Hey Guys (and girls)

I just did a 400 small block swap in my 91 RS. I have a few questions.

1) Does anyone know the horsepower of a 76 400?
2) After all was done, i hook the timing light up and when i turn it on, after about 15 seconds, the engine dies . Does this sound like a distributor problem to you?
3) what are some easy mods i can do to add some horse here and there.

Thanks guys.

 

1) 175@3600

 

thats it? For a 400 small block?! wow. The 305 had 190; there has got to be more. lol. I atleast hope so.

 

anyone?

 

He's correct.
but the 400 has so much more potential..

 

so you mean to say that a 305 has more horse than i 400 small block? I was thinking along the lines of 300horse. The 350 was pushing that much.

 

you're talking about a stock motor,right? The 400s from the mid 70s on up were built for low-rpm-off-idle torque. They had like 300 lbs/ft @1800(?) rpm of torque. The distributer curves were plotted to reduce emissions. After 1976 the 400s were only used in trucks and vans. You compare it to the 190hp 305. It made that power at 4800 rpm.

 

so, the swap was a bad idea? lol. A little to late.

 

first mod would be a nice set of cylinder heads, and ditch the 400 heads because they are junk. Also check your fuel pressure, it could be the reason(s) behind your engine stalling

 

alright. I will do.

 

No, not a bad idea. Torque is the rotational force of, say, your crankshaft. A 305 has 240 lbs/ft of torque. Your 400 has 300. If your goal is to have the fastest 1/4 miler, you need to upgrade some components. If your goal is to have a fun street car, you've made a good choice. Check your driving habits and see how often you're above 4000 rpm. Anywhere below that and your 400 will feel like a faster car than your 305, especially right off an idle.

 

When running it, i never go over 5500rpm. Well, atleast in the 305. It seemed like the 305 didnt do jack **** after 5500 so i would stay there. When regular driving, i shift roughly at 3500. Im not really big on track racing but i def. would like to run it a few times just to get a time.

 

Did you use your TBI on it, or some sort of carb?

What did you do for the fuel system, and exhaust?

 

Kinda on/off subject... if you put a 400 in a camaro from those firebirds.. could you somehow put the shaker on there too?.. if so how much modding would you need to do (besides cutting your stock hood) i always liked it and thought of doing it.. now seems like a good time to ask?

 

i took the TBI off the 305 and put it on there & i bought headers and I (ME!) did 6 hours of custom exhaust work. lol. PAIN IN THE ***! So much marking and welding. About the shaker, i have nooo clue. Never thought about it. It would be really cool though.

 

No one got any other ideas?

 

anyone?

 

u surly tuned the crap out of the prom didnt you? and theres probably no way the stock fuel pump, injectors, or any of that will come close to feedin that 400. im workin on a 406 build at the moment and im gonna convert to carb most definately. if you didnt change any of ur fuel system or tune it uve got a lot of work still ahead...

 

I dont know. I was told it would work. lol. Now, im screwed. Guess ill check the fuel pressure and see what thats about. it stays on when i give constant gas but other than that, it'll die.

 

yea im not too well versed in the tuning stuff but the stickies on the DIY board get you about everything you need to kno. that TBI system will work all you need is bigger injectors and a good tune.

the TB itself will limit you to about 300 horse (so ive been told) because of the cfm it will flow. your not screwed but it will take some more work. the stock 305 fuel pump will probably have to go nd youll need a new regulator but it will work.

the reason it dies is because the prom (computer) thinks its feeding 305 cubes and its actually feedin 400. i probably wouldnt run it a whole lot more on that tune because its probably really really lean. once you get the tuning equiptment and the knowledge you need to do it you have it runnin after 2 or 3 burns but after that how close you get it to perfect is how many more burns you make.

heres a few things to get you started:

https://www.thirdgen.org/forums/diy-...uide-book.html

https://www.thirdgen.org/forums/tbi/...free-tune.html

 

You should check out the sticky about 305-350 TBI. It's either in the engine swap section or the TBI section. Do that stuff first and then you'll be in a better position.

I did this swap a long time ago. I also used a 76 400, from a caprice. I only used the short block. The cam and heads were just awful. I used L98 iron heads (we put steam holes in them) and a performer RPM intake with a TBI adapter (made by me.) I also used a stock 454 throttle body with injectors from a 1 ton truck. A TPI fuel pump rounded out the mix, along with a hot cam. I had an aftermarket chip back then and no clue about tuning. It cost me 400 bucks to get a superchip that worked well. 1 3/4" SLP headers were also used.

Bottom line, you've got a little more work to do to run good. You've got a good platform to start with, though!

 

TBI.

 

But is it possible that its just not getting enough spark so it wont stay running?

 

Not really. If it's getting enough to start at all, it's getting enough to keep running. Whether you're losing spark is a different matter.