Tuning Questions

[MJS73]

Can someone give me some advice on how to tune my Chally? The motor hasn't been running as well as it should ever since the top end of the engine was re-worked earlier this spring (valve springs, pushrods, roller rockers, etc.). 

Motor is a 360, Edelbrock heads, Holley 770 Street Avenger.  Complete specs on the motor are at www.mikes73.com/engine.html.

Some of the things I've noticed:

• idles somewhat choppy at startup, hesitates on initial acceleration
• backfires (pops from engine) on heavy acceleration
• dies when accelerator is floored when cold (backfires when floored when warm)

I pulled a plug, here is what it looks like:



I've also heard conflicting opinions on whether the carb is too big or if an Edelbrock 650 (Thunder AVS) would be better.  It's strictly a street car/cruiser.
Thanks,
Mike

[GoodysGotaCuda]

I'm sure the Holley can be made to run just fine on that engine. However since you seem new to tuning a carb and also mentioned that it is strickly a Cruising car, the Edelbrock AVS is a great turn-key carb. And very hard to kill.

[BB73Challenger]

Plug don't look that bad, how about vacuum leaks?
What's your timing set at?

[422STROKER]

I'm running the 770 on mine too, it is choppy at first fire up as well, I wonder if it is a choke thing.  The squirters are small on them stock OOTB.  but i haven't had any of those issues and all I've done is set the idle mixture and curb idle screw so far.  i would check your timing and the curve on the distributor.  I had some issues with inital wanting more but the total was way too much when I got it there.

Tom

[MEK-Dangerfield]

Is your accelerator pump working correctly? If you pump the gas pedal, you should see the carb throat wet with gas on the primary side. Popping thru the carb leads me to believe a lean condition exists, but your spark plug looks OK.    For what it's worth, my car really doesn't run right until warmed up.



  Mike

[nivvy]

how far discoloed down on the plug.......

[BacardiCBR]

If I was in your situation, and I wanted to set it and forget it (cruise) - GET THE EDELBROCK and you'll be a happy guy 

BTW, I run a Holley, but that's because I don't mind farting with it

[MJS73]

I'm running the 770 on mine too, it is choppy at first fire up as well, I wonder if it is a choke thing.

I thought about that, too, but see MEK's response below about the accelerator pump.

how far discolored down on the plug.......

Just the end of the tip as in the photo.

Is your accelerator pump working correctly? If you pump the gas pedal, you should see the carb throat wet with gas on the primary side. Popping thru the carb leads me to believe a lean condition exists, but your spark plug looks OK.

Funny you say that, someone told me that they thought the accelerator pump spring was too stiff, that it didn't open as quickly as it should.  Does that make sense?

If I was in your situation, and I wanted to set it and forget it (cruise) - GET THE EDELBROCK and you'll be a happy guy   BTW, I run a Holley, but that's because I don't mind farting with it]

I'd kinda like to keep the Holley, but I get the feeling they're higher maintenance.  The Edelbrock's looking like a better choice, or the Edelbrock fuel injection setup.

MJS73

[422STROKER]

Get the one you got going right.  Maybe a bigger shot will help.  I used the dvd that came with it to learn a bit.  It goes through all the adjustments pretty well.  What kind of timing are you running?  Mine liked a bunch of initial to run nice.  I have it at 16 initial and 36 total mechanical.  I think it would take more(initial) too, just haven't gotten that far.

Tom

[Chryco Psycho]

the jetting looks good just adjust the accelerator pump to get rid of the bog
 make sure the re is no play in the pump arm first then change the squirter to a lrger size if the bog persists last change the pump cam cam

[nivvy]

Dont like edlebrocks.....Get a Holley .... Just my opinion 

[ntstlgl1970]

the jetting looks good just adjust the accelerator pump to get rid of the bog
 make sure the re is no play in the pump arm first then change the squirter to a lrger size if the bog persists last change the pump cam cam

after confirming there is no play, can also try the #2 hole on the pump cam to bring in the shot a little earlier.

[MJS73]

Went to look at the carb and start tuning it and discovered the mixture screw is missing on the rear. Gone!  That could cause it to run poorly, huh?

MJS73

[422STROKER]

I don't think there are mixture screws on the rear of mine either.

Tom

[torredcuda]

Holleys do`nt need any more manitenance than an Eddy and are more tunable,just need to set it up for your engine combo and you`ll be good.