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73-87 Chevy _ GMC Trucks => 73-87 Chevy & GMC Trucks => Topic started by: 425hp87chevy on June 08, 2010, 09:25:13 pm

Title: big block to small block and back?
Post by: 425hp87chevy on June 08, 2010, 09:25:13 pm: I have a 87 1/2 ton 4x4 350 throttle body with a 4 speed. and a 91 1/2 ton 4x4 454 throttle body 5 speed. I need to switch motors in the trucks (454 in 87 and 350 in the 91) and i want to leave the tranys. Exhaust I'm not worried about. Will the transmissions bolt up? can i switch the bell housing? Will my wire harnesses work. And what do i have to do with the engine mounts. Any input/advice welcome and any other information needed i can supply. I'm usually good at this stuff but I'm a small SBC guy, big block and throttle bodies are not my thing ???
Title: Re: big block to small block and back?
Post by: Irish_Alley on June 09, 2010, 01:28:24 am: the bellhousing to engine are the same the bell housing to transmision i want to say they are all most sure if its a sm465 and nv4500 for 91 im almost sure they are the same. just remembered about the trans how you going to work the transfer cases the 87 is passengers side drop and the 91 is drivers side. need to know what transfer cases and transmisions you have
Title: Re: big block to small block and back?
Post by: Blazin on June 09, 2010, 06:33:23 am: They will bolt to the bell housing no problem. You said your leaving the trans so the transfer case issue won't be an issue.
Title: Re: big block to small block and back?
Post by: 425hp87chevy on June 09, 2010, 10:49:11 am: i am leaving the tranys, what about motor mounts, what do i have to change
Title: Re: big block to small block and back?
Post by: Irish_Alley on June 09, 2010, 08:31:43 pm: Didn't read it right. Thanks blaz
Title: Re: big block to small block and back?
Post by: bigblock73 on June 11, 2010, 02:35:58 pm: Engine mounts are the same as well
Title: Re: big block to small block and back?
Post by: DnStClr on June 12, 2010, 04:50:08 pm: For the wiring harness, both trucks use the same ecm, 1227747, so the harnesses should be the same too.