Six Pack POURING Gas in the Motor-What's Up?

[PurpleBeeper]

My six pack setup is really dumping fuel in the motor and giving the rings a good washing. At idle I get a ton of smoke out of the tail pipes and after about 20 min. at idle I had an extra quart (of gas) in my oil pan. What's wrong?

I just rebuilt the carbs....
-drilled metering block holes behing power valve
- 1.5 power valve (I have about 2" vacuum at idle - old purple 292/509 cam)
- drilled outboard metering plates
-50cc accelerator pump
- small yellow outboard springs

I expected it would run a little rich.....but not this rich! Any ideas where to start? I'm not positive of what sizes I drilled the metering block/plates (drilled a couple years ago) but I know I followed some "text book" recommendations for a "stock" motor. I put the 1.5 power valve in to avoid this problem (low vacuum) but it didn't work apparently.

Thanks!

 

[rolling_Thunder]

6 packs... hmmmm I would start with double checking your float levels. The cam is another culprit - the low vac definitely makes tuning the cars a real MFer...

 

[Kowal]

Floats. Maybe one is sticking.

 

[lewtot184]

piece of junk in the needle and seat. check the fuel pressure too, you don't state what pump your using. 2" of vacuum at idle is horrible, even with a 292 cam; something else is wrong. why and how big did you drill the pvcr and metering plates? you don't need a 50cc pump. put the 30cc pump back on with a white or green pump cam and step the squirter down to a .028 with tubes.

 

[Supershafts]

I have a bigger cam with my 6pk and she idles as smooth as my f.i. jeep...

You have a needle & seat/ PV or float level problem

 

[PurpleBeeper]

I checked all 3 carbs' floats and the levels were right (spills a little gas when the screws are out and you shake the car). Power valve---maybe--the car did "cough" a few times (checked and it's a 2.5 power valve). How easy is it to blow power valves? I can't remember what sizes I drilled the outer plates or the holes in the metering block behind the power valve. I think I used the recommendations out of a Direct Connection book from the 80's. Junk in a needle/seat sounds possible. I have 2 fuel filters, but maybe.

I ran this setup sucessfully in the 80's before I drilled any holes with just the short yellow springs, 35cc pump and the biggest pump cam I could find. FYI #66 jets.

The cam was bought in '83 and I read somewhere that those old 292/509 cams are more like 305 advertised duration. I centerlined it (4-deg advance) but the headers glowed and it ran hot so I put the 0-deg. bushing in. The fuel pump is a holley blue set at 7psi but I have seen it hit 9psi. Maybe forcing fuel past the needle/seats??? With the low vacuum I have to turn the idle up around 1000-1200 rpm so I also think my idle circuit useless.

Lately I've been thinking about just putting it back "stock" and working up from there. I have some #35 metering plates on the way, but I'm struggling to find a "stock" metering block.

 

[lewtot184]

i think the 509 cams are actually [email protected], 108lsa. 9lbs will blow thru the needle and seats. if you used the old jet info where the pvcr is drilled to .052 on both sides your o.k. the metering orifices in the plates might be a little fat at wot with the old info but shouldn't hurt idle. i'd take a look at the distributor to make sure the centrifugal weights and advance plate are moving freely. power valves are easy to pop if your getting spitting thru the carbs. i would think that engine should idle between 8-10 inches vacuum in nuetral without too much trouble. i'm using a mechanical engle thats about 295 degrees on the seat, .510 lift and i can get 15 inches in neutral at 950rpm, 11 inches in gear with 9.3:1 compression.

 

[tpodwdog]

If you have a quart of gasoline in the oil pan....you got more problems than just tempermental carbs my friend!

 

[PurpleBeeper]

If you have a quart of gasoline in the oil pan....you got more problems than just tempermental carbs my friend!

Yeah, I checked the oil & noticed the fuel smell and changed the oil/filter (that's when I found the "extra quart") and I put a 750 vac. secondary carb & intake on it until I figure this out.

As for the low vacuum, these original carbs are a little sloppy where the throttle shafts go through the base plates (vacuum leak). Who can put bushings in cheap/well? I'm in Chicago. HOWEVER, I don't have any better vacuum with the 750 either and it's always been that way with this cam.

Thanks for the info lewtot! I think I will start by checking the needle/seats and turing down the fuel pressure regulator. It's actually good for me to run a little rich at WOT since I've got a 250-shot of NOS on it now.

Anyone have more carb tuning tips? I've got "about" 10.5 compression (old TRW L2295 pistons with the domes milled off flat), 906 heads and 3.91 gears. I've run a second 3/8" fuel line for the nitrous and plan on adding another holley blue pump (have dual feed fuel sump on stock tank)

 

[lewtot184]

i've been messing with six paks since 1970 and the best advice i can give is "don't try to re-engineer them". they don't need much more than richening the idle circuts and main metering in the center carb. i don't use any special gadgets or parts. i don't try to modify the vacuum system for the end carbs, just some spring changes as needed. no big accelerator pumps or squirters, no big jets.

 

[Meep-Meep]

Going on your description I'd have to agree with others that say start looking at fuel pressure and floats. Also these Holleys have the o-ring around the needle and seat assy and if it leaks the fuel will bypass the float, but normally that results in fuel geysering out of the bowl vent. Or the hole in the bowl where the o- ring seals may be worn or damaged to the point the o-ring doesn't seal and it may be time to change bowls.

2" of vacuum (if that is measured in neutral) is ridiculous even with that cam, however, in gear it's possible. Go back and set your idle stop screw so it's about one turn from the throttle blades being seated in the bores and make sure the outboard carb throttle blades are seated completely. Then set your timing and see if it even idles. Have you done a cranking compression check? Do you have vacuum leaks? Those pistons with the dome milled off should be zero deck or darn close to it. Do you recall where they were at TDC?

I would also go back to undrilled plates and stock 63 jets just to get a baseline, and also agree with lew that only minor changes may be necessary with a stock manifold.

 

[lewtot184]

i use 65 jets, 6.5 power valve, .028 squirter, green pump cam and stock 30cc pump in the center carb (this is with a [email protected], .510 lift mech cam). i'm running .093 main metering orifices with stock plates in the end carbs, purple springs in the vacuum pods (full length yellows work good too), idle mixture screws turned out 7/8 of a turn. the main tuning i do is for driveability. my experience has been to get them to drive nice and they will take care of WOT on their own.

 

[nelly.hartley]

I would also go back to undrilled plates and stock 63 jets just to get a baseline, and also agree with lew that only minor changes may be necessary with a stock manifold.I ahve to look into this further.

 

[mslisaj]

I have two of these monster systems. They run perfectly until I have a backfire for what ever reason and 1 out of three times it will pop the power valve in the center carburetor. I buy power valves 4 at a time to keep in stock when this problem arises. This is what I would check. The rest of the carburetor's are pretty bullet proof. But in my experience with these systems that is where I would look.

Float level of course is the first thing and the easiest to check. But if that is all in line then you know where to look...................

Their great systems when their working and nothing looks better under the hood. Plus the power so they are worth the trouble............

Good luck...........

Lisa

 

[moparpoor]

I have run into this problem a few times.They made a few different gaskest for the center carb meter block.Chances are you have the wrong one.It will have one small extra hole in it.It will literally fill the motor up with fuel.This is an easy thing to miss.You really can't see it unless you know what you are looking for or match it up to the correct gasket.Hope this helps!!!

 

[PurpleBeeper]

I have run into this problem a few times.They made a few different gaskest for the center carb meter block.Chances are you have the wrong one.It will have one small extra hole in it.It will literally fill the motor up with fuel.This is an easy thing to miss.You really can't see it unless you know what you are looking for or match it up to the correct gasket.Hope this helps!!!

Hey Poor,

Your gasket idea would explain A LOT. Any chance someone has a picture of the correct + wrong metering block gasket? I have no idea really and the original gaskets are long gone. I'll take another look at the power valve and needle/seats too.

 

[coloradodave]

"They run perfectly until I have a backfire for what ever reason and 1 out of three times it will pop the power valve in the center carburetor. I buy power valves 4 at a time to keep in stock when this problem arises."


FYI: Holley makes a $7.00 kit that adds a small bb to the power valve canal. This will cure your problem of blowing power valves. Summit and Jegs have them. All newer Holleys have this modification from the factory.

 

[mslisaj]

FYI: Holley makes a $7.00 kit that adds a small bb to the power valve canal. This will cure your problem of blowing power valves. Summit and Jegs have them. All newer Holleys have this modification from the factory.

Excellent information. I have two set ups. One on my Satellite and the other is on a 440 in a show truck I built. Both of these sit for extended periods and when I start them sometimes I'll get a backfire and then I'm pulling carbs. I will certainly be Google'ing this question to find that kit. It would make my Six Paks perfect then.

I so appreciate this information....... Thank you immensely!

Lisa

Went to Summit last night and got the Holley Kit. It contains two balls, springs and seats so it's enough for both carburetors. Can't thank you enough Coloradodave as this has plagued me for years.

 

[RustyRatRod]

That's a hideously small amount of vacuum....even for that cam. Here is the correct procedure for choosing a power valve, straight from Holley.

http://www.holley.com/data/TechService/Technical/power_valves.pdf

Notice it says to divide the vacuum reading in half, and choose the closest power valve to that number. Obviously, you cannot do that. I suspect you have other issues. Can you see fuel dripping down any of the carburetor throats? If so, you have something much worse than a simple blown power valve.

I am not sure I understand your modification. You say you drilled the metering block holes behind the power valve? What does this accomplish supposedly? Although I have limited experience with six packs, carburetors have been one of my specialties for a very long time. The power valve circuit is a pretty smart one. It knows what to do as long as it's clean.

 

[Gpuller]

Make sure the metering block gaskets are correct. I just ran into this problem after someone else rebuilt some carbs.

It had this gasket installed and it was filling the motor with gas.

It needed this gasket.

I damn near pulled my hair out trying to figure out why it was so rich.