SBC progressive 6x2 questions and pics

My engine is a 357 ci. sbc, 0 deck height, flat tops with 2 valve reliefs, 76cc heads flat milled about .030. Last week I had a lean problem but fixed that by making sure the throttle plates in the 4 outer secondary carbs shut tight. I also plugged the idle mixture ports. I also installed 58 jets in the 2 primary carbs. When I take it for a ride everytime I push in the clutch to slow down it loads up and dies. i have to keep cleaning(reving) it out. I have the reg set at 2.5 lbs. What size jets are you guys running in the center carbs? Any suggestions or help would be appreciated......Mike

Here's some pics a couple guys asked to see.

 

your scaring me.. I was not expecting it to be that difficult to set up (I am in the process of rebuilding my 97's for my 6x2)

 

Im gettin' scared too...we're setting up 6 Holley 94's for our 327. How are all you 6x2 SBC guys running your setups?
-Dean

 

Your too rich. Try a 51. FYI, The linkage finally comes with instructions. Do yuo have the rears even hooked up?

 

I had 51's in when it was to lean, but I can put them back in and try it now that all my vacuum leaks are fixed(secondary throttle plate gap).

I got rid of the rod from the kit that goes from the front carb to the back one and bought some ends that fit the stock balls and ran it on the other side(last pic)

 

It's probably not, I just tend to overthink things and make them more difficult than they really are

 

Hotrodjosh (97heaven.com) was featured in Hot Rod mag with a 6x2 setup for a sbc.Give him a call. 630-665-CARB.We'll both be in the shop after 5pm tonight.

 

its a good thing you got rid of the rod in the last photo...now with the motor running rev it up and close the throtal look down in the carbs see if any are dripping?... if not rev it up look if (spray bars)they
are spraying or dripping?...or you can try to block off two carbs at a time and find the problem carb...phil

 

DO you have a fake firewall? i see you have the tank out, but the Booster mounts to the back of the dash? or is the pic fooling me?

Sorry not to contribute more, but that threw me for a loop

 

If they are dripping, what is the fix ? I ran my 6x2 327 at the track last night and have this horrible hesitation off the line, almost sounds like it shuts down, complete silence, and about 2 1/2 to 3 seconds later it takes off like a ****d ape. It clicked off o 14.6, If I could only get this thing to launch off idle it would run a real good time. The thing runs great on the street. I am only running the outer four carbs right now, and have different jets in all four coners from 48 to 51's, only did that because I did what the plugs seemed to want after reading them. I have also played with the pump sqirter cam but still have this horrible hesitation. Did not mean to hijack your post but did not make sence to start another on 6x2's when you have been talking about them, so we can all learn something from it, maybe. I am running the fuel pressure at 2 1/2 psi. Just do not know where to go with it now, it is not back firing at all,and the carbs seem to be squirting. I have the powervalves blocked in them also.Anyone have any ideas.................Thanks Littleman

 

try slightly bigger squirters and see what happens.......Marq

 

. There was some interesting discussion on the flathead board about the Power Valve gaskets in the rebuild kits not fitting the new PV correctly allowing an internal leak even with a new gasket. Some have gone to a copper crush gasket to seal the leak.

 

How are you launching it? If you're flooring it from idle, you can expect this since you're opening up 6 carbs at once- Quite a vacuum change for the engine to adjust to. If you are loading up on it and launching against the converter (if you've got an automatic) or revving and dropping the clutch (if it's a stick), you can tailor your launch to sidestep the bog. Giving the engine as much RPM as possible before flooring it is critical with so many carbs. The bigger squirters can help TONS if the engine can take the squirt. Most can- I've fixed more bogs by going to a larger pump shot than any other thing. Sometimes tuners think the engine is getting "flooded" with too much pump shot. I don't think I've ever seen this happen to a point where the engine bogged down from it. Black smoke (rich condition) is one thing, but bogging is an entirely different animal. The correct pump shot, timing, and launch technique will cure this right up.

Scotch~!

 

I dont know how to run them but your setup is sweet!

 

Thanks for the info Scotch, I am only running four carbs, all the corners for now, and yes it is a automatic, I did try to load the rpms up on the converter but made no change. I am thinking because I have gotten it to run so well on the street by taking the fuel away. Now Iam running this thing balls out, I need to up my jet size up alot. What do you think about that logic? Then if that does not do it, drill the squirters. I am thinking that I will have to change the set up from street to strip every time I go to the strip which I do not mind at all. I can keep the drilled squirters and larger jets aside for the track. I just want this thing to make a full p***, it should be quick if I can get it to launch, it marches hard once it is going.........Thanks Littleman[/QUOTE]



Man..How much converter are you running? I bet that thing might just need a little more stall speed to level off and it'd run like stink...Does it feel like it'd like to launch with a little more rpm?

Scotch~!

 

Man..How much converter are you running? I bet that thing might just need a little more stall speed to level off and it'd run like stink...Does it feel like it'd like to launch with a little more rpm?

Scotch, I have a Isky cam .464 lift and 221@50 dur., If I remember I put in a B&M 2000, I think it was like only 1000 over stock, but will have to check my paper work to see which one I bought. But still think it is all in the carbs and not enough fuel...Littleman

 

I'd LOVE to have a day with this setup to fine-tune it. Your cam isn't big enough to piss off the converter, but I'd still want one rated at 2,500 or so. I think having a few more stall RPM would ensure all the carbs were open enough to get them off the idle circuit at launch. The right pump squirt and timing would set it off. It just requires time and thought...

Scotch~!

 

Scotch, have you ever tried running smaller than standard power valves in 2 of the carbs and pluggin' off the other 2? I would think with the wide open throttle and no vacuum you are starving the motor. I kinda think a shot from the p/v on launch would help? What's your take?

 

It's a tough call to do "blind" because I can't read plugs, EGTs, or even listen to it. I have run staggered jets, power valves, etc. in multi-carb setups based on what the engine tells me it wants. Typically, in a 4-carb setup where each carb is positioned over a pair of intake ports, you want to run the same size power valve but jetting could be different depending on how efficiently each carb is feeding its respective ports. Goofy stuff like casting differences, fuel feed, the condition of each carb, and even firing order will have an effect.

With 3 carbs (tri-power) you can focus on the center carb and work on getting the outboard units to work with it. With 6 carbs, it's similar, where you can focus on getting the center two to work flawlessly, and then tweak on the outboard four to work with them. With four, it's tougher because you don't have "primary" and "secondary" carbs, but rather they're all working all the time. I play with vacuum, jetting, opening rate (linkage), and the other stuff I mentioned (plugs, EGTs, etc.) to get in in sync, and you'd be amazed how much difference little adjustments (like a degree of timing) can have on these setups. Typically, I run a hotter plug, too- or at least experiment with different types of plug to find which work best. Since multi-carb setups are typically rich, hotter plugs often help a little.

I've also learned these setups like higher-stall converters when launching and idling. If the engine load is heavy from the converter at low rpm, it can bog. If the engine can freewheel a few more rpm with a looser converter, the engine seems to be able to "keep up" with the carbs more effectively.

Each one is different, and unique. It's really hard to help someone out on the tuneup on a message board...but I'm dumb enough to keep trying.

Scotch~!

 

It sounds like a power valve problem for both of you.
One needs more o the other needs less.
The numbers on Holley power valves have nothing to do with the size. It is the vacuum at which they open .
You need to check your vacuum at idle and fit power valves which will remain closed at idle but open soon after the you get on it. I.e when the vacuum drops below the preset figure. ( Number on the valve.)
58 mains are probably OK for two carbs on the 357 as long as the power valves in the other four carbs are blocked off and the ones in the center carbs are closing when you get off the gas.
Also check your float level, both open and closing pos***ion are important.

The problem with using only some of the carbs on a six carb setup is fuel distribution, the cylinders furthest away will run leaner than those next to the carbs. 5 and 7 on a SBC fire sequentially so in a log manifold 7 will always be a bit leaner than the rest if the jets are all the same.
The problem with racing using the outer four is probably the opposite....no power valves to compensate for the sudden gulp of air from four 94s.
You have about 780cfm all opening at once, it takes a pretty good SBC to use that from low down, especially if there is no ppower valve to cover it, the pumps will have no chance of doing that job on their own.
Pump duration is more important than bigger squirters, set the arms for the longest stroke in the pump piston, and make sure that the plunger is in good nick. Also make sure the check balls at the bottom of the pump chamber are not corroded or stuck. You probably need to open the idle jets a turn each and up the idle a bit for racing, to help the transfer from idle circut to progression..... once more make sure the progression /emulsion tubes are clean .

 

Everything that you mentioned for my set up I have done or checked, Thanks Littleman.......I think from the 14.6-to 16.0 it ran for the first time last week, and playin with it and taking it back the next week and running 13.3 is a huge gain and the correct changes in the right direction..

 

Sounds like you got a leash on this thing Littleman...Nice work!

I don't think I can do anything more to help ya, but if there is anything you need or want to talk about, let me know.

Scotch~!

 

Got the truck running 12.94 last night at the track at 104.6 mph, still nedded to bump the jets up more, maybe drill out the squirters alittle more, and may put in my vega converter..............................Littleman

 

NICE! Glad to hear its going well.

I was at a pal's dyno shop yesterday and saw he'd wired up NINE (9) wide-band oxygen sensors to the dyno so he can fine-tune EFI stuff. He's got one on each header tube and one downstream.

First thing I thought of? "Man...I bet we could dial in Littleman's setup on here!"

Glad to hear it's going well, and please keep updating us (me!). I'm dying to see what kind of difference the converter makes...and the squirters too! My only concern about jets is the potential for loss of performance anywhere else but wide-open. I bet you can lower the quarter-mile time, but you may sacrifice something in street driveability. I know you were pretty happy with how it acted and ran on the street, and I'd hate to hear you lost any of that capability...even for another tenth or two...

Scotch~!

 

Congrats Dave, I don't know too many people that have multiple carb setups that run good at all.

Breaking into the 12's with a 6x2 setup makes you the HAMB expert. It may not be that big a deal for single 4 barrel setup, but that's huge for 6x2's.

 

Scotch, you want to play with a set up. Maybe I will drive my sedan up and let you have as much fun as you want on my 6x2 set up..............

this is the first time i have played with Strombergs and the whole power valve and jet thing has me confused.........

I will be asking alot of questions as I get closer to it running (in a few weeks)