Need Specific on 350 to 454 swap in custom suburban

[MuddiGGEr25]

Ok some of you may recognise my burb Cliffy. 1988 V10 Chassis with a 1987 TBI 5.7L (which is currently giving me headaches) 3/4 ton C6P (i think) axles and springs from a 1984 K20 6.2L 4.10AR, 235/85R16 LR E. and getting a 4" cast iron block lift in the back to "rake" it a little unloaded, and try to keep it level when loaded or towing. I have a built TH350 and as you can see in the pic it handled 18,000lbs GCW like a champ so im not worried about hurting it.

I just traded a generator for a 454 long block, the seller stated the engine would be complete with carb, I guess my definitions of "block" and "engine" as complete are different than his, but I had driven over 100 miles to meet up and already been waiting 4 weeks.

There is a pic attached of the block, as well as the burb pulling a 11,000lb load for proof.

I have read many forums but everyone says that "everything" except brackets will just swap over from SBC to BBC, now here is where i dont want you to get confuzzled, I have a rebuilt 400ci SBC with only 3900 miles on the rebuilt and 88900 on the engine total. It is complete, but seized the 400 SBC is a 1979 chassis, and I want to get it fully dressed and install it in Cliffy and install the TBI 350 in the RV since the doghouse wont allow for a BBC without mods and I want to to retain as much "stock" appearance as i can for the wife's sake, well atleast until it gets a 4x4 conversion and a lift kit XD

What I want to know if i can do is this:

After cleaning the block, covers, etc.

1. Install the 4bbl quadrajet from the 400 to the 454 since its been rebuilt less than 3 years ago and is in immaculate shape

2. Pull the distributor out of the 400 and install it in the 454 after figuring out how to find TDC on #1

3. Fan from the 400 should bolt right on the water pump of the 454 yes?

4. My 350 PS pump should bolt up to the 454 bracket correct? im in need of a new pump in anycase so not a huge deal if i have to order one, just so long as it has the right hose connections


There is more im sure, but for starters this should be good.

The following is what i already know i will need to do.

1. I know I will need a externally balanced flexplate that has both TH350 and TH400 bolt holes, I am thinking of using the TH400 converter in the TH350 and keeping the TH350 converter with the TBI 350 and use it in the TH400, please tell me if this will not work. I can use the TH350 TC on the 454 if i have to, just thought I might keep the TC with the engine it was spec'd for, and the TH400 TC will be closer spec'd to match the higher TQ of the 454, i hope i didn't confuse you.

2. Alternator should bolt right up its a basic 10SI alt.

3. the "towers" are still on the 454 so i should be able to clear the fan shroud fine

4. a pressure regulator to bring the fuel from 12PSI-8PSI, however I ran my motorcraft 2bbl at 12PSI for over 900 miles with no illeffects, but it was easier to start in the winter, im not sure if the quadrajet is more picky

5. I would like some recommendation on headers or manifolds and tips/tricks, I will probably just get a used pair for the time being from a local dirt track team, but long term i might upgrade


As far as i know the rest should be just plug and play i think, unless im missing something major which is very possible lol

Thanks in advance, I am intending to do the swap either the end of next week or around the 1st. I want my RV running by mid april lol

[Engineer]

Sounds like you have it all figured out. I don't see any red flags in your post except:

Torque converter from the TH350 and TH400 will interchange and vice/versa as long as the torque converter from the TH350 is not a lock up style. Some early TH400s had a variable pitch stator but they are so rare and so seldom used in Chevy applications that I shouldn't even mention them.

Headers? I use the factory manifolds if I can. However if the need for headers is there my experiences will only allow me to use Hooker headers. They cost a little more but are worth it.

Good luck.

[Engineer]

Oh, one other thing, with that three groove pulley on your 454, I found that the water pump pulley that came with my 400SB worked just fine using that same crankshaft pulley that you have in that pic.

The trick is making sure the water pump pulley from the 400SB (or 350, or 305) came off an engine with factory A/C.

The crankshaft pulley on your 454 is indicative of your engine having had factory A/C.

[MuddiGGEr25]

Sounds like you have it all figured out. I don't see any red flags in your post except:

Torque converter from the TH350 and TH400 will interchange and vice/versa as long as the torque converter from the TH350 is not a lock up style. Some early TH400s had a variable pitch stator but they are so rare and so seldom used in Chevy applications that I shouldn't even mention them.

Its a TH400 from a 1979 G30 chassis so I probably wont have to worry about that part I hope 

Headers? I use the factory manifolds if I can. However if the need for headers is there my experiences will only allow me to use Hooker headers. They cost a little more but are worth it.


I am looking into headers because they put it into a custom mud truck albiet it was a beefed up 1/2 ton with 10bolts i think so I dont think it was delivering alot of tq past original specs, I was told by word of mouth is has approximately 81,000 on it. but no idea if it is stock or whatnot.   

Good luck.

Thanks lol im gonna need it XD

Oh, one other thing, with that three groove pulley on your 454, I found that the water pump pulley that came with my 400SB worked just fine using that same crankshaft pulley that you have in that pic.

The trick is making sure the water pump pulley from the 400SB (or 350, or 305) came off an engine with factory A/C.


The SBC 400 that i have does have factory A/C and smog but smog is getting ditched when i install the 350 TBI into the motorhome lol but the 350 tbi has the dual serp and Vbelt design so ill have to keep the serp pulley for the Alt on the RV if i am thinking correctly but I think I can attach the 400SB PS pump right to the 350tbi block and call it good since they are both on the drivers side

The crankshaft pulley on your 454 is indicative of your engine having had factory A/C.

[MuddiGGEr25]

Ok well due to a temporary layoff lasting longer than expected, i will be doing the cheaper route.  I will be taking the 400 out of the RV and just dropping the 454 in and bolt it to the TH400, i will be bypassing the factory dash AC since i will be running the RV A/C when driving.  not sure about the PS pump or brackets if they will swap or not, hoping so