[curtis73]

I think with common engines, its just the proliferation of experience. If I post a question that goes something like, "how much hp will I get with X heads, this compression, this cam, these exhaust manifolds, etc..." chances are there are four guys on this board who have done a nearly identical assembly and had it dynoed.

Its also just good old fashioned guessing. You can get really close just knowing about how much cam and compression it takes to get a 350 to make X hp.

The other phrase I HAAATTTE is "balanced and blueprinted." Bulls#!t. You slapped new bearings and pistons in an untouched 30-over shortblock. That does NOT mean B&B.

[hardhatz]

Well, I have a .030 over 350 with a cam, headers, manifold, MSD ignition, and pocket-ported heads. According to my fanny-dyno, it makes 223.75 HP @ 4750 RPM, with enough torque to spill 2.4 ounces for Pepsi from the cup in the drink holder, or spin a tire on sharp right-hand turns. Deduct 5% for each 1000 ft elevation above sea level. Your mileage may vary. Not valid in Rhode Island, or if you are left-handed.

[glen242]

Originally Posted by hardhatz

Well, I have a .030 over 350 with a cam, headers, manifold, MSD ignition, and pocket-ported heads. According to my fanny-dyno, it makes 223.75 HP @ 4750 RPM, with enough torque to spill 2.4 ounces for Pepsi from the cup in the drink holder, or spin a tire on sharp right-hand turns. Deduct 5% for each 1000 ft elevation above sea level. Your mileage may vary. Not valid in Rhode Island, or if you are left-handed.

Thanks for your VALUABLE INTELLEGENT input.

[barnym17]

I think a lot of it is computer dynos and optomistic parts selection.I.E "there ain't no way my engine is that weak I better use the max ported flow numbers" I use ea pro but anything it tells me I knock abou a hundo off the top to be realistic. Altho around here the dirt hobbystock motors have been turning between 550 to 690 on a real pump.The 690 version was a real Bad a** 427 stroker Ford with N351 heads a lot of work.

[barnym17]

Real funny thing the Ford popped at the end of last year owner threw in a 350 with mild hyd cam no comp. and was almost as fast proving once again in dirt racing setup and driver is where it is at.

[opelitis5]

On your next trip down the 1/4 mile, multiply your E.T. times your speed and see what you come up with... Should be 1320 if you are close to the ultimate setup... If over 1320 you are leaving power on the table and under 1320 which not many people are, your engine is overly-efficient.. Check it out!!!
There is / was a dyno book published that if you knew the weight of your car and the trap speed there was a certain HP level that you had... Witten by a Dr. Dean Hill entitled "Pocket Dyno"... There are other computative features in this neat booklet...
Starting this weekend at a track near Mtl. called Sanair, they are trying out a Speed times ET system of racing in which reaction times and dial-in times do not even come into play.... The closest one to 1320 as in the first paragraph wins a pretty big purse. Believe it to be $2G. Can run as many times as you want, and again reaction times and dial in times are not important in the least... Supposed to be some sort of European racing system and much safer for the competitors... Will be interesting to see how many cars show up as many racers with big $$$ cars have stated they want nothing to do with this in any way... Still 2G is a lot of scratch... We will see...

[upstand2]

"If over 1320 you are leaving power on the table and under 1320 which not many people are, your engine is overly-efficient.."
This sounds like traction , not HP.
Because my car with a 305 running 15.8@86mph =1358.8
and the same car with a 383 runs 12.9@105=1354.5
Pretty close. But the 383 is making way more HP!

[opelitis5]

This was the way it was explained to me... As I said one has to figure out why the numbers are over 1320... Looks like traction on the 383... Reaction times and dial-ins are non existent.. Maybe a shorter tire on the 305 would bring up the revs and bring down the 1358 to the 1320 magical number... Maybe if the 383 was "walked off the line" things would change... I don't know. This is a brand new type of competition if you'd want to call it that.
The money is great at 2G per Sund. and you can get as many runs as you want. How one would go about getting the 1320 is going to be interesting.
Slamming the brakes on or having the proper gearing would certainly help if the numbers are somewhat near or below 1320.

[oldbogie]

Originally Posted by glen242

Many people say they have a 400-500 HP SBC. Displacement from 327 to 400 CI.

Where these HP numbers come from is usually not quoted, but very rarely, an engine dyno is cited, numbers usually supplied by whoever sold the engine.

A chassis dyno reading, and I know these numbers can be massaged, is usually never supplied by the car owner, so that a comparison can be made between engine and chassis dyno numbers. Rule of thumb was, I believe, 15-18% manual and 20% and up automatic drive train loss. Does this "rule of thumb" still hold true?

My prior 350, stock 180HP, according to GM, with a cam, new heads, 9.2CR, long tube 1 5/8" headers, ST10 transmission, and Performer intake, measured 217 RWHP on a Mustang dyno. Using the 20% loss figure I came up with 271 Engine HP. Not too bad, I thought. Was my math correct?

I guess what I am asking is "how do you know what your engine specs are if it has never been on a reputable engine or chassis dyno"? Some say 1/4 mile speed will tell you, but how about driver error during the run, wheel spin, etc.? Computer sims can be manipulated, by what is input, to give different results.

I see people stating they have 450-500 HP on engines that are less built than my present 383 and wonder where the numbers came from, as they are usually never stated. Are we turning into ricers where we take each alleged HP increase from each separate aftermarket part and add them together and then add the total of them to our factory HP?

Maybe I'm just an old fart, but I find it hard to believe that 1.3 HP/CI, in a 383, is easy to get on a NA STREET CAR.

I once told someone on a Corvette Forum that there were more 400+ HP SBC cars on the internet than on the street, and I stick by this statement.

You might want to consider this post just an old man/hotrodders vent.

Comments welcome.

What do you expect; we live in an age where an Indiana cop claims he radar-ed a kid driving his old man's Subaru at a 147 miles an hour and that fake performance magazine Road and Track prints it.

We've know forever that the cops fake radar data and the courts swear to it. But anybody that's really gone a 147 miles an hour knows it takes a crap pile more rocket science everywhere in the vehicle than simply having big horsepower numbers to go that fast and not experience free flight.

Combat story; Many years ago I was at the San Diego County fair where there was an Ambulance company with a display claiming to get 450 horse out of a 390 Caddie engine. At the time I had a highly modified 390cid/401 HP Ford and getting 450 hp out of it, on the dyno, I was sweating blood. How they did it with a mild street cam, single Rochester WCFB four barrel carb, cast iron exhaust manifolds, etc. and an automatic transmission is apparently way beyond my abilities. Apparently you need a degree in advertising instead of engineering to do stuff like that.

Bogie

[American Thunder]

I have $10.5k in my 332" 302 motor. Reliable HP doesnt come cheap. And making 500+ hp from a n/a small block requires a lot of cam. No way around it.

The twin of my motor made 530 hp on an engine dyno, so that's what I go by. I installed it in a Mustang II that I lightened, the car weighs in at 2550 lbs without me.
With 275/40ZR17 street radials, 3.10 gears with a detroit locker carrier,(9" housing I swapped in from a 1959 T-Bird donor) a custom built manually-shifted C4 "mighty mite" transmission from Dynamic with 5000 rpm converter, the car will hit 85 mph in about 6 seconds using half throttle. At 140 mph, it will pin me into the seat the same way it does at 60 mph, and I'm not sure where it would stop pulling, as I let off it long before the motor reaches its limit of 8500 rpm.

My recipe for 500 hp from 332 cubic inches is 10.95:1 compression, 260 deg dur @.050" solid lifter cam with .625" lift. Victor Jr intake, jetted 750 Race Demon, machined TFS Track-heat heads with o-rings, 5.5" eagle H-beam rods with floating pins, JE ultralight forged pistons, ARP fasteners, forged billet steel crankshaft, billet steel main stud girdle, Melling 85 psi oil pump, SVO race pump shaft, Cloyes double roller timing set, MSD ignition and distr. set at 20 degs initial advance, +18 deg more by 1500 rpm. I enlarged and smoothed the oil return holes in the block to avoid oil starvation at high rpm.
I run underdrive pullies and swapped to manual steering to save weight(about 35 lbs!) and wasted hp. I also have dual mr. gasket electric fans to save wasted hp.
Fine tuning of the fuel and ignition curves is critical for making maximum power. Even if you have the right parts, the wrong state of tune will prohibit you from reaching your hp goal.

I'm figuring on 400-425 hp at the wheels, I'll have it on the chassis dyno this summer, hopefully I'm not disappointed.

When I look over various uploaded videos on the internet, it seems that everyone's car is making 600 hp at the wheels, yet in the videos they post, at full throttle, the skinny street radials arent spinning. Hmm.
The import guys seem especially prone to claims of 600+ rwhp from .001 liter or whatever motors with hairdryers, and again, no tire smoke at all.

Anyway, here's a couple of my own videos.
Half throttle run up to 85:
http://videos.streetfire.net/video/1...-all_14098.htm

And the gratuitous smoke show:
http://videos.streetfire.net/video/B...g-II_11661.htm