I keep geting different estimates on what my h.p. will be

ive got a fresh 355 with the lt-4 hot cam
'90 vette heads w/5 angle grind 1.6 rockers
tpis mini ram w/58 mm t.b.
short headers
paxton sn 93 charger with 8-9 psi pulley

any recomendations on precautions for longevity?

 

Don't use LT4 hotcam, especially for a boosted engine. You want a cam made for boost. Or at least a cam with more than 114 degrees of LSA. I'd say if you get the right cam maybe 450hp unless you get better heads.

 

Thats a missleading statement. Whats the overlap of the LT4 cam?

I just checked. -5 degrees. I.e, no overlap. Seems to me it would be a decent blower cam. Should peak cyl pressure nicely.

-- Joe

 

That's a good point. I assumed there was at least some overlap.

 

so you say 450 rear wheel or flywheel h.p.???

 

i'd say rwhp

 

I meant flywheel, but it's just a guess and doesn't really mean anything. It would make plenty of power, just how much is up to tuning.

 

Actually, you should be able to calculate it fairly close by working out the rpm that the blower will be spinning with those pulleys and seeing what the airflow is at that rpm… at that point airflow is proportionate to hp with the proper amount of fuel mixed with it, so you’re down to a rather simple educated guess.

Not having a compressor map or the pulleys in question to measure I’d be guessing.

 

Whats the formula for that mark?

-- Joe

 

For blower rpm? I think it would just be as easy as

(De/Db)RPMe=RPMb

Where D=pulley diameter, e=at engine and b=at blower

Right??

And then you'd just need to see how much air your blower is moving at that rpm???

 

Well, you can go quite a bit more complicated (and I usually do when I do) but the rule of thumb is that airflow at the compressor inlet in lb/min * 10 (it’s actually a little bit more then that) - compressor drive losses = hp

 

Are 90 Vette heads that good?

I doubt you would see 450 hp at the wheels. Maybe 400.

 

No, the vette heads pretty much suck, but you only need to come up with about 220cfm on the intake port and properly match everything else to see 450 hp NA. If someone knows how many cfm that blower will move with the pulleys that he wants to run then we could make a pretty decent guess at the power output and the boost that it will see.

 

i appreiciate the help and hope we can narrow the guessing to an accurate calculation