sammicurr86

Going to be replacing my 350 with a turn key 455 come fall (with a th400 trans). Going to have someone build it form me. The engine will be used as an everyday driver/weekend strip warrior (on occasion).

I'm looking to get 500hp on pump gas, BUT my friend said that's not a good idea as it exceeds the cubic inch of the engine, which will result in things breaking, therefore making the car UN-reliable and not suited as an everyday driver.

Is this true? Should I not exceed 450hp on pump gas?

My main concern is reliability, but I also want enough power to shame some ricers and beamers. I'm not an engine guru, but what do you guys think?

What is the ideal medium for long lasting reliability and power?

cutlassefi

What's your budget? That can sometimes effect the potential reliability in trying to achieve 500hp.

sammicurr86

$4000-$7000

cutlassefi

If you're willing to spend upwards of 7k then you'll be able to make 500hp reliably as long as you're willing to do some of the work yourself.

Lee_A

There are SOOOOOO many impressive-sounding numbers thrown around in the car world, and few people REALLY understand what those numbers mean.


I own a chassis dyno. Customers have nicknamed the dyno "The Heartbreaker." We have dozens of people each year who have "500" or "550" horsepower motors, and many of them don't even put 300hp to the wheels.


It is one thing to make good power on an engine dyno, which will typically use large headers with smooth tubes, no mufflers, an electric waterpump, no air filter, and a fuel system that is way more than adequate at supplying the needed volume and pressure. Once installed in a car, with headers that have tight bends to actually fit inside the chassis, real world mufflers, all the accessories,... power drops.


Generally speaking, a given motor will make certain amount of torque. A 455 will make a very good amount of torque, if built properly. Horsepower is a function of torque at a certain rpm: (torque x rpm)/5252 = horsepower. To make more HP, you have to shift the torque to higher RPM, and doing so will COST you torque at lower RPM. Also the 455 Olds isn't most efficient motor to work at higher RPM.


I had a 455 that barely put 315 hp to the wheels. But, it was a MONSTER off the line. For the first 4 or 5 seconds of a race, it blasted ahead of many 500+ horsepower motors.


My suggestion: do not build your motor to achieve some arbitrary horsepower number that just happens to sound cool. Instead, talk to people who have build well-performing motors and tell them what gears you plan to run, what stall speed you are willing to run, what sort of exhaust, and what actual performance characteristics you desire - then let them design an engine for you.


For street cars, BIG torque is more fun than BIG HP.

deadeyejedi

well said lee .if i may jump in ? is there a general percentage drop that you notice betwwen the engine dyno hp and the at the wheel dyno hp .ive always been curiuos to know what the 1970 455 would be rated at with the newer system rating they used in the 70's?

rccktmn2

Along with what Lee said there is also a percentage of HP and torque that is lost in the transmission and drivetrain. If your clutch is wore out, transmission is slipping etc. all will add up to HP and TQ loss. Those impressive numbers will drop because of this, anything you bolt to the engine will also have some power loss associated with it, A/C, P/S, etc.

deadeyejedi

So I would consider at the wheel hp and torque to be the real world numbers .

svnt442

That is subjective. You can dyno an engine with all of the accessories installed to get a real world at the crank number, but most engine dynos don't do that so that they can get the highest number possible. I personally have never been a fan of that approach because it gives a false number due to it not being the configuration that the engine will be operating in.
If you want the net then a chassis dyno is the only way to fly.

Lee_A

One of these days, I'll make a page on my website that shows RWHP (rear wheel horsepower) differences I've witnessed ON THE SAME motor by changing various components - torque converters (up to 100hp difference), air filter systems (30+), mufflers (30+), etc.


Manual transmissions will lose the least. An automatic with a lock-up converter than can be locked for the test will be close to a manual. A stock torque converter will be next, and the looser the converter the lower the readings will be.


Chassis dyno numbers with really loose converters are deceptive, as it does NOT indicate how the car will run at the track.


With that said: a manual with excellent support systems (exhaust, fuel supply, air filter, etc.) will probably lose 18-22%. A lock-up automatic maybe 20% to 22, and non-lock converters from 22 to 30+.

wr1970

I wouldn't even take a 315 hp to the wheels 455 to a track. But that is me. Sounds like lee had a bone stock engine in a heavy car. Care to tell us what specs were of this car? Everyone has to start some where. It takes a lot to make a car work good at a track stock or not.

matt69olds

About 15 years ago my car was featured in Car Crafts Street Machine National 10 dyno proven power combinations. At the time, the car ran 12:40s (7.90s eighth mile) it dynoed 319 at the wheels. If I remember correctly, tje torque was around 440. The problem with chassis dyno has been explained before, its just a number. If you make changes, and can compare dyno runs to previous test, and see improvements, then a dyno becomes a tuning tool.

wr1970

I would say the dyno had wrong number on your rear wheel hp estimate. Should be close to 340. If you know weight of car mph and et.you can plug that into a racing clac. I have found that Wallace racing calc on line to be in the ball park. JMO

cutlassefi

I don't agree with much of this and I'll tell you why.
Why not do both, engine and chassis? At the very least you can compare how changes in the exhaust etc can effect hp.
Lee/Randy- I dyno engines with mufflers and at operating temps. I also offer "measured" AND "corrected" power. At least that way it's more apples to apples. Just ask your engine dyno guy to do the same.
And by having the comparison between engine and chassis numbers you may be able to pinpoint the issues, i.e. is the carb drop base too low that it's effecting air intake and subsequent air/fuel mixtures etc? And if you have an inadequate fuel system then that's your fault. If the engine dyno has ample fuel flow then your vehicle should have the same. That doesn't make any sense otherwise.
On top of that use a datalogger and measure engine vs driveshaft speed, that'll tell you a lot about your converter.
I could go on and on but you get my drift. The more info you have, the better and quicker you'll diagnose the issues that are keeping you from your goal.

JMO.

wr1970

I don't agree with some of your points. If the car works good at the track it will work great on the street. Sure you can tune it on a engine dyno but that will not account for squat once it is in the car because to many variables. You can do chassis dyno's but will not give you weather or track conditions. The op did say weekend track warrior and street car.

rad

for just a street toy and a weekend warrior you'll have alot of fun just building an engine with cam, intake, headers and a good exhaust system, have the heads (non J heads) done with a quality valve job, you wont see 500 horse more then likely but youll see 500ftlbs and thats where it matters anyways

Lee_A

I've not found a calculator yet, that will consistently match ACTUAL dyno numbers to ACTUAL timeslips. Most of the calculators seem close when you are dealing wither motors with more HP than torque (SBC's and such). When you are dealing with high-torque motors, the calculators always suggest you have more HP than what is actually measured.


At one time my Cutlass had a mild 455, G heads, CompCam 270, stock exhaust manifolds. Race weight around 3700 at the time, and it ran 13.2's @ 102, and put 275hp to the wheels. I got more HP out of it later, but never got to take it back down the track.


I later had an '03 Mach 1, stock, manual tranny, and it put 277 to the wheels, with a race weight just under 3500. I ran 12.99 @ 106 on 3 different times.


My '67 Firebird was dyno'ed at just under 380rwhp, 455 Pontiac, iron heads, headers, 3.42 gears, pump gas. It's race weight was just under 3500, and it was running 11.5's @ 115 at that time.


All of these motors, even the little 4.6 DOHC in the Mach, made noticeably more torque than HP.

RetroRanger

I just tried out the wallace calc on my late model car w known rwhp, weight and accepted stock 1/4 mile times, it was pretty much right there.....

wr1970

I checked and wallace is close to your estimate where ever you got the figure on cutlass. 275 is what you stated. Wallace with et 286 rwhp. Off of mph 283 rwhp. I think that is ball park and a good guide. Not to hijack this thread if you have a reply just pm me. I thank you for the info Lee.