Hey everyone.  I've just got through most of the design stages of project Typhoon (my 1985ish GMC pickup) and I've been trying to figure out what shyould power it.  I've been doing some diggin and I found the three engines that might be it.  First there is the 454 7.4 Liter V8 from Chevy/GMC.  I know that will have plenty of power.  Next there is the 350 5.7 liter V8 from Chevy/GMC.  A little less power but better on the gas which is always a good thing.  Finally there is the Optimizer 6500 v8 Turbo Desil (sorry i cant spell it)  This is the engine that the military puts in their Humvees.  Which one should it be.  I really like the Optimizer but never got anything on its performance.  Doesnt need to go 0-60 in 4.0 just get me though the mud and up some hills.  Oh yeah the plan is to run tires sizes from 35 to 38 not quite sure which ones i want yet.  The engine will also determine the tranny i use so this is just step one in a long process.  Let me know any pros and cons of each engine or if anyone has any experience with any of them  

the gas engines are pretty easy to get parts for.  

I wouldn't bother with the diesel (proper spelling), unless you're planning on a major heavy-duty front suspension setup.  I don't know much about the Optimizer, but if it's what's in the Hum-Vee, it'sbuilt to Mil-spec and very heavy.  Being an NC mudrunner, I know that the lighter the rig, the better.  If you're only planning to run 35s, you'd be just fine with the 4.3 that came in your truck.

I don't remember if those Typhoons (that's the Jimmy-based, right?) came with Vortec heads yet or not.  But even then you'd be fine with 4.10 or so gears and D44 axles.  But if you insist on the V8, I'd go with the reliable 350.  It's easily built-up and parts are a dime-a-dozen.  You didn't specify your running gear (axles, trans, and t-case) but the 454 is overkill unless you plan on doing mud-drags.

Anything else?

duda73

Oh yeah, I almost forgot...

Along with the diesel being heavy as crap, it also won't spin your tires well at the low end of its power band to help sling the goo out of your treads. 

As far as the tranny, the SM465 manual is a stout trans, as is the TH700.  The TH700 can be upgraded easily with a shift kit made by several different manufacturers. 

Thanks for the tranny info.  I totally forgot that GMC made a Typhoon SUV based after the Jimmy.  I just called it project typhoon cause thats what I'm going to name the truck when finished (i like naming stuff after weather phenomona).  Its going to be a 1985 GMC pickup.  Looking back throught the engines, and the info about the low end of the Optimizer I am leaning towards the 350, which is still a good strong engine that i should also have no problem finding.  As for axels I was thinking about a Dana 60 in he rear if i cant find a Dana 70 from a dodge.  I dont know about the front, I'd like something thats Dana 60 strength cause its going to be punished when its totally complete, but I might be able to get away with a Dana 44.  I agrgee that the 464 might be a little bit of overkill but hey, we're guys, we like power. Thanks for the help.  If anyone knows anything about teh OPtimizer 6500 let me know cause I'm still interested in what that engine can do. 

Don't let the Milspec cool name fool you, (I've never heard it called the Optimizer 6500, but I know which engine you are talking about) I am in the military and the HMMWV engine you are talking about is a piece of junk.  It's a naturally aspirated non turbo GM 6.5 liter diesel very similar to what you might find in a mid '80's Blazer or Suburban.  If you go diesel, you have to get a turbodiesel to get decent torque and HP.  Unless you do a lot of towing, the diesel's probably not what you want.  How about a 383 stroker (350 bored .030 over with 400 crank)? It won't cost you much more than a stock 350 and you can easily get 400hp/450 lb-ft TQ and better on gas than the 454. Or forget the gas mileage and just go for the 502 Ramjet!  

Hey thanks for the info.  I think I'll stay away from the 502 until gas drops to about 50 cents a gallon.   

OK, so I was fooled by your truck name.  My bad!

I'd have to agree with the 383.

DUDA