how much boost can a stock 400m handle?

 

How many miles are on the engine? Also, is it carberated? If carberated, are you looking at an up-draft or a down-draft system? If EFI, what year as it could be using SPEED DENSITY or MAF for fuel delivery. If EFI with MAF, you can normally go up to about 5 PSI of boost with no modifications of the spark and fuel system. If EFI with SPEED DENSITY, then it gets a little more tricky. Then again, you also need to look at the age of the suporting systems.

 

it has a carb and has about 100000 miles but might rebuild. just wondering