# 65 Tripower idle AF ratio moving around



## Scott06 (May 6, 2020)

Have a 65 389 with 65 tripower. Engine is essential stock except for 068 High Lift cam from Spotts and SE single wire electronic ignition conversion. 

restored a tripower this spring including throttle plate restoration/shafts, drilled out idle tubes per reccomendations from Pontiac Tripower. New floats needles seats etc. 

Installed a AF ratio meter and have a weird situation at idle. periodically during long idle sessions when I'm adjusting things the AF ratio will dip down from 13.8 or so where it seems to idle best as low as 12:1. Some times was floating as high as 14.5. Almost stalls it out at the rich end. 

Was thnking fuel pressure measured about 6 psi so I put a fuel pressure regulator to set it at 3.5-4 psi made no difference. A little stumped maybe thinking fuel pump which is like 25 years old may need replacement or open fuel tank and check the sock on the end? 

Any thoughts? Vacum is steady at 15" or so, never has been as high as I liked but at least consistent


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## Lemans guy (Oct 14, 2014)

Fuel sock, could be. Fuel filter, a rubber line collapsing and opening as fuel pump vacumn sucks on the feed line. Are your rear tank lines where they connect to the frame new and proper rubber for today’s gas? Likewise fuel pump internal rubber diaphragm must be compatible with today’s gas.

Floats in carb could be sticking, broken rubber in a fuel line moving.

A dithering distributor vacumn can can effect timing, as timing effects RPM’s. Just disconnect and plug the vac can and see if the fluctuation goes away. If it dithers in and out at idle it could mess up the idle. I have also repaired fluctuating idle from an improperly shimmed distributor. The gear rides up and down on the cam gear and you cannot get a steady idle.

However more likely it is fuel related, but if you really can’t locate it you can check the distributor gear endplay. Also check whether it does it in park or drive if automatic, is it different with a load on it. May help you diagnose it as well. Worn distributary cap and rotor, or improperly attached distributor cap….this happens easily and frequently. I never replace a distributor cap without verifying with a mirror the exact fit. Put many on I was sure were right, and had other guys do the same, they were certain from the turn and the feel. But the visual check revealed they were catywampas, and that will give ignition problems. But it still runs.

A missing cylinder can cause erratic running as well.

please consider ignition issues as secondary, as your problem is most likely in the fuel system. With steady vacumn you have eliminated vac leak.


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## 67ventwindow (Mar 3, 2020)

Scott06 said:


> when I'm adjusting things the AF ratio will dip down from 13.8 or so where it seems to idle best as low as 12:1. Some times was floating as high as 14.5.


 What are you adjusting? And this only occurs when your doing these adjustments?


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## Scott06 (May 6, 2020)

Lemans guy said:


> Fuel sock, could be. Fuel filter, a rubber line collapsing and opening as fuel pump vacumn sucks on the feed line. Are your rear tank lines where they connect to the frame new and proper rubber for today’s gas? Likewise fuel pump internal rubber diaphragm must be compatible with today’s gas.
> 
> Floats in carb could be sticking, broken rubber in a fuel line moving.
> 
> ...


Thanks for the reply fuel lines filter etc are all new and ethanol koser. Fuel pump ... probably put in around the time ethanol was coming into play but cant say for sure, its taken me 30 years to get this far in the resto...

Ill check the vacum cam as it seems very sensitive to having vac advance on full not ported vacum to idle well. Running about 6 intial plus vac can so 16-18 at idle. I did shim the distributor recently and that defintiely tightened up my spark timing as I had some wander on the timing light historically. 

its not so much running erratic its the A/F ratio swing still idles pretty good unless it gets really rich then stumbles a bit but when the AF ratio (with no adjustments made) leans back out it recovers never really stalls.


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## Scott06 (May 6, 2020)

67ventwindow said:


> What are you adjusting? And this only occurs when your doing these adjustments?


nothing thats the issue. I'll just have it idling for 10 minutes and periodically the AF will drift up and down. thought the pressure regulator would cure it but didnt make a difference, actually seemed to make it worse. Thinking Ill start with fuel pump and opening the tank, its been 30 years since it was open and car mostly sitting .


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## PontiacJim (Dec 29, 2012)

Scott06 said:


> Thanks for the reply fuel lines filter etc are all new and ethanol koser. Fuel pump ... probably put in around the time ethanol was coming into play but cant say for sure, its taken me 30 years to get this far in the resto...
> 
> Ill check the vacum cam as it seems very sensitive to having vac advance on full not ported vacum to idle well. Running about 6 intial plus vac can so 16-18 at idle. I did shim the distributor recently and that defintiely tightened up my spark timing as I had some wander on the timing light historically.
> 
> its not so much running erratic its the A/F ratio swing still idles pretty good unless it gets really rich then stumbles a bit but when the AF ratio (with no adjustments made) leans back out it recovers never really stalls.


Almost sounds like a float or needle/seat issue as fuel may be spilling into the carb just enough before the float can catch up or needle/seat are closed. Just another thing to check.

Make sure your choke is not acting up on you and fluttering around. Maybe wire it wide open just to eliminate it as cause.

Remove the air cleaner to make sure it is not acting as a restriction. Your AF readings should change as often you want the air filter on to do this, but you can at least watch the AF meter and see if it remains steady or it too moves around without the air filter.


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## 67ventwindow (Mar 3, 2020)

PontiacJim said:


> Almost sounds like a float or needle/seat issue as fuel may be spilling into the carb just enough before the float can catch up or needle/seat are closed. Just another thing to check.


 Are you using the two piece inlet valve or a roto disc type ?


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## Scott06 (May 6, 2020)

PontiacJim said:


> Almost sounds like a float or needle/seat issue as fuel may be spilling into the carb just enough before the float can catch up or needle/seat are closed. Just another thing to check.
> 
> Make sure your choke is not acting up on you and fluttering around. Maybe wire it wide open just to eliminate it as cause.
> 
> Remove the air cleaner to make sure it is not acting as a restriction. Your AF readings should change as often you want the air filter on to do this, but you can at least watch the AF meter and see if it remains steady or it too moves around without the air filter.


Choke is open and it does this with or with out the air filter. Ill recheck the needle seat but seems to be ok currently

thanks for the tips


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## Scott06 (May 6, 2020)

67ventwindow said:


> Are you using the two piece inlet valve or a roto disc type ?


This is the needle and seat im using Needle and Seat replacements.


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## PontiacJim (Dec 29, 2012)

Scott06 said:


> This is the needle and seat im using Needle and Seat replacements.



Definitely NOT a fan of that style needle and seat with the flat bottom type rubber seal - that could be your issue if the needle is not closing off the fuel flow well enough and gas is still seeping past the needle/seat.

I would not use anything other than a needle having a taper to seal the seat - a more positive and better seal. I have used those all metal type without the rubber tip - they suck as well and usually had to replace them shortly after using them. it was what was being put in the rebuild kits at the time.









Needle and_Seats for Rochester 2bbl Carburetors


Needle and_Seats for Rochester 2bbl Carburetors



www.carburetion.com


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## Scott06 (May 6, 2020)

PontiacJim said:


> Definitely NOT a fan of that style needle and seat with the flat bottom type rubber seal - that could be your issue if the needle is not closing off the fuel flow well enough and gas is still seeping past the needle/seat.
> 
> I would not use anything other than a needle having a taper to seal the seat - a more positive and better seal. I have used those all metal type without the rubber tip - they suck as well and usually had to replace them shortly after using them. it was what was being put in the rebuild kits at the time.
> 
> ...


Ill try a different needle and seat, easy enough to replace


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## PontiacJim (Dec 29, 2012)

Scott06 said:


> Ill try a different needle and seat, easy enough to replace


Ya, just another thing to try that may do the trick. I find the tapered style needles just seem to seal much better.


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## Scott06 (May 6, 2020)

Just to follow up on this, seems like fuel pressure was the issue. I tried the needle and seat replacement no difference. noticed that it seemed to be taking a long time to refill the fuel bowl after opening carb, replaced 30 year old pump and filter, found issue to be worse…front carb had fuel coming out of it.

reinstalled fuel pressure reg. Issue was the summit liquid filled gauge i was using changes pressure with temp. Set it to 3.5 psi immediately after starting, when it gets hot pressure reads zero … basically useless gauge. Bottom line it works much better now holds 13.5-14.0 afr at idle now doesn’t dip down to 12.0 like it was doing periodically.

have yet to drive it because its cold now and its a convertible with no top.

guess the tripower is very sensitive to fuel pressure? I had no issue with the edlebrock 4 bbl i was running before.

so still have some choke fast idle cam issues to work out and play with jetting. Assume the drift at idle Im seeing is either as good as it gets, related to engine health or vacuum (16-17”), or maybe adjust float drop?

one other question, had some redish deposits in carbs i assume is fuel tank corrosion related. Anyonehave feedback on quality of replacement tanks ? Ames has comments about needing to bend filler neck. If aftermarket tanks suck qualitatively I may just try refinish my tank with sealer etc.


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## Baaad65 (Aug 29, 2019)

Pertaining to the pressure gauge I had the same problem and when I researched it that's what it was, heat expands the oil inside creating pressure which drove the needle to almost zero boy that was a head scratcher as how is the car driving great with no fuel pressure? Simple fix was to pull the rubber plug and drain most of the oil out, now it's accurate but a little shaky, not a big deal.


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## Scott06 (May 6, 2020)

Ill try draining some out thanks.


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