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‘65 GTO, 400, 4spd, Tri-Power
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Discussion Starter · #1 ·
Just getting my fresh tripower setup running this weekend for the first time since swapping from 4bbl. Its finally running pretty well, lots of power, idles ok'ish (still tweaking the air/fuel mix). Got the overheating issue solved by removing the thermostat (thanks lust4speed for the tips in the other thread).

Now my issue is that when I stomp on the throttle and release it (in neutral or when changing gears), the RPMs return very slowly, so when going through the gears, it wont drop down fast enough to properly shift. Its responsive when on throttle, but very slow to return when letting off.

Throttle pedal/cable/linkage appears to be working fine, no lag or anything hanging up there, and returns quickly, so its pointing to something in the carb or fuel delivery. I am running a fuel pressure regulator just before the filter and have tried adjusting that, but dosent seem to change anything (currently set to around 4psi)

Any ideas?
 

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Just getting my fresh tripower setup running this weekend for the first time since swapping from 4bbl. Its finally running pretty well, lots of power, idles ok'ish (still tweaking the air/fuel mix). Got the overheating issue solved by removing the thermostat (thanks lust4speed for the tips in the other thread).
Now my issue is that when I stomp on the throttle and release it (in neutral or when changing gears), the RPMs return very slowly, so when going through the gears, it wont drop down fast enough to properly shift. Its responsive when on throttle, but very slow to return when letting off.

Throttle pedal/cable/linkage appears to be working fine, no lag or anything hanging up there, and returns quickly, so its pointing to something in the carb or fuel delivery. I am running a fuel pressure regulator just before the filter and have tried adjusting that, but dosent seem to change anything (currently set to around 4psi)

Any ideas?
Hello Jesse - Did you ever get an answer? I have the same issue and see that the Idle Vent Valve could be the problem as the throttle return spring isn't strong enough to push up the tab. Would like to know how to properly adjust it rather than just add another spring or start bending stuff. Or find out the problem is somewhere else.
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1967 Lemans 1967 GTO parts car
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I just went out and tried the vent on my 64 tripower setup. Using the side of my finger to open the throttle i could barely feel the difference when it lifted the cap off the vent. The carb has not been rebuilt. Should be an easy check if its the vent. Its just the one screw.
 

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‘65 GTO, 400, 4spd, Tri-Power
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Discussion Starter · #4 ·
Havent figured out my issues yet, but currently have a shop going over the car that knows a lot more then I do about carbs, so hoping they can figure it out. They have so far found a ton of vacuum issues, as well as rear cab float (tri-power) was cracked/leaking and sinking causing flooding...likely the cause of most of the stalling out/etc. Will update!
 

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1967 Lemans 1967 GTO parts car
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Good to hear you are making headway with your carbs. I think I should double check the floats while its on the bench. Making 50 year old parts reliable means triple checking everything twice.
 

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Havent figured out my issues yet, but currently have a shop going over the car that knows a lot more then I do about carbs, so hoping they can figure it out. They have so far found a ton of vacuum issues, as well as rear cab float (tri-power) was cracked/leaking and sinking causing flooding...likely the cause of most of the stalling out/etc. Will update!

Hmmmm. Guess the reputable specialist who went through your carbs isn't so good? Seen claims like this before and the "specialist" was a self applied label so he could charge $$$ for half baked work. At least you are moving forward.

JesseLyon - "The carbs and intake were purchased used on Craigslist and I had them all rebuilt by a reputable specialist. He said they were all in fine shape, and that I "shouldnt have any problems".
 

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‘65 GTO, 400, 4spd, Tri-Power
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Discussion Starter · #7 ·
Hmmmm. Guess the reputable specialist who went through your carbs isn't so good? Seen claims like this before and the "specialist" was a self applied label so he could charge $$$ for half baked work. At least you are moving forward.

JesseLyon - "The carbs and intake were purchased used on Craigslist and I had them all rebuilt by a reputable specialist. He said they were all in fine shape, and that I "shouldnt have any problems".
That’s right Jim. You get what you pay for!
 

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The 16 year old bought himself a quad. Chain broke and cracked the case cover. Running perfectly till then, the story goes. Replaced the case cover and put gas in it. Float sank like a stone, fuel pouring every where, shut off the fuel. Petcock leaks more than the bowl. Get the carb off and he shows me the bowl. I asked where the bowl gasket is, he tells me there is none. I show him where Suzuki has a different opinion on the need for a gasket. I dont trust others work until I see what they have done.
 

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Just a stab but can you or did you have someone mash the throttle while you watch the linkage? Did you try a heavier spring or tighter position? Linkage lubed good? Nothing too loose where a nut gets caught dragging on an angle if you know what I mean? Check the throttle blades with the carb off ? Did you disconnect carbs one at a time as to eliminate where a problem might be? Had a tripower in the mid '80's but didn't have this problem that I can remember...just trying to give you a light bulb on moment 👍
 

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Discussion Starter · #10 ·
Just a stab but can you or did you have someone mash the throttle while you watch the linkage? Did you try a heavier spring or tighter position? Linkage lubed good? Nothing too loose where a nut gets caught dragging on an angle if you know what I mean? Check the throttle blades with the carb off ? Did you disconnect carbs one at a time as to eliminate where a problem might be? Had a tripower in the mid '80's but didn't have this problem that I can remember...just trying to give you a light bulb on moment 👍
sorry, should have stated that this issue seems to have been cleared up with fixing a bunch of vacuum leaks and replacing the bad float. We’re now on to a bit of hesitation at low throttle which appears to be fuel pump related...but it seems fixing one issue just leads to another. Maybe time to stop chasing problems and do Pontiac Jim’s concourse Restoration ;)
 

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LOL. What fun would our cars be if we were not chasing/fixing/improving/upgrading/modifying one thing or another. How boring it would be to have a turn key car that you just drive. That's why I own a new car - that what they are for. (y)
 

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Sorry didn't see that, you know what they say most carburator problems are really timing issues. Isn't fuel pump problems usually related to high rpms? Have you watched your fuel pressure gauge when accelerating, is it dropping bad, I would think there's enough fuel in the bowls for mild acceleration. Did you bump up your pressure on the regulator? I'm running 5-7 psi with a 110gph pump. Does it do it when the motors hot..fuel boiling away? Mild acceleration means the problem is in the center carb?
 
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