I'm wanting to put a stock sbc 400 with a Holley 750 carb and Turbo 400 in my third gen camaro but I was told that this combination would be terrible on MPG. I'm wanting a nice car that gets decent gas mileage and that can kick it if need be. I was also told that putting in a 2500 stall converter would help this. I don't have alot of money to sink into the car right now either. Does anyone have any suggestions for me?

 

What is in your car now?

If it is a 305 carb with TH700, you can put the 400 under the 305 control system, upgrade the exhaust, rebuild the tranny, and maintain decent economy with good power.

If you have TBI, it will be a little more difficult, but still possible.

Some more details on the 400 would be helpful. "Stock" can mean a whole lot of things. Typically, stock 400 heads are better door stops than performance or economy heads.

The "not a lot of money" part is a bit of a concern. The typical 3rd gen 305 exhaust (assuming you have a 305) is pretty bad. Getting decent flowing headers and exhaust will set you back about $1k alone. But, decent flowing headers and exhaust will make more difference to both power and economy than any other mod you can do.

And, typically, the stock TH700 doesn't take well to more torque, which a 400 will have in spades. Typical rebuilds and better converter will run you around $1500-$1800. Just a higher stall converter with nothing else done to the car may help seat-of-the-pants power, but it will hurt economy.

Regardless, I would NOT do the TH400. It is a tough transmission, but it will kill you for gas mileage, and requires a different crossmember and driveshaft. The car will get off the line better with a TH700 than a TH400 while producing better cruising economy. Sell the TH400 to finance what will better achieve your goals.

 

I always forget details.....lol

I'm in the process of buying the car so don't know much about it other than that it doesn't have an engine/trans so I'm going to use what I already have. My neighbor gave me a glasspack (don't know much else about it).

The guy had a 383 stroker in it but he's keeping that, don't know if it was carb or tbi. I was just trying to get some advice before I start working on the car. I'm going to pull the 400/400 out of a 3/4 ton pickup I have so was going to work on engine/tranny while its out for easier access.

Thanks for any and all advice

 

the 700 can do alot more than the 400 with a rebuild, and its a tad better on "economy" i mean either way you look at it your mpg isnt gonna be great, throw an ls engine and your getting closer to good mileage. i wouldnt work with t.b.i my truck has it, its good for low end torque but other than that theres better things to work with. also you say your on a tight leash with cash, be weary of that, because when you look at it, it may seem cheap but it also could ending costing more than you thought and you project will be on hold for quite awhile, trust me iv been there

 

Since the PO had a 383, your exhaust system might be decent, if that stays with the car.
You can surely sell the TH400 for enough to cover a used 700R-4. As for strength, all of the L98 third gens were rated to more torque than any late-'70s 400.
With a 700R-4, you should be able to do better than 20 mpg on the highway.
With a TH400, you might do mid teens, if you run a 2.73:1 axle. But a 700R-4 with a 3.23:1 or so will feel much better, all the time.
The main thing is to make sure that whatever 700R-4 you get has nothing in the pan but dark red fluid, and get some kind of guarantee in writing, or an exchange policy if it comes from a salvage yard.
The best 700R-4s are '88-'93. But if the choice is a used '88 versus a freshly built '85. I'd probably go for the '85.
With the 400, forget the 2500 stall torque converter for now.

 

you mention a 750cfm carb? save some gas and use a 650 prob pick one up cheap i don't think that would hurt even though its a 400 would it guys?

 

650 should do fine, if you have enough id look into one of those fuel injected carb setups, i heard those have pretty darn good mileage and tuning capabilities........just something to look into

 

For what that costs, better to buy either a fully built 700R-4, or a pair of AFR heads.

 

Have ya'll heard anything good/bad about Edelbrock Performer intakes? A guy I know is interested in a truck I have for sale but he's offered cash and the intake. Just wanted to see if it would be good to put on that 400 that I have.

 

A pic would help, but Edelbrock is the biggest name in aftermarket intakes for Chevy. Good stuff, but many different offering.

 

It's comparable to a stock LG4/L69 intake.

 

Not really. I remember an old magazine article where they rebuilt an L69, with a Comp 203/212-110 cam, and made 200 HP at 5000 RPM. Then they swapped the stock intake for a 3701, and made 225 HP at 5000 RPM.
That's 25 HP with no other mods.

 

Yeah, I'd take that article with a grain of salt.

 

Why? Hot Rod has twice shown the same improvements on Goodwrench 350s.
Heck, just look at the 2 manifolds, the improvements are obvious. E doesn't kink the runners like GM did.

 

The oil pan on the 400's won't clear your k member. You'll need an aftermarket pan. I used the canton racing one on mine. That'll run you around $300 tho unfortunately :/

 

edelbrock, yes has a decent product, but there is much better, they are ore or less a big name that your average joe can get a couple hp out of.