Blower Carbs -Jetting- Idle-Plugs
 

This is the same engines as described in another post but I'll describe them again.

454's set up similar to the 600sc's
Twin 700 holleys. 420 Mega Blowers. Aluminum Dart Pro 1 Heads running about 7.5 - 8 compression @ 5 lbs boost. I have been running NGK R5671A-8 plugs and prier to this they were the -9's.

I'm fouling plugs all the time unless I take this out and run the hell out of it and get it good and warm. I have two categories of questions. Fouled plugs and idle problems.

The Carbs are set up with 78 primary jets with 4.5 PV. and the secondary is set up with 86 jets no PV. It looks to me like the primary is running a little rich. The stock 600sc calls for 74 and 84 accordingly. Could this make that much difference.

Next question is on idle problems. This does the basic rolling idle and I've tried everything to tune it out. I think that some of my fouled plugs might be from over rich idle mixture. I was wondering if the secondary idle circuits should be set less than the primary and/or should the throttle plates be opened up to expose the transfer slots.

I don't know what size air bleeds these have but I guess that could be some of the problem.

Bottom line: I haven't changed this set up from the previous owner and I don't think he changed anything from the initial set up that he bought. Nikerson had initially set up the carbs so, I would think that this should work better than it is.

If you have any ideas or suggestions, I would love to hear them.

Thanks Bob

Call Dean Nickerson, I'm sure he would be glad to help you. If you expose the transfer slots you will be even richer than you are now. Being too rich will make the blower roll condition. Have you leaned out the idle screws yet. There is a compromise here. The proper mixture on a warm engine will be lean on a cold engine, and cause a rough idle until it warms up. If others agree, I would lean out just the primary jets one or two sizes, and see what happens to the loading up problem. You should buy an assortment of jets from Jegs or Summit, you will save a lot of money.
Good luck, John B

Also, you should try to plot your vacuum pressure under the carburetors. When the vacuum is under 4.5 in, you will be running full rich, which may be all the time your on plane. You will probably have time to investigate this subject before spring. Try searching the web on this subject, there are many good articles.
JB

Yes I understand what your saying about the secodary transfer slot. I just thought it might help ballance everything out.

Don't want to dog Nickerson but, they weren't much help unless I wanted to send them to them for a big buck rebuild. Like I mentioned ealier. They were originaly set up by them so I would have thought they would have some more information for me too.

That's why I'm trying here.

Thanks, Bob

Bottom line, what is your vacuum @ idle???? Do you still have your power valves installed? Your idle vacuum needs to be 2" vac below that. ie- Idle vac is 8" primary power valve needs to be 6.0 or less. This will solve your rich problems at idle. I can help to walk you through the changing of the power valves if need b. The other thing you want to look at is vacuum at WOT, it should be minimum 2" less than the power valves. Mine is @ 0" vacuum. all good. But idle is your concern now.....