GMC motor swap 350 to 454

**CodyKidd** · January 6th, 2011, 06:47 PM

i have a 1974 gmc with a 350 and wanted to know
if the 454 will drop right in?....

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**sweld** · January 6th, 2011, 06:53 PM

yep it will just have to change motor mounts, might be a few other odds and ends but no biggies

**OVERKILL 19** · January 6th, 2011, 07:06 PM

Originally Posted by CodyKidd

i have a 1974 gmc with a 350 and wanted to know
if the 454 will drop right in?....

4x4? Headers will be different. Oil pan will need to be close to what you had. Get your 454 with all the accesorys. It will make you life easier.

**Mongrol** · February 4th, 2011, 10:57 AM

Also you should change the rad for the extra cooling the 454 requires.

**lane3030** · February 9th, 2011, 04:25 PM

if it's a standard, the clutch might have to be modified a bit, on my 85 if you let the clutch out it'd grind real bad, simple fix, but easier if you take the tranny rad etc.

**Rockwerx** · February 10th, 2011, 09:28 AM

I have done quite a few engine swaps and yes it can be done.

I have an 85 GMC 4x4 with a 454 in it. This truck came with a 350 700R4 transmission. A big block rad is one of the first things you want to install after installing the larger engine. The 454 eventually fried the factory 700R4 (with a Transgo shift kit). Installed a rebuilt T350 with a few goodies and it held the aprox 300hp/400ftlbs perfect for many years. 3 weeks ago I baked the transmission while plowing snow (it was my snow plow truck) when a line broke off of the transmission cooler though. I may go with a T400 this time although my engine combo does not really require it...mild to medium engine build running on propane. If you are running more torque and hp than stock then go with a built T400 and transmission cooler right from the get go.

Good luck with your project!

**rsw84** · February 10th, 2011, 09:31 AM

ya dude and when you get that SB out, have a look at the cross member thats riveted from frame rail to frame rail under the motor, alot of tiimes that thiing is tweeked and needs a little beefin up ...

**polarice** · February 10th, 2011, 12:40 PM

Originally Posted by rsw84

ya dude and when you get that SB out, have a look at the cross member thats riveted from frame rail to frame rail under the motor, alot of tiimes that thiing is tweeked and needs a little beefin up ...

dont forget the suspension might need stiffer springs as well

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**JMCX** · February 10th, 2011, 09:52 PM

I did this swap years ago. Pretty sure the motor mounts are the same but the 454 flywheel/flexplate has a balance weight, 350's don't. So use the right one. And ditto on the rad, the small block one won't cut it.