8BA running rich

W

waltere

Senior Member
I would like to pick some brains. I am running an 8BA, with a 30 over bore, 4" crank, Isky 400 cam, and a pair of 97's. I have them jetted with 45's and uncertain of power valve size. The motor runs great but seams to be rich. (smells rich, plugs are black, tail pipe black), I friend is suggesting progressive linkage and plugging the idol circuits on the rear carburetor. Can you give me any advise on what to do in this situation.
Thanks in advance
Walter
 
Progressive linkage with duals is not a great idee...fuel distribution will be uneven between cylinders.
Install an Air/Fuel meter and rejet the carbs...A/F meters ain´t to expensive and beats guessing...
 
I have a 21 Stud with 2 97s and have had good success with 42 jets and 69 power valves. Like you, I was running very rich.
 
Whatever you do,don't listen to your friend. As noted, drop down a couple sizes on the mains and check what you have for power valves.
 
This actually works. Get q block of plate and block one carb, or jus take it off and run one carb. THis works quite well and you can drive the car with little if the carb is right. The 400jr is a very hot cam and it shouldn't idle slow. 750 or better. Too much gas can wash oil from the cylinders and ruin the rings
 
One other thing often overlooked is the little chrome airfulters are like running a choke. I had 43 mains (maybe even less) on my 97s for years with the little chrome filters and if I pulled them off and drove around the block the car would barely run...
 
I have used a couple of sets of these adjustable jets on two 94' intakes and they really let you adjust. run it awhile and "read" the plugs
 
keep re jetting it takes time but it works. Find a good dyno in your area its worth it in the end. Ive ended up with 39 mains and 70 Pvs in mine alot leaner than i thought was needed but it worked super drivable and gets around 25mpg now not 10 maybe
 
Thanks for the input. 50droptop I am going to try your Idea. I have a new set of jets and power valves. I will report back!
Thanks
 
Ok guys a few more suggestions would be helpful. I am now at #65 PV and #43 jets. Runs much better but after about 120 miles on a new set of plugs they still look like I am to rich. Should I try another set of smaller jets? different Power valves?
Thanks in advance!
 
you just have to keep trying to see what works personally a dyno is the way to go much quicker and you can tell whats going on other wise a vac gauge, a A/F meter a good stretch of quite road and a bucket load of patience
 
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