Go Back   The Supercar Registry > General Discussion > Technical & Restoration


Reply
 
Thread Tools Display Modes
  #1  
Old 05-10-2020, 04:41 PM
napa68's Avatar
napa68 napa68 is online now
SCR Sponsor
 
Join Date: Oct 2008
Location: Presque Isle, WI
Posts: 3,233
Thanks: 4,361
Thanked 3,070 Times in 903 Posts
Default Quadrajet question

I have a new car I am working on and trying to improve it's cold start / transition performance. The car (71 455 HO Pontiac) will start right away, but it is really rich! The choke and choke pull off is operating just as it should. It will not take any sort of throttle as it gets really rich.

What I did notice is that it appears to have fuel coming out of the primary air bleeds when you try to blip the throttle (and it stumbles). I have not noticed that on any other quadrajets before. Is it a sign of the float being too high? When it's warm, runs great. Plugs look good, and oil does not smell like there is any sort of fuel dilution. Admittedly, I have not checked engine timing. This is a relatively fresh engine build (1500 miles) and about 2 years old.

I am told Cliff Riggles did the carb and built it to the engine specs.

Am I on to something? I just feel it should run much better in cold transition.

Thanks for your consideration,
Tim
Reply With Quote
Click here to view all the pictures posted in this thread...
  #2  
Old 05-10-2020, 04:50 PM
tjs44 tjs44 is online now
Yenko Contributing Member
 
Join Date: Nov 2003
Location: long beach,ca
Posts: 895
Thanks: 3
Thanked 171 Times in 73 Posts
Default

Give Cliff a call or email.He can also be reached on the PY site.Tom
Reply With Quote
  #3  
Old 05-11-2020, 02:34 PM
olredalert olredalert is online now
Yenko Contributing Member
 
Join Date: Dec 2002
Location: Marine City, Mi.
Posts: 8,826
Thanks: 27,252
Thanked 3,758 Times in 1,593 Posts
Default

----My 69 SJ GP had similar problems and I sent the carb to Eric. Couldn't be any better now going on 4/5 years.....Bill S
Reply With Quote
The Following User Says Thank You to olredalert For This Useful Post:
napa68 (05-11-2020)
  #4  
Old 05-11-2020, 04:47 PM
Lynn Lynn is offline
Yenko Contributing Member
 
Join Date: Feb 2005
Location: Oklahoma
Posts: 6,916
Thanks: 32
Thanked 2,473 Times in 1,154 Posts
Default

Could be as simple as a sunk float. Sometimes those floats get saturated and start to sink. Instead of solid brass floats, they are nitrophyl. However, if Cliff recently went through it, this isn't likely. Still possible, just not likely.

The other possibility is the fuel pump. Get a fuel pressure gauge and plumb it inline. Start it up. I would not be surprised if it is 10 - 12 psi. Should be 4 - 6. For some reason, almost ALL of the manufacturers of the new mechanical fuel pumps are using a spring that is TOO STRONG!!! I guess they though if some is good, more is better. That spring determines pressure. Over 7 psi, and most needle and seat valves are just overwhelmed.

Some guys use a needle and seat with a smaller diameter seat. The smaller surface area means it can withstand more pressure before being overwhelmed. I DON'T like this approach, especially on a big cube motor, as that now smaller seat diameter also restricts fuel, and you may starve the engine during a long full throttle run. I have a couple cars I just gave up on mechanical pumps and went to a low pressure electric pump. Kind of a pain, but it is getting really hard to find a good mechanical pump.
__________________
Don't believe everything you read on the internet ... Ben Franklin

Last edited by Lynn; 05-11-2020 at 10:38 PM.
Reply With Quote
  #5  
Old 05-11-2020, 04:53 PM
WILMASBOYL78's Avatar
WILMASBOYL78 WILMASBOYL78 is offline
Yenko Contributing Member
 
Join Date: Jul 2003
Location: new york
Posts: 8,171
Thanks: 1
Thanked 1,597 Times in 491 Posts
Post QJ Issues...

Quote:
Originally Posted by olredalert View Post
----My 69 SJ GP had similar problems and I sent the carb to Eric. Couldn't be any better now going on 4/5 years.....Bill S
X2

-wilma
__________________
02 Berger 380hp #95
Lots of L78 Novas
Join National Nostalgic Nova!
70 Orange Cooler
69 Camaro
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 03:35 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.

O Garage vBulletin Plugins by Drive Thru Online, Inc.