1991 suburban 350 to 454

[ww228king]

OK guys! I am new to the forum so this may have been mentioned before, but here we go... I have a 1991 4x4 1500 suburban with a blowed 350 FI. I have been given a free 1995 2wd 2500 suburban 454 FI engine. Nothing wrong with the 454, he just swapped out to a new crate 502. Here are somethings that I know that i will need: headers, intake to change to carb, bigger radiator, and prolly do some motor mount mods. Ok i need to know what headers will work what will i need to do about the motor mounts and what other problems will i be running into. I will be bolting it up to the existing tranny. Ok guys tell what you know. Thanks!

[streetstar]

First off welcome to the boards --- second --- Why are you switching to a carb? your tbi system should support the needs of a mild big block with maybe an injector change and a computer re-program at most -- a carb will make this motor run worse , the heads are designed to work with an EFI system. The tbi big block is a low hp, high torque motor and a carb might take away some of that famous big block torque , then you wouldnt be any better off power wise than a 350

The motor mounts are the same and you can get headers from Sandersen, Hedman, and Doug Thorley. I would hold off on the bigger radiator too, unless you get it hooked up and it starts running hot all the time --- a small block radiator wll most likely be sufficient for this engine unless you do a lot of towing. But if you just wanna play it safe and money is not an issue, a new rad. should cost you maybe $200

[rcbildr]

A few months ago I switched from a 454 to a 350 in my brother's 84 Suburban. The engine mounts are the same, and I had no problems. One thing to consider is a new shroud for the radiator fan, The 454 is a few inshces longer and it will move the fan closer to the radiator.

[ww228king]

cool!!! thanks for the info guys...so you are saying that i should have no problem dropping this motor in and could use the same computer to keep the TPI on the 454. I didnt know that i could use the same computer. I will be getting everything on the engine i just need to to trace down the wiring and retrofit?

[streetstar]

Originally Posted by ww228king

cool!!! thanks for the info guys...so you are saying that i should have no problem dropping this motor in and could use the same computer to keep the TPI on the 454. I didnt know that i could use the same computer. I will be getting everything on the engine i just need to to trace down the wiring and retrofit?

I have seen stock based 350 TBI systems used on 383 stroker conversions that were in a much wilder state of tune than a stock 454. So, it should be fine, but you can check with a couple of companies that specialize in TBI conversions. I only know of S&P (or is it SLP?) Performance in Mena , AR, but you should be able to do a google search and get all the info you need

[ww228king]

I tryed to find something on how to use a 350 FI system to feed 454, but no luck.

[streetstar]

http://www.hotrodlane.cc/

Drop these guys an email - they can point you in the right direction. Your computer and throttle body does not really care what size motor it is sitting on top of -- it will work as is, but will not be optimum unless you change the injector nozzles to nozzles with a larger size

[ww228king]

i have all the tbi stuff for the 454..... i email them about my issue. I will post their response. Thanks!!!!

[ww228king]

Here is the response... I put an X in the price so i would'nt get into trouble will advertizing issues. I am so glad thati dont have to change to carb. Thanks guys for all yoru help and i promise that it will not the last time.

Strangely the 1991 computer system was used in the 1987-89 454 trucks as well and then GM decided to change computer systems for the 454 trucks for some reason. The 1995 454 is a high pressure TBI system unlike your low pressure 350 TBI system which means you will have to change the fuel pump to a high pressure pump. I use a FPG001 from www.apeusa.com and you can use the 91 350 wiring harness but you will have to make some alterations for the IAC valve on the wiring harness for the 454 throttle body. Custom chip is $xxx shipped to run the 454 with the 4L60 transmission in your 91 suburban. I do recommend changing the cam in that 454 while you have it out. The Edelbrock 2162 cam will make that 454 perform more like a 454 should without making the gas mileage any worse.

[streetstar]

cool - glad those guys had some answers. The driveability of the tbi over a carb will be worth spending a couple more bucks on over a carb conversion if you use it as a driver and not a hot rod

good luck with it

[screwballl]

may want to look into a 3/4 ton 4L80 transmission to handle that higher torque... I have heard of issues (that you may or may not have) relating to the big block transfer using the previous tranny