350 to 454 swap?

[vjfelix55]

Ok guys I have a predicament. I have 2 trucks:

81 c20
81 k20

The c20 has a 454
The k20 has a 350

Both of the trucks need a motor rebuild and I bought the c20 originally to put the 454 in the k20. So assuming I wanna Do the swap, what will I need that's new? (Fuel lines? Etc) Are the mounts the same? If not what do I need to make it sit in the same spot as the sb motor? Or should I stick with the sb? Has anyone done this before? Thanks

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[Engineer]

Been done a zillion times.

Use the motor mounts that come with the 454. Both will work but I have found that using 350 mounts on the 454 will cause the fan to rub the bottom of the fan shroud.

Use all of the parts from the 454 truck in the K10. MAKE SURE you don't use the 350 flywheel on the 454. Everything else should be obvious.

Posted from my CB using ch.19.

[Irish_Alley]

beside from having the big block why do you want to do this? if it was me i stay away from the big blocks, i dont know why but i much rather get a 350 and get her running right. also inspections might be an issue.

[ehjorten]

From my experience on my 1991 V3500, the small block and big block motor mounts are different.  The 454 mounts are larger and have a different mounting pattern to the frame.  Also...the Frame side mounting brackets that are bolted to the frame are different!  You will need to unbolt them from the frame and swap those as well.

[vjfelix55]

beside from having the big block why do you want to do this? if it was me i stay away from the big blocks, i dont know why but i much rather get a 350 and get her running right. also inspections might be an issue.

Well I have a friend that swapped a 454 into his blazer that was originally a 350 and he always says "once you go big block you never go back" and the little time I did have to drive the 454 before my friend broke cam bearings and blew head gasket that truck was powerful

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[vjfelix55]

Been done a zillion times.

Use the motor mounts that come with the 454. Both will work but I have found that using 350 mounts on the 454 will cause the fan to rub the bottom of the fan shroud.

Use all of the parts from the 454 truck in the K10. MAKE SURE you don't use the 350 flywheel on the 454. Everything else should be obvious.

Posted from my CB using ch.19.

Ok and will the 205 transfer case work with the th400 tranny? Or will I need a new one or can I use the th350

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[Irish_Alley]

dont change the trans or transfer case. i understand about the power of the big block and cant argue with it. just i would talk to some people on here about building a small block and get good power out of it

[82silverado]

Big Block is the way to go IMHO.

[Irish_Alley]

rubbish  lol

[Rattler12]

Ain't no substitute for cubic inches........and you'll pass everything but a gas station..... if you want to fill the tank up cut the motor off....

[Irish_Alley]

my thing about the 454 is you have to feed all those CI no matter if you need the power or not. my buddy has a 454 in a 90 crew best he could get i want to say 7 or 8 (th400). now in my 91 crew i had a 350 and 4l80e we never lined them up or anything but i was getting 12 going 80 on the highway. even a 90s 454 (99) can only get 10-14 with OD. if you need the power with the 350 you just floor it and you can get it. if youre towing sure the 454 is better then the 350 cause you have all the power down low

[Trucker2k16]

Sorry for replying 3 years later i have a 1991 v3500 im putting a 383 in and im using the 454 mounts but i see where someone says the frame mounts are different that bolt to frame.