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ok so question 1: can a stock 350 take low boost (6-8 psi) and still be relatively reliable? and what about the whole drivetrain? can a stock 700R4 take 400-500 HP?
and question 2: has anyone bought a $1000 twin turbo ebay kit and have it just explode after 3 days of use or are they reliable if you take care of them?
in case you are wondering this would be going on a 1991 suburban. it has tbi but i will be converting that to either a holley TBI or a carburetor.
I will answer this based on boost from a blower, as thats what I am familiar with and have ran for 25 years, I would not take the chance of 6-8 lbs on a "stock" motor simply becasue your stock motor is 25 years old, if it was a fresh rebuild with stock components I would run 3-5 lbs maybe, and yes you will get a thrill with 3-5 lbs, heck even when a supercharger or turbo is not on boost it will greatly improve power as its still providing much more volumetric effeciency over normal aspirated, even at 0 lbs of boost you are at 100% VE something tough to do with a high performance motor without a bunch of work. As for streetable, the more power you get out of it the more "picky" the motor will be on fuel quality, quantity & air temp, its just the way higher horsepower motors are, watch the drag races in a cool evening and you will see what I mean. I wouldn't even think about this unless your "stock" motor is rebuilt or in 100% shape, not a daily mode of transportation and even then run low boost, before you find out what the "weak link" is on the motor. I run 5-6 lbs with forged pistons, 4 bolt main and rebuilt rods with ARP bolts and a much larger fuel pump and lines than stock (1/2") and have good luck
As for the turbo kit, you get what you pay for and those chinese bearings will be humming on a turbo I am sure, buyer beware. As for the transmission I will let someone else more knowledable answer that.
From my experiences with 700R4's, no way will a stock one handle 300hp let a lone 4-500hp. You're going to need a good reman built to your needs with a good torque converter to handle boost if that's the way you want to go. Check out on3performance for good china turbos. Others I don't know about. I'm too leary to buy one and find out the hard way.
Welcome to CHR!
You’ve been given great info, re; turbo by Matt – listen to him as he knows the turbo stuff real well. As to the transmission, I’d be more concerned with the torque that you’re going to experience. A stock 700-R4 is good for 350 lb/ft – not nearly enough to handle the turbo. Lots of options for bullet proof aftermarket that will take double that number, but be prepared to drop between $1600 - $2K for the transmission and a new converter.