Aftermarket Horsepower?

[AKRAY4PLAY]

Stallion,
engine horse power is not effected by gearing. gearing effects how the power is applied to the ground. if you are running a tall gear like a 3.08:1, the engine is loaded more in the lower rpm range. if you have a deep gear like 4.88:1, then the loading is moved up in the rpm range. what Bossvette was trying to explain is the mechanical advantage of a deeper gear. say you have a 500 pound block and a two foot pry bar. it will take a lot of force to move the block. but if you increase the length of the pry bar to four feet, the effort is cut down by roughly half. with the ease of movement of the longer bar, you pay the penalty of half the distence of movement. basically lower gear ratios will get thing rolling quickly with low hp figures, but you pay the penalty of how fast you can go because rpms are gained at an increased rate. the key to drag racing is getting the lowest gear you can without hitting your rpm limit before the end of the track. that way you will get the most mechanical advantage out of the power you make and not waste it on over reving or over loading. the whole package determines performance. sorry if i confused you any more, Brian.

 

[Stallion]

Stallion,
engine horse power is not effected by gearing. gearing effects how the power is applied to the ground. if you are running a tall gear like a 3.08:1, the engine is loaded more in the lower rpm range. if you have a deep gear like 4.88:1, then the loading is moved up in the rpm range. what Bossvette was trying to explain is the mechanical advantage of a deeper gear. say you have a 500 pound block and a two foot pry bar. it will take a lot of force to move the block. but if you increase the length of the pry bar to four feet, the effort is cut down by roughly half. with the ease of movement of the longer bar, you pay the penalty of half the distence of movement. basically lower gear ratios will get thing rolling quickly with low hp figures, but you pay the penalty of how fast you can go because rpms are gained at an increased rate. the key to drag racing is getting the lowest gear you can without hitting your rpm limit before the end of the track. that way you will get the most mechanical advantage out of the power you make and not waste it on over reving or over loading. the whole package determines performance. sorry if i confused you any more, Brian.

But isn't that in relation to torque at the wheels?

 

[bossvette]

I don't understand. :confused

the car is a package and to to be effective it must be treated as such.

gears don't change horsepower, your engine makes x amount of horsepower at any given rpm. A change from a 3:08 to a 3:70 in a street car will give you greater acceleration at a cost of gas milage (engine turns more rpms at highway speed) and top end (assuming you could reach rev limit before).


Matching the rear gear to the application is very important as Brian stated that is why the circle track guys run quick changes

for a street car the "bang for the buck" and "seat of the pants" a gear change is high on the list

 

[Evolution1980]

Stallion,

Let me give you a very simplified answer in addition to the ones above. First, completely ignore HP and Tq...just forget about it for now.

OK...

Gearing: It's a ratio, as you've seen. 3.08 to 1... 4.11 to 1... 3.73 to 1... etc

I'm going to overly (and technically incorrect) state this to make a point. Let's say your engine connects directly to the driveshaft, and the driveshaft to the rear end gearbox, and the gearbox has the shafts that connect to and spin the wheels.

The ratio refers to how many times the driveshaft makes a complete revolution to make the rear tires go 1 full revolution. So, if you have a 3.08 rear end ("gearing"), the engine needs to rotate the driveshaft exactly 3.08 revolutions to make the wheels go around once.
If you had 4.11 gears, the driveshaft would have to rotate (or spin around) 4.11 times to make the rears wheels go around once.
So assuming that point is clear, let's move on and add a little more to the concept, shall we???

(Come to think of it, this is exactly no different than gearing on your 3,10, or 18 speed bike.)
Let's think of a bike since you are probably more visually familiar with that.

You have a 10 speed bike, and you have 2 sprockets up front (big and small) and 5 in the back (bigger to smaller). We are only going to concern ourselves with the sprockets that you pedal...the two up front.

When you want to start out on your bike, you put it in first gear, which is the smaller gear. That would be your 4.11 gear. If you counted how many times your feet made a complete revolution to make the rear tire spin one full revolution, you'd see that you had peddle a full revolution 4.11 times.
You can pedal really fast to get the bike moving quickly, but you also get to the point where are peddling as fast as you can, but aren't really travelling fast. It's easy to get the bike moving quickly, but you (the "engine") run out of rpms quickly because your legs can't peddle any faster.
Now, as you know, that's the gear that you try to pop wheelies with. Why? Because it gives you the most mechanical advantage, or torque, to get the rear wheel spinning.

RECAP: What do you have with this 4.11 gear? You can accelerate fast, but your top speed is low because you ("the engine") reached your max peddle-power ("RPM") quickly.

Now let's remember what happens if you try to start with with the larger sprocket...we'll call this the 2.73 gear...
You need to stand up sometimes and really mash those peddles down to get yourself moving. Why? Because you have less mechanical advantage. You are only going to have to peddle 2.73 revolutions to get your tire to make 1 full rotation. Of course, you certainly don't have enough mechanical advantage (or torque) to pop a wheelie.
But...what happens now once you are moving??? That's right!...it gets easier to peddle AND you will be travelling much faster before your legs run out of steam. Pretending the ratios were 4:1 and 2:1 for simplicity, once you get rolling, you only need to peddle around twice to get to the same travelling speed that you'd have to peddle 4 around times with the 4:1 gear.

So that's basically it in a nutshell. Cars work essentially the exact same way.
If you want to go fast off the line (such as a drag strip), you put in smaller/"shorter" gears such as a 4.11. If you want a faster top speed (or simply lower cruising RPMs at higher speed), you go to a larger/"taller" 2.73 gear.

Does that make things clearer for you?

If you want to know how engine torque and HP fit into that, just ask and the conversation can be continued...

 

[Glensgages]

Sorry I haven't replied to Stallion's question until now:
I get few, if-any, E-mail notifications from this Forum, altho I click the box each and every time.....
:confused

I'm sorry if I implied that deeper gears increased the HP of my '82;
as stated earlier, it ALLOWS the available HP/TQ to "be-used" quicker, as-in the acceleration needed for 1/4-mile racing.

Evolution1980's analogy to the various sppeds on a bicycle is very good:
I've used it before, trying to explain the effects of gear-ratio on performance, but I've explained it a bit differently.....

Suppose you are driving a 10-speed bicycle, and we'll relate that to your car:
"YOU" are the motor, and the various gears are the combination transmission/rear-end gears.

No-matter WHAT we do to the gearing, "YOU" will only make the same amount of 'power' (leg-speed/power), in the case of your Corvette, it would be HP/TQ.

Assuming your C3 has a 3-speed automatic transmission (THM350/THM400), you would be using ONLY 3-consecutive gears of the various 10 gear-combinations of the 10-speed bike.......
but WHICH 3-consecutive gear-combinations?????
:confused

If I'd ONLY allow you to use 8th, 9th, and 10th gear, you would be very sluggish out of the hole, but killer on the top-end
(if you can 'see' this clearer, think about various NASCAR tracks, like Daytona/Talladega, or Martinsville/Richmond...).

Conversely, if I ONLY allowed you to use 1st, 2nd, and 3rd gears on the 10-speed bike, you'd explode from the line, but be 'winded' by 50'..... not much top-end speed, correct?

Now, if you were 'racing' your bicycle at Daytona or Talladega, both high-banked, high-spped tri-ovals, with long, sweeping curves, at distances over 2.5 miles, 'acceleration' wouldn't be a concern:
TOP-SPEED would be, hence, you might use ONLY 8th, 9th, and 10th speeds (gears).

At the flat, tight-turn, short straight-away.533-mile oval at Martinsville, Va., top-speed would NOT be a concern:
ACCELERATING off the turns would-be, so you might use ONLY speeds (gears) 1, 2, and 3.

"YOU" haven't increased your leg-speed/power, but the gearing has allowed the available speed/power of your legs to be-used to it's fullest in each scenario.

When I said my 1/4-mile trap-speed had gone-up 5 MPH due to a rear-gear change, maybe now you can see why:
with the OEM 2.87:1 gears, I was trapping at just 3100 RPM (I think?????), but with the 3.73s, I'm now trapping at 41-4300.
I am now getting to USE the power made in the higher RPMs BEFORE I pass the 1/4-mile mark, without MAKING any-more HP/TQ than I did before.

One guy I spoke with finally understood it when we "said" that 2.87:1 gears would equate to speeds 8, 9, and 10 on his bike;
3.36 gears would be like speeds 5, 6, and 7;
while 4.56 gears would be like speeds 1, 2, and 3.....

Hope this helps.....

 

[Stallion]

Perfect explanations! Thanks.

If you want to know how engine torque and HP fit into that, just ask and the conversation can be continued...

Actually, that would be great. I'm pretty confident with torque, but I still struggle with the actual technical definition of horsepower. I once heard that torque is acceleration, and horsepower is speed. Is this true about hp?

 

[Evolution1980]

I once heard that torque is acceleration, and horsepower is speed. Is this true about hp?

There are better people to explain the difference, so I won't really try. I'll let someone else chime in so I don't confuse you.
All I can say is that HP is simply torque applied over a period of time.

 

[maxrevs85]

After following this thread for a bit I.m not sure what bolt-ons made the most HP. I thought maybe it was the 3.75 " crank bolted to the bottom of the block and then thought maybe it was the 6.0 rods bolted to the crank and then i thought it was the AFR heads bolted to the block and then the TPIS TPI bolted to the heads , and then maybe the 58mm throttle body bolted to the TPI...Boltons?? ....uhhh.... all of them?:confused :confused

 

[bossvette]

After following this thread for a bit I.m not sure what bolt-ons made the most HP. I thought maybe it was the 3.75 " crank bolted to the bottom of the block and then thought maybe it was the 6.0 rods bolted to the crank and then i thought it was the AFR heads bolted to the block and then the TPIS TPI bolted to the heads , and then maybe the 58mm throttle body bolted to the TPI...Boltons?? ....uhhh.... all of them?:confused :confused

depends on your skill level what a "bolt-on" is

 

[maxrevs85]

Hehe, I couldnt help myself , just messin........Honestly though,I think it did start with a few simple bolt-ons and then it all went crazy!!!...but thats the way it usually goes with me, all or none.:eyerole

 

[Tom Bryant]

TJ,
Assuming that yor engine is in good shape and is a sound starting point and you are looking for some more stomp without going nuts, I would first optimize what you already have. By 1973 fuel and ignition curves were already being calibrated for emissions to the detriment of performance. Taking your distributor in to a shop to have it set up is a good idea but a better one is to take the whole car into a dyno shop. Have them set up the distributor and the fuel curve in that Q-Jet on the dyno where you can see the actual results. Your butt dyno will notice the difference.

If you have ever seen the metering rods from a mid '70s Q-Jet (very fat little suckers) next to the ones out of a late '60s carb (nearly needles) you will wonder how your car even ran. A good carb rebuild should accompany that tuning process. Also if the shaft or bushings in the distributor are worn that needs to be addressed.

Next I would look at the gearing. If nobody has changed anything your '73 L48 probably has a 3.08 rear gear although it could have a 3.36. The good news is that it should have a wide ratio 4 speed with a 2.52 low gear. That helps you get moving faster. I would change that 3.08 rear gear to a 3.55. If it has the 3.36 I'd leave it alone if I wanted to do any extended interstate driving. There isn't enough difference between the 3.55 and the 3.36 to pay for the gear change.

Next step would be to try a set of roller rockers (self aligning). Stamped rockers don't deliver a true 1.5:1 ratio. You might even want to step up to a 1.6 ratio. Engine dynos almost always show measurable improvement when switching to rockers with an accurate ratio.

After that, if you still want more, I'd say it's time for a total package concept. Several changes that compliment each other being all done at the same time. Again I'm thinking that you want a nice driving car that has a lot of stomp. Being right in the middle of rebuilding and upgrading a set of 76cc smogger heads right now I can tell you point blank that there is no way you can compete performance wise or financially modifying your original heads compared to a new set of Vortecs. When you get your old heads to the machine shop you will find worn valve guides and worn valve stems. This means that you will have to pay for cleaning, magniflux (crack checking) new valve guides and labor, new valves, seals, springs, retainers, keepers plus machine operations like surfacing, 3 angle valve job plus screw in studs, guide plates and associated labor if you decide you want to up the spring pressures more than just a little.

Then you will still have to pay for a good street porting job that includes bowl blending and port matching. After all of this they still will fall short of the performance you will get with a new pair of straight out of the box Vortecs and you will have more $$ in them. I'm going to have a bout $400. in my heads with the checking and machine operations and new valves, better springs and I only need exhaust guides. I'm doing all of the port and chamber work myself. I'm keeping the spring presures where the press in studs will live.

So for the total package concept I'd suggest Vortec heads, GM or Edelbrock Vortec intake that is necessary to bolt to the heads, reuse the optimized Q-Jet, run a cam of around 214 intake/224 exhaust duration@ .050 lift and .445 intake/.465 exhaust lift on a 110-112 degree lobe center.
This will give your Corvette a good 2500-3000 cruising rpm at around 70 mph on the interstate and a very usable 2000-4500 basic rpm range for 95% of your normal driving. Shifting at 6000-6500 when you get the urge will be no problem either. This will give you some lope and still have good daily driving manners.

The balance of the package will be a set of headers (1 5/8" minimum primary tube size and 1 3/4" would be ok) and a 2 1/2" exhaust system with Flowmaster 40 Series mufflers.

A trip back to the dyno shop to dial in the carb to the new combo and you will be cruising in style.

Tom

 

[Jack]

I recently re-visited Dave Cooper's vette shop at Farmington MO. Dave had for sale a very nice set of used aluminum sbc vette heads (? 12556463 ?) http://www.sallee-chevrolet.com/Cylinder_Heads/images/12556463.jpg ... I think same/similar as found on ZZ4 crate motor. Their small chambers (about 58cc?) wouldn't work with anything I've got ... but should be great for later C3's having dished pistons. I recall Dave wanted $400 - $500 for the pair and they were in very good shape. dcooper@r-dracing.com
JACK:gap

 

[zachh]

I dont think hp has anything to do with "top speed", but it helps with acceleration. The more the power, the less the engine gets "bogged down"
The less the engine gets "bogged down", the faster you'll move. Im not 100%sure where torque comes in to play. Im guessin' its what throws your ass into the seat when you gun it?
zachh

 

[Evolution1980]

I dont think hp has anything to do with "top speed", but it helps with acceleration. The more the power, the less the engine gets "bogged down"
The less the engine gets "bogged down", the faster you'll move. Im not 100%sure where torque comes in to play. Im guessin' its what throws your ass into the seat when you gun it?
zachh

Woohoo! ZachH gets the award for Thread Ressurection! hahaha... :L
Just messin' with ya, Zach...

HP and gearing is what gives you top speed. HP doesn't help with accelerations. That's what torque is for. Torque gets you moving, HP keeps you moving (kinda-sorta). But yes, torque is what tosses you back in your seat (hence, torque (not HP) equals ability to accelerate)

 

[zachh]

Woohoo! ZachH gets the award for Thread Ressurection! hahaha... :L
Just messin' with ya, Zach...

HP and gearing is what gives you top speed. HP doesn't help with accelerations. That's what torque is for. Torque gets you moving, HP keeps you moving (kinda-sorta). But yes, torque is what tosses you back in your seat (hence, torque (not HP) equals ability to accelerate)

Thats what Im here for.
Nice paint... the vette
zachh

 

[80Vette]

Easy!

The fastest & most economical way to make your Vette faster is to go to Wal-Mart & get new floor mats, stickers that say "TURBO" and a chrome exhaust tip.


THOSE will make (you think) it's faster!:L

 

[Curtis]

And don't forget those big letters for the top of your windshield to remind you what kind of crutch you drive. Now that would really look fast. NOT !!

 

[wallyknoch]

My best 1/4 mile improvement is because of my roller push rods

 

[nmaier88]

If you had 4.11 gears, the driveshaft would have to rotate (or spin around) 4.11 times to make the rears wheels go around once.

Did you seriously just clarify the word "rotate"?


I believe what had gotten Stallion confused in the first place was this comment.

My stock '82 ran 15.704 @ 86 MPH w/ OEM 2.87 gears (86 MPH @ 3500 lbs calculates to 151 RWHP);
with 3.73 gears, it ran 15.003 @ 91 MPH (179 RWHP),

I don't know how he used quarter mile time and MPH to calculate your RWHP, but surely it is not at all accurate. There is no way to factor in traction, suspension, and driver skill, along with many other factors.

 

[Evolution1980]

...

Pssst! You're replying to a thread that hasn't had any activity since January 2007...

In other news... Welcome to the