#41  
Old 09-26-2021, 05:48 PM
gtorich gtorich is offline
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Ok thanks for all the comparisons. For kicks I took the vacuum advance off to see if that would change anything. Not really. My initial is at 23 right now and all in at 35 on timing.

After car warms up idle usually moves 1 to 1.5 points on 02. My cruise does seem to get better as the car warms up, but it fluctuates from 11-13.5 depending on rpm.

I am going to put an ask out on a new thread to see if anyone near me is mechanic near me good at Pontiac tripower tuning to have them take a look as another set of live eyes. As u say, hard to do online. Lets see. Appreciate all the help guys. And yes maybe the 62 are right.
Midnight, dont know if this will help or not..........i have a 455 with the Old Faithful cam, but i did run this with my 60919 cam before..........these carbs were done by Dick Boneski.......havent gotten to install my a/f guage, so not sure where my numbers would be but so far no issues whats so ever with this set up. Not sure if this helps or not.

Rich
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  #42  
Old 09-26-2021, 05:49 PM
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LOL, one day im gonna figure why this stuff is always upside down.

Rich

  #43  
Old 09-26-2021, 07:38 PM
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Got them, thanks rich. I can see them. Dick has been helping me, I am going to reach out and see if he has time to build a center for me while I continue to fiddle with this one. just drive it as is for now, i did make it to a show today
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  #44  
Old 09-27-2021, 09:42 AM
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Can someone post a picture of where the idle bypass restrictors are. I never new to check the opening size. I don't know if those were opened up to .052

Thanks , Dave

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Old 09-27-2021, 10:46 AM
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Compliments of Dick b. The two holes in the top corner on each side
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  #46  
Old 09-27-2021, 10:47 AM
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Where the drill bit is

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Old 09-27-2021, 10:51 AM
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I was unaware that it is common to modify some of those things.

Specifically, the power valve hole size, idle vents, and idle bypass restrictors.

I think for my car, just the tubes and throttle base idle mixture tubes are modified.

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  #48  
Old 09-28-2021, 01:03 PM
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Where the drill bit is
Thanks, I will check them this winter

  #49  
Old 09-28-2021, 04:29 PM
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Thanks, I will check them this winter
The size of the idle bypass restrictors are critical if an aftermarket cam is installed. The stock Tri-Power center carbs have them at .043" or .046". I've found that with a cam similar to the RAIV cam, .052" is a good starting point. Some more radical cams require .059" or larger.

The idle tubes in stock Tri-Power center carbs are usually .032"-.035". For a cam similar to the RAIV, the tubes need to be .038"-.040". With more radical cams, the tubes need to be .040"-.043".

The idle vents above the brass tubes should be about .040"

The throttle base idle screw holes are usually .070". I usually enlarge them to .078" so the screws can be adjusted further in with the same flow allowed.

Most stock end carbs have .066" or .068" jets. With a mild cam, I put .070" jets in the end carbs. Any cam similar to or beyond a RAIV, .073" jets.

Center carbs, whether pre-'66 or '66, begin with .063" jets. With a more radical cam, you may need .064" or .065" jets.

I've found that cutting five turns off the power valve rod spring will suffice for most aftermarket cams.

Unless you do the above, your engine will not idle or perform well with an aftermarket cam.

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  #50  
Old 09-29-2021, 07:59 AM
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Thanks Dick

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Old 10-02-2021, 11:33 AM
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just to update here - I plugged the power valve entirely and it did not seem to have a lot of effect at low cruise 2K-3K (still in the 12's. above 3K rpm it did seem to get better with a range of 13-14.5 ish. The car drives fine at cruise, there is no issue - just that dam af meter telling me its not ideal. Going to head out to show on long island tomorrow about 30 miles away, so will see how extended driving does without a pv. i suppose the lack of a pv is masking some other issue, but I am inclined to not put it back in but hard to discern if it delivers any power benefit with seat of pants test.

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Old 10-02-2021, 12:15 PM
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At cuise, the power valve would be closed. When vacuum drops under acceleration, the spring/rod pushes the valve open, effectively richening the fuel/air mixture. The four holes in the power valve are .070" each, so the effect is considerable, compared to the two main jets at somewhere near .063".

I'm surprised you don't notice poor throttle response under acceleration with the power valve disabled. One would expect sluggish response with only the main jets in the circuit. I'm assuming you are speaking of light acceleration without the end carbs actuated.. I've never tried what you've done, but would like to hear from others who may have insight into this scenario.

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  #53  
Old 10-03-2021, 10:20 PM
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Yep. I just wanted to see if perhaps the pv was leaking at cruise. With the plug going in and being tested and cruise not improving, seems like pv is not leaking anywhere. Rechecked float, it’s fine. Put pv back in and am back to where I was a couple posts ago. Dick, I dropped you a pm, if you have bandwidth to take on a project would love to connect. Ty…

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Old 10-03-2021, 11:50 PM
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just to update here - I plugged the power valve entirely and it did not seem to have a lot of effect at low cruise 2K-3K (still in the 12's. above 3K rpm it did seem to get better with a range of 13-14.5 ish. The car drives fine at cruise, there is no issue - just that dam af meter telling me its not ideal. Going to head out to show on long island tomorrow about 30 miles away, so will see how extended driving does without a pv. i suppose the lack of a pv is masking some other issue, but I am inclined to not put it back in but hard to discern if it delivers any power benefit with seat of pants test.
May I ask what your AFR objective is? I don't think your AFR numbers are too bad. Also, Dick can correct me if I'm wrong, but the power piston spring, actuated by vacuum adds fuel at cruise where you have a rich issue. Maybe a spring adjustment?

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  #55  
Old 10-04-2021, 09:29 AM
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WB - maybe that is the problem. I was assuming I needed to be as close to 14.7. as possible to make most HP. Perhaps that is not the case? Like I said, the car sees to drive fine, but hard to tell performance-wise, (which is why i was asking about dyno tuning in another thread). When the richness was really bad - 10ish all the time, i was getting black plugs. plugs now are much cleaner on strap, ring around the edge still has some minor black depending on cylinder. I did move up a spark plug in heat. so maybe I should stop fixating on 14.7?

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Old 10-04-2021, 10:30 AM
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I have tri-power and an O2 gauge as well. My warm idle AFR is 13.5- 14.25. I cruise at 13 - 13.5. WOT is 12.5 - 13. The gauge can bounce around a lot.

If I had 10, that would be a problem. I don't see what you have as a problem. Maybe you could down jet one more size on the center carbs or adjust that power piston spring.

It is better to run a little rich vs. a little lean I hear. Also, from: https://www.safrtool.com/SAFR-AFR-values.asp

6 AFR - Rich Burn Limit (engine fully warm)
9 AFR - Black Smoke | Low Power
11.5 AFR - Best Rich Torque at Wide Open Throttle (WOT)
12.2 AFR - Safe Best Power at Wide Open Throttle (WOT)
13.3 AFR - Lean Best Torque
14.6 AFR - Stoichimometirc Air/Fuel Ratio Value (Stoich)
15.5 AFR - Lean Cruise
16.5 AFR - Usual Best Economy
18 AFR - Carbureted Lean Burn Limit
22+ AFR - EEC / EFI Lean Burn Limit

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  #57  
Old 10-04-2021, 12:20 PM
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WB - maybe that is the problem. I was assuming I needed to be as close to 14.7. as possible to make most HP. Perhaps that is not the case? so maybe I should stop fixating on 14.7?
14.7 to 1 air fuel ratio is when all of the bad stuff is eliminated coming out of the tail pipes.
That is a EMISSIONS and F.E. Number. OEMS are required to run there because of emissions laws.

12.5 to 12.7 to 1 air fuel ratio is where a lot of engines make best power.
Since you are after best power, you have your information screwed up OR
whoever gave you that information was in wrong.

ASSUME got you chasing your tail in the WRONG direction.

KNOW or ASK is much better.

Tom V.

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  #58  
Old 10-04-2021, 01:28 PM
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Yep. I just wanted to see if perhaps the pv was leaking at cruise. With the plug going in and being tested and cruise not improving, seems like pv is not leaking anywhere. Rechecked float, its fine. Put pv back in and am back to where I was a couple posts ago. Dick, I dropped you a pm, if you have bandwidth to take on a project would love to connect. Ty
I did not receive your PM. you can text to 920-450-1040 or email to bocoogto@charter.net

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  #59  
Old 10-04-2021, 09:06 PM
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WB thanks for that table and info on how you are running with a similar setup. Really good info. And yes Tom, that "assume" seems to have once again got the better of me. Appreciate all your guys advice and help. Hopefully it will be useful to other along the way too. But seems like I am not in as bad spot as I thought.

With that said, Dick, I will circle back as I want to build a back up carb that is closer to my original aspiration of larger venturi. I'll drop you a line...

thanks again all.

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