Thread: 78 Trans Am getting some love
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07-04-2020 08:40 PM #106
Here's a carb tuning log to help you keep track;
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07-05-2020 11:43 AM #107
To help you, I need to know the jets and rods you have installed.
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07-05-2020 01:02 PM #108
My Sunday afternoon snooze got a little long
From the factory it has 56/40 primary needles in it, then I installed 58/44's in. I have some 54/38's that I did not try but they have a smaller diameter which would be going the wrong direction in my mind. So now I have 58/44 primary needles.
Factory primary jets are 89 with 91 and 87 in my kit, I installed the 87
Factory secondary is 86 with 88 and 84 in the kit, I installed 84
I still have the factory 6" hg step up spring in it.
These are the jets available in the 625 cfm kit which will fit in my 750
Primary main jet assorment of .074, .076, .080 and .082
Secondary main jet assortment of .078 and .082
Metring rod assortment of .056/.048, .058/.050, .058/.052, .060/.050, .062/.054 and .064/.056
Step-Up spring assortment of orange, blue, yellow and silver springsSeth
God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis
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07-05-2020 01:12 PM #109
I’m changing oil, plugs, wires, cap and rotor on mine today. In the morning I’ll finish with cleaning the air bleeds and changing the coolant, then out I go! Lol!!!Seth
God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis
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07-05-2020 02:55 PM #110
Dang it! Sorry for ya. I've spent my share of time hooked to a tow, I understand.
Even the old mechanical pumps have their problems (probably due to todays fuel additives). After the 3rd one went out on mine (what a bugger to change, had to pull the inner fender out to get to it), I converted to electric and never looked back.
My cruise got diverted by a honey do list, LOL! I'll have to wait til tomorrow...
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07-05-2020 03:42 PM #111
STREET DEMON FACTORY SPECS;
750 stock jets = primary #89, secondary #86
750 stock rods = 56/40
You installed;
jets = primary #87 (2 steps leaner), secondary #84 (2 steps leaner)
rods = 58/44 (1-1/2 step leaner)
AFR @ idle = 12, AFR @ cruise = 12, AFR @ WOT = 10-11.5
You’re going in the right direction, stay on the primary and rods, should be able to dial it in with them. Change the rods to a 60/50 that will lean the cruise 1 step and lean WOT 3 steps, see what that does. May have to drop primary jets to #82 and rods back to 56/40 rods, to get the cruise. Then if the WOT is still rich 56/48 rods.To lean = smaller jets and/or larger rods
NOTE;
To richen = larger jets and/or smaller rods
1 - jet size change (.003) with no rod change = 2 steps >/< (richer/leaner)
1 - rod size change (.002) with no jet change = 1 steps >/< (richer/leaner)Last edited by 36 sedan; 07-05-2020 at 05:12 PM. Reason: Spelling
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07-05-2020 03:45 PM #112
1,200 feet elevation is one of the reasons it's running rich. Hang in there, you're almost there.
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07-05-2020 05:17 PM #113
Watch the timing for detonation at WOT, 39° is pushing it and may actually lose power.
Good job on the vacuum. AFR gauges are great! Just remember a miss fire will read lean, always check and read the plugs.Seth
God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis
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07-05-2020 05:38 PM #114
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07-07-2020 07:16 PM #115
We're getting close now. I have the 82 primary with the 56/40 needle and its running at 13 cruise and 11.5-12 WOT, that is an average of course, it's real hard to read perfect because of the constant rpm change on WOT. I'll try the 56/48 rods tomorrow and see how it acts. Holley recommends 13.5 cruise and 12.5 WOT, what are your thoughts on that? I know on my gauge as soon as it hits 14 the bar goes into the yellow instead of green. Another question is the AFR gauge will climb to 13.5 -14.5 if I'm climbing a slight hill giving it a little extra gas, is this normal?
On a side note this is kinda fun noticing the changes in how it runs. For the first time since I've owned the car it broke the tires loose when I shifted to second, not just a chirp or a squawk. It has 3.23 gears so their a kinda tall for grabbing rubber in all gears.Last edited by 53 Chevy5; 07-07-2020 at 07:50 PM.
Seth
God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis
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07-07-2020 08:13 PM #116
Almost there, 11.5-12 WOT is GREAT (I prefer this for WOT). What do the plugs say?
13 cruise is a good cruise, but a little on the rich side. Great for responsiveness, but mileage will suffer a little. 14 is a better compromise (let me think about the work around on this). What do the plugs say?
13.5-14 on slight load means the enrichment circuit is not coming in soon enough, install Heavier springs and it'll pull better.
Here's a chart that will help;Last edited by 36 sedan; 07-07-2020 at 08:18 PM. Reason: Listed spring tension wrong, corrected from light to heavy
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07-07-2020 08:20 PM #117
Here's a spring chart that will help;
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07-07-2020 09:43 PM #118
Install the 58/44 rods, it will lean cruise and WOT slightly.
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07-08-2020 11:10 AM #119
I think I just got myself into trouble. The TA carb It's getting closer to being tuned in, and I would like some real world 1/4 mile times to compare some adjustments. I was wondering how to measure times accurately and then all sudden I thought, there has to be an app for that, yep, I was right lol. I found one that will start as soon as your car starts moving, and it will measure and keep track of anything you want. This could end up costing me some money lolSeth
God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis
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07-08-2020 08:33 PM #120
Here is my nightly update, I drove it again with the 58/44 rods in and it seemed like everything was just a bit rich yet, low 13's and low 11's, a bit richer than what I thought it had the other night. I put in the 60/50 with the 82 primary that are in now vs the 87 that were in there the last time I tried them and my numbers are nearly perfect. 13.5-14 cruise and 12.5 WOT , 12.5 is leaner than you like, but still good? The only issue I have yet is it will still lean out with slight throttle up to 15-16, and that is with my heaviest spring, the silver one. The motor does start to run out of steam at about 5000 rpm's but it seems to pull real good up to 4500 ish. I was thinking about bumping up the secondary jet again. every time I type this the engine is too hot to pull plugs for youSeth
God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing. C.S.Lewis
Welcome to CHR. I think that you need to hook up your vacuum advance. At part throttle when cruising you have less air and fuel in each cylinder, and the air-fuel mixture is not as densely packed...
MSD 8360 distributor vacuum advance