I just came upon a nice deal on a 400 CI Chevy SB...Said to have about 500HP...I was wondering if i could put this in my 85 Trans Am My T/A has an auto 700r4 Trans

 

yes, you can install a 400 as long as it's a chevy motor and not a pontiac. if its a chevy motor it will bolt right in, however, will the 700 hold up to 500 hp. probably not.

 

Well, if the 700 r4 wont hold the HP What should i get for it then...A TH-350?

 

there are a number of choices available, first: you could have the 700R4 built up for racing or buy one that is already done, second: you could get a TH-350 that is done up for racing but that requires a swap kit to install because of the factory torque arm, or third: you could get a TH-400 this too would require a swap kit.

OR---- if you really like shifting you could get a good strong 5 or 6 speed and go that route.

do a search on the topic and you'll find as many options as you have fingers and toes. the above are just a few of the more popular ones.

 

Ok...Would it be cheaper to just buy a built up transmission or would it be cheaper to get my current 700r4 Built up??
Will my engine mounts for my 305 be good enough for a 400 or do i need to get new mounts..I have TPI if i put a 400 with a carb will there be sufficent hood clearance?...Also can my stock rear end undertake that much power?

 

Were can i find a 700r4 built good enough for the 400?

 

i've got a sbc 400 and have th350 behind it. b&m makes a change over kit so you can use the th350 with the stock crossmember and torque arm. costs around $80

 

But i dont want to buy another trans if i already got a 700r4 i can use

 

If that engine has 500hp then you can't use the 700r4 as it is. From what I remember Pro-Built-Automatics sells built 700r4's but they are pretty pricey. Over $1,200 I think.

http://www.pro-built.net is the link you want.

 

for what you get thats not pricey

 

See sig
We'll see how long its gonna last and its got good stuff in it, not as good as ProBuilts I'm sure.

If it goes, a T56 would be tempting, but theres a guy in another thread wanting to go with an auto. Go figure

 

I call anything thats expensive to me pricey, regardless of the quality. Put it this way, I know PBA trannies are good, but that doesnt' mean I can afford to drop $1,300 on an automatic.

 

find a 75-80 truck or van with sbc400 engine and it should have a th400 behind it, also the th400 are behind the 80s 3/4 tons and 1 ons with 350 ! they are short tail 29" overall length from bell back to tail end, you wil need the ypoke off the truck driveshaft and a conversion U joint from napa to go from f body size caps to the truck caps and change shaft length too

look slike i am getting ready to install 400sbc th400 77 truck drivetrain into the 82 trans am, i found a donor: a 77 G20 van 400 th400 today for 200 bucks runs and drives ! im gonna use 68 ram horn exhaust manifolds, the ones with 45 degree angle back,, they will clear top of engine cradle in GM RWd cars !

 

If you can find a local tranny person that has the ability to build a killer 700r4, they go that route and use the one you have. In not you will need to buy a different one--I'm sure you can get some money out of the old 700r4. GM made a ton of 1/2 chevy pickups with a sbc400 and th350 tranny. If you plan on driving this car on the highway, you will probably want the overdrive 700r4. Drive your car around town and on the interstate/highway in 3rd gear and see if you like it. Next, you will need a better rear-end. The stock 10 bolt isn't going to last long with that power. Probably need to upgrade the cooling system. Suspension mods, like subframe connectors, will also probably be needed(if you don't have them). The 400 chevy isn't any bigger externally, so do some searches on the carb board on what will fit. I'm running a holley carb and stealth intake with a 14x3 K&N drop-base air filter under the stock hood.