Technical SBC question

have been running lakester headers with baffles...car ran flawlessly....changed to block hugger headers with flowmaster mufflers

the engine runs very well thru entire range, low speed and high and acceleration, however it now has a slight blubber when leaving the line, only lasts for a sec but its there and it wasn't before...has a new edelbrock carb and engine is in primo shape, 68 350, 4 bolt main, auto tranny....before i start adjusting this and that, would like some input as to what may be causing the blubbering...its not a stumble but a blubber for a second as soon as you step on the throttle...also, when idling in the garage it smells fat, so this may be the issue, but the plugs are not sooty, but brown, not tan...thanx in advance guys

 

Increased back pressure I'm guessing? Maybe needs a little more squirter?

 

Video of the issue please

 

A metering rod and spring change may take care of it. Download the tuning manual from edelbrocks site, lots of tuning info there.

 

I agree with mad mikey. Start the car and open the covers holding the metering rod's and pistons. With the car running, the rod's should be sucked down into the jets. If they are bouncing at idle, you need weaker springs under the pistons. If the rod's are bouncing, change the springs. If the rod's are down, try a bigger rod diameter.

 

Lloyd may be right. The new system may be a little more restrictive compared to the old headers.
But it might actually be slightly richer. I would start with leaning out the idle screws a little and maybe put the accelerator pump levers in the leaner (less squirt) position. Those changes are easy to back out of if they don't help.

 

Hey I've been backwards before Bob lmao!

 

Just a quick update on this issue....I picked up a tuning kit and found that the metering rods were down at idle but would not pop up when blipping the throttle...I changed to the next stiffer spring and it works perfectly...at idle the meter is planted down, blip the throttle and the metering rod jumps open.....drive down the road and the blubber or flutter (whatever it actually was) is gone so I am assuming the engine needed a little extra shot when leaving the line....I kinda figured this as I had tried to move the accelerator pump to the longest shot hole and it helped, so here's where I looked when I got the kit.....moved the accelerator link back to the middle and next stiffer springs did the job......thanks all for making me look this direction...

 

Thanks for the update, glad you got it all sorted out!

 

Thank you for posting what you did & how it worked. !!

 

Glad you got it sorted out . I think you will find as you learn more about the edelbrock carb, they are pretty easy to tune and dial in. Thanks for updating us. Mike.

 

block huggers often = reversion.

The problem may be that the exhaust is traveling back up to the valve. Short tubes into a collector have that problem sometimes.

 

I think your right.....I was surprised when I had to change to a stronger spring...was expecting to need a weaker spring