New to boost here, I am building new engine and have some basic questions.

Building 2 bolt 355 LT1 with:
Mahle forged .030" flat pistons
Forged connecting rods
Refreshed stock LT1 crankshaft
LE2 heads
LE 1.5 camshaft
Ported LT1 intake
All bolt ons and stuff in signiture.

I understand that a supercharger on a stck shortblock will quickly blow it up, but how will it fare with my setup as descibed above?

How much boost could I run and ensure engine longevity and near zero risk of supercharger related failure?

Thanks

 

Well I have a few questions:

What compression ratio? Why the stock crankshaft? Who's "forged" conntecting rods?

 

With the LE2 heads and Impala head gaskets approximately 11.2 to 1.
With the stock heads gaskets about 10.7 to 1.

The crank, I have been told by most that its fairly robust up to 500HP plus machining will be free. The rods will be Eagle H-beams. Maybe I am wrong here.

I dont want insane boost, just something reasonable.

 

That's a very high compression ratio if your looking to run boost. I would definitely look into getting some dished pistons to drop it down.

I'm running an 8.8:1 with totally stock heads, Felpro 1074s, and some -31cc JE pistons.

 

Is there a maximum amount of boost I can run with this CR that wont blow things up.

 

not much over 6-8psi... the problem you'll run into is that you'll have to pull so much timing to keep it from detonating that you won't make much extra power with the added boost. dropping the compression ratio is the only way you'll be able to add boost and keep the timing at a point where you gain some real power.

 

Point taken, what 6-8# blowers do you guys like?

 

I have a 355 with stock steel crank and rods,it has8-1cr brodex heads 2_4s on a 671 hamton blower .It runs pump gas ive been running it about 6 years and its dependable and quick

 

if you are at that high of a compression ratio already and have bought all the parts.. you went the wrong way.. boost raises your dynamic compression ratio so that 11.2:1 will be exponentially higher for each pound of boost you add. your static compression ratio on a forced inducted motor is similar to a NA motor.. you should gauge what your goals are.. for example if you know you are going to shoot for 500rwhp... you can do this on an lt1 with heads and smallish cam and about 10 pounds of boost reliably.. so you build the motor for 10 pounds of boost. now this is in a "build it and leave it alone" context.. most of us are so enamoured by how the boost feels we start dropping pulley diameters to get more power.. its just addictive.. so taking this truth into consideration.. instead of building a 9.5:1 SCR motor I would recommend putting something closer in the 9:1SCR range and making up for it with a little extra boost. with a blower car, your boost is already pretty much present even at idle with built up pressure in the intake tract pre throttle blades being bled off by a bypass valve.. so once you blip the throttle, the plenum is very quickly pressurised so your torque numbers come on quickly from increased port velocity even at lower RPM's... you are not as dependent on compression to make power as you are the extra pressure from the blower.

so.. my recomendation here is to swap those pistons or change heads. ift he motor is still on the stand and the pistons are still in the box, you should be able to move them pretty quick on ebay or the for sale section and go with a purpose duty piston that lands you at the 9:1 SCR and go from their.

as for blowers.. the P1SC kit WILL get you there.. but I would go ahead and jump right into the D1sc and save the hassle and expense of upgrading down the road since you will have a forged motor. the more serious recomendation is to go ahead and grab a eagle crank while the motor is apart and do it right the first time rather then spend money twice pulling and replacing down the road.. I say leave it stock or build it to the hilt.. cause the latter requires just as much work and money to do each time and laying out for the crank now will be cheaper then gaskets and all the rest that would need to be done if the stocker fails or if you have to worry about breaking it from pushing its design limits!

Chris

 

Boom-shakalaka.

9:1 SCR + forged motor + correct fuel system = How fast do you want to go?