Holley 650 double pumper rebuild issue - float bowls spilling fuel out of vents

[Coupester]

Hey guys, I just rebuilt my Holley 650 DP using a genuine Holley 4150/4160 rebuild kit from Kragen.

The motor starts great and settles to an idle but soon there after the vents start spilling fuel out of the primary float bowl.

Are there any springs that should support the floats? One is labeled 2, the other 3, they appear to be the same size, but I'm not 100% sure.

I'm 99% sure the rebuild went without a hitch. Everything was replaced, no stripped threads, and no extra parts were left over but a few washers that I'm pretty sure are used on the vacuum secondary carbs.

Any help very much appreciated!

[firehart2]

you may take it back apart and make sure that the front float doesnt have a pin hole in it. Brass floats can tend to develop a leak and fill with fuel from time to time.

[460capri]

If you replaced the needle and seat then you need to set the float height . I just use clear view sight plugs to help set the float level . To start take the top screw off the top of the bowl and make sure the needle is about even with the jam nut or a little lower if its not do that now and then reinstall the screw and see if that helps but you want the gas level to just be just at the bottom edge of the bowls brass plug this is why I use the sight plugs as you dont have to worry about spilling any gas on the intake to see what the level is . Good luck .

[Coupester]

The floats are plastic, they are not brass in this case. Do the plastic ones tend to get pinhole leaks as well?

[firehart2]

I cant say that they "tend" to, but they very well could. I know thats not much help, but you might take off the front bowl just to make sure.

[Coupester]

Whoops forgot to mention I did take it apart... and the bowls were empty, so I'm pretty sure I can eliminate the pinhole leak possibility.

Are the floats spring loaded like the vacuum secondary carbs? Right now they just float around.

[rob]

there is a spring

or maybe not, let me think..

[Coupester]

Originally Posted by 460capri

If you replaced the needle and seat then you need to set the float height . I just use clear view sight plugs to help set the float level . To start take the top screw off the top of the bowl and make sure the needle is about even with the jam nut or a little lower if its not do that now and then reinstall the screw and see if that helps but you want the gas level to just be just at the bottom edge of the bowls brass plug this is why I use the sight plugs as you dont have to worry about spilling any gas on the intake to see what the level is . Good luck .

The needle and seat were brand new (came with the Holley kit) and I definitely made sure they were flush with the nut to start out with. Fuel still totally comes out the bowl vents.

Did I forget to install something regarding the floats maybe?

Or, maybe I have too much fuel pressure? The gauge I have mounted on the fuel log goes from 0-100psi unfortuantely so it's a little tricky to monitor it anyways because of all the fuel it dumps out of the vent tubes immediately...

[rob]

did you adjust the float levels before putting it back together?

too much fp can caust your problem and so can misadjusted float level.

sometimes the needle will stick and needs a nice tap on top of the bowl.

[Coupester]

Originally Posted by rob

did you adjust the float levels before putting it back together?

too much fp can caust your problem and so can misadjusted float level.

sometimes the needle will stick and needs a nice tap on top of the bowl.

The float levels are adjusted when everything is together right? By twisting the needle and seat clockwise to lower the float level, and counter clockwise to raise the float level... ?

I thought that maybe it's possible that because I'm not running a return line on my Carter mechanical pump that maybe the fuel pressure is too high. I doubt this is the reason because I tested two other vacuum secondary carbs on the motor and they had no problems with fuel spilling out of the vents (although they were vacuum secondary carbs ... perhaps the transfer tube somehow can lower the fuel pressure whereas it can't on a mechanical secondary carb because there is no transfer tube)?

Just has an inlet and outlet to the carb, no return:

[rob]

they get set initially before installing. was probably a paper ruler with your kit. google the directions.

once you do that then you adjust with it running from the top.

i've run the carter 120 or 130 mechanical in the past with no problems.

[Coupester]

Rob, is there supposed to be a spring? I had two springs leftover, but I sorta figured out by looking at the rebuild diagram that they went ahead of the filters inside the bowl inlets... these springs are low in tension and coincidentally they fit right into a recession on the metering block... but I see no way how they could be used... they would be riding on the side part of the float itself.

[rob]

on a dp, i don't think there is a spring.

[rob]

have you tried lowering the fuel level? (clockwise)

[Coupester]

I wish I could find a double pumper rebuild diagram. The diagram they include with the kits are for vacuum secondaries... irritating. I paid high attention to detail, so I'm confident I did it correct. I'll call the Holley tech line tomorrow and see if they can recommend something to try.

[rob]

dp is center mount float, no spring.

loosen the locknut and lower the needle.

[rob]

once it stops overflowing, adjust just under the site.

[Coupester]

Looking at the videos on youtube, I think I might have installed the floats upside down... I'll check and post back up.

Otherwise, you're saying let the fuel dump out? Im pretty sure it will KEEP dumping out?

[My84GT4vho]

Remove bowl hold upsidedown adjust float till it looks level and reinstall.

[rob]

it does not need to be running to lower

[1bd90notch]

doesnt sound like a fuel pressure issue since your using a mechanical pump its a float level adjustment ill attatch a link for you to read hopefully it worksholley.com/data/TechService/Technical/Adjusting Your Carburetor.pdf

[Coupester]

Guys I figured out the problem... took the carb apart last night to inspect. When I went to reinstall the power valve, I tightened it a little bit harder than the first time. It seems there might have been some minor porosity on the threads where the power valve threads into the metering block, which gave me the impression the power valve was snug even thought it wasn't. I'm pretty sure fuel was leaking past the power valve and straight through to the bowl vents...

Anyways, thank you all for your help and I'm sure i'll be posting many more threads as I try and tune this bad boy.

Does anyone have any baseline jet suggestions for me? 600 DP 4776, b-cam, explorer longblock, weiand stealth intake, longtubes... The jets that are in there are 66 / 73 and I'm using the stock 6.5 powervalve that came with the rebuild kit.

Thanks,
Chris

[SVTCobra347]

What size were the needle & seats that came with the kit? If they're too big they'll let to much fuel through for the carb despite properly adjusted floats and it's gotta go somewhere...

If the floats are adjusted properly and the needle and seat is the correct size you won't have the issue you're having.

You can test the needle and seat to see if it's stopping properly.. with the bowl off the carb, hook a hose to the fuel inlet. Blow lightly on the hose and move the float up by hand, if it's working properly it'll stop the airflow.

Setting your floats is easy.. I pre-set them with them off the car. The pre-setting should be so that the edge of the float is just visible through the sight plug hole. Do this on both sides. Then fire up the car, remove the sight plugs one at a time and look. There shouldn't be fuel coming out at this point. Adjust the float on the bowl you are looking at until fuel just barely trickles out of the sight plug. Tighten everything carefully to lock it and move to the next one. Do your primary first then the secondary.



Oh and BTW there isn't an inlet and outlet on a Double Pumper (or any holley with center hung floats, such as a Street Avenger) there's two separate inlets...

[460capri]

Originally Posted by SVTCobra347

What size were the needle & seats that came with the kit? If they're too big they'll let to much fuel through for the carb despite properly adjusted floats and it's gotta go somewhere...

NO . When fuel enters the bowl the float raises up and it closes the needle & seat and stops the flow of fuel to the bowl but if the fuel pressure is to high it will over power the needle & seat and continue to fill the bowl and will then overflow out of the vent .

[Coupester]

The needle and seats were the ones that were included in the 4150/4160 rebuild kit...

One small question, is this the right order for the inlet "filters" (I think that's what those little gold things are... either restrictors or inlets):

[460capri]

double post

[460capri]

Originally Posted by Coupester

The needle and seats were the ones that were included in the 4150/4160 rebuild kit...

One small question, is this the right order for the inlet "filters" (I think that's what those little gold things are... either restrictors or inlets):

Put yourself a good inline filter on before the carb and throw that other junk away all you need is the gasket and fitting for each inlet .here is a pic of my old setup I had a filter in the rear next to the fuel cell but I am changing the setup now .

[Coupester]

Ok guys, an update to my carb issues. Regarding the first problem I had with fuel spilling out of the vents, I'm pressure sure it was caused by the fact that I had two power valve gaskets stacked on top of each other. Once I removed one of the gaskets (and used the best looking one), it fixed the fuel spilling out of the vents problem.

But after I get the motor running for a few minutes, it keeps surging until it is warmed up... I know it's an issue with the double pumper as I have a new 600 vacuum secondary carb that I use for testing... two pumps of the pedal and she starts right up and settles down to idle.

A few days ago, I tore the carb apart for inspection again...

I realized I had installed the main body to throtte plate screws in the wrong holes, so I changed that per a picture I found online. Also, my 4150/4160 rebuild kit came with three different gaskets... I lined them all up with the main body holes and picked the closest fit. Once I fixed the correct location of the screws (turns out more than 6 of the holes are threaded) and I changed the gasket, the car would start up and idle better, but not like the vacuum secondary carb...the double pumper still surges for quite a while before it settles to an idle.

Once the car idles, which takes a minute or two of surging and me holding the throttle open a lil bit and goosing it so it won't die, I adjust the float levels, primary first, until fuel just barely trickles out of the sight plugs... I know my floats are adjusted correctly, and the needle and seats are brand new that were included in the rebuild kit (is it possible for the needle and seats to go bad from too much fuel pressure??). As a side note, I was running my Carter mechanical fuel pump with no regulator, and I noticed fuel was actually seeping out of the new gasket between the primary metering block and the main body. Once I installed a 12-803 Holley regulator and set pressure to 5.5 psi, that problem went away, but the surging idle problem still exists... On a side note, when I shut the motor off, I can hear fuel trickling down the intake... but I know for sure the floats are not too high?

**Is it possible I have a bad power valve gasket? I read online that a guy dealt with a bad gasket. The power valve is 100% brand new and I know it's not blown out because I did the Holley recommended trick... tightening the idle mixture screws all the way in the see if the motor dies, which it does.

Anyhow, here are a few random pictures of the gasket scenario I have been messing with, this is the gasket I initially used:


Here are the two other gaskets that came with the kit:


Here is a picture of the bottom of the metering block itself (btw - I made sure to thoroughly clean off all the old gasket material before installing the new gasket):


And a picture of how I finally installed the throttle plate to main body screws:


Sorry for the suuuuuuper long winded post, but I know that with a little help I can have this thing running the way it should.

[stangcoupe58]

Originally Posted by rob

dp is center mount float, no spring.

loosen the locknut and lower the needle.

WHOA WHOA WHOA... really????? tHE CENTER HUNG DOES NOT HAVE A SPRING? Sorry for the caps... WOW I bet that solves why My primary float cant make its mind whether to flood out or run empty. the fuel level has never stayed full without overflowing or running empty and it had a spring on it. Only was it stayed full without overflowing is when Im on the gas....

Holley 750 DP