Track Pics (dial-up beware)
Race Director
Joined: Jan 2003
Posts: 15,175
Likes: 86
From: State of Confusion
Re: Track Pics (Indynut)
Nice-looking Vette; what's she run (can't make-out the dial-in)?
:confused:
The original tach in my '79 Z28 is dead-on, confirmed by an engine diagnostic machine (eye-balling 4000 on the tach, it ACTUALLY is 3980+), AND a shift-light.
Has the rear-gears been swapped-out, and the speedo-gear not corrected?????
Still not sure whats with my tach, I'm thinking I'm about 500 rpms off at 60mph and as much as 900 rpm off at 98 mph's. Are these tachs know for being inaccurate after 24 years.
The original tach in my '79 Z28 is dead-on, confirmed by an engine diagnostic machine (eye-balling 4000 on the tach, it ACTUALLY is 3980+), AND a shift-light.
Has the rear-gears been swapped-out, and the speedo-gear not corrected?????
Thread Starter
Pro
Joined: Oct 2000
Posts: 629
Likes: 1
Re: Track Pics (Indynut)
Left click on the pics for full size view. Best time this year is 14.03 but that weekend (Big headwind) ran many 14.10's. Went on to take 3rd place in the Street class. The car does run very consistant, just wanna go faster all the time..... :steering: :steering:
Race Director
Joined: Jan 2003
Posts: 15,175
Likes: 86
From: State of Confusion
Re: Track Pics (Indynut)
Best time this year is 14.03 but that weekend (Big headwind) ran many 14.10's. Went on to take 3rd place in the Street class.
Getting into the Semi-Finals is great! 2 more round-wins, and YOU'RE BUYING!!!
The car does run very consistant, just wanna go faster all the time.....
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Thread Starter
Pro
Joined: Oct 2000
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Re: Track Pics (Glensgages)
OK, here's more info on my car. Since I posted I've been under the car and changed the rear diff fluid and check out the numbers. I've spun the tires and counted the revs of the driveshaft and also decoded the rear end. My car has 3:55's in it. It is a 1979, L-48 with an automatic. I have added headers, and an Edelbrock Performer Cam and Intake. I've recurved the distributor. Timing is set at 36 degrees total, like Lars advised with the recurve. Is the stock convertor the problem or is my tach not accurate. A review of the details goes like this.
60 mph's is 3100 rpm
60 foot times 2.13 is the best
almost 5500 rpm at the end of the 1/4, @ 98 mph
car weighs 3640 with me in it
rear end is 3:55
trans is a TH350 and is my next thing to tweak. I'm planning on a total rebuild and also a shift kit and was planning on a new convertor (B&M or TCI with about 2400 stall) to help my 60 foots and also my ETs.
Could my tach be messin me up a bit here or what?
With those gears (3:55's) should I have a better mph than I have?
60 mph's is 3100 rpm
60 foot times 2.13 is the best
almost 5500 rpm at the end of the 1/4, @ 98 mph
car weighs 3640 with me in it
rear end is 3:55
trans is a TH350 and is my next thing to tweak. I'm planning on a total rebuild and also a shift kit and was planning on a new convertor (B&M or TCI with about 2400 stall) to help my 60 foots and also my ETs.
Could my tach be messin me up a bit here or what?
With those gears (3:55's) should I have a better mph than I have?
Race Director
Joined: Jan 2003
Posts: 15,175
Likes: 86
From: State of Confusion
Re: Track Pics (Indynut)
Here's a formula to figger gear ratios, tire heights, RPMs, etc. (you can run it in different configurations...)
RPM x .9 (automatic converter slippage) x.006 (a 'factor', incorporating 'pi', amongst other things) x 1/2 tire height (in INCHES!!!) divided by gear ratio = MPH.....
If yer 'serious' about your racin', try the TCI piece (ATI better yet) for durability. A higher-stall converter will DEFINITELY 'wake-up' your 60' times,.....IF you still hook! What tires you running? Size?
If TOTALLY rebuilding the THM350, and can 'afford' it, consider an 'extra-low gear-set', available from TCI, also. The THM350 gears are 2.52, 1.52, & 1:1, but with the TCI-set, it'll be 2.75, 1.57, & 1:1 (you 3.55s will 'feel' like 3.90s in 1st gear {2.75 x 3.55 div by 2.52 = 3.94x}, yet 3rd remains 1:1, for 'cruising'). ***NOTE*** This'll result in 'wider' RPM-drops on the shift, but my 355" pulls it nicely***
I doubt the gears you run are 'affecting' your trap MPH much; 20+ years ago, my Z ran 14.40s @ 97+ with 3.42:1 gears. Going to 4.11s resulted in 14-teens, but still @ 97-98 MPH.
If you're still 'PULLING' (not just 'reving') at 5500, I think 3.73s/3.90s would maximize your ET/MPH figures (3.73s with the TCI 'low-gears' think they're 4.11s; the 3.90s are like 4.30s...), and if you're still hauling-***** @ 6000 RPM, try 4.11s (feels like 4.56s with the tranny-gears), or 4.33s (4.80s!!!).
I think with sticky tires & a converter, 13s are a cinch; deeper gears (both THM350 & rear-end) will result in mid-13s INTO that head-wind....
P.S. :'77-'79 Z28s, equipped with a stick, came with 3.73 gears STANDARD, with essentially the same motor (LM1) as your L48. If you keep the Rs below 6000, I think the bottom-end will 'take' whatever you try 'dishing-out'; my LM1 did!!!
[Modified by Glensgages, 10:41 PM 9/5/2003]
RPM x .9 (automatic converter slippage) x.006 (a 'factor', incorporating 'pi', amongst other things) x 1/2 tire height (in INCHES!!!) divided by gear ratio = MPH.....
If yer 'serious' about your racin', try the TCI piece (ATI better yet) for durability. A higher-stall converter will DEFINITELY 'wake-up' your 60' times,.....IF you still hook! What tires you running? Size?
If TOTALLY rebuilding the THM350, and can 'afford' it, consider an 'extra-low gear-set', available from TCI, also. The THM350 gears are 2.52, 1.52, & 1:1, but with the TCI-set, it'll be 2.75, 1.57, & 1:1 (you 3.55s will 'feel' like 3.90s in 1st gear {2.75 x 3.55 div by 2.52 = 3.94x}, yet 3rd remains 1:1, for 'cruising'). ***NOTE*** This'll result in 'wider' RPM-drops on the shift, but my 355" pulls it nicely***
I doubt the gears you run are 'affecting' your trap MPH much; 20+ years ago, my Z ran 14.40s @ 97+ with 3.42:1 gears. Going to 4.11s resulted in 14-teens, but still @ 97-98 MPH.
If you're still 'PULLING' (not just 'reving') at 5500, I think 3.73s/3.90s would maximize your ET/MPH figures (3.73s with the TCI 'low-gears' think they're 4.11s; the 3.90s are like 4.30s...), and if you're still hauling-***** @ 6000 RPM, try 4.11s (feels like 4.56s with the tranny-gears), or 4.33s (4.80s!!!).
I think with sticky tires & a converter, 13s are a cinch; deeper gears (both THM350 & rear-end) will result in mid-13s INTO that head-wind....
P.S. :'77-'79 Z28s, equipped with a stick, came with 3.73 gears STANDARD, with essentially the same motor (LM1) as your L48. If you keep the Rs below 6000, I think the bottom-end will 'take' whatever you try 'dishing-out'; my LM1 did!!!
[Modified by Glensgages, 10:41 PM 9/5/2003]
