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#41
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Rich |
#42
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LOL, one day im gonna figure why this stuff is always upside down.
Rich |
#43
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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
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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 |
#45
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Compliments of Dick b. The two holes in the top corner on each side
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#46
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Where the drill bit is…
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#47
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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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1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#48
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Thanks, I will check them this winter
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#49
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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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BONESTOCK GOATS '64 GTO Tripower Hardtop (Wife's Car) '64 GTO Tripower Post Coupe (My Car) '99 Bonneville SE Sedan |
#50
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Thanks Dick
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#51
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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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#52
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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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BONESTOCK GOATS '64 GTO Tripower Hardtop (Wife's Car) '64 GTO Tripower Post Coupe (My Car) '99 Bonneville SE Sedan |
#53
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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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#54
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Quote:
__________________
1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#55
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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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#56
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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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1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#57
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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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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#58
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Quote:
__________________
BONESTOCK GOATS '64 GTO Tripower Hardtop (Wife's Car) '64 GTO Tripower Post Coupe (My Car) '99 Bonneville SE Sedan |
#59
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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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