Thread: Secondary woes

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Okay heres the deal, I have a fairly new SBC 350 slightly modded with an Edelbrock performer intake, headers and a rebuilt quadrajet. The deal is that I'lll be cruising down the freeway around 65MPH and I'll open up the secondaries and the engine will start making a popping noise (backfiring/too rich?) at the same time the engine shutters slightly, It only seems to do this when im around 65-70MPH. On the other hand I can be cruising around 45MPH with it whining at 5000 RPM with the secondaries open and it performs top notch. So I don't think its related to engine speed.

EDIT:

It won't shutter/pop at anything slower than 60MPH

And if it matters Im running a 700R4 tranny.

http://www.clubhotrod.com/forums/sho...784#post112784

read this and check those secondaries close 79C10.

Originally posted by 79C10
Okay heres the deal, I have a fairly new SBC 350 slightly modded with an Edelbrock performer intake, headers and a rebuilt quadrajet. The deal is that I'lll be cruising down the freeway around 65MPH and I'll open up the secondaries and the engine will start making a popping noise (backfiring/too rich?) at the same time the engine shutters slightly, It only seems to do this when im around 65-70MPH. On the other hand I can be cruising around 45MPH with it whining at 5000 RPM with the secondaries open and it performs top notch. So I don't think its related to engine speed.

EDIT:

It won't shutter/pop at anything slower than 60MPH

And if it matters Im running a 700R4 tranny.

What do the plugs look like?

I don't know, I'll pull 'em tomorrow and snap pics.

Almost sounds like you are running out of fuel. What kind of fuel pump are you running?

Maybe your vacuum advance isn't pulling off quickly enough when you come up to WOT.

Too rich won't cause "popping", its too lean. Running out of fuel is a possibility, but I'd try new plugs. You can't tell a bad plug by looking at 'em, especially in a SBC, they're plug eaters. Also, don't use Champions, one or two of every batch will quit in a week or so. Plug wires will also cause it.

Originally posted by Oldf100fordman
Almost sounds like you are running out of fuel. What kind of fuel pump are you running?

As far as I know its the stock mechanical one. Also I have a fuel filter hooked up right before the carb and I can see into the filter & sometimes is not even half way full when the motor is at idle, and it won't rise if I hold the motor at a higher rpm.

"I have a fuel filter hooked up right before the carb"
if its a Q-JET there should be a filter in the carb. also. i'd do away with one of them.

Well I assumed since on the front of the carb it said "<------ Filter" that it meant attach a filter before the carb in the fuel line. Heres a pic of my setup, and the level of fuel that you see in the filter is about as high as it goes regardless of rpm.

http://www.xylicon.com/box/otherstuf...left_small.jpg
http://www.xylicon.com/box/otherstuf...ight_small.jpg

So I guess I'll pull the external filter off and see if that helps, or Ill get a new fuel pump.

Thanks for all the info.

there should be a filter behind that big nut. take that one out and use the ext. one. if its made of brass they were bad about stopping up. take it out.

http://www.carburetion.com/diags/4mv.jpg

here is what it looks like.

Originally posted by R Pope
Too rich won't cause "popping", its too lean. Running out of fuel is a possibility, but I'd try new plugs. You can't tell a bad plug by looking at 'em, especially in a SBC, they're plug eaters. Also, don't use Champions, one or two of every batch will quit in a week or so. Plug wires will also cause it.

Ron, I beg to differ.For the past 15 or more years I have been reading plugs.I make a pass, kill the engine pull the plugs and if they look black I keep (leaning it down) two jets sizes at a time.When I reach a (carmel color) I know I am very close.When it hits light tan I stop.To give you an idea of how close I was last time after I switched carbs we went back to the dyno and did a few pulls.EGT averaged 1310 not bad for a guy just reading plugs.I have used this method for many years only to burn just two pistons.The only plugs I really can't read are those on alcohol or when someone has added something to the gas.

erik...sure you can read a lot from a plug, like jetting, oil burning, etc., but you can't tell if its any good by looking at it. Some brand new ones won't fire.

Originally posted by R Pope
erik...sure you can read a lot from a plug, like jetting, oil burning, etc., but you can't tell if its any good by looking at it. Some brand new ones won't fire.

I mis-understood what you where saying.I do agree with the Chaampion statment.I switched from AC TO NGK 5 years back no problems.