350 to 250 swap

[longbeach]

I have an 86 silverado K20 with 350, TH400. I'd like to do a swap for an inline 6. Will motor mounts and bell housings all line up. Are there certain years that will work and others that won't. Thanks

 

[Ken B]

i went from 250 to 350 and the motor mounts had to be set to the secondary set of holes. I have a th350 trans and it bolted right up....dunno if this helps or not. just my experiences

 

[longbeach]

Thanks, everything helps.

 

[Ken B]

i kept my 250 intact and mounted on engine stand....if i want/need to swap back it wouldnt be too bad

 

[RayS]

I swapped a 292 in place of a 350. The engine mounts stay in same place. But you need to use the six clam shell motor mounts as they are taller.

 

[AuroraGirl]

I swapped a 292 in place of a 350. The engine mounts stay in same place. But you need to use the six clam shell motor mounts as they are taller.

what do you mean by "six" :O

 

[AuroraGirl]

i went from 250 to 350 and the motor mounts had to be set to the secondary set of holes. I have a th350 trans and it bolted right up....dunno if this helps or not. just my experiences

That TH350 if it is for a 250 is under-equipped to handle a small block. Factory I6 TH350 have.. I forget which parts.. but they are not made to the same durability or what have you. They have less of something inside, I know, but just letting you know in case it was the OE th350.

"the stall speed is not the only difference, the 6 cylinder units had taller pistons in the drums...that means less clutches. Forward drum has 4 ,direct has 3,"
"The 6 cylinder used lighter springs in the governer"

if your truck doesnt see HD use I would think it would be OK but nature of a V8 power delivery vs a i6 may affect things, so just be careful I guess

 

[Ken B]

No heavy use planned but great Information