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Guest Anonymous

How High Can a Stock L28T go?

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Guest Anonymous

How many horsepower can an L28T (F54 block, stock rods, pistons, crank. P90 head) make without mechanical breakage?

With a basic rebuild with a goal of 300-350 HP, are their any structural mods necessary? For example ARP rod bolts?

When does it become necessary to convert to forged pistons? Waht about full floating small end bearings, stainless steel valves,etc?

My goal ist to make 300-350 hp using a fresh stock bottom end with maybe ARP rod bolts. What approximate psi wuld be needed for this hp level (using T4/T5 turbo, sds, nice intercooler, stock intake and exhaust manifolds).

All these questions are really important to me as I am trying to decide whether to stick with my turbo engine plus sds or go with a v8 conversion. Thanks a bunch!

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Guest Fast Frog

Dr Graham:

 

I bought my 76 Z in Nov 75. I've had 3 diff turbos, 2 diff hds, 2 engines with intercooler, alcohol/water injection, aftermarket FI and other upgrades. HP for the last turbo setup was around 325+/- @ 4600 ft elev. I finally decided to do a V8 conversion for greater power thru out the lower end driving range (2000-5500rpm) of a "street" vehicle.

 

So I don't take up more space and time on this public forum, if you'd like more details of my past turbo setups and why I went to a V8 conversion, contact me at [email protected]

 

Rick

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300 rwhp is right on the edge of what the stock pistons can handle reliably. The pistons can live at this power level, and maybe even a little more, provided you never make any tuning mistakes.

 

The problem with the stock pistons is that the ring lands won't stand up to much detonation. At those power levels, there just isn't much margin for error. The good news is that broken ring lands don't generally cause much additional damage to the engine, as the broken pieces are usually retained by the rings, provided you catch it in a reasonable amount of time. You do still have to replace the pistons, obviously.

 

If you really want to make that much power, I'd personally forego the stock pistons and go straight to forged. The first broken set of stock pistons will end up costing you about the same as a decent set of forged pistons, anyway.

 

The full floating pins are probably not absolutely necessary, unless you plan to do a lot of sustained high rpm driving. SS valves are probably a good idea, though, or maybe ceramic coatings on the face of the stock valves. Again, more margin for errors in tuning.

 

Also, I'll never recommend against using ARP products (always a good idea), but for 300rwhp, the stock rods are plenty strong. If you were going to go with ARP hardware, you might as well go the whole nine yards - ARP main bearing studs, head studs, and rod bolts - it's not that much more expensive.

 

As far as boost levels, you will probably have to run ~12-14psi to get 300rwhp, depending on how well your system is tuned, how well the engine breathes, how efficient the turbo is, etc.

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