Thread: how much HP do you think this engine will have

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Ive got a 350 4bolt thats been bord 30 over with flat top pistons shaved heads with 3 angle valve grind edelbrok preformer aluminum manifold holly 600 duble pumper k&n air filter holly headers and a 260 comp cam and stock 350 stroke what do you think the HP will ruffly be on this engine

I'm going to say around 250 HP.

guessing someones horsepower is like guessing a girls weight?? do ya tell em what the want to hear or just pick a number??? Get it together and run in on a chassis dyno. This will give you the real world horsepower that is actually making it to the ground, not a WAG about what the number might be at the crank.

I figured I'd bring some of my previous comments on HP back.


Beings as how I've made a couple of comments about about HP numbers here in the last couple of days, I thought I should explain my position on them and the reasons for it.

Do you know what HP your talking about??

Gross HP (engine HP as determined by an engine Dyno without any accessories and usually under ideal conditions and with a "laboratory" intake and exhaust).


Net HP ( more real world with all the accessories connected and and standard intake and exhaust systems).

Rear wheel HP (What a Chassis Dyno will see at the tires after the drive train eats up it's fair share of HP)



Brake HP (HP= RPM X Torque divided by 5252) is a mathimatical formula that needs to be based on real values. Without those real values (and the only way I know to establish those are on a Dyno) you can skew the numbers to say almost anything you want to.

Even factory HP ratings from the 60s (and after seeing some of the numbers on the new preformance cars I think some of those too) were/are often either optimistic or grossly under rated. In most cases the numbers were based on a blueprinted engine with optimised fuel and exhaust systems. These tollerances are of course not carried over to the assembly line. In the case of the under rated engines (the 426 Hemi and some of the COPO Chevy big Blocks come to mind) the HP number was pulled at an RPM much lower than the actual peak HP was generated at.

This is also pretty much the same story with engines and engine kits you buy that advertise a certain HP. In many cases they had ONE optimised engine that really did generate those HP numbers, at that specific altitude, at that particular temp, on that particular day with a specific intake and exhaust.... AND in many cases these are "CORRECTED" numbers to take certain variables into account (and usually raise the HP numbers that are then advertised).

IMO the computer programs are little more than an educated guess. There are certain variables in even 2 "identical" engines (friction loss, cylinder imbalance, cylinder leakage etc come to mind) that the program would have to take into account. Many people also have a tendency to be a little optimistic when plugging in the variables. Additionally, without taking into account things like intake/exhaust runner volume, legnth and texture (i.e. the actual efficiency or tunning of the intake and exhaust systems) the numbers become a best guess.

Finally, an engine on a dyno is little more than a fancy coffee table. It's what the CAR (truck or what ever) actually does that matters. All the HP in the world does not mean anything if the rest of the combination is not "dialed in" to use it.

I say 245

the 4 bolt mains gotta be worth 50 HP, & than the K&N filter must be another 50 HP

Originally posted by Streets
What did the Dyno slip say??

I still say you are bad to the bone.

Originally posted by Stepside454
the 4 bolt mains gotta be worth 50 HP, & than the K&N filter must be another 50 HP

... and you ain't no better.

chevyman, don't let these guys get you down. My guess would be, under 200 rear wheel hp.

I'm going for the 200-260 Hp range but, the trip to the Dyno woulden't hurt.

I'm going to say 150 to 500
Pleeeease....... I'm kidin'
Gotta admit tho, I probeee' got it covered
It's bean a lo-o-o-o-ng day what ken eye say .

Ya after I wrote that thread I figued I would probibly get answers like that I gess stupit Questions deserve stupid answers and I dont actually have dino slipes And Im not going to I think its a waste of time unless your doing some serous raceing I just wanted to get a ruff idea
and pro70z28 that was a good answer You got it covered man