hartsmike

Thinking of building a 350 horse 350 with maybe a lopy cam similar to the CC305, T-56 6 speed and the current 273 gears.. Problem is, when I was a teenager I had a third gen with factory 700 R4 Trans and Rear and put a massive cammed 350 in. Back then, I didn't know about shift kits or stall converters. I do remember how disappointed I was in the performance because the car that the cammed 350 came out of was a first gen camaro and would lay rubber for 40 feet or so.

My question is, with the possible set up, can anyone tell me how it would run? The only thing I can think to clarify is maybe how it would run in a quarter mile? Second, If I put 410 rear in to give more grunt, what would the fuel milage drop to? If anyone has done this please chime in! Really would like to do the LSX conversion but just don't have the funding for that and I'm not mechanically inclined.

big gear head

You will not like the T56 with the 2.73 gears. You probably need at least a 3.73 or 4.10 to be able to use the .50 overdrive with a cam like that. You are also going to need a very good drive shaft to prevent a bad vibration at around 60 MPH and up.

hartsmike

[QUOTE=big gear head;5421491]You will not like the T56 with the 2.73 gears. You probably need at least a 3.73 or 4.10 to be able to use the .50 overdrive with a cam like that. You are also going to need a very good drive shaft to prevent a bad vibration at around 60 MPH and up.[/QU Will a cam like that just make it too heavy on the top end with those high gears (273)? Also, how hard and expensive would it be to change out the gears and which would be better for performance and milage for cruising-410 or 373!

big gear head

A big cam takes away the bottom end torque that is required to pull at low RPMs in overdrive. I know many people whtih the 4th gen Camaros who went with 4.56 gears because of the .50 overdrive. A 4.10 would probably work petty well. Just remember to get a good drive shaft too. I would get at least a 3.5 inch tube.

Changing gears is usually not a job for the average person. You must know how to set the pinion depth, bearing prelaod and backlash to get the correct contact pattern. You also must know how to read the contact pattern to know what adjustments need to be made to the pinion depth and backlash. There are a few special tools needed for the job.

sofakingdom

iTrader: (1)

He's right about the gears; I have a T-56 and the stock gears (3.73), and they aren't really enough. 4.10s would be better for sure. And I don't even really have all that much cam, to where the motor is unhappy being pinned below 3000 RPM all the time. But, 6th is completely useless below about 65 mph; the motor is doing about 1300 RPM or so under those conditions. Kinda hard to expect an engine to produce meaningful power at basically idle speed.

You would HATE the setup you're talking about. Your description of your previous experience is EXACTLY what you'd get, except WORSE, because a manual doesn't even have the amount of "slip" that an auto does. A manual is all metallic all the time (except while the clutch pedal is pressed). It won't have ANY "leave" WHATSOEVER, and will only start to "get up on the pipe" at about 60 in 1st gear. I doubt you'd even be able to comfortably use 4th gear most of the time, LET ALONE 5th & 6th. All around, NOT a good plan.

Frankly I think you would get BETTER gas mileage with the 4.10s than with 2.73s, because the motor would be up into a range of RPM where it could have a prayer of being at least somewhat efficient.

Personally I don't find changing gears to be all that much of an ordeal, depending on the choice of gears, especially not in this model of rear. For example, I have NEVER taken apart a factory-built 7.5", 7.625", or 8.5" 10-bolt, and found ANYTHING BUT a .035" pinion shim; leading me to believe that the factory was able to accurately control at least that ONE aspect of machining the housing (which is of course what you're shimming, NOT the gears and carrier). EVERY SINGLE ONE I've ever built, I've just put a new .035" back into, and it was fine. Now, with non-stock gears such as the Richmond drag-race ones, that's NOT NECESSARILY true; but stick with GOOD QUALITY stock type gears such as Motive, Superior, Precision, US Gear (avoid the cheeeeeeep offshore cheeeeeeeeep sloppy cheeeeeeeeeeeeeeeeep crappy ones), and setup is a breeze, requiring very little measurement. A honed-out pinion tail bearing, and using a "crush sleeve eliminator" instead of a cruch sleeve, make it even easier.

hartsmike

My rear brakes are drum so if I were to up-grade to disk brakes and lower rear, would I be better off finding a 4th gen rear and sliding it in?

sofakingdom

iTrader: (1)

Yes that would be a GREAT path to take; far better than spending money on a 26-spline axle, 2 series, drum brake one.

big gear head

A 4th gen rear end is going to be wider. You may need to adjust the backspacing on your rear wheels to keep the tires under the car. The LSI rear ends are better than the LT1 rear ends.

hartsmike

[QUOTE=sofakingdom;5422469]Yes that would be a GREAT path to take; far better than spending money on a 26-spline axle, 2 series, drum brake one.[/QU Would I have to get spacers in order to run factory wheels and if I do, will they stick out so far that the factory rims and tires look bad or rather not good?

vetteoz

iTrader: (13)

The new diff is wider than yours , if you bolt your existing wheels on the tires will hang further out.
You would need different wheels that have the center moved out ( the backspacing as noted above ) to suit the wider diff
so the tires are back in the original position
You only use spacers if the new diff is NARROWER

sofakingdom

iTrader: (1)

Right: can't run the factory wheels from one of these cars without making it look stupid and poseur, with those little skinny pizza-cutter things that came on all these cars stuck out past the fenders. But, you could run stock 4th gen or C5 or C6 wheels, or any aftermarket one with the same fitment. They'd fit perfect onthe rear but you'd need 1¾" - 2" spacer adapters on the front, or in the case of aftermarket, run the late-model backspacing on the rear and the early-model (near 0 offset) backspacing on the front. That way you'd NOT ONLY get the better gears AND better brakes, BUT ALSO better-size tires, in a modern size that you can actually buy something high-quality in.

hartsmike

Would I have to get spacers to be able to run the factory tires and rims with fourth gen rear?

naf

iTrader: (7)

No. The 4th gen rear is a hair wider than yours. Can't take away space. The stock wheels will stick out past the fenders.

sofakingdom

iTrader: (1)

Not sure what kind of hair you got there bro, but.... they're about 1-5/8" different on each side.

But yeah, unless you know where to go to buy a spacer that takes space out instead of what all the ones I've ever seen do which is put space in, that won't help. It'll just make it worse.

Every one of these cars I've ever seen that had a 4th gen rear with 3rd gen wheels on it, looked like cold leftover yesterday's a$$. The wheels are out past the fender lip, which by itself might not be too bad. But, from the back, it makes the car look like one those of those swamp buggy rail things they race in the swamps in FL and LA; little narrow pizza-cutters, too narrow. The 16"s are bad enough, but the 15" ones are completely laughable.

vetteoz

iTrader: (13)

What part of

'The new diff is wider than yours , you only use spacers if the new diff is NARROWER "

didn't you understand?

naf

iTrader: (7)

exactly. since parris island in 1990 i've let it grow out some, so 1-5/8" is probably the longest one up there.

hartsmike

Thanks for the help guys. I've got internet on phone but for some reason thirdgen.org doesn't let my phone go to second page. Probably just phone. I'm thinking that I'd like to retain the stock look. I've gone over many times in my head putting 92 GFX on it and Z06 wheels but like a guy said several months ago you don't see many stock IROC's. I'm going to keep the black paint and gold IROC sticker so might as well keep the factory rims.

sofakingdom

iTrader: (1)

True enough; but you see even fewer people who would care if they saw one, and fewer still who would know the difference.

So, IMO crippling your car on the off chance that you JUST MIGHT meet either of the last 2 people on Earth meeting those qualifications, instead of DRIVING the car YOU want to DRIVE, would be a serious mistake.

hartsmike

LOL That's true. As of right now I would rather have it looking factory unless Chip Foose (spelling) were to come and get it.