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RD46290 03-10-2013 05:16 PM

350 tbi
 
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

oldbogie 03-11-2013 01:48 PM

Quote:

Originally Posted by RD46290 (Post 1655450)
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?"




Bogie
Bogie

RD46290 03-11-2013 04:51 PM

Thanks for the reply Bogie. I have been trying to make a decision on the engine replacement for about a month now. As I said I am not an expert on this and was just wanting to beef up the new engine I am putting in. I am almost thinking the best thing to do is go with the more stock 350/200 engine and add a couple things to get a little more HP, but if I was able come up with some more $ have you or anyone else dealt with Blueprint engines? I found this engine today and it looks like it would work with my set up.
Blueprint Engines BP38301CT Blueprint Engines SB-Chevy 383ci TBI Truck Engines

oldbogie 03-11-2013 05:51 PM

Quote:

Originally Posted by RD46290 (Post 1655827)
Thanks for the reply Bogie. I have been trying to make a decision on the engine replacement for about a month now. As I said I am not an expert on this and was just wanting to beef up the new engine I am putting in. I am almost thinking the best thing to do is go with the more stock 350/200 engine and add a couple things to get a little more HP, but if I was able come up with some more $ have you or anyone else dealt with Blueprint engines? I found this engine today and it looks like it would work with my set up.
Blueprint Engines BP38301CT Blueprint Engines SB-Chevy 383ci TBI Truck Engines

This is a stroker 383 with a good crank and rebuilt rods with beefec up bolts, the heads I'm gussing these are Swirl Ports as they say modified stock heads with with larger valves for what they are worth on those ports. The swirl vane limits the 350 to about 4500 RPM. Larger valves won't change that without some serious port grinding to eliminate the swirl vane.

The cam is about as far as you can push TBI with a chip which I see is included without some extraordinary effort.

280 horses @4700 RPM is the advertised, it actaully is a pretty flat curve getting close to that level 4200-4300 then just hanging there. You'll pick up a lot of torque just from the larger displacement and longer stroke. The horsepower is really limited by the TBI's fuel and air delivery capacity. There are 670 cfm TBI's out there Holley or 454 GM used a 2 or 1-7/8's throttle bore respectivly. But the issue is really how much fuel can you deliver with 2 injectors and 280 hp is about it again without getting into fancy mods to the injectors, read that expensive. You can crack 330 hp with just two injectors but getter there but they will empty your wallet as fast as your gas tank.

All in all this isn't bad, like I said getting big power numbers out of TBI ain't easy or cheap, this engine is right on that limit where it costs really big bucks to go further. But given your existing engine has been rated somewhere between 190 and 210 HP (GM seems to change the rating from year to year with no apparent changes to the engine) so 280 HP will be felt by you.

GM 383 Engine Specs (BP38301CT) | BluePrint Engines

Bogie


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