1968 Buick Skylark
Just did an LS sway with a 5.3. Runs great stop sign to stop sign BUT pops at appx 50% throttle.
**I've removed the linkage to the rear butterflies, to isolate primary, reinstalling it does not change the POP**
I've built and tuned many NA carbs... BUT i have more to learn with the blow thru.

If i knew the ballpark set up on the carb, i would be able to determine if the "POP" is rich or lean.
with the carb hat and turbos, i can't tell.
I understand that the O2 sensor read oxygen and will read lean when not burning all the fuel..
so i might have a rich back fire and a lean meter reading....
Thanks!

SET UP
JunkYard gen3 5.3 .030 ring gap
MSD 6014 "Set to-Truck HO"
Stage 1 cam
Twin GT35's
Aeromotive pump and regulator
Holley 750 HP
QuickStage- Boost ref power valves primary and secondaries.
Holly carb Hat
Vent tube extensions appx 8" long Pri/Sec

E85

Primary
IFR .032"
Jet #84
PVRC .082"
BRPV 1 turn in from flush
AB 70/31
50cc

Secondary
IFR .032"
JET #90
PVRC (stock/not drilled) .056
AB 70/31
50cc

 

Hey Tim..let me see if i can help you with that POP.
looking at your jetting you should be close enough to NOT be have a backfire.
You didnt mention your sec. power valve setting..
my exp try setting the front PV in 2 turns in and the rear 3 turns in.. that should help.
you're looking to open them when boost reaches appx 3lbs Pri/ 7-10 lbs rear.

WOW hey Tim..That did it.. Thanks a Million!!! You are the best!

 

So... talking to yourself on a forum?

 

FYI.
Pop is lean.
Rich will struggle but drive thru it.
Based on the air bleed config I would expect it to lean pop.
Bleeds are big and IFR is small.

You didnt mention if it lean popped in boost at 50%. ???

 

The answer was in the air bleeds.
tbird was a big help.
He suggested
.042 IFR
.059 LSB
.018 HSB

i simply put wires in the bleeds to test.
Motor was dead rich @ 9.0AFR's
Also recommended to add timing, i put it at 30*
Problem fixed!
To the track for testing...