Pontiac GTO Forum banner
1 - 10 of 10 Posts

· Registered
Joined
·
9 Posts
Discussion Starter · #1 ·
So finally finishing my mechanical freshen up on my 83k original mile GTO. Installed an original rebuilt Delco 6550, ran great at first, but then it started flood the center carb after it warmed up. Checked the pressure and it is putting out 7psi. Specs say 5 to 6.5 but I keep reading that 3-4psi being recommended. Any ideas besides pressure regulator?

Thanks
Vehicle Car Motor vehicle Auto part Gas
 

· Registered
Joined
·
9 Posts
Discussion Starter · #3 ·
Hi rocket6t5.

Have you verified that your center carb float level is correct?
View attachment 160966 View attachment 160967

Have you tried using Phenolic carb insulators. As I’m sure you’re aware, the ethanol in todays fuel (some states have more than others), reduce the boiling point of the fuel which causes them to seep out of the carbs.

Float level is correct. Arrived yesterday, installing phenolic insulators today!
I'll let you know how it turns out.
 

· Registered
Joined
·
218 Posts
So finally finishing my mechanical freshen up on my 83k original mile GTO. Installed an original rebuilt Delco 6550, ran great at first, but then it started flood the center carb after it warmed up. Checked the pressure and it is putting out 7psi. Specs say 5 to 6.5 but I keep reading that 3-4psi being recommended. Any ideas besides pressure regulator?

Thanks
View attachment 160965
7 is too high for a tripower.

I ran into same issue on my 65 set up. installed new fuel pump, flooding out front carb... installed the pressure regulator that pontiac tripower sell works great about 3.5 psi.

if you haven‘t i would check the float isnt damaged and needle and seat is free of debris abefore doing the regulator.
 

· Registered
461 stroker 1967 GTO Convertible
Joined
·
113 Posts
Yep, tripower need 3-4 psi max to not flood.…ask me how I know.

Check out the guys at pontiactripower.com, lots of good info there including their dvd and plenty of parts. If you email them they will tell you to install a regulator, im running a tripower on my butler motor and it’s set to 3.5 psi, making over 500 hp.
 

· Registered
461 stroker 1967 GTO Convertible
Joined
·
113 Posts
7 is too high for a tripower.

I ran into same issue on my 65 set up. installed new fuel pump, flooding out front carb... installed the pressure regulator that pontiac tripower sell works great about 3.5 psi.

if you haven‘t i would check the float isnt damaged and needle and seat is free of debris abefore doing the regulator.
This is exactly right.
 

· Registered
Joined
·
488 Posts
The redeeming factor on Tri-Powers over a Quadrajet is the Tri-Power engine has three needle and seat inlets to draw fuel from. The combined inlet area allows a much lower fuel pressure and still deliver all the fuel the engine needs.

I've hid the Holley 1-4 pound regulator about 4" up from the fuel pump and it's out of sight from the top of the engine bay. While we really didn't consider gravity and orientation of the regulator when we put it in, it has been totally happy running in a vertical position.

A few years ago we received some bad floats made in China. The solder was okay for several months after installation but gave up allowing the float to start to sink and flood out the engine. My guess was the float was air tight until there was a spot where possibly the soldering flux and not the solder was keeping it sound, and the flux finally was dissolved by the gasoline. We had one float go bad and replaced it, then a few months later the second one gave up. At that point we replaced the second and third floats and no new float problems.
 

· Registered
Joined
·
9 Posts
Discussion Starter · #8 ·
The redeeming factor on Tri-Powers over a Quadrajet is the Tri-Power engine has three needle and seat inlets to draw fuel from. The combined inlet area allows a much lower fuel pressure and still deliver all the fuel the engine needs.

I've hid the Holley 1-4 pound regulator about 4" up from the fuel pump and it's out of sight from the top of the engine bay. While we really didn't consider gravity and orientation of the regulator when we put it in, it has been totally happy running in a vertical position.

A few years ago we received some bad floats made in China. The solder was okay for several months after installation but gave up allowing the float to start to sink and flood out the engine. My guess was the float was air tight until there was a spot where possibly the soldering flux and not the solder was keeping it sound, and the flux finally was dissolved by the gasoline. We had one float go bad and replaced it, then a few months later the second one gave up. At that point we replaced the second and third floats and no new float problems.
I'll know a little more today, hopefully it's finely sorted. But it turned out to be two issues. 1st was the pressure which was too high, then after installing the Holley it was still flooding. It wasn't pouring gas into it by like before but just stumbling on acceleration. 2nd issue turned out to be the "new" seat was manufactured a hair too small and fuel was coming in at the base the seat, gasket should have helped but didn't. New needle and seat installed and going back on the car today. I'll keep you all updated.
 

· Registered
Joined
·
9 Posts
Discussion Starter · #9 ·
I'll know a little more today, hopefully it's finely sorted. But it turned out to be two issues. 1st was the pressure which was too high, then after installing the Holley it was still flooding. It wasn't pouring gas into it by like before but just stumbling on acceleration. 2nd issue turned out to be the "new" seat was manufactured a hair too small and fuel was coming in at the base the seat, gasket should have helped but didn't. New needle and seat installed and going back on the car today. I'll keep you all updated.
Car is up and running, finally! Running too rich, so installing new jets today!
Thanks for all your input!
 

· Registered
Joined
·
218 Posts
Car is up and running, finally! Running too rich, so installing new jets today!
Thanks for all your input!
Im running a basically stock 65 389 only variance is spots 068 high lift cam which i think is same as a summit 2801…

running 63 jets in center carb and 70’s on end carbs . This is what pontiac tripower guys recommended. On the afr meter had like 13.5 at idle 14.5-15.5 part thrtottle cruise and if i recall correctly was 13.0 give or take a tad at WOT. I tried 61 s in center didnt seemed better with the 63 s, certainly a touch rich but doesn’t seem to ping except a touch if accelerating in too high a gear. i think i need to bring my total advance down a few degrees…
 
1 - 10 of 10 Posts
Top