Fishing for opinions here. I recently purchased a 1990 Blazer with a running but high milage 5.7 EFI. It is hooked up to a 700R4 not sure about the diff gears but not concerned. Anyway. I am going to pull the motor and as per my friend who is a mechanic has said. No need for a 4 bolt block you are not looking to race it. 2 bolt is fine. So what I think would be the smart thing to do is build something that provides good torque at a street driving rpm range and yet will be a good set up to tow a 17 foot travel trailer with as well. I don't ever plan on using my truck to climb rocks just want a really peppy motor and drive train setup. All that being said. Where would you go with this engine and transmission/differential gear configuration. There are so many head options, intake options, cam options. I am a bit over whelmed. Do I turn it into a 383 (which I am all good with) or what. I have a lot of time to work on this it is my project and I certainly want to lay the best common sense plans down before I buy a single part. Thanks guys. I got tired of the car forums. everyone there is looking to build a street racer with high compression and all that jazz. I am a truck guy and want to do this Blazer proud. on a side note I intend on adding about 4"of lift and maybe some 33's or there abouts and I do have a 1977 complete good running 454 and 400HT in an old motorhome that I can pull and use.

 

Budget will determine which way I would suggest you go. If your going cheaply $1500 will do a decent rebuild and tune on your engine as long as you don't need machine work. If your looking more at $3000 I would suggest a big block swap or a nice crate smallblock with warranty. If you really want the best bang for buck, a 5.3 or 6.0 would be great options, but are more involved.

As for your transmission, have it rebuilt by a reputable shop or use a decent kit like a monster-in-a-box and it will hold up to your modest power expectations.

Differentials and gearing is a whole separate ordeal. You are pretty limited to stock front diff which is already the weakest link in the driveline but can upgrade to a 14bolt semi-floater and retain your 6 lug bolt pattern with the benefit of bigger rear drums for better towing. Tire size will determine which ratio, then all you need is to decide on adding locker/LSD or staying open/ Gov-lok.

 

Their is another option I did not throw out there but it was because two different mechanics told me I should stick with the small block, but a few years ago I bought a 1977 Chevy Champion Motorhome. I got it for $800 the motorhome is crap but it has a sweet 454/400HT in it that only has 56,000 miles on it, the guy that owned it was a mechanic and kept it up, just used it for a hunting cabin up in Colorado mostly. I was originally going to use this motor and use it swap out the 350 but again i was told it would be a headache so I got discouraged. So you guys tell me whats the issue here. If I did do a 454 swap can the blazer handle it or will i just shred the transmission, transfer case and differentials? and as I assume I gotta upgrade all that plus maybe more springs etc. So what do i need to be looking for? Any links to parts etc would be appreciated so I can at least get a ball par figure on my cost to go one way or the other. I mean part of building a good truck and making it something that a real owner would appreciate is in the details. So far I have the whole front end off and have stripped everything down to bare metal and gave it all a nice coat of rust encapsulator paint. Just need to figure where to go with this motor thing. I won't lie the 454 is sitting right there but I don't want to go "damn its to powerful and won't work"

 

 

Do you want to retain TBI if you use the 454? A trip to the junkyard will net you all the parts that are 454 specific for a factory TBI setup to put on your motorhome engine. Basically a plug and play swap if you went that way. Pros: cheap and easy low rpm torque Cons: heavier and only slightly more powerful than your 350 tbi ~35hp.

If you retain the TBI on your 350 and rebuild do some reading on here: Harris Performance, INC | GM Fuel injection for the average guy

I would use the 700r4 behind either engine as anything without overdrive will drive you crazy and limit how much you actually use your truck. It needs rebuilt and beefed up regardless.

AN LS based swap (5.3 or 6.0) will be the most fuel efficient but also the most involved as you will be changing the entire fuel, electrical, mounting and instrumentation to work with the modern powerplant. The 700r4 can be used behind them but requires specific flexplate and spacer due to the different style crankshaft and some of the electronic transmissions that came behind them will work with your t-case, your mounting location will determine if the driveshafts need altered.

A lift kit will help with clearance and any weight increase if you decide to change engines/transmissions, but may complicate getting the drivelines at the correct length and angles.

 

Thanks for all your input. I have been thinking long and hard about it and the reality is that a blazer has a short wheel base and no matter what motor is in it, It will never be a good towing vehicle and since I do own a 2005 F350 that is paid for and have towed things to hell and back in, building the Blazer to tow a TT is really is not that big a deal and probably not wise anyway. I just thought maybe the ability to tow with the Blazer would be useful. So that brings me back to my 350 build. I'll save that 454 for another day. I could just rebuild it as stock and retain that 300,000 mile TBI reliability that it seems to be famous for, but seeing as I seriously doubt i'll even live another 300,000 miles lol why not add some good old fashioned low end torque and 0-60 get up and go. What to do, what to do. I need a solid blue print Guaranteed I will swap out the heads and intake (Vortec, aftermarket) I really don't care just want it to make good power and not totally kill me at the pump.