Allpar Forums banner
1 - 4 of 4 Posts

·
Premium Member
Joined
·
20,348 Posts
Welcome to the forum. Sounds like the secondaries need adjusting, they are opening too soon and bogging, leaning out. Get yourself a vacuum secondary spring kit, contains about five or six different springs in it, all color coded. Start with the two heaviest, as in heavy in the rear vacuum canister and medium heavy in the front. The process is to slow down the secondaries from opening too fast and going lean (the bog), by swapping in the next lighter spring for the previous one until you start to bog once again, then go to the previous setup. So numbered one(heavy) through five (very light), start with 1 and 2, then go to one and three, then two and three, then two and four, then three and four. You will get to the point where they open according to the vacuum signal and not too soon, whcih is what you want. Let us know how it goes.

A second thing you will want to do, also, is slow down your vacuum advance springs, too. Big blocks don't like fast advance, so you should have a heavy spring and a medium spring in it, total advance of 38 degrees, too much will give you a little ping sometimes.
 

·
Premium Member
Joined
·
20,348 Posts
I was thinking about that last night and couldn't remember if I had added that or not. You or your friend know how to figure that out, right? The butterfly portion of the rotor shaft that is part of the mechanical advance has a number stamped on it, which is either 14 or 17. Double this number is the mechanical advance available, so 28 or 34. From there the 28 is best so you can have (or should have) no more than 10 degrees at the crank, so you should back yours down just a few degrees, kind of hard on the starter at this point, especially when warm, and then the heavy and medium springs under there will make it nice and smooth, especially with those 4.10s in the rear. Oh, and too much advance tends to have a history of both bad gas mileage, and broken pistons, so not worth pushing it.
 

·
Premium Member
Joined
·
20,348 Posts
If the carbs are new it shouldn't be an issue. On the other hand, the hole would be used to adjust the resistance on the back side of the vacuum diaphram and it should not have been altered under most circumstances.
 

·
Premium Member
Joined
·
20,348 Posts
You can enjoy it the way it is, or you could experiment just a little bit and see if there is a little bit more to eek out of her. This is kind of where the exhaust gas sniffer comes into play, make sure it isn't on the lean side.
 
1 - 4 of 4 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top