BBC to SBC Swap

[BHRS]

Hi, I have an original '72 C10 Longbox 402 BBC, A/C, PS, and TH-400 that I want to swap to a 350 SBC. I am keeping the TH-400, PS, and A/C-what do I need to do this swap? I know I need new engine mount towers and mounts, but what else will I need?

Thanks-

[trusty72]

ac compressor mounts and power steering mounts for a sbc. im assuming your doing it for fuel mileage?

[BHRS]

Originally Posted by trusty72

ac compressor mounts and power steering mounts for a sbc. im assuming your doing it for fuel mileage?

Yes I am for the most part. I have a nice original '71 350 4-bolt main engine needing a rebuild and would be the replacement when the 402 finally has to be replaced. Since the truck will be my everyday driver very shortly, I want everything ready so the 350 can go in when needed.

[kwmech]

Originally Posted by BHRS

......................................I know I need new engine mount towers and mounts, but what else will I need?

Thanks-

No you don't, you can use the same stuff and just have the engine sit where the 402 did

[Longhorn Man]

You'll need all new acc mounting brackets, exhaust manifolds/headers, mounts would be nice, but not needed, rad hoses, a small block fan shroud (the right mounts will make sure the right shroud will fit)... there may be a few more odds and ends too

[BB72CHEVKT]

Let me know if you decide to sell the motor and accessories.

[BHRS]

Originally Posted by BB72CHEVKT

Let me know if you decide to sell the motor and accessories.

Sorry I am going to sell of any of the original parts.

-Brian

[1-PU70]

Im getting 13MPG (city and highway combo) with my 402-700R4-3:73 rear and 31" tires.It has a roller cam, HEI, high rise cast iron intake and a 800cfm QJ from Jet. Factory AC and PS. I dont think you can do much better with a 350 and t400. I would get an overdrive trans and matched gears for the rear and you might be around 18MPG. Just my opinion. And run a Q-Jet carb.

[junkyardjohn]

IF YOU KEEP THE 72 BIG BLOCK TOWERS YOU CAN JUST USE THE 73 UP CLAMSHELL MOUNTS. THEY ARE MUCH STRONGER & EASIER TO LINE UP ON AN INSTALLATION. I REALIZE THEY AREN'T 100% CONCOURSE CORRECT, BUT NEITHER IS A SMALL BLOCK IF YOUR TRUCK WAS BORN WITH A BIG BLOCK, & THEY ARE A VERY NICE UPGRADE. IN MY OPINION. (BUT YOU KNOW WHAT THEY SAY ABOUT OPINIONS) I'VE HAD 6 CYL.S & THEN BIG BLOCKS IN THE SAME TRUCK & ONLY HAD ABOUT A 2 MPG DIFFERENCE, SO DON'T EXPECT A BIG IMPROVEMENT IN MILLIAGE. JOHN

[capev86]

like said above...run a q-jet (or tbi swap) and put in an overdrive!!!

if you want to get the mileage of a 350 (or better) but have more of that big block punch......make it a 377 (or 383 if it needs to be more than a hone job). i have a 406sbc w/ low miles on a rebuild to put in my 72 burb otherwise i'd make a stroker small block out of my stock 307 (it would be a 354 w/ just a crank swap).

an RV grind roller valvetrain is another great idea for daily driver duty!

[junkyardjohn]

Originally Posted by capev86

like said above...run a q-jet (or tbi swap) and put in an overdrive!!!
if you want to get the mileage of a 350 (or better) but have more of that big block punch......make it a 377 (or 383 if it needs to be more than a hone job). i have a 406sbc w/ low miles on a rebuild to put in my 72 burb otherwise i'd make a stroker small block out of my stock 307 (it would be a 354 w/ just a crank swap).
an RV grind roller valvetrain is another great idea for daily driver duty!

A ROLLER CAM IS GOOD.. THE ADDITION OF FULL ROLLER ROCKERS IS EVEN BETTER.. YOUR TALKING BETWEEN $800 & $1000 & IT WILL NOT FREE UP A BUNCH OF HORSE POWER ON A STOCK MOTOR (MAYBE 1 OR 2% AT MOST). SAME THING WITH A PERECTLY BUILT & TUNED QUADRAJET. 99.9 % OF THE GENERAL POPULATION CAN'T DO EITHER. (MYSELF INCLUDED) I'D BUY A TICKET TO SEE YOU HONE ENOUGH OUT OF A STANDARD BORE 350 TO MAKE IT A 377 CU. IN.. I THINK YOU HAVE YOUR NUMBERS MIXED UP. A STANDARD 350, .030 OVERBORE IS 355 CU. IN. ALSO MAKING A STROKER IS JUST A LITTLE BIT MORE INVOLVED THAN JUST REPLACING A CRANK WITH A LONGER THROW. 307 TURNED INTO A 354 CU. IN. MOTOR WITH JUST A CRANK SWAP?? NOT WITHOUT A MAGIC WAND. I JUST LOVE FREE ADVICE. ARE YOU MAD AT THIS GUY?? OR JUST CONFUSED?? JOHN

[capev86]

I'D BUY A TICKET TO SEE YOU HONE ENOUGH OUT OF A STANDARD BORE 350 TO MAKE IT A 377 CU. IN

i think you are the confused one. you combine the crank from a 400 small block with the bore of a 350 and you get a 377. most people just bore it .03 over and get a 383.

i have done the calculations:

pistons from a 305 with a 400 crank makes a 325

pistons from a 307 with 400 crank makes a 354


my 406 is a 400 bored .03. remember that the 305 has tiny pistons with the 3-1/2 stroke (same crank as the 350), whereas the 307 has the 327's 3-1/4" stroke with slightly smaller diameter pistons than the 327/350 uses.

[j_cst_10]

I have a 2002 Chevy Silverado with a 5.3 LS and an overdrive trans and get around 16-17. 18mpg with a carb'd big block and an overdrive might be stretchin it...........

[junkyardjohn]

if you want to get the mileage of a 350 (or better) but have more of that big block punch......make it a 377 (or 383 if it needs to be more than a hone job). REREAD YOUR POST. SOUNDS LIKE YOU ARE CLAIMING YOU CAN HONE ABOUT .160 OUT OF YOUR 350 TO MAKE IT A 377 CID. I DON'T BELIEVE YOU CAN . (I KNOW YOU CAN'T) YOU NEVER MENTIONED A CRANK UNTIL YOU SECOND POST, & I'M A LITTLE RUSTY AT MINDREADING. IF YOU GIVE ADVICE, ITS VERY HELPFUL TO SUPPLY ALL THE INFORMATION OF PARTS COMPONENTS INVOLVED, JOHN