the N/A 606 is good to maybe 250-300 but thats pushing it the rods are the weak point on it. if you check dieselmekens face book he has pictures of a few people that grenaded N/A engines trying to get more power. as for the turbo engine on a stock engine as long as everything is healthy they have no issue running at around 500 HP the issue becomes the turbo sizing and where you want the power band. a lot of people run HX35 or similar sized turbos making around 300 maxed out but with some down low grunt. you can also go for a HX40 or similar but then you are not seeing real spool until around 4000 rpm. you also need a better exhaust manifold and large intercooler if you intend to push the engine past maybe 250. with rods, cams, manifolds, porting, and some other internal work its possible to break 800 HP so the block and pistons are not the limit its just fuel air and at some point rod strength you need to think about. while there is some after-market for the 606 its still an oddball compared to a Chevy 350 so there will be a lot of custom fab no matter what route you take.

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1985 300D om617: 8mm M pump 175cc 5200rpm, holset he221w @ 30psi, large A2W ic, compounds on the way.
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