small to big block... whats involved?

[Metal Twister]

I was just given a fresh rebuilt throttle body 454 and a 2x4 700r4. So what is involved in swapping out the 350 with the 454 in a 77 Jimmy frame. Only 100 lbs or so difference in weight so motor mounts, larger radiator, the ecu and retro fit the exhaust system? Will the TH350 hang for a while with a big block?

 

[sweetk30]

exaust / check flex plate to fit convortor bolt pattern and its for a ext balenced 454 / rad hoses might be little diffrent / front drive acc brackets / if tbi = new chip and few parts .

dist swaps over as long as NON tall deck bbc . motor mounts swap over unbolt from block and swap .

and if th350 good and built good it will hold fine . just keep it cool.

otherwise not a hard swap at all.

 

[Metal Twister]

exaust / check flex plate to fit convortor bolt pattern and its for a ext balenced 454 / rad hoses might be little diffrent / front drive acc brackets / if tbi = new chip and few parts .

dist swaps over as long as NON tall deck bbc . motor mounts swap over unbolt from block and swap .

and if th350 good and built good it will hold fine . just keep it cool.

otherwise not a hard swap at all.

Thanks for the input actually he gave me the whole running 1 ton van so all the accessories are on the engine except my billion watt alternator. thinking the motor mounts might land in the same spot? My main concern was will the drive shafts still be in the same location?

 

[wage92]

motor mounts are the same, drive shafts should be the same as well i believe...but dont quote me on that, someone else should know.

 

[76zimmer]

driveshafts should remain, most BBC installs are taken up with the extra length ahead of the motor mounts not behind it, so the trans position should remain the same.
wonder about your radiator....that BBC will make some heat!

 

[byggyns]

Also, if you are planning to use the TBI on a previously non-TBI vehicle, you need the fuel supply from an 87+ TBI blazer: tank, sender with pump, fuel / return lines, & fittings. The later tanks and diesel tanks have baffles that you need when you run an in-tank pump.

Either that, or you can recalibrate the carb you have on the '77 (Q-jet?) and get an external pump and new intake for the 454. I'm assuming the 454 is a late enough year that it is not machined for a mechanical pump and that there isn't an eccentric on the cam for it.


I am also not an expert on the PROM or ECM issues if you use the older non-computer controlled trans with the TBI, like not having a VSS output to the computer. That may cause issues, but I've not personally played with adding fuel injection to a previously carbed vehicle, so I don't know for sure.

 

[ChrisPerry]

Just FYI, remember that if you are in California. A 77 has to be smogged. If you convert to a TBI454 you need to put the correct smog equipment for the year of the motor to register it for the street.

 

[cuervo]

Just FYI, remember that if you are in California. A 77 has to be smogged. If you convert to a TBI454 you need to put the correct smog equipment for the year of the motor to register it for the street.

One more reason to move out of Cali!!

 

[Metal Twister]

One more reason to move out of Cali!!

Hey thanks for all the good advise here. Being I am getting the whole running van I think the fuel tank, and radiator etc. can be transferred over to my frame. Im kinda of the bastard child here because while it is a 77 frame the body is registered as a 74 and that's what I'm staying with! Of course the body is a bit different as well!

 

[sweetk30]

van tank will be 40 gal more comon i have parted 3 out and thay all had 40 gal.

and it will NOT slip in the frame rails of a truck . just a hair to wide.

 

[Metal Twister]

van tank will be 40 gal more comon i have parted 3 out and thay all had 40 gal.

and it will NOT slip in the frame rails of a truck . just a hair to wide.

I do have a tank out of an 86ish burb that is a bit longer than my stock tank but no return line. Thinking a return line nipple would be easy to install. Also saw somewhere a replacement fuel sender access panel that has the return line plumbing built into it?

 

[sweetk30]

newer tbi sender will swap in but no baffle in older tank for tbi/efi fuel pump to run at 1/4 tank or less correctly.

and if i recall there just longer than blazer 31 gal is all .