Renwick

I had posted about this a little bit ago then I went to correct a typo in the title of the post and the thread got deleted somehow.

Long story short us that I got a Corvette with a 434 stroker in it . Dyno was 550 HP at 5800 RPM and torque was 505 at 5000 RPM. The cam is a Lunati 10120705. I don't know a lot of the other parts because it was built before I got it and the previous owner died.

My questions were

1. Given the dyno results and cam what torque converter and rear gear combo would be good. I want it to be a fast street car with potential to do drag racing and not primarily a drag race car. I don't want to lose the ability to drive on the highway.


2. Since I can forsee the possibility of eventually increasing horsepower or using nitrous for dragstrip runs at some point I'd like to have the transmission and rear end be able to handle that. It has a TH400 automatic and I know it can be built up with a 36 element sprag, etc. to handle 1000+HP. Is this the best option? Are there other transmissions that I should consider. Are there any transmissions with overdrive that can handle 1000HP since then I may be able to but a higher rear gear in it?

3. I have read the stock IRS can't handle that amount of horsepower. I have heard about 12 bolt conversions from Tom's, Ford 9 inch conversions, and the Ridetech rear end from the 48 hour Corvette. Are there any other options? What are the benefits and drawbacks of each?

And before someone asks why I want to build a rear end and transmission capable of handling 1000 HP in a car that has half that I'm already considering changing the rear gear and transmission so if I do that I may as well build it tough the first time instead of having to do it again later if I ever do modify the engine.


Before it got deleted GKull suggested an overdrive trasmission with 3.7 or 4.11 gears. Now that would mean only a 4L80E or 700R4. 4L80E requires a computer and I have heard the 700R4 can't handle high horsepower well.

Now using a beefed up TH400 would be easiest but wouldn't have overdrive so would likely require a different rear end ratio, unless I'm wrong, because there is no overdrive. The Tom's 12 bolt is only available in 3.73 and 4.11 gears. Would 3.73 gears be bad for my current engine build given the dyno results without overdrive?

Renwick

My math could ge wrong but I calculated best potential 1/4 mile time and speed with this

http://www.wallaceracing.com/et-hp-mph.php

It gave me 130 mph as the speed.

I then put it in this equation to find the best rear gear

http://www.badasscars.com/index.cfm/...rod/prd446.htm


(RPM x Tire Diameter)/ (MPH x 336)

(5800 x 25)/ (130×336) = 3.31

so something around a 3.5 rear end per this equation.

the page for the cam suggests a 4.11 rear gear


https://www.jegs.com/i/Lunati/638/10120705/10002/-1

So I'm not sure. What would be best with or without overdrive.

Renwick

Before it got deleted Gkull said

"While driving and drag racing my 79 Vette it was my POSI cases that always broke. So I went to Tom's best posi unit something like a Stage 8's. Richmond gear 4.11 with HD everything in the stock 8 3/4 IRS. When you break your outers buy the best from Tom's. Everything has to be heavy duty down to the 500+ pound rear springs. All my differential is solid mounted. If you add in the rear end and the suspension upgrades you have about $5000 invested in the rear end area using a 8 3/4 stock iron IRS built to exceed your present motor and a 125 shot . 9 inch irs is closer to $10,000 solid rear axles with 4 link, but then you need a roll cage. so that could be more than $10k. I use 12 inch slicks and everything is fine"

So now I'm wondering why would I need a Roll Cage with a solid rear axle and not if I kept IRS? Figured that would be a given for racing regardless.

Also cost isn't a big issue for me. Mostly just being able to find someone to do it and have it done right. I'd rather pay $10k once than pay $5k now and the have to pay another 10k later if the first thing wasn't good enough.

gkull

4 link drag racing narrowed solid axles rear ends require a specialized rear cage for attachment points

C3 vettes can run any stock configuration IRS.

gkull

Where is the rest of the original post that I made?

Renwick

For some reason the whole thread got deleted when I tried to correct a typo. I'm not sure. I had to redo the whole post.

Renwick

Does it still need that if I use this?

http://autofabcart.net/1968-1982corv...4-linkkit.aspx

fishslayer143

One question...Did you recently win the LOTTERY? Cause you are about to spend an assload of cash to make that car have and handle 1000 HP... or is this just a wish list?

Renwick

I didn't win the lottery but I have enough money. I figure if I spend say $15k on the rear end, $5-7k on the trasmission, and $5k on brakes that's less than a new Corvette plus I always wanted a C3.

Since I was a little kid and I saw a 77 Corvette for sale I always wanted one. Being a little kid at the time I had no money and offered to mow the owner's lawn forever if he would sell give me the car. He didn't take me up on it. But I stayed obsessed with Corvettes my entire life and read about them. I got really interested in the big blocks like the L88 and ZL1 and the stuff Lingenfelter was doing in the 80s and just dreamed of building a high horsepower monster Corvette.

I worked my butt off for many years. Now I can finally can do what I always dreamed of. Some people spend money on expensive vacations or other things. This is what I want to spend my money on. So no it isn't a joke post or just a wish list. I am trying to formulate a plan to actually do this.

AGrey

Good for you Renwick! I don't have any knowledge to provide you but I wish you well in your endeavor!

Renwick

Thanks!

gkull

I'm not sure how that 4 link fits.

bmans vette

Here's your original thread on this subject.

Good luck with your project. Welcome to the forum.

Bman (Dennis)

https://www.corvetteforum.com/forums...questions.html

ajrothm

I'm not sure what happened to my reply before but... it all depends on how fast you want to go. If you are shooting for 9s, I'd do the 12 bolt IRS build...If low to mid 10s, say 1.45 and slower 60's, a "Super 10 bolt" built by Mike Dyers or Gary Ramadei will hold hp. With 550 hp, you're not gonna trap 130 mph, unless the car is REALLY light, and everything is maximized in the combo.

With a small block, and staying with a T400 with a good converter, I would probably go 3.55 or 3.73 gears and 28" tires...Especially if you're more concerned about ETs then freeway rpms.
If you go with an OD trans like a 4L80e, then I'd probably go 3.73/4.10 gears since you have OD and can lock the converter. I'd use a custom built FTI 9.5" converter in that combo.

It really depends on the rpm range the engine is capable of and where it noses over. 3.73 and 28"s would likely be the best combo.

There is a lot more variables involved. Really depends on how focused you are on the drag strip performance vs streetability.

The FASTEST combo would likely be the T400, 8" ATI tree master converter, spec'd for your combo, 3.73s and a lot of weight reduction.

Renwick

Everything got deleted because I tried to correct a typo and it just deleted everything for some reason.

I would say my focus will be 80% street and 20% strip. I do want highway driving capability because I live 30 miles from the nearest drag strip and 60 miles from the nearest city.

The engine noses over at 5800 rpm I think. The HP went down after that and the dyno sheet only went to 6000 rpm.

Your info was really helpful. With that I'm wondering if I put in a 3.73 would highway driving for 60 miles be impossible/difficult? Because if it needs a 3.5 ratio for that then it means I can't do the Tom's 12 bolt (they only do 3.73 or 4.11) and am limited to a Ford 9 inch conversion unless I do an overdive transmission.

Kacyc3

@70 mph 3.70 gears 28 in tall tire and no overdrive will be 3200 rpm + torque convertor slippage..3500 rpm total maybe.. do you want to drive at those rpms for those lengths of time? 3.55s with same tires and trans is 3062 rpm
@60 2800 rpm ish, 2600 rpm ish

gkull

I like IRS because I also like to go around corners fast. I have something like the so called super 10 bolts and it has lasted for 100's upon 100's of 1/4 miles runs. forum name of GTR1999 Super 10 bolt" built by Gary Ramadei will get you going. I used an 800 hp 700R4 with a 3800 stall 9.5 inch. I installed a 7500 rpm solid roller 427 SBC. When I did that even with a full roll cage I wouldn't let my wife drive the car because it was feasibly dangerous. Because of the TC traction became a problem and you could loop the car from a 50 mph rolling start. The fix was a 5 speed manual tranny.

It's not going to take you very long to figure out that you have an underpowered mild built 434 and you need to think about future rpm and power levels. you can do a search on my name about roll cages, brakes, and differential and come up with a wealth of knowledge. I never hit the lotto. I just used to try and budget only $10,000 on my vette per year, but I blew a few motors and rear ends over the years and the cost of racing tires per year beat up my budget.

If I bought a C3 today with a 434 and a auto tranny. The first thing I would do is to make it safe and have a 8 point cage installed with racing seats and 5-6 point belts. Then I would install a roller cam, big heads, headers with 3 inch dual exhaust and cross over pipe. I replaced things as they broke or to a extent preventative medicine. My Vette has about 178K miles and it has had probably 15-20 motors, 8 transmissions. So many rebuilds on the rear ends that I just keep a complete ready to install spare. one with 3,55 gears and the other with 4.11. My vette has met the 3000 lbs class minimum with driver and 1/2 a tank of gas in the past.

I have has good luck with a super 10 rear end, but i'm also in the sub 700 hp class and I don't beat the crud out of things.


https://www.corvetteforum.com/forums...ag-racing.html

Renwick

You are correct that the engine is underpowered for what it could be. I don't plan on touching the engine aside from maintenance until I get the drivetrain where it can handle it. There are a ton of engine builders here so that is much easier to find.

It's hard to find people that build the drivetrain up here so I'd like to do it one time and overkill it rather than do it 10 times. Especially since I may have to have it sent out of state to do the work even once.

I don't want it to be so insane that it has no traction and isn't really driveable on the street. I want to do some drag racing mostly for fun but mostly it will be a street car but durable enough that I won't have to worry about going fast. Your focus seems to be more on the drag racing side primarily which is cool but a bit different than mine.

ajrothm

Honestly, with that engine's rpm range, its more of a midrange grunt motor, so it would still run ok with taller gears. 80% street is a BIG difference then your original post of wanting 1000hp compatible stuff... You are talking a huge spectrum, mainly dictated by budget and desires.

If you want to spend a lot of money, do the 4L80 with the computer, 9.5" FTI converter, then go with the Toms 12 bolt IRS with 3.73s. With that combo, you could slap a 540 motor in it down the road and the drivetrain is all set. Just prepare to spend about $18k for the trans to the diff with everything you need.

A more budget way to go, rebuild the T400, use a custom built converter to match your current engine, then do a Super 10 bolt IRS, run 3.36 gears and run 27-28" tires. 70 mph is 3000 rpms and you can easily drive it anywhere you want. This combo would likely be less then $8k from the trans to the diff. Would still give you SOME room to grow and will handle mid 10 sec ETs no problem. This is basically the setup I have put 26k miles on, driven cross country, and made over 100 track passes in the mid 10s on. I don't think I would trust the diff much quicker then low 10s, maybe 9.90s if it didn't leave REAL hard.

Renwick

I would like to avoid this and still stick with an automatic. If I went with a lower stall speed torque converter would it avoid that?

Where did you get your 800HP 700R4? I look them up and even beefy ones seem to be rated for only 600-650HP.