Question on power gain if I...

[gk666]

Alright so we all know that the feedback carb is the worst invention of all time and sh*ts gay... so I have a question for before I do the motor swap... since it's gonna be a few months until i get the 400 block ready I'm wondering what kind of power gain I'm looking at with full exhaust, a decent carb and zero emissions sh*t... Right now the feedback on it is lean and theres a flat spot and tuning that out is just not going to happen, NOT WHILST IM STILL A MAN... and I'm gonna get a full exhaust since it will bolt up to damn near anything i put under that big ol hood, except for the big block i plan on putting under there someday... btw if any of you were wondering, i know i been on this forum for like 2 or more months now but iv had like zero opportunities to take pictures because I'm always busy, I'm going to take pictures this weekend of my baby ^^.

 

[RITTER]

Removing the external engine emissions components is just a weigh savings pretty much. The big emission gains are going to be through you heads, intake, cam, and carburetor. You want to stay away from small valve/big chamber mid-late 70's heads (unless there is some machine work in plan for them) If you set this combination up right you can see huge power gains. There are just so many different combinations to work with. A good carburetor well help a lot. If you are running this as a daily driver, I wouldn't put anything bigger than a 600cfm or a larger "cfm" spreadbore. A full exhaust system is great for driveability and, if it is setup correctly, it can give you some significant power gains.

 

[gk666]

theres 250000 miles on the motor... granted the 305 is a rock but doing top end on high mileage motor is always a bad idea... its like BAM 6 months later everything falls to sh*t... thanks for the info though... i was mostly considering a 600 carb... they are like 150 bucks remanned from edelbrock.. i think that should hold over well for a few months until the swap was ready

 

[RITTER]

:shock: yeah, that is quite a but of mileage for any big modifications. A carburetor and headers and exhaust wouldn't hurt anything.
What kind of swap will you be doing?

 

[gk666]

i have a 400 sb in a caprice to go in... havent decided on power and where its gonna be yet... i still havent looked at very many combinations of heads or any internals... i just know that i have the motor and its perfectly good .... I think im gonna put most of it on the bottom end the way a v8 should be, not one of those tall road runners... and im looking looking to get about 350-400 horse... ill have to take some time soon to sort through my options... but number arent important really i just want a badass gas guzzlin biddy to get me through town... i dont want to have to bore it out but i might if the sidewalls need it and so i still have to make a few decisions on power and output and rpm levels but quick and ****ing fun is the most important thing to me

 

[gk666]

maybe someone like yourself or whoever can give me a suggestion on head/internal setup if i give some pre requisites... I already said im looking for a mid range amount of power, still streetable but I want it to buck... its gotta be able to burn the hoosiers that are on it right now off... im thinking 350+ hp and 350+ lbs and i would like to see it all at lower rpm... not so low that once i get to 4 grand i have zero torque but id like to keep it giddy at red lights... its gonna have historic tags and i have zero need or want for anything emission related... i also said i am not in a hurry to bore it out any but that is still on the table for debate... as of right now everyone i talk to has a different idea of who makes the best pistons so if i could get a suggestion on decently priced decently made piston cam rings seals rockers kit that would be cool... im not doing it budgest style but im not building a RIDICULOUS ENGINE HERE... its not gonna get an *ss whooping every day but i do like to get on it when im at a red light... i mean when the person behind me at a red light cant see... the emotion in the air at that time is priceless... im also not going for a huge duration cam, i dont need to to damn near stall when im at a red light hahaha... other than that i cant really think of anything else... there is no forced induction in the equation so dont suggest it and dont hesitate for suggest something that would conflict with said induction... thanks for any kind of suggestion you can offer - or anyone elses build thread you can point me to

 

[RITTER]

A 400ci SBC would have absolutely no problem putting out 350+hp/ft.lbs torque. The bottom end is not where you make your power, although it must be able to handle your valvetrain. A decent hyper flattop 4-valve relief piston would be more than enough for a N/A SBC. Your top end combination is THE MOST important part of the whole equation. If I were to start my entire build all over again, I would have just purchased a top end kit from DART or Edelbrock and slapped that on my shortblock :idea: These kits are proven and come from very reputable manufacturers. viewtopic.php?f=13&t=25303

 

[gk666]

thats a similar idea to one of my other ideas which i was pretty certain would make the horsepower i wanted... yes heads are pretty much the most important but if you rebuild the top end... the bottom end crashes its like getting a heart transplant when your liver is failing... i was thinking maybe getting the bare block thermal cleaned and getting OE internals ( except I might swap with a crank shaft from a different motor because iv heard of people using a couple different cranks to increase the stroke and it comes out beautifully...) and then buying a top end kit... that would theoretically be a cheaper build and get the numbers im looking for and if what iv been told was true it would put the power in the right spot

 

[megaladon6]

not sure, but i don't think you can swap cranks on a 400. usually the 400 crank with cut down journals goes into a 350 to make a 383. a 350 crank in a 400 would be a beast, but the 350 journals are much smaller.
anyhow, a good cheap build on a 400 that will get great all around power--xe274 cam and vortec heads with 9.5-10:1 compression (i prefer d-dish pistons for the better quench area than flattops) you'll be over 400hp and torque on 87 octane, have longterm reliability, and a pretty flat torque curve. or a 290 or so cam and the bowtie vortecs. you won't lose the bottom end, but you'd probably be around 500hp
for a carb on any size v8--always the q-jet. you could have a non-ccc q-jet on the 305, retune it and put it on the 400, retune again and put it on a 500ci caddy motor! their max air flow is 800-850cfm, but can be tuned down easily to 600, maybe less.

 

[carpenter383]

It all boils down to what your budget is, you need to start with a realistic budget with room for the extras nobody thinks about.
You can put a 350 crank in a 400 block, it makes a 377. You can either get thicker main bearings or buy an aftermarket crank made with bigger mains to fit a 400 block. You are loosing 1/4" of stroke by doing this and in my oppinion it dosen't make sence especially on a street motor where you want torque.
I've seen stock 400 short blocks take alot of abuse at the drag strip, so for what your talking about I think you'd be fine with a stock bottom end. BUT if it's in the budget then throw some money at a good crank/rods/pistons and have it internally ballanced.
There are kits to build a 454 small block, but it takes deep pockets :wink:
Vortecs on a 400 would make a very nice street engine and they are budget friendly too, and the 274 cam sounds about right, but I'd run flat tops, and saying dished pistons are better for quench than flat tops is backwards. Flat tops are better for squish any day! Decking the block or using thin head gaskets also helps squish. Squish (or quench) is just how close the piston gets to the flat part of the combustion chamber. The closer the better (within a safe margin) The benifit of tighter squish is it crates turbulence which helps combustion efficiency.