Carburetor Selection

[Meep-Meep]

I found most carb problems come from the ethanol blended fuel. This stuff does not like to sit in a hot fuel bowl and the best you can do to minimize the typical problems is to block the heat crossover in the intake and put some sort of an insulated spacer. Even that won't cure the issues but will help. The only known cure (in my opinion) is fuel injection - even the throttle body type.

If you have a bone stock motor a 650 AFB with the slightly smaller primaries would be my first choice, especially with stock exhaust manifolds. A 750 will work too but you may have a stumble when mashing the go pedal under load. The Holley 750 vac secondary with a heavy spring in the diaphragm will be more forgiving under full throttle / heavy load conditions. With carb CFM it's always best to err on the conservative side. And I will say this again, make sure you get a carb that has street calibration.

 

[FridayGt]

Geez ... I went and made my own Excel worksheet ... :laughing1: ... well at least I remembered some basic geometry from the 70's ... Mr. McKeon would be so proud.

Hey, you're a step ahead of me. I can't use excel to save my life. lol.

750 is a great street 440 cfm.the edelbrock uses"air flow"to actuate the secondaries,with a regulating weighted flapper.the holley uses a vacuum signal to regulate the opening of the secondaries.for the most part they work about the same.the edelbrock is a bit easyer to work on,the holley is far more adjustable.both should work great with minimal adjusting.

Thank you for breaking down the difference for me, it makes it a lot easier for me to understand. I kept just finding answers that it didn't matter or make much of a difference, but I still wanted to understand the basic principles behind what was happening with the carb.

I went ahead and ordered the Eddie 1407. Primarily because between the Holley 750 vac sec that was tried on it before and the Eddie 1411, it just came to life with the Edelbrock. The 1407 is essentially the same carb, just with a manual choke. I ordered it through my shop and the price to me was $285 with free priority overnight. It'll be there first thing in the morning for me. I'll get it swapped and let you guys know the end result and how she takes it. I'll also breakdown the old one, rebuild it to learn and put it on the shelf as a back up. Heck, if it runs well enough that I would trust using it myself, I might sell it to fund my rear diff. project. But, time will tell.

 

[FridayGt]

Ok, well, I pulled off the old carb last night and set-up the new one. I've gotta be honest, that was a thousand times easier than I ever would have anticipated considering I had never done it before.

Once I got everything set-up, I primed it, and it fired right up! Right out of the box. Now, granted, that was with the choke helping it out as it wanted my engine to idle at about 500 RPM cold without it.... lol. Obviously have some fine tuning to do, but does it sound wierd to say that just sitting there in an idle it sounded and felt like it came back to life? I'm going to take the old one apart and see what I find out about why it was doing what it was doing and let you guys know. Until then, I'm changing out all my spark plugs and fuel and air filters and putting this carb through its paces. Thanks again everyone.