Originally Posted by RD46290
Hello, I am a novice when it comes to engine repair, but need to replace my stock 350TBI in my 91 K5 Blazer due to the piston pin knocking. I am wanting to put a 350 back in but one with a little more HP. It looks like I am kinda limited(unless I go with an expensive custom engine) due to it being fuel injected. I have found the GM 350/260 that I think will work with my set up but not positive. Can anyone give any suggestions on this or different ways to go please. I can spend about $2200 on engine. Thanks in advance
The engine you're looking (10067353) at is not the right engine for your application. The GM replacement for your 91 is GM12568758.
The engine you're looking at will not bolt to your intake. This would require that you rebuild or replace the swirl port heads of your 91 engine for installtion on the new long block. This would be an added expense in order to install the TBI or you'd buy a 4 barrel intake for this new long block engne with an adapter plate for the TBI and probably have to do a lot of work to get the EGR mounted and working. Elimination of the EGR takes a programming change to the computer's chip. If you don't do this the engine will run lean at cruise, frying pistons. So you can't just leave it off.
The GM12568758 is a direct replacement long block so the manifolds intake and exhaust will bolt right up. check here Chevrolet Performance 12568758 GM Goodwrench 1987-95 Truck 350ci/200HP Engine
Your TBI engine can be built up a little but TBI is very sensitive to manifold vacuum, you will find this called Absolute Manifold Pressure with regard to this engine. What mostly enhances performance is a cam change but cams reduce manifold vacuum (increase absolute pressure) which quickly screws up the metering as the computer is hard preprogrammed to look for specific relationships that exist between manifold vacuum and RPM by throttle position and by transmission gear selection and road speed it doesn't know nor can it do anything else. A new chip with a new program has to be made for all these new relationships that would exist with a new cam or any other changes that when incorporated changes these relationships; this is not cheap and doesn't always work on the first try. If 2200 dollars is your budget there really isn't much wiggle room for a performance build, these EFI motors very quickly get expensive and complex to mess around with. It can be done but you'd have to put about another 800 to 1000 bucks in the pot.
Then you get to the question; "will the tranny put up with a fresh young high power filly bolted on its input shaft?"