six pack runs like crap

[zimcuda]

I picked up 3 six-pack carbs and the manifold for free this summer and thought they would be great on my 440.  "Linkage is all you'll need" I was told.  After tearing them open to rebuild I found half the parts missing and some mods that made them almost useless.  Now that I finally have them on the car it runs pretty bad.  One thing I need to verify before persuing other avenues is if the metering block is the right one.   Can anyone tell me the correct metering block part # for the center carb?  The one I have has 34R 6105-B stamped around the vacuum nipple.  The carb # is 4391.  I can't find any listings from holley to verify if it is correct.  Also, will any of the aftermarket metering blocks available work well for these center carbs.  None of them specifically list for them, but aren't the 4150/4160 blocks compatible?  The one I have, however, doesn't have passages drilled where the idle restrictors would normally be, just to the left and right of the power valve.  Do these carbs not use them?  I'm mildly familiar with the holley's, but not with the slight variations from model to model.  Any help would be greatly appreciated. 

[cudabob496]

I have a 72 service manual with a lot of info for servicing, troubleshooting, and complete rebuild of the 6 pack setup. It shows the center carb number as R-6404A for the 440 engine. Might want to get one of these manuals. But I'd be glad to answer specific questions from my manual. Not seeing a metering block number anywhere.

[Chryco Psycho]

I do not have the # handy for the correct metering block But it should have idle screws on the side of the metering block so you must have a secondary block , I would contact Promax & get a set of the outboard plates & a proper metering block , you will be far ahead trying to tune it

[zimcuda]

Thanks for the advice.  No use guessing on a part of unknown origin and function when I can get a better piece made specifically for the carb and have much better tuning ability. 

[cudabob496]

My service manual has tuning tips as well, such as qualifying the choke control lever, fast idle cam postion adjustment, choke unloader adjustment, vacuum kick adjustment, fast idle speed adj, bowl vent valve clearance, pump lever clearance, outboard carb throttle adj, idle speed adj, fast carb idle, and wet fuel level adj.

[zimcuda]

I received the metering block and outboard jet plates from promax the other day.  They asked me alot of questions about my car and engine setup so they could install the proper bleeds and jets for me.  I spent this afternoon re-assembling everything and putting the carbs back on the car.  Even a turkey overdose couldn't stop me.  Hopefully, I'll be able to take the car out for a spin in the next couple days to see how everything works, if the weather holds out.  My only worry are the #83 jets installed in the outboard plates.  These are alot larger than the stock plate's drilled holes, but I figure they know what is best for their own product.  If its too rich I can just install different jets, how ingenious!  I'll let you know how it goes, and thanks for all your advice.

[Chryco Psycho]

CAn`t wait for the results

[cudabob496]

From my 72 service manual the main metering jet on the center carb is a #62.

[Chryco Psycho]

62 is correct for the center carb , the outboards are a guess , being almost 30% larger 86 may not be far off

[AprilsPink72Cuda]

You're just going to have to bring your car to Carlisle this year and get Chryco to tue it for ya, lol.  (Sorry, but mine has never run better since he played with it
!) Thanks CP!

[6packCuda]

I put the promax jet plates on my 451 and tuned it on a dyno and ended up with 85s in the outboards.

[zimcuda]

Got the car out for a drive yesterday.  The top end performance of these carbs over the edelbrock 750 they replaced is amazing.  I would have never guessed there was so much potential laying in this engine waiting to be released.  It always felt strong on top, but now can be downright scary, as the 275's start breaking loose in second gear at 50mph as it winds up, even with the 2.76 gears that are in it.  However, I still have two issues to fix.  The secondaries are opening way too fast, causing the car to fall on its face momentarily once they open, even if the rpm's are up before mashing it.  This condition is gone if they are disconnected.  I should be able to get the secondary spring kit and straighten that up without too much drama.  The second issue has me a little baffled.  The midrange drivability is terrible.  The engine has no response and sounds flat during steady throttle and light acceleration from idle on up .  It will also pop, sputter, and backfire when slowly squeezing down the throttle.  Then suddenly the exhaust note turns crisp and the car takes off like a rocket.  This occurs even with the secondaries disconnected, so I think I need to concentrate on the center carb 1st.  I installed the promax metering block with #64 jets, 6.5 power valve and 31 squirters.  The engine idles nice and the top end is near perfect.  I don't know the cam specs and the builder doesn't remember (its been about five years), but I have about 12" vacuum in N, 9-10 in gear and climbs to 18-20 at light cruise.  The condition doesn't seem to be related to load level, as it can occur at any point both above and below the power valve opening vacuum level.  Strangely, I had this exact condition with the old carb and was the prime reason for replacing it in the 1st place, its just much more pronounced with the holleys, but identical in occurance.  Its plagued this engine since it was built and I'd love to get it solved.  Either I'm missing something obvious or this engine needs something outside the range of the average combination.  Any help is greatly welcomed and I'll provide all the additional info needed that I can.   
If I can't get it solved, C.P. and Carlisle might be the only option left, if he's willing.

[MEK-Dangerfield]

As for your second problem, it sounds like you are running lean. How do your spark plugs look? When you are the top end, the squirters are helping you out, so it's the steady cruising speed only that's the problem?


  Mike

[zimcuda]

With the old carb all plugs were spot on.  Once the holleys were installed initially the rear plugs were lean, the fronts were rich and the centers were perfect.  I adjusted the front and rear secondary idle screws to get them all correct.  As the throttle is opened slowly at cruise the sputtering progressively worsens until suddenly it just smooths right out.  I have a pair of #68 jets I could install but that seems like it would be too much.  With the top end running so well, I would think the jetting is close.  Forgot to mention the timing is 12/36.  I,ve tried 8-18 initial timing and but it made no difference.  It definately feels like a mixture issue, I just don't know what I can change other than the jets to correct it.  I thougt it might be with the transition slot, but its open and working properly.  And both carbs had the issue.  If it is too lean, how can I richen it without richening the top end. 

[MEK-Dangerfield]

At this point, my guess is your squirter size is probably too small. My guess for the day.   


  Mike