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Discussion Starter · #1 ·
I posted this on other sites but didn't get any answers. I figure this bunch will have more to add to my post.

Searching around for ways to optimize my drive train for when I put my 265 in my car, I ran across an interesting bit of info. Here is the link. http://www.musclecardiy.com/performa...d-winning-car/
Has what seem to be some good insight from a dedicated racer.
Related to this, I am trying to pick the best SLR or Launch ratio I can but not have granny gear in first. I will be upgrading my rearend first to a 12 bolt with 4:11's. With my 2.64 first gear Super T-10 gives me a ratio of 10.85. Based on the Stroke to Weight chart I attached, I should look to be at around 11.6. I am thinking of upgrading to some type of 5 speed to have over drive for trips to the track with the 4:11's. If I have a 2.94 first gear in my 5 speed, I will be at 12.08. It ends up being a .5 bigger. Do you think that with the lack of low end of torque with the 265 that I will still be alright ? None of my racing is going to be hole shot launches. Thoughts and suggestions are all welcome.

I forgot to add, I will be running a 28.5-29 inch street tire. I wonder if that will help offset the .5 over ratio.
 

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My thoughts. You say you've got a 12 bolt and are going with 4:11s. My first suggestion is get the carrier that is designed to use the 4:00 ratio series gears. If you have a 3:00 ratio carrier and use a ring gear spacer you stand an excellent chance of shearing the ring gear bolts, especially with a stick; I'm speaking from experience here.
My humble opinion on charts and theory. According to theory a Bumble Bee shouldn't be able to fly, but it does and quite well. After market high performance parts mfgs. have their theoretical HP and torque charts for their engine kits. I've yet to meet anyone who has come close to those numbers. I'm sure there may be people out there who have I've just never met one.
You've got a fairly heavy car with a smaller engine and probably 2 bolt mains. Getting that weight moving will be putting a heavy load on your crank (hopefully you're using a forged crank) and the rest of the drive train so you don't want to go crazy with your launch. My suggestion, trial and error. I'd start at 4500 rpm and go from there. If the car bogs go up in RPM; if you just blister the street tires go down and/or release a little pressure, not to much though. Just remember, something may be great in theory but practical application is a whole other animal.
Again, my humble opinion
 

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Discussion Starter · #3 ·
Thanks sbauman2 ! To the best of my knowledge, it is a 4 series carrier and I agree I wouldn't want to run a gear spacer and long bolts. I agree that the only way you know your real numbers is from the real world. I was only using the chart as a gauge to have starting point. My car weighs right around 3200 lbs. as it sits and I will continue to do some tricks to make it as light as possible with the little .060 over 265. It is a 2 bolt main, all ARP bolts through the whole engine and it is a 56 265 forged crank with a high end balancing job on the rotating assembly.
I never plan on launching hard. The plan for know is to always rum good street tires. I want it to be a fun streetable car that I can drive to the track and run a respectable time for what the build is. I am just trying to shoot for the most realistic theoretical starting point so I can at least start at what seems to be the best combo and then work from there. I know I see everywhere that it is said your launch ratio should be 9-11. I thought the chart I attached was interesting because it made more sense show a weight to engine stroke comparison. My thinking was and of course it's theory, is that that if I were to be at 12 for a ratio, it might be of a benefit with this little engine because everybody else bases modern day number on a 327, 350, 383 etc...
This engine will be in the 10.5 to 11:1 compression range, mildly ported aluminum L98 58cc GM heads, blocked is decked .010 and domed pistons, with a hydraulic roller cam right under .500 of lift with a 210-220 ish max duration @ .050 lift and a 110-112 LSA. I am going to try a number of different manifolds to see what works best.

I know I am not building 10 second car, I am just trying to build something that is a bit of a step up from my current mild 350. I think the bench racing and challenge of seeing what can be had from this engine with much more modern technology and a properly set up drivetrain is just fun. I know I could buy the off the shelf engine kit for something bigger but is the fun in that !
 

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I think it may take some time to find the optimum launch rpm for the combo and street tires. The combination of a 3000 lb. + car, and a stout small bore SBC on street tires will be interesting to say the least. You may end up at least swapping to a good pair of slicks for the track, so you can keep the launch rpm higher, and stay in the 265's power band.
 

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Discussion Starter · #5 ·
Thanks 1946 Austin. I figured this would a bit of trial and error, just wanted to think about first and try to be in a fair starting place. I don't plan on running it at the track with slicks so my thinking was to get a combo that made it easier on mild launches to keep it from bogging down but not a Granny gear in first.
 

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Bogging down with most street tires shouldn't be an issue if the little 265 has enough HP. I don't swap tires on my Austin at the strip, and it works fine with 3.73 gears, 355 SBC, TH350, and 29" M&H drag radials. I run the same 3.73 gears behind the 464c.i. BBC in my Falcon, with Super T10, and 30" tires, but have to switch rear tires. The 10"x30" Hurst cheater slicks hook up fantastic on the street, but are too hard to hook on a rubber coated drag strip launch. I swap to 10.5x15x30" Goodyear wrinkle walls for the strip. The Hurst will simply spin the entire 1/8 mile.
 
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