409 Questions

[rstreet]

For the FE,s?

Uh Uh you are sharp!
Robert

 

[409acoupe]

View attachment 70767
With the intake runners traced out, it looks like you have a problem with the left side of the carburetor.

I will be pulling the carbs off to put the phenolic spacers on so i can sneak a peak again at the primary carb. I rebuilt all of them and the primary got new throttle blades and shaft. jets, all new gaskets etc. Motor idles great now with the new bases and proper tune. I have just put in new plugs but haven't had a chance to drive it yet as we are getting storms these last couple days and into the weekend. I did get 61 jets to swap out but i'm leery to put them in until i try the new plugs and see if they end up the same. i'll take it for a good rip and see if the motor behaves differently.

 

[wristpin]

Long time ago I bought a set of Champion plugs and installed them in a 283 engine. Ran like crap! Changed them out for AC and problem went away? Just saying

Champion are crap. Like James says it looks like you have an issue with half of carb but I'd also look in spark plug cross reference book and get NGK plugs. In my experiance NGK's run great where other plugs wont even fire under the compression.

 

[Don Jacks]

While I've heard from reputable sources that NGK's aren't as good as they used to be,Champon's have sucked since the early 80's.Example;When my 86 Caviler 2.8 needed plugs,I researched the Champion catalog for the right plug.There were 2 2.8 v6's in the Chevrolet car line up in 86,one with a carb.,the other[mine] which had MPFI.Chevrolet's spec's called for the MPFI ngines plugs to be one heat range colder than the plug listed for the engine with the carb.Champion said that both engines used the same plug.This begs the question,who do you believe,the man who made the engine,or the outfit that just sells parts?

 

[409acoupe]

Champion are crap. Like James says it looks like you have an issue with half of carb but I'd also look in spark plug cross reference book and get NGK plugs. In my experiance NGK's run great where other plugs wont even fire under the compression.

Plugs that were in it were NGK gr5’s and so I’ve put the same ones in for now. Was toying with the idea of trying the 4’s which are one heat range higher but thought I’d try the same ones first now that all the general tuning is basically done so I can see what these new plugs do. Don’t like to make too many changes all at once so I can more easily track how the motor responds

 

[La Hot Rods]

Good plan, one change at a time, but there are many things one can check without changing anything.