Click on image for the lowdown. 
====
| | | Forums66 Topics128,077 Posts1,056,013 Members48,433 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: May 2007 Posts: 6 Junior Member | | Junior Member Joined: May 2007 Posts: 6 | I'm having a real bad lean problem with the 5200 holley I just put on my truck. It runs great on the primary but, backfires through the intake when the secondary opens. I just went through the dizzy new points, condenser, cap, rotor, plugs. The vacum and dwell are good, the vacum advance is working, and the timing I've ran from 4btc all the way to 12btc. I've done quarter turns on the air/fuel screw from a turn all the out. The sweet spot is about 3-3 1/2 turns. Still the same so I think it's got to be the jets. Anyone got any insight or suggestions??? Right now it's running a .60 primary and .50 secondary. Oh and yeah I even rechecked the float on the brand new rebuild I got from Langdon's. You never know ;-) | | | | | Joined: Nov 2006 Posts: 677 Shop Shark | | Shop Shark Joined: Nov 2006 Posts: 677 | vindog420,
Does it have a power valve ? The little rubber diaphragm has a tendency to tear, It is especially vulnerable to engine backfires. When the engine sneezes back through the intake manifold, it generally will kill the power valve.
It's just a thought...
420 ? Hmmm...Lol
Some people are like Slinkies, Their not really good for nothing... But they still bring a smile to your face when you push them down the stairs. 1951 3100 350 TBI Gallery Toddzilla... "$old" | | | | | Joined: Jun 2004 Posts: 8,597 Riding in the Passing Lane | | Riding in the Passing Lane Joined: Jun 2004 Posts: 8,597 | Seems like the secondary jets are usually larger then the primary.
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne SuperIn the Gallery Forum | | | | | Joined: May 2007 Posts: 6 Junior Member | | Junior Member Joined: May 2007 Posts: 6 | OooOooOoo I gots it figured out. The fuel pump went south. Got a new one under $20. Stovebolts are fuggin' great. Thanx for all ya' alls help.
ViNDoG | | | | | Joined: Oct 2005 Posts: 1,317 Shop Shark | | Shop Shark Joined: Oct 2005 Posts: 1,317 | I've run both the single Holley and the dual Carter/Webers on my 235....discovered that the mechanical pump supplied a little too MUCH pressure. Added an inexpensive adjustable regulator and inline gauge.(AutoZone) I keep my fuel pressure at 3-3.5 pounds at the carb and have had no problems with starving or flooding, or dumping fuel into the intake after I shut down the engine.
Dave | | | | | Joined: Dec 2000 Posts: 506 Shop Shark | | Shop Shark Joined: Dec 2000 Posts: 506 | vindog,
If your 3+1/2 out your idle jet is too small. The idle jet is under the brass screw on the choke side (primary side) on the Holley/Weber 32/36. If you are running a 235 chevy with some mild cam and headers you'll need a 65,70 or 75. The idle circuit takes you all the way up til about 2000 rpm. Put in a 65, set the idle down low without stalling, and readjust so it is not more than 1+1/2 out. If its out more than 1+1/2 put the 70 or the 75 til you have it adjusted out not more than 1+1/2 out with a good vac 19+. Thats your first step before you start changing main jets, air or emulsion tubes. Put on a good holley regulator that you can adjust down to not more than 3+1/2 lbs, chevy pumps can put out as much as 7 lbs, way too much for the sensitive weber needle and seat.
"Drugs are money, money is power, power is security." - Kent Heiner
Nedrow population 2212
Carbon footprint family of 2/11 tonnes of CO2/yr
| | | | | Joined: Oct 2005 Posts: 1,317 Shop Shark | | Shop Shark Joined: Oct 2005 Posts: 1,317 | 52 PU...some very useful information! And the more I think about it, many of the Holley/Weber, Carter/Weber problems that folks might experience, in addition to getting rid of vacuum leaks, are related to excessive fuel pressure. I used a regulator and gauge when I added the single H/W to my old engine and also on my new engine with the dual Carter/Webers. I've experienced no problems what-so-ever, all the way from idle up through the secondaries.
This may be the key to getting good performance right out of the box.
Dave | | |
|
|
