Well my 305 took its last breath recently and gave me a good reason to start building a motor. I looked at a 400 today the guy said its out of an early 70s truck, I just have a few questions before i consider this swap.

Does it matter if the motor is pontiac or chevy?
Will the motor bolt right up or will i need different motor mounts?
Will my TPI bolt right up to the 400? if not what mods need to be made?
Any other problems i may run into feel free to let me know. I'm seriously considering buying the motor.

 

Couple more questions...

Is it worth swappin over my factory TPI or should i go a different route like...HSR? If so, will there be any fitment issues under my RA hood?

 

Yes. Big time.

Same mounts.

All depends on what heads you plan to run.

I'd ditch the TPI, and go carb. Convert to a roller setup. But that's M.O......

Don't wanna start some Anti/Pro TPI war here........lol

 

IT matters alot if it is pontiac or Chevy.

Try for Chevy as everything will bolt up to is as it is a standard SBC.

Trans, TPI the works.

If Pontiac ... keep looking as it will cost you more then you want.

I would consider upgrading to the HSR, and yes it will fit under your RA hood. It fits under a stock Camaro hood so there should be no issues.

 

OK so im 90% sure the motor is out of an early 70s chevy truck, will it bolt up to my 700r tranny or will there be another problem there? I dont really wanna go carb i'd like to run TPI or HSR...what, if any, head modifications need to be made to run TPI or HSR?

 

It will bolt up to anything that any other smallblock will bolt up to.

 

in the late 70s/early 80s GM decided that the small block chevy will be their corporate engine.

until then, Pontiacs had Pontiac motors, Chevys had Chevy motors, ect...

all 3rdgen V8s are small block chevys. it makes no diff if it came from a camaro or firebird.

with the exception of the last couple years of the 2ndgen previous pontiac firebirds had pontiac motors... totally diffrent then chevy motors.

 

Ok so your the 1 year that I can never figure out which is which so ill give you both.
85 and back has perimeter bolts for the valve cover ( 4 bolts on the side of the covers.)
that is that same all the way back to when the SBC was first coming out. Which is the same as the 400 your getting.

everything will bolt up fine but your injectors will not like you. too weak coming from a 305 to power an extra 95ci's. so I would upgrade to all 350 stuff which is basically a chip a knock sensor and injectors (can't think of anything else)


Now if your 305 is actually setup like 87+ (valve cover has 4 bolts going in the middle of the cover) then you cannot use your intake on the heads that come with the 400. What you would need to do, would be to find a set of L98 heads (cheapest solution) and drop those on the shortblock, this would raise compression for you as well, this would allow you to keep your intake as well. Again upgrade the chip/injectors to 350 model.

Also upgrading to 350 injectors and chip will allow you to run your engine, but by no means will you be seeing your max potential ... chip burning becomes essential.

Overall if you can I would get an aftermarket intake like the HSR or MR or SR. or even get a converted LT1 intake.

 

If it did come out of a truck, and it looks the same as your 305, then its a Chevy 400. The pontiac 400 looked quite different (its bigger than a BBC) and never came in trucks because pontiac never built trucks.

The 400 will drop right in place of the 305. The mounts are the same, and all the needed bolt holes are in the same place. As for the TPI bolting up, it looks like you have an '86 TPI, so it would bolt up to an old-style head. I'd ditch the TPI though. It just can't breathe. It will be like sticking a rolled up sock in the throttle body of a 305 TPI.

If you don't already know, the 400 is externally balanced, the 305 is internally balanced. Because of this, you'll have to have your flywheel or flexplate "unbalanced" to the 400 spec.

 

This is a lot of usefull info guys i apreciate it a lot...Yes i have the 86 TPI. If i buy this motor i planned on just doing some port work on the heads and going with an aftermarket cam. Also if i was gonna stick with the TPI I was gonna go with after market runners/base but its sounding like the HSR would be the way to go? (budget wise..) I would pick up some SVO injectors and burn a custom PROM. Any other info I may need to know will be apreciated.

 

You're better off throwing out the stock 400 heads.

 

...for?

 

for almost any other heads.


remember the 400 is from the smog era. before they had engine management controls, they tried to control emissions mechanicly.

so they did queer things like make heads that flow like crud, and tiny ports... basicly cutting power because less power is less fuel and less air, making less emissions.


you can port and polish and dump $1000 into thoes heads, and some stock vortecs, or $500 Iron Eagles will out flow them.

 

Try some L98 heads they have 64cc chambers and should work nice. Also what type of pistons are in it, dished or FT.

 

Remember to have steam holes drilled in whatever heads you buy to replace the crappy stock heads from the 400.

 

With those heads, you'll want dished pistons. With flat tops, you'll be well over 11:1

 

the TPI intake flows barely enough air for a 350 much less a 400 because the TPI set up was designed for a 305. That is why the LT1 is so different because it was designed to pull in enough air for a 350.. If you don't upgrade the intake you will not have your max potential.

 

dont worry i know this...