I am filling the holes, putting the check ball in and putting stock jetting in hopes of curing what ever went wrong.

By any chance did you screw around with spark plug heet range or lifter/ lash adjustment? Do you back off your lifters during the winter and readjust them in the spring? 1/2 turn on valve lash will effect how a engine runs/starts if its a hydrolic cam. Plug heat range will also have a effect on how rich or lean it runs.

[1fastdeuce]

Put the carb on the bench and hook an electric fuel pump to it and see if there is fuel dripping from somewhere.

[B.G.]

list # 9381(the one i just sold) was not 1 to 1, it has standard progressive linkage. The 1 to 1 version has a big eccentric slot on the linkage-I believe...

[Firebird454]

Put the carb on the bench and hook an electric fuel pump to it and see if there is fuel dripping from somewhere.

Good idea.

[BLUE66]

Pm sent.

What size jets do you have in the carb that is screwed up?
Does it run poor all the time?
Idle bad, cruise bad, WOT,???
Look down the carb while idling and make sure there is no gas dripping from the boosters.
Check the base screws, etc. etc.
Put it on the bench with a pump as Shane stated.

[Firebird454]

stock jets 78/82. car starts up and idles fine for a few minutes, then loads up and quits. If I give it throttle it will clean up momentarily. i put $25 and got a whole 6 miles. I put the 3310 back on and it ran fine, put another $25 and hotrodded it for 30 miles and I still have some left.

[1fastdeuce]

One other thing I thought of today was does it have the right metering block to base gaskets?

[BLUE66]

One other thing I thought of today was does it have the right metering block to base gaskets?

I was thinking the same thing too, there has to be fuel leaking internally from somewhere. Wrong gaskets, warped metering block, etc. etc.
Sounds like it had some "professional" tuning done, LOL.

[Firebird454]

Well, I just put my BG 850 dble pumper back together, and its looking promising:) Last time I used it it had developed similar problems as the 870 VS. I can tell it needs new excellerator pumps, but it starts up and Idles good. It has some decent snap once you get past the hesitation. I just put in a new rear float and two new needleand seats. I think the problem may have been a bent spring on the float, but not sure. So I have another carb to try at the next RSD. I hope it works good! The butt dyno says its making more power than the 3310.

[1fastdeuce]

It probably needs a bigger pump cam or squirters. If the squirters are shooting a good stream, the pumps are more then likely good. The hesitation is from not enough gas when the throttle blades open creating a lean condition.

[Firebird454]

I have the green pumpcam in the primaries and stock in the secondaries with 31 squirters

[Firebird454]

when should I be using a 50 cc pump in the front? Or is that just not a good idea?

[1fastdeuce]

when should I be using a 50 cc pump in the front? Or is that just not a good idea?

You shouldn't have to worry about a 50 cc pump, a 30 is sufficient. Depending on how quick your engine revs is going to determine what pump cam to use and change squirters to tune it in then. I almost always used the blue pump cam and have used squirters as big as 52.

[Firebird454]

did you haveto do anything to make the blue pump cam work? I tried putting one on and it made it so my pump shot was maxed out at idle, and the arm would hit the back side of my throttle cable stud not allowing it to open up. Am I supposed to have to bend the arm to get it to work or did I get a deffective pump cam.

[Firebird454]

Weird. It works just fine on my 870. WTF.

[Firebird454]

The Barry grant arm has a raised edge. I cut back the stud. Blue pump cam works good now. I have it on position 2.

[1fastdeuce]

If it seems to rev slower, either put a smaller pump cam of smaller squirters. If it still hesitates, put on bigger squirters.

[Firebird454]

It revs quick, the only time it hesitates is if I am in drive and put it to the floor real quick. I have no kickdown, the tranny I bought didn't have the little rod installed to hook it up. Not sure if that means I have to tune the secondary pump. I have the blue cam with 37 squirter in the primary and stock pump cam and 35 squirter in the secondary.

[1fastdeuce]

I get the carb to stop hesitating on the primary and work the hesitation out of the secondaries then.