EXHAUST MANIFOLDS

Two different styles of manifolds fit the 65-70 B body (excluding the 66 427 solid lifter engine which used Corvette exhaust manifolds). I am told these manifolds which have superior flow to the lower horsepower manifolds only fit 1965 and 1966 but have never verified that.

For the regular manifolds, 65-67 B bodies use one style, 68-70 use another style and they do not interchange. The 65-67 B body only units are not so easy to find, the 68-70 are much easier because they fit a number of other models also and they are used into the 70's.

 Until I can find more detailed info for B body only, this might help-

3856297 65 396 LH 325 HP
3856301 65 396 LH 425 HP Corvette
3856302 65 396 RH 425 HP Corvette
3856306 65 396 RH Passenger 325 HP
3857297 65 396 LH Passenger 325 HP
3868874 65-66 396 RH Chevelle 325, 360 & 375 HP Z-16
3869925 65 396 LH Chevelle 375 HP Z-16
3872770 66 396 RH
3880827 66-69 427 & 454 LH Corvette
3880828 66-72 427 & 454 RH Corvette 270,365,390 &425 HP with and without A.I.R. LS-5 & LS-6
3880869 70-72 454 LH Corvette 365 & 425 HP with and without A.I.R. LS-5 & LS-6
3883827 66 427 LH Passenger
3883828 66 427 RH Passenger
3883999 66 396 LH Chevelle 325, 360 & 375 HP
3884504 66-67 396 & 427 RH Passenger 325, 385 & 390 HP
3892307 66-67 396 & 427 LH Passenger 325 & 390 HP
3902401 67 396 LH Chevelle
3904399 66 396 LH
3909879 67-70 396, 427 & 454 LH Chevelle, Camaro and Nova 325, 350, 375, 425, 430 & 450 HP LS-6 COPO
3909880 67 396 RH Chevelle and Camaro 325, 350 & 375 HP
3914613 68-70 396 & 427 LH Passenger 265, 325, 335, 345, 390 & 425 HP
3916178 68-70 396, 427 & 454 RH Chevelle, Camaro, Nova and Passenger 325, 350, 375, 425, 430 & 450 HP COPO LS-5 & LS-6
3969869 70-74 454 LH Corvette 270, 365 & 390 HP with and without A.I.R. LS-5
3989310 71-72 402 & 454 RH Chevelle, Camaro, Monte Carlo and Passenger
3989343 71-72 402 & 454 LH Chevelle, Camaro, Monte Carlo and Passenger
3994045 73-75 454 LH Police

STARTER

This is for the most part fairly easy. Whatever starter you have on your car now will fit on the big block as long as you are using the same flywheel or flexplate. If you are swapping to a 454 you will be getting a different flywheel or flexplate from what you were previously running  because of the 454 being externally balanced. In that case, just make sure you have a starter for the 168 tooth gear which all 454's used. If you are swapping from automatic to a manual trans at the same time you must get the correct starter with the cast iron nose with the correct special starter bolts which fit the cast iron nose only. Link to the starter bolt details-

327 396 427 Starter Bolts - Canadian Poncho (activeboard.com)

The starter brace (which is most important, don't install a starter without a brace on it) is unique to big blocks so if you are using your small block starter on the big block you will need to get the proper brace. It is still available new from GM, part number 3965588.

Use the same attaching bolts that the starter used with the small block.

CLUTCH PILOT BUSHING

This one is pretty important and of course you only need to do this if you are running a manual transmission.

The clutch pilot bushing you will buy depends on the year of crankshaft you are using. The link to this thread will help you determine what you need-

 

 Pilot bushing when converting from automatic to manual trans. - Canadian Poncho (activeboard.com)

OIL PRESSURE SWITCH/ SENDER

The oil pressure switch from a small block will fit a big block but it doesn't mount in the same place. Small blocks have it beside the distributor, big blocks have it down by the oil filter. Most small blocks have a 1/8" pipe thread female port for the unit. On big blocks the port is 1/4" female pipe thread so you must by a fitting that is 1/4" male pipe thread with 1/8" female pipe thread. Also, they use an elbow to point the sending unit up because on the big blocks it comes sideways out of the block and the sending unit will interfere with exhaust or clutch linkage. 

FUEL SYSTEM

If your car is currently a 6 cylinder, 283 or 307 it likely has a 5/16" fuel line from the tank to the pump. You can get away with it unless you are planning lots of hard, higher RPM driving in which case you may end up with the engine starving for fuel. The big blocks all had 3 /8" line the whole way from tank to carb. 

I tend to shy away from NOS fuel pumps which are still somewhat easy to find because I'm concerned they likely don't have the correct diaphragm in there to stand up to ethanol which almost everyone has now in their fuel.

If you are trying to make your big block swap look stock, you'll have a brute of a time finding a correct looking fuel pump. For 1965 and 1966 the pump looks different vs 67 and up.  All the ones out there are a nasty looking housing vs the original with one exception I've been able to find. That is the O'Reillys's pump M16210 (US auto parts store) that is the same style as original. The 67 and up pump is readily available from a number of suppliers. The difference is the way the fuel outlet threads into the pump.  See this thread-

Canadian Poncho (activeboard.com)

That's all I have for now, feel free to add questions, comments, part numbers etc and especially add any experience you've had with obstacles you've had to overcome with the swap if I've missed it in the notes above. I can edit your comments into the appropriate section above as required.

It will be a bit before I can get at it but that's a good idea, I'll work on that upgrade.

Thanks Mark for confirming that for 67.

My first ever big block swap was in 1978, a 68 Chev 427 being dropped into a 283 66 Grande Parisienne. I initially tried just pulling the 427 from the 68 and dropping it into the 66. The 68 engine mounts would not fit over the 66 small block towers. I simply removed the 283 engine mounts and bolted them to the 427, then dropped it in.

Here is some numbers/info from my files/conversion...

1.. 65-67 Chev and 67-68 Camaro are the same for.. P/S brackets, A/C brackets, and Alt. ( 3884506 upper, 3878264 bottom) The BB power steering pump is different then the SB, also the reservoir is rare.
2.. 66 rads, upper hose is on dr side
3.. Rad spacer is thin for BB, the wide (4") is for the SB. You need the the thin spacer to get correct spacing for water pump and fan shroud.
NOTE.. I'm not sure for Poncho (Carl?), but BB Chev, there were 3 different shrouds. SB plastic, BB plastic, and a metal shroud. (BB plastic being repod)
4.. Alt pulley 3844100 3 5/8" across ( I have a spare)
5.. water pump 1968 short, 69-72 long
6.. Starter nose 1965721 cast iron
7.. Power steering pulley 3873847 deep pulley
8.. Water pump pulley 3864480 or 3906656 (7 1/4")
9.. Crank pulley 3869978 (casting# not part#) 3 belt
** You need ALL of these parts for BB conversion to get the alignment and geometry correct for the front of the engine to coincide with the rad and shroud.
10. Exhaust manifolds 3880827 L 3880828 R for B body cars. Corvette manifolds will work, but very tight on drivers side to install oil filter 3994045 or 3969869

HTH

Tom, when you do a conversion will you be looking to make it like the regular 427 or the L72 solid lifter 425 horse 427? The reason I ask is, some of the numbers Bruce mentions in his post are for the L72 427 only, they aren't used on the 390 horse 427.