8 inch or 9 inch?

About to narrow a housing for my Spider and trying to decide weather to put a 8 inch or 9 inch in it.

The new engine going in the car should be putting out somewhere around 385-400 horsepower and will have a T5 built by Dugan Racing to handle the power behind it. Also haven't decided on what gear I should go with, either 3.70's or 4.11 limited slip? (or whatever is available close to those) Have also thought about nitrous just for a little extra fun, but that would be a ways down the road if it won't run what I want it to in the 1/4. I will be removing a little more weight, and relocating some weight to the trunk, hope to keep the car under 1900 pounds at most. I do plan to take it to Commerce with some decent tires so the rear needs to handle the abuse without shredding the pinion gear like the stocker did.

My dad thinks I should go with a 9 inch but to me that seems a little overkill in such a small light car. I'm thinking I could save a few pounds and parasitic loss in the drive line by going with a 8 inch. I also think the 3.70 gear would be ideal for the car, since I want to be able to cruise down the interstate to Commerce and (hopefully) back. LOL

I have several spare 8 inches out of Mavericks, and a spare 9 inch out of a '68 F100. Any thoughts?

 

If it were mine, I'd use an 8.

 

Either rear, but I'd think a "lighter" gear, like a 3:25 or 3:30 would be more than enough for the V-8, small car combo power-wise, and would provide better gas economy.


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8inch

 

i think the 8" would be okay for the street. i guess the question i'd be asking is if you take it to the track, what are you going to be dumping the clutch at. the t-5 is going to abuse the rear a lot more than an automatic will. especially if you add some nitrous. i think if i had both i would go with the 9" for peace of mind.

 

i,d go with the 9 inch. I agree with don. 385 is alot of ponies for an 8 inch.
I,d have a good differential and some stout axles too. where is the engine gonna make it's power ? is the cam better at mid range? top end? alot of things affect gear selection. the t5 has a pretty low 1st gear...all depends on what you wanna do with the car. maybe put some wings on it it's gonna fly!

 

I'm not going to abuse the hell out of it at the strip, but I'm not going to drive it like a granny either. I plan to get the axles from Moser once I shorten the housing and figure out what I need. The cam in the engine currently is a Comp XE262H. The short block is the one that was in Dan's '71 Grabber when he tried to run it on Diesel. I know it's .030 over, I don't remember what pistons are in it. I am putting my Edlebrock Performer RPM heads on it (2.02/1.60 stainless valves), and trying to decide between using my Edlebrock Performer RPM intake, or selling that and getting a Torker 289 intake. I'm also not sure about the carb, currently I am running a vacuum secondary Holley that is either 550 or 600 CFM. I think I'm going to need more carb. I'm still researching alot of this, I'm open to any suggestions on any part of the engine. Ignition will be MSD 6AL box and Blaster II coil, Mallory unilite distributor and Taylor wires.

Gas mileage is not a concern. I put 3,500 miles on this car with a 4.56 gear and 3 speed (really a 2 speed, 1st gear was useless). If it gets better then 10 mpg, I'll be happy. But it better go like a bad out of hell. I have the Maverick to squeeze gas mileage out of.

 

An 8 inch should be fine IMO.

 

Since it will have to be narrowed anyway, I'd go with the 8' and a good set of aftermarket axles. As light as the car is, the 8 should be stout enough. I think the T-5 will be the weakest link. I would run a heavier oil in it than what the factory uses, maybe a 20W or 30W with some Lucas mixed in. With the overdrive in the T5, you should be able to get away with a lower rear gear, but I don't think I'd go lower than a 3:80 or so.

 

The T5 should not be a problem since it was rebuilt accordingly to handle the power. I'm not going to abuse it (excessive power shifting, ect.) It was suggested to me that I run Royal Purple MAX ATF in the trans, so that's what I intend to do. I will probably run Royal Purple synthetic gear oil in the rear end also.

Looks like I will be going with the 8 inch.

 

i hope it lasts for you. i know you don't plan on beating on it, but we all know what it's like to want to go faster. the only reason i haven't is because my class limits me to 12.00. the standard tranny hits the rear end much harder than the auto.

 

My bet is that you will be nowhere near 400hp with this cam in a 302. The combination sounds decent but this cam will hold you back.

 

I'd probably go with the 8" if it were me. That car will be very light and probably pretty traction limited due to wheelwell size anyway. Besides, you've got a bunch of them so you can blow a few up without having to buy anything.

 

Fred, what cam would you recommend? 400 horse was an (I'm sure a little exaggerated) claim from desktop dyno software. I'm open to any suggestions. Needs to have somewhat decent street manners, but a little lope to the idle is obviously not a bad thing.

Ray, I may have several housings, but I do not have, nor can I afford several center chunks! Traction is certainly a limitation, but it does hook up surprisingly well if you can get it out of the hole without spinning too much. Car has a 4 link rear suspension with a pan hard bar, works pretty well.

 

It's a XE268H cam and the compression ratio is 9.5 to 1 with E-5 heads that has 1.90/1.60 valves. With that combo and his Edelbrock heads, he should be around 375 HP. I would stick with the Performer intake just so you'll have a little more bottom end for the street. That engine, a T-5, and 3.70 gear will be hellacious in that 1800 lb. car.