Big block ????s

[screamin_c102]

OK say I just happened to get my hands on a complete running 454 powered '73 C20 wth a TH400.

What would I need parts wise to swap the 454 and TH400 into my 71 C10.
I currently have the factory 307 and TH350.

I figure it should be relatively straight forward as our trucks came with the 402 BBC and the engine crossmember from the '73 is very close to the '71s

Will the mounts and towers fit my '71?

Will the '73 454 exhaust manifolds work in the '71?

Will the tranny crossmember need to be replaced or can I use my TH350 mount and crossmember?

What about the drive shaft, will it need to be shortened, will the TH350 yoke fit the TH400?

Will I need any special linkages ie. throttle, trans, etc.

[screamin_c102]

anybody?

[TireSmoke420]

dont see why it wouldnt be a direc swap. exept for maybbe the drive shaft but im not sure. i got the BB turb 400 comb in my truck

[tomatocity]

I don't know what you paid but a 454 th400 combo is very nice.

The engines for a 4x4 and BB sit further to the rear.

Your dizzy will fit but it is close.

BB motor mounts for sure.

What do you mean by 'towers'?

Not sure about the exhaust manifolds but that would be nice. you will most likely need to re-fit your exhaust pipes that connect to the manifolds.

Will the tranny crossmember need to be replaced or can I use my TH350 mount and crossmember? don't know.

What about the drive shaft, will it need to be shortened, will the TH350 yoke fit the TH400? if the crossmember is the same then the driveline should fit.

Will I need any special linkages ie. throttle, trans, etc. Do you have a cable throttle? if not this would be a good time to install one. transmission kickdown might be different.

What about alternator brackets, AC brackets, water pump spacing, pulleys, fan shroud, radiator hoses, fuel pump, is the fuel line the same size?, etc.

This should be a good project. Take your time and plan ahead. Take pictures, make lists for parts and tasks, cuss and drink less, eat well, sleep well, and call your mother and tell her you love her. Can't hurt and will take your mind off the future bottle necks

[Tx Firefighter]

Originally Posted by screamin_c10

Will the mounts and towers fit my '71? Not directly. You would have to modify slightly as the later truck's frame is taller. It's easier to use factory big block mounts for an earlier truck

Will the '73 454 exhaust manifolds work in the '71? Yes

Will the tranny crossmember need to be replaced or can I use my TH350 mount and crossmember? A TH350 and TH400 use the same crossmember. It will likely need to be moved, but the holes will be in the framerails. GM drilled the rails for this combo.

What about the drive shaft, will it need to be shortened, will the TH350 yoke fit the TH400? TH400 uses a different yoke. Whether the driveshaft needs mods depends on which length of TH350 you have now. You will need to install the new combo and measure to know for sure.

Will I need any special linkages ie. throttle, trans, etc. The TH400 uses an electric kickdown. The TH350 uses a cable. You will need to swap the TH400 donor truck's switch and wiring into your truck.

Frankly, I've done a few big block swaps and won't do another again. I'm too picky about stuff and wound up nickle and diming myself to death buying the original early model big block trinkets to make the swap completely original looking.

The 73 engine will be equipped with a long water pump and bracket set. The 71 would have had a short pump and bracket set. When you install the later, longer, stuff into the early truck, it won't allow you to use the factory fan shroud, as the engine will extend too far forward. You will have to either modify a fan shroud or find one that works off another vehicle. It's for this reason that I wound up spending big bucks for early original big block parts to make the later model 454 fit into my trucks. I didn't want to modify anything, I wanted it all factory looking like my trucks were original big block trucks. If you're not concerned with this, your swap will be easier than mine were.

[bowtie]

just to add ^

bigger rad

posibbly different front springs, although I didn't change mine and it works fine.

posi always helps

and a raise at work to pay for the extra fuel...

[screamin_c102]

Thanks for the info guys.

TXfirefighter, do you have any pics?