Help! 454 bog/die on accel

[Dylan86]

I don't really care if it's edelbrocks info or a guys personal experience I'm just wanting it to run right. I got my springs in I tried the spring according to half my vacuum and it still bogged then threw the 8" springs in and it fixed my bog. So I guess personal experience won this round....Just now need the jet to fix the lean under heavy acceleration.

[rich weyand]

OK, here's what's going on. LynnJr is right in that Edelbrock says the springs should be half the vacuum. (I've been saying the springs in pounds (#) instead of inches, because that's how springs are normally rated, but Edelbrock labels them in inches, to correspond to inches of vacuum.) And that's probably close for most applications. BUT: you and I suspect you are running way lean. The pistons up is the richer position, and you can run an engine way rich and it will still run, but way lean and the fire goes out, as you have seen.

Thus my recommendation: put in the biggest springs and see what that does. Now, once you get the cruise circuit tuned, you may be able to back off a size, see what that does. If it's still OK, do it again. When you get a bog, back up one.

So, LynnJr is trying to hit the sweet spot right off. I am saying go to the heaviest spring first and see what you have. You can always back off -- move the onset of the richer power circuit down the throttle pedal -- and walk to the correct setting by testing. Engines are all so different, they breathe so differently because of the cams, that testing is more valuable than instructions written for the generic case.

I'm curious as to what vacuum reading you get at idle. It may be the case now with the 8" springs that you are *always* in the power circuit -- that the vacuum is low enough that the springs always win, and, given how lean you are, that is helping a lot.

In my case, I think I am pulling about 18 inches of vacuum at idle with my marine cam. I actually had to stretch the 8" springs to get my power circuit to kick in soon enough.

You are still going to be shooting in the dark without getting an A/FR meter on that beast. Do you know anybody around your parts who has one you can borrow?

[rich weyand]

Dylan, another question. When you say "Just now need the jet to fix the lean under heavy acceleration", do you mean when the secondaries start to come in? On the Edelbrock, you can feel it mechanically in the throttle pedal when you pick up the secondaries. Is it running right until then, and going lean when you hit the secondaries? Or is it still going lean before you hit the secondaries?

[Dylan86]

Originally Posted by rich weyand

Dylan, another question. When you say "Just now need the jet to fix the lean under heavy acceleration", do you mean when the secondaries start to come in? On the Edelbrock, you can feel it mechanically in the throttle pedal when you pick up the secondaries. Is it running right until then, and going lean when you hit the secondaries? Or is it still going lean before you hit the secondaries?

I'm not 100% sure to be honest if it's before or after... I don't feel a change through the pedal. All I know is when your giving it more throttle (above quarter throttle accel) it seams to still act lean and feel underpowered like a hesitation. But the bog causing me to not be able to accel unless babying it is gone. I'm running 12-13 inches at idle. And no I have to order a meter and it's over a week away... I also retimed a bit more advanced 35° total. And used the upper vacuum port for my advance. It seems to like that more also.

[rich weyand]

Interesting that it likes ported vacuum. A lean mixture burns slower, so you would think it would like the advance at idle. 35-36* of total advance sounds right to this SBC guy, but I don't know if that sounds right or not for a BB.

At least it sounds like you have it now so it's driveable. Getting the meter on it will give you the answers to a lot of questions, that's for sure!

BTW, for the meter, the bung for the O2 sensor has to be welded/brazed into the exhaust. My recommendation is to weld it into the exhaust pipe a few inches behind the header flange. The sensor has to be at least a bit above horizontal, in the upper half of the pipe, so it doesn't catch water and debris. I had a muffler shop install mine. They cut a 6" length out of the exhaust pipe, drilled the hole, brazed in the bung, cleaned up the threads with a tap, then brazed the section of exhaust pipe back in.

When putting the meter in, I screw the O2 sensor in first. I drop that end of the wire harness down the front of the firewall, and go under the truck and plug in the O2 sensor. Then I hook the wire harness around the drivers side windshield wiper shaft and run it in through the vent window. I put the meter in the recess in the dash with a piece of foam around it to hold it in place (I don't have A/C, so I have that little storage recess) and I plug the meter into the cigar lighter. They say to hard wire it, but it's not a permanent install and the cigar lighter works fine for occasional testing.

[Dylan86]

The trucks not lean at idle. In fact it's a bit rich. So the lower advance seems to be good. And ya I'm going to need to get that meter/ sensor to properly tune this in.