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LT1 to 383 rebuild - Trick Flow 195 Gen X Heads - CompCams LT1 XR276HR12 - 32lb injectors - 1.5 Rock
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Is anyone running and if so could you post a picture of what a taller rear tire would look like on our car? I have MTT-6275: 275/40R17 (25.7” high tire) on the front and looking for what a taller MTT-3472: 305/45R17 (27.8” high tire) would look like on the rear. I know most of us run the same height tire front and back. Interested to see what the older school talker back tire would look like. Thank you.
 

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LT1 to 383 rebuild - Trick Flow 195 Gen X Heads - CompCams LT1 XR276HR12 - 32lb injectors - 1.5 Rock
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Font Material property Gadget Technology Automotive tire
 

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I'll post some pics in a few. I have a 345/40/17 Toyo TQ DR on the rear (about 28") and a 275/40/17 up front (25.7").

I also have adjustable coil overs so I may have my stance a little more raked than a generic non adjustable setup, but I set it up to look good with my 'cruising' setup which has the same height all around (335/35/17 out back).

right now with the 28" tire out back the car is stupid raked. It looks awesome, but It's a little annoying to drive. You have to be very careful not to drag the front on stuff and the car doesn't feel as well balanced in turns as it does with the same height all around. I'm sure leveling out the springs would help some though.
 
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Car is very much a work in progress, still have to work on body work and paint but i've been too busy blowing up 4l60e's. Finally swapping to an 80E.

I think these are my most up to date pics, I have tweaked the stance a little here and there since I set the car up, mostly raising the front up a little. Earlier pics I have of it looked nasty, car was slammed down low and raked like crazy but it was really undrivable with a 3" exhaust. Even as is, I have V band flanges and 3 Pedals LS Swap LT headers that have about the best ground clearance out there for an LS swap long tube and I still scrape up the v bands a bit on dip/steep driveways.
 

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Should also mention, I don't have ABS so no worries there for me.
 

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My overall take on it is the car will look bad ass, won't be dangerous to drive or anything (other than the ABS issue) but it's really only good for a drag car setup. Not beneficial for hard cornering, then again running a drag radial out back usually isn't regardless of the height difference anyway. It definitely has a cool look though and a taller DR is going to hook up easier than a low sidewall so it should be a plus in the traction department.
 

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How much additional traction do your 345/40-17's provide? Just a seat of the pants feeling? Not looking for data beyond spitballing?
The yardstick is what matters. Bad to the bone.
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The Toyos really aren't the greatest drag radial out there, they aren't anywhere near as aggressive of a compound as an ET-R or Hoosier DOT but they are way more streetable. They actually feel great cruising, on the highway, even in corners surprisingly.

But back to traction....from a cold hit, without heating them up and dropping pressure, they kind of suck. From a dig, I'll spin clean through 3rd and the spinning only really stops when I run out of testicular fortitude to stay in it when the car starts to get sideways while really picking up speed in 3rd. Video is a dig, no priming, rolled sort of gently into it off the line, about 75 degrees 20psi and also down a bunch of HP from where it is now (old pulley combo).

When heated up, aired down, on a hot pavement in the summer, they will hook up eventually from slow rolls and when they finally gain traction, it hooks VIOLENTLY (enough to destroy the sprag on my last 60e despite utilizing the overrun clutch in D)

Only ever got the car to one event so far between transmission failures, and it was on an abandoned runway that hasn't been used since the 90's.

Rolled off the line, half throttle till the 1/8th was up, pedaled it a few times all with 100lbs of strapped down ballast in the trunk and the car was still squirrelly at 100. When it finally straightened out and hooked, it pulled like a freight train but was only able to run a [email protected] Hard to see the car (right lane) but you can hear the wheel spin in the tone.
Pass before that I had a shift timing issue I had to work out so didn't shift out of second, ran a [email protected] but my 1/8th mile time was over a second faster than the 12.8 pass (go figure).

That track was ridiculously bad though. Cars with much less power than me were struggling to run anywhere close to their usual times. My buddy's dead consistent high 12 second 01 T/A couldn't get out of the 15's LOL. I also didn't heat them up nearly as much as I should have, the sheer size of them takes a really long burnout to get them up to temp.

Hopefully going to see how they work out on prepped tracks this coming season now that I have the 80e in the car. Really hoping I can get the car into the 10's with them, that's all I want. Down the road i'll put something stickier on it, but for now I like driving it/racing it in "street trim".
 
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Also just a side note, video where I'm in the right lane, coincidentally I was lined up next to a bolt ons PPV. He ran a pretty respectable time given the conditions ( believe a [email protected] 100) but it must have scared the crap out of him when I finally got some traction in the big end because i came by him like a freight train. 😂. Really cool getting to battle it out with another generation of a v8 "Chevy" (holden) sedan.
 
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Also just a side note, video where I'm in the right lane, coincidentally I was lined up next to a bolt ons PPV. He ran a pretty respectable time given the conditions ( believe a [email protected] 100) but it must have scared the crap out of him when I finally got some traction in the big end because i came by him like a freight train. 😂. Really cool getting to battle it out with another generation of a v8 "Chevy" (holden) sedan.
Hey, is this a regular thing at Calverton? Last time I crossed those runways, F-14s and A-6s were still using them :)
 

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My Holden Caprice has a T-56 with a 2.66:1 first gear and a 0.50 sixth gear. The HSV 6 speed automatic has a 4.06:1 first gear and a 0.66 sixth gear
It's easy to see why the T-56 cars often had differential ratios of 3.23 up to 3.91
What year ? Pictures ? I must be mistaken , surprised to see a T56 long after they went to a TR6060.
 

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@Jack R

I would say the car is over geared, but it really isn't . the 3.73's on the 28" tire would put me through the traps at a perfect RPM for the MPH I think the car SHOULD trap on a good, clean pass. The car just needs a much better tire and some adjustments made to the suspension to hook but that's probably not something i'll be doing anytime soon, since I like the car as is and don't really have a desire to turn it into a one trick pony (or put the rear at risk on a sticky tire after spending two seasons breaking built 4l60e's LOL). My tuner swears it's a low 10 second car based on him tuning many CTSV's making the same power on his dyno with roughly the same weight but i'll be more than happy if I could scrape high 10's on the Toyos. If I can't this spring, then i'll probably change my mind about making those changes and putting a good tire on it.

As far as street driving, the 3.73's are definitely a bit much. Even when I had 335/35/17 Hoosier DOT's on the car it still didn't hook well on the street. The 4l80e made power delivery much smoother and more controllable with the longer first gear but now I wind out a bit higher than I'd like to on the highway in OD when I'm running my 26" tire setup (335/35/17). It's pretty good with the 28" tire.

I do plan to swap out to 3.42s at some point but I don't think i'd want to go lower than that. WOT, i'm sure the car will still move out hard with a 3.08 or whatever but it's still a big heavy car, doesn't have the benefit of 6 gears and the 4l80e's shallower first makes me think the car wouldn't have as nice part throttle street manners as it does now if I go too low on the gearing. I'd go with 3.42's just to cut the highway RPM's down a bit and get it back down to where it was with the .70 OD of the 60e.

As far as ride height goes, in some of the pics I posted, I did have the coil overs adjusted with some rake to the car in addition to the dramatic front and rear tire height difference. Since then though, i've raised the front up a bit keep my V band flanges from getting destroyed lol. Now the car sits much more level with the 27/28" tire combo and the front coil overs raised a bit.

6l80e Is a great transmission but it definitely isn't "factory rated" for anywhere near the power levels i'm at. they ARE capable however, in the hands of the right tuner, of handling a lot of power thanks in part to torque management. My tuner has cars making running 150mph in the 1/4 on stock 6l80e's. He tried to talk me into one for the impala, but for a few reasons I decided to go with the 80e. Fitment issues, having to rewire everything/use a different TCM and the cost of building one 'properly' all weighed on me. For every 6l80 or 6l90 you see holding up to 700whp you hear of one popping, even with great tuners, and to build one right costs a fortune. A well built 4l80e is just a lot stronger for a lot cheaper although I really do wish I had 6 gears and a .67 overdrive.
 

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Johnny K, thought this might be helpful. I was able to dig up some really old pics from my old computer of my 96 back when it had Hotchkis springs, 275/50/17 rear and 255/50/17 front Nitto NT450s, rear tires I think were about 3/4" taller than the front.

Sorry for the bad quality, they are a picture of a picture taken on an old digital cam back in 2005. I know I have some on flat ground too, if I come across them i'll post em. Might give you a better idea of what it looks like on a more typical suspension setup. So glad I took the stupid exhaust tips off the American Thunder tailpipes shortly after these pics. Don't know what I was thinking there.

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SSandman , like you don't already know, its always going going to be a balancing act between correct RPM through the traps in the 1-1 ratio gear vs the cruise RPM you are happy with. 🤔
 

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SSandman , like you don't already know, its always going going to be a balancing act between correct RPM through the traps in the 1-1 ratio gear vs the cruise RPM you are happy with. 🤔
Exactly! For me, the balance between E/T and highway RPM's is heavily biased towards highway RPM's. I track the car a few times a year, and it's a mid 90's 4 door land yacht so i'm pretty happy with whatever it does. I do want to be able to drive the car on longer trips, to the track 3 hours away, to out of state shows etc... so highway RPM's is a lot more important to me.

I think the car would feel great on the highway with something as low as a 3.23 but I also worry a bit about how 'light' the car will feel around town in stop and go, especially now with the longer 1st gear of the 80e. It's still a 4400lb car, and I enjoy how you can cruise it around now barely touching the pedal and the car moves around effortlessly at barely off idle RPM's completely out of boost.

Biggest issue for me is there not being any wide size 27 or 28" tall tires out there for 17" wheels that aren't drag radials. . The pilot sports I have in 335/35/17 and 275/40/17 are amazing all around performers but I hate everything about the height. Ground clearance sucks and even with a 3.42, highwayRPM's will be higher than I'd like. If I ran 3.23's, I think ET would start to take a bigger hit then when running a 28" tall drag radial and 60 footing is probably going to be a struggle with a 26" tall DR (not to mention limited choices). The addition of the .75 OD in the 80e didn't help as now i'm fighting that too in regards to highway cruising RPM

So it becomes not just a balancing act between highway RPM and trap RPM with a single tire size but balancing all that with a 2" tire height difference between my street and drag setups.
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... think the car would feel great on the highway with something as low as 3.23, but I also worry a bit about how 'light' the car will feel around town in stop and go, especially now with the longer 1st gear of the 4L80E.
It's still a 4400lb car, and I enjoy how you can cruise it around now barely touching the pedal and the car moves around effortlessly at barely off idle RpMs completely out of boost.
8.48 vs 8.01
5.06 vs 4.78
3.42 vs 3.23
2.56 vs 2.42
Forced to guess, IFF you truly prioritize highway cruising and street drivability over ET or trap speed, how much more PART-throttle are you REALLY gonna need with 3.23 vs 3.42?
You'd just spend ever so slightly more time in 'the lower gear(s)' with 3.23, than you'd with 3.42.
Maybe make your shift points a wee lil bit more eager to downshift with 3.23?
 

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Probably best to follow Jack R's advice as he is one of very few here that has a low 10 second full weight car on 255 street tires. Out of my league.
With a 6L80E, or a 4L80E?

Too bad SSandman can't get his hands on:
1) a 6L90E from an LGH DuraMax van
2) Jeff Green's 4L60E builder
However, in both cases, 4L80E costs less in terms of time, effort, material, and costs.
 
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