This is my first post here, be gentle...

I dont want to seem like Im looking for exact numbers and parameters to build an engine, Im just looking for general guidance for now.

What are some engine/tranny combos to get a 70' Roadrunner into the 9.5 1/4 mile range?

Im looking at building a 440/512 stroker (440 source) with an EFI system of some kind and Trickflow heads. But I am open to other options, Im here to learn.

Blow through supercharger? NOS?

If Im correct a blower motor should be built at around 8.5 compression, is that the same for a NOS motor?

NOS will like 13:1.

We need to know more about your Road Runner, to know what it takes to run 9.50. Is it mostly stock now? Weight is a key factor. B bodies car weigh between 2800lbs and 4500lbs race ready.

Where do you plan on racing it?

Denver requires more effort than Jersey.

Is this a race car or a street car? If it is a race car then you just sort out the power to weight ratio and dial in the suspension. A street car needs a lot of power to run that kind of number since the car is heavy and the suspension isn't very good.

Breaking into the 9s in CO would be fine, 9.8ish.

I want to keep it mostly stock as far as weight goes I believe. Keep all sheet metal except for the hood and keep full interior.

Very interesting, I had no idea.

Build an E85 car and add some NOS?

This is why Im asking these dumb questions.

Guesstimate of car weight?

I have no idea, I thought they would all be close. Right now it has no engine or tranny.

As Andy said, if it’s a street/strip car, you’re going to need to make more power per pound than a dedicated race car.

9.8’s in Co(Denver) in a typical race weight street/strip car(3800lbs), you’ll need more power than a stock block will live a long happy life.

I’d be shooting for 850-ish “Standard corrected horsepower”.

Thanks man. Thats right where I was thinking I would need to be on the low end of the HP rating.

I know turbos make up for the thin air up here, does NOS act the same way?

For what its worth Im leaving CO here pretty soon for the midwest.

If it helps. My stripped and race ready 1970 Road Runner with light weight everything I could get my hands on. Fiberglass doors, fenders, hood, trunk lid, and Bumpers. Lexan for windows, aluminum dash, no interior, 10 point mild steel cage and, aluminum front hubs. Plastic seat aluminum heads, manifold, master cylinder, and radiator. Dana 60 with split mono leafs, Torsion bars in front and, stock K frame. 200Lbs driver and 5 gallons of fuel = 2850Lbs. I was hoping to get 9.?? out of it with a very healthy 500" stroker.

Digger73 (Mike)

Count on not getting it right the first time, and shoot for 1,000 at least as to the hard structural parts.
Starting from scratch with minimal in-house fabrication capacity, I'd try a big Procharger and 200 nitrous.

I understand, but I really want to get the bottom end and heads correct the 1st time, I dont want to waste that much money.

What size Procharger? F1? Im fairly certain I cant drop the coin for one of their race versions.

What your asking to achieve is going to take a few $$, your going to need 800++ HP and the suspension to help make it happen.

I have been playing big blocks on and off the strip for many years.
Im running a stock block 547, Indy topped with tunnel ram in my street 71 Barracuda that comes in at 3750 lb, I have not gone 9 yet, managed a 10.1 @ 135.
I have just changed the converter to a new 5000 and the rear shocks to Viking double adjustable in the hope of running that 9

Im no turbo guru but maybe that is your answer cause I know that doing it with just carbs is not that easy or cheap.
Good luck.

Well, NA is a lot harder. If what Im reading is correct you should be able to run low 9s with a power adder of some kind?

If your lucky and skillful
Getting the mass moving quickly and efficiently is the hard part of getting a real quick 60 ft. time so it will make the high to mid nine ET in the 1/4 mile like your wanting, it will probably need to be in the mid 1.30 or quicker in the 60 fts.

Plenty of ways to go, personally I would build a mild 650>750hp 572ci motor using TF270's or -1's (ported), use a $$$$ Indy block or similar aftermarket block as at 800+hp a stock block won't last too long, do it once. Then add NOS. It doesn't have to be 13:1CR, 11:1 will work and with the right cam still be premium pump gas friendly for the street, use 1 of Dominic's sorted dominators.

At say 3800lbs race weight you'll need 875 actual track hp to go 9.50@141. Use something like Mono leafs/caltracs and some good shocks, make sure your car is stiff enough to handle the mega torque you'll have....you should only need a 200>250 shot to achieve your goal...my 2c's.

We have a guy here in UK (Tig who is a member here) who runs a 3900lbs+ Challenger with a 572 NA motor, street car interior with stereo at I believe 11.1 last time I spoke to him, .730 Roller, Caltracs/4.10's/29.5" slicks and a single Dom, has run a best of 9.6@140+, currently running 2 x Doms and 572-13's and running 9.7's still needing a bit of sorting I think.

You might want to talk to an8sec70cuda (Chip). He has a stock weight 70 'Cuda with a KB 572 that runs 9's on motor, 8's on spray. It's a street car. He has his combo figured out very well and can probably give you some pointers on the suspension and drivetrain. You would need the same, if not more power out of your engine, and like previously stated, a stock block will not live long in that environment.

Welcome to Moparts!Going low 10.0 is not that hard but that other 1/2 sec is going to be tough.