Rochester Quadrajets tend to mystify people because of the various model names assigned to them by GM.
Add to that a redesign in the '70s and the confusion only grows.
In this video we'll learn the different model names and also how to differentiate between early and later-model Qjets. Enjoy!
750 vs. 800cfm Rochester Quadrajets-how to tell them apart
There exists a ton of misinformation regarding the actual airflow capacity
of the Rochester Quadrajet. Not many people know how many variations there
are or how to tell them apart.
Here is a simple video explaining how to identify each size based on
casting design. I will cover the "cfm-limited" carbs in a separate video.
New quadrajet set up
New air-gap manifold and custom/rebuilt q-jet. Sounds good but I still need
to set the timing on the distributor and the carb is tuned already. Hope
you like, nothing to fancy just a few revs and walk around...the Exhaust is true dual no x/h pipe and it has
cherry bomb glasspacks(3 inch)
How to identify 4 barrel carburetors
Here's a guide to help identify the most common 4bbl carbs including
Edelbrock, Quadrajet, Holley and Thermoquad.
There are a few older or more obsolete carbs not shown including Rochester
4G, Autolite-Motorcraft 4100/4300/4350 and Carter WCFB that I'll detail in
the future provided I can actually find one.
'77 Chevy K20: Quadrajet Choke Pull Off and Fast Idle Cam Observations
1977 Chevy K20. 350 crate engine. Rochester Quadrajet 4MV carburetor with
Truck suffers from unexplained hesitation and bogging when in forward
gears. Tends to rev just fine after a few minutes of mixed idling and high
revving. Checking choke operations as well as a possible sticky fast idle
cam as part of the process of elimination.
- Truck is allowed to idle/warm up until 2:25 mark, at which point the
engine is revved to about 2,000 rpm, and can be heard bogging (a hissing
sound can be heard). The fast idle cam is seen dropping. Fuel flow can be
seen in the glass-cased fuel filter right before the carb as remaining
- The engine is revved again about three more time up until 3:00 minute
mark. The engine revs slightly higher, but the hissing and bogging can
still be heard.
- Engine is revved again at the 3:35 mark, slightly past the 3,000 rpm
mark. Hesitation and hissing still evident, but less so than before.
- Engine revved at the 4:25 mark to about 4,000 rpm. No hesitation or
- Transmission is slowly shift through every gear starting at 4:55 mark.
Shifted back into Park at 5:05 mark.
- Engine revved again at 5:10 and 5:17 marks to 4,000 rpm. No hesitation or
hissing is heard.
To read up on the discussion, please visit the following thread:
Setting the timing and adjusting the carb
Set the timing by ear, and got the idle slowed down so I could do a little
adjusting on the carb. I'll do more when it's cold, so I can set the
choke and all. Love the way it's sounding..
1958 Cadillac Runs After 15 Years!
I bought this Cadillac and it hadn't run in 15 years. It was missing the
carburetor and the previous owner I guess thought that was the problem.
Well, the carb was lost by the mechanic over the years. I borrowed one from
a 1963 Pontiac parts car I have. Turns out the fuel pump was bad but I got
it running in 20 second spurts with a gravity feed. I used a funnel, a hose
and filled it with gasoline. It worked until the gas ran out but it was a
good way to test a few things. At least I spark, compression and oil
pressure and that all the valves were opening and closing.