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Car runs like crap under load, please help


Arvizu9618

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What car has:

 

SBC 350, TH350, HEI, Headers, Edelbrock 1406 with electric choke, stock cam, plugs gapped at .060

 

Idles well with 8 degrees base timing, idle is ~900 in Park, Vacuum advance is not adjustable and it is hooked up to manifold vacuum, have no idea what my total timing is.

 

I have checked all the Taylor ignition wires for burns (none), 5 and 7 are separated well, and firing order is correct.

 

My lean best idle is set for highest vacuum, which is ~20 and it is steady.

 

What car does:

 

Car does more than run like crap under load, it also puts out some real noxious odors at idle.

 

Anyways, when I punch the car on the freeway, it bogs and sputters, I also hear what sounds like a backfire but in the exhaust. I have checked the exhaust manifold bolts, they are tight and gaskets are good.

 

When I reach cruising speed, the car is having a hard time running steady, kind of like there is a misfire going on at cruise. 

 

Any suggestions/tips to fix would be appreciated

 

Thanx,

 

Art

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first your plug gap is to wide, bring it down to .045

 

sounds like you have a lean condition

check your filter and fuel pressure first

if those check OK then you will want to give it more fuel, Edelbrock carbs are very adjustable, you will need a kit for it and they have very good instructions on how to tune it

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Hey Sam and Jason, thx for the replies. Sam, I have the jets set to stock on the carb, wouldn't setting the mixture to more rich worsen the exhaust fumes that I'm getting now? Thx again

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   Sam has hit it dead on...   the stratospheric hydrocarbons are causing the smell and will cause your eyes to burn.  The engine's begging for a richer fuel mixture.

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Everybody thinks that smell is a rich condition when actually it's a lean condition, open your idle jets another 1/4 turn screw what the vacuum gauge says

this is just to help with your idle, one thing at a time!

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Art,

 

You've already gotten excellent advice so I'll just add a note about re-calibrating your 1406 Edlebrock if you decide you need to after correcting/adjusting the other factors.

 

Your 1406 comes from the factory calibrated specifically for economy so it has a smaller diameter main jet (.098") and a larger diameter metering rod (.075" X .047") than the 1405 (also 600 cfm) which is calibrated for street performance.  That just means it has a lean bias in stock form.  

 

As Sam said, you can easily re-calibrate your 1406 with one of Edlebrock's #1487 Calibration Kits which you can find on eBay, Jegs or Summit.  The first thing I would do is go to the Edlebrock website and download their excellent Owner's Manual (it's free).  Read the first few pages until you have a basic understanding of how the three fuel circuits (idle, primary and secondary) work and how the jets, metering rods, and springs work together in combination to give you the performance characteristics you want for your engine and driving style.

 

Next, study the 1406 Calibration Reference Chart on page 12 of the Owner's manual.  Your stock calibration is dead center (#1) on that graph.  All of the solid black circles are calibration options that you can easily achieve with the jets, rods and springs provided in the 1487 Calibration Kit.  Moving up and right will richen your carb.  For example, if you want to richen both the cruise and power modes of the primary circuit (used for all but idling and heavy acceleration), you can simply replace the current metering rods with the #1455 pair (.073" X .042") without changing the .098" primary jets and get a 7% richer cruise mode and a 6% richer power mode.  Of course, you can go well beyond that if necessary by changing to the #1449 rods (.070 X .037").  Next would be replacing your .098" primary jets with the .101" set and using the #1459 rods (.075" X .047") which is a bit more involved but still fairly quick and easy to do.  And there are other possibilities.

 

The key is reading the Owner's manual and following their instructions.  You can also change the step-up piston spring, the secondary jets (also provided in the Calibration Kit) and the linkage position on your accelerator pump arm, any or all of which might help your acceleration problems.

 

By all means, first check and fix the other things suggested (plug gap, fuel pressure/flow, choke operation, timing, etc.), but don't be afraid to recalibrate your 1406 after all of that, especially if your top priority is not fuel economy.  It's pretty inexpensive and easy to recalibrate your Edelbrock over a fairly wide performance range.

 

Good luck!

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Thanks again to all that replied, I definitely learned something.

 

I will be re-gapping my plugs and getting the #1487 cal kit

 

I'll post the results when I'm done

 

thanks

 

Art

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  • 6 months later...

Here's an update to my problem:

 

I replaced the ignition module with a known good spare in my toolbox and set the base timing to 12 btdc, no more spitting and sputtering.

 

I suspected that the noxious odor and bluish smoke at startup might be attributed to bad valve stem seals.

 

Sure enough I removed springs on Cyl. 1 and all spark plugs (fouled) and found only the intake had a seal, exh. did not, same with other cyl's :nutz:

 

I replaced and installed with the old school umbrella type seals and an o-ring seal for safe measure on each valve, replced all plugs with .045 gap, set valve lash and voila, engine runs like a champ now! 

 

Unrelated to my problem, I also found that the radiator was only a one row rad, upgraded to a 3 row brass rad

 

You just can't depend other peoples work, unfortunately...

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I do see white smoke at warm up for few minutes, Curious if i need to replace seals? If so, hpw easy is it to replace the seals as I replaced spark plus with .035 gap?

PM sent

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