Question is in the title... basically I'm curious because tonite I came across a 99-ish Mustang GT on the highway and we hit it a few times, and every time, he pulled about a car out in front of me from 50 mph. I had 2 passengers in the car with me, big old boys - one was 280, the other 240, so they certainly didn't help, HOWEVER...

...my engine dynoed 557hp/540tq at the crank through race headers and mufflers. I'm willing to subtract about 30 once it's hooked to my exhaust.

I pulled over and spoke with the Mustang owner and he claimed to have 305 to the wheels. Now something just doesn't add up here, does it? I'm thinking my car should be GOOD for mid-low 12's.

It's a 60 over 454, with 557/540 at the crank, running through a big 11" Hughes 3500 stall and B&M TH400. 3.90 gears and a GV overdrive...

-Chris

It's not the 400 that's your problem..

It uses virtually no more HP to turn at a steady state than a Th350 or Glide...

Two Bubba's in the car hurt you more than anything, as well as what your car weighs probably.

We have Mustang customers with 300-310 rwhp running low 12's in daily driver cars, one guy has run high 11's.

those stangs weigh about what, 3200 lbs, you had at least 700 lbs more car plus two big dudes, so thats alot of weight.

Nothing wrong with a TH400! I'm into shaving off the wt. this winter. Just saved 90# by going to Wilwood 4 wh disc brakes! Will also be replacing very heavy stock doors with fiberglass ones and Lexan! Hoping to shed 3/10ths! Just work on tuning your combo, get track time and wahlah you'll be blowin that stang away! :D

Sorry guys the Turbo 400 is a VERY heavy (sucks hp) tranny. I have seen it average 30-35% power loss on 700-900 hp motors. Don't believe me? take your 557 hp motor to a chassis dyno.

Originally posted by 69 Ratt Vette:
Sorry guys the Turbo 400 is a VERY heavy (sucks hp) tranny. I have seen it average 30-35% power loss on 700-900 hp motors. Don't believe me? take your 557 hp motor to a chassis dyno. Well, I made the swap from a th350 to a th400, everything else the same including converter, etc. Car ran the same numbers with both trans...actually car has ran quicker & faster now with the th400 than it ever did with the th350.

I don't buy all the hype or rumors that a th400 will slow a car down over a th350, or that it robs a bunch more power. IIRC, the th400 itself only weighs 15 lbs or so more than a th350.

(going to the 30 to 35% comment) Thats not an entirely fair analysis. Some engine dyno's are more forgiving than others. Some chassis dyno's have trouble dealing with race oriented converters. For a non-lockup TH400 with 700+ hp infront of it, its really not sound logic to go from what could be a loose engine dyno onto a plain roller chassis dyno and have 30% 'dissapear' on the way. To take it the other way, if I held my dyno #s as absolute hp #s and not just a tuning method, I only had an 18% loss to the rear. I just had a stingy engine dyno.
If a TH400 really "ate" a 700hp motor down to 490rwhp, (700*.7), I bet people would be looking for a more efficent transmission. Quickly..
While they aren't a manual, 35% is a huge loss. If he put out 425 or so on a chassis dyno, he probably should lose from a side by side to a 500lb lighter car to begin with, never mind carrying himself and two other big guys.
30 or 35% of 700 or 900hp is huge #. Unless its your shop or your dyno putting them together, then a dyno running shop headers and a velocity stack on the carb sucking cold air from outside in is going to be more generous than it should.

just .02..

I think its like 35lbs more..I saw somewhere that a th350 takes 35HP and a th400 takes 50HP

Never said it would slow the car down, although logic would point to that. Where the gear ratios the same in the 350 and 400 Todd. Good points on the chassis versus engine dynos. I have seen several several motors go from engine to chassis dynos with 400's and they ate up a bunch of power 30-35%.

Just reporting what I saw.

No doubt he needs to find some skinnier buddies.

Originally posted by 69 Ratt Vette:
Never said it would slow the car down, although logic would point to that. Where the gear ratios the same in the 350 and 400 Todd. Good points on the chassis versus engine dynos. I have seen several several motors go from engine to chassis dynos with 400's and they ate up a bunch of power 30-35%.

Just reporting what I saw.

No doubt he needs to find some skinnier buddies. Nope, standard 2.52 ratio th350, 2.48 ratio th400. I seriously doubt any of us could tell a difference in the ET slip with .04 difference in trans gear ratio.

Thanks for the reply Garret.

For anyone interested...

http://www.camaros.net/cgi-bin/forum/ultimatebb.cgi/topic/4/9621.html

Definitive weight comparison of a th400 vs th350.

Guys,
All the numbers you read about TH350 vs. TH400, vs. ? whatever for HP are bogus.

There will be very little HP difference between any two transmission begind a given motor with a given converter.

Most of the HP loss would be due to the pump. A TH350 and 400 share the same pump gears. That goes to say they have similar pump capacities and HP losses.

Yes the parts are heavier in a TH400...
Yes a Th400 is heavier.
That MAY result in a slower ET, but if you hold a motor at a steady rpm on a dyno through the trans, the output will be the same.

Once the internals are in motion, they are not consuming HP, they DO consume more HP to spin up if they are heavier...that's why cars after the very last fraction of a second will use lighter parts. Those cars are fast enough, and rpm up quickly enough to realize the HP losses created from heavier parts. A typical street/strip ride is going to have a negligable effect.

But you should see minimal difference in ET or RWHP numbers between transmissions

You also cannot assign an exact HP loss to a specific model of trans, nor an exact % difference.

Most of the HP loss is happening in the pump and loss of efficiency in the converter.

A 14 lb drum turning 4000 rpm, is going to consume no more HP than a 4 lb drum at 4000 rpm.

A 14 lb drum from 2500-6000 rpm in 1.5 seconds will consume more than a 4 lb drum under the same conditions. Not enough to show up on a low 12 second car though smile.gif

An object in motion tends to stay in motion...

sorry I didn't mean to come across like that, i just reread my post. Jake said basically what I was trying to say just more eloquently, its not really fair to say a model xxx trans takes yy% hp, and model yyy takes xx%. too many things going on.

matt

well 402 i checked your web site and you have a 72 chevelle 4000lbs mustang 3400lbs?
2 buds 620lbs driver 200lbs
you 200lbs ?
total 4820lbs total 3600lbs
aero drag huge very small
next time ditch the buds and go from a standing start. aero drag is a major hp robber

well that chart didn't come out right, but i hope you get my drift

Originally posted by 69 Ratt Vette:
Sorry guys the Turbo 400 is a VERY heavy (sucks hp) tranny. I have seen it average 30-35% power loss on 700-900 hp motors. Don't believe me? take your 557 hp motor to a chassis dyno. We dynoed Tim Kerrigan's big block Chevelle a while back and he lost right at 20% in the drive train with a TH400. IIRC, it was dynoed in LA at 640 on the engine dyno and we came up with about 520 rwhp, so that's about 20%.

Let me take a different tack on this topic.

Unless you take your car to a chassis dyno you will never really know how much power is "getting to the ground". Guess on the power loss of your in car setup if you want, you are probably a lot further off than you think. Your flywheel power numbers are nice - but they really don't matter.

You state that your engine power numbers were achieved with race headers/mufflers. Especially on a big block, you would be amazed at how much power your street headers and exhaust system may be robbing. Even if your headers were perfect for your engine's needs, maybe your pipes and mufflers are crappy.

A worn or damaged performance torque converter may seem to perform okay, meanwhile it could be a gross power waster. Its pretty easy to check converter efficiency in regards to rpm loss differentials. At the drag strip finish line, or on a chassis dyno pull, just compare actual observed mph vs theoretical "locked" up mph. The math: (rpm x tire diameter x 2.96) all divided by (differential ratio x 1,000) = theoretical no-slip mph. Let's say your actual mph was 110 and your theoretical mph for the actual rpms was 135, then you are only ~ 81% rpm efficient. Where did the other 19% go? If no trans slippage then your torque converter is not very efficient. Happens all the time, especially with street miles over time. An efficient non-lock up converter generally only loses from 3% to 8% of rpms.

The GearVendors OD helps your mileage and lowers highway rpms, but it is yet another friction point probably costing you a couple of percent in horsepower.

Of course, the Bubba anchors did not improve your performance. Some Mustang GTs can weigh ~ 3,000 lbs, and that is the not so secret reason for their excellent performance.

Another thing that doesn't matter is what a street racer "says" about the power of his car - like they have any reason to be honest :D

Thomas

fwiw, and I'm not saying this is typical or isn't (like thomas said, exhaust, mufflers, so on) all play a part. I had an about 18% loss from the engine dyno to a tight converter. The loss % went up a little bit (if you want to take a more aggressive converter at face value) to around 20% with a converter that slipped at right about smack dab on 9%. Right now I have a new converter that hasn't been tested at the track, but I'm not expecting any dyno time with it. Its supposed to be a little tighter than the one I had, around 6%. I don't know what my busted & slippings trans puked into it, I hope the new converter will get by with just a flush.
got off track, but I've had 18-21 % loss that I've experienced. I think one variable here that is hard to account for though is how 'strict' the engine dyno operator is. I'd think the amount of influence (over a dynojet anyway) that the dyno operator has is alot less on a chassis dyno than on an engine dyno.

.02

matt

A chassis dyno does not tell you what you are getting to the ground. It is only a number, and depending on how the car is strapped down will play a large role in the actual number it makes.

There was an article in a magazine last year where they tested this theory and the hp number was vastly different even with one click on the tie-down strap. The weight of the rollers, and the dyno itself will have an effect on the numbers.

Accuracy does not equal precision. If the numbers are repeatable then you have precision but it will not be accurate. Same goes for engine dynos.

I know everyone does it with their dyno numbers for the "big dick factor" but keep in mind you are comparing two numbers that are wrong to get your % loss. Almost as silly as trying to calculate a DCR with static variables. LOL :D

The only true dyno is the dragstrip - I am very curious what the corrected difference in ET would be for someone to change from a TH400 to a lenco for example at different horsepower levels - only that could convince me to buy a converter-less tranny for the $$$ they charge. Does anyone on here have any datapoints for us?

I don't find that the straps have a whole lot of effect on the dyno reading. We routinely take cars on and off the dyno to move them to the rack for repairs then strap them back on and repeat within a couple of hp.

You don't have to strap down the lower horsepower cars that tight as compared to a high hp car so in the case of mine, there was more load on the rear end/axle bearings than if there were 10 people standing in my trunk.

The car was getting significantly more power to the ground at the track than it measured on the dyno. the dyno number is just that - a number.

Hi onovakind67 and all you other team Chevelle members. That Chevelle with it's unknown exhaust system and three BIG occupants was surely at a big disadvantage against a lightweight Mustang. The exhaust system alone could has deminished that motor's power by a hundred horsepower if it necks down to a 2 1/2" size. I ran a 425-427" Ford Fairlane once with my 442 Oldsmobile, which were both '66 models. He tried it first with five people in his car and i had two extra. I buried him ( about five cars of daylight). We went to another spot and he emptied all the people out and we went again, different story ( he beat me by about one car of daylight). Weight matters more than about any other variable. I've found the 350 Turbo to be about one tenth quicker and 1.5 MPH faster then the 400 Turbo in back to back testing on my son's car. I wasn't aware that Tim Kerrigan had changed over to a Turbo 400 from his five speed, but it's been a long time since i've talked to him on the phone, he's a real nice guy. I've also seen cars Dyno higher that still couldn't outrun my son's Chevelle. I have concluded that the Chassis Dyno is a usefull tool but it still won't predict what a car's going to run with great accuracy. One local guy here has a 502 crate motor in a '57 Pontiac which gained over 40 H.P. at the Dynojet and slowed down 2 tenths at the strip. Went back to the original tuning at picked right back up. P.S... The T-400 is about 20 lbs. heavier than the T-350.

Harold,
I disagree with the .1 second loss anmd 1.5 MPH difference being typical on a TH350-400 swap.

Most swaps see ZERO difference, some see differences in the hundreths.

If you had that much difference, somnething else changed (converter?), or something was astray in the 400 (too tight clutch packs, endplay, slippage, etc.)

I DO agree with you that a 400 is more than 6 lbs heavier than a 350 though...

20 may be too much but 6 is not enough...

Just the center support and planets of the 400 would add more than 6 lbs...

Wouldnt the higher first gear in a 400 account for some of the e.t. loss? It sure seems like my car picked up after swapping the th350 back in, but the 400 may have some internal issues. A 400 is definately more than 6lbs heavier, 350 out 400 in,400 out 400 back in, 400 out 350 back in,,,its more than 6lbs :D I hope to do one more swap, 350 out 400 back in and last me for 2-3 years.

...my engine dynoed 557hp/540tq at the crank through race headers and mufflers

subtract about 30-50hp for the accessories drive also. Water pumps alone suck 15-20hp @ high RPM, then you have your fan @ 10-15hp, alternator, and powersteering pump. Then your exhaust it locking up 15-20hp and 3 speed auto suck about 35hp @ 5000rpm and OD autos suck 40-45hp @ 5000rpm. I think on an Rear wheel dyno you would be LUCKY to crack 450rwhp.

Also with an Auto tranny that does NOT have a lockup converter you NEVER get accurate rwhp numbers.

Okay, so a real test of "power to the ground" is your mph at the end of the 1/4 mile. If you look beyond the torque spike and leveling of horsepower that a high stall non-lockup converter show on a chassis dyno, then there still is relavance for chassis dyno pulls for *most* people here on Team Chevelle. Ryan's car is an absolute freak of a street car, but in a very good steroid way. For sure, Ryan's car with well beyond 1,000+++ hp will show significantly different chassis dyno results based on how it is strapped down.

Next time lose the bubbas :D

Better yet, why not eliminate all mystery and actually make some passes at the dragstrip. Be aware that you will probably find that the car doesn't run as quick and fast as you think. Lots of guys get humbled the first time they run their car. If you take the time to really sort out everything and dial it in, then that rustang may be in trouble the next time you meet up.

Oh yeah, an engine dyno or a chassis dyno should be thought of as a tuning tool. More information is always good when you are testing what does and does not work. Otherwise, take it to the track and see how everything translates performance wise.
Thomas

Hey guys, thanks for the responses. I was just curious to know how much a TH400 was typically responsible for. Just FYI, my converter is a Hughes 11" 3000 stall, and is non-lockup. So, like some of you have said, it would be tough to know exactly what it "puts down."

I'm happy with how it runs right now, and think that there's definitely some tweaking to be done, both with the engine and the suspension to get the best possible pass out of it. I'm a full time college student, so I don't really have a lot of opportunity to get out and drag race the thing at a track. We have 2 eighth mile tracks close, and the closest quarter is in Ennis. If I do make a trip down, I'll definitely post the results.

Some other people have told me that a 305rwhp GT has the potential to run low, low 12's, so considering the 2 football players in my car, I think I faired quite well in our little 'battle' :D . I have a lot of plans for this car, but as of now, it's just really my daily driver, and I'm not too preoccupied with making it run the fastest 1/4 possible, know what I mean?

One day, I'd love to get it painted, put a fiberglass front clip on it, and maybe even drop in a manual, but one day at a time till I get there. smile.gif

I appreciate all of your input. graemlins/beers.gif

O.k...something is definitely wrong here, OR, that mustang had some serious dollars invested in it.


If your motor dynoed 557 hp, your car should be MUCH quicker than a low 12 second car with correct gearing (3.90-4.10), more like a low 11 sec car.

BUT.....did you keep everything from the dyno? Same Distributor? Same timing curve? Same Carb and jetting? Same fuel pressure? Same size headers?

A new 305 hp mustang is NOT going to turn low 12s out of the box, and quite frankly even with two big dudes in the car, you should have still pulled on him. Yes te extra ballast is hurting you, but he shouldnt have pulled on you.

Go over your whole setup

Originally posted by Big Block Dave:
O.k...something is definitely wrong here, OR, that mustang had some serious dollars invested in it.


If your motor dynoed 557 hp, your car should be MUCH quicker than a low 12 second car with correct gearing (3.90-4.10), more like a low 11 sec car.

BUT.....did you keep everything from the dyno? Same Distributor? Same timing curve? Same Carb and jetting? Same fuel pressure? Same size headers?

A new 305 hp mustang is NOT going to turn low 12s out of the box, and quite frankly even with two big dudes in the car, you should have still pulled on him. Yes te extra ballast is hurting you, but he shouldnt have pulled on you.

Go over your whole setup I've come to the conclusion, along with the rest of most of the people that posted in here, that my automatic TH400, coupled with a GV overdrive, and 2 'bubba anchors' contributed to my loss.

I've been sniffing around my Mustang friends and inquiring on GT's, and have come to learn that they weigh significantly less. My friend has a similar setup in a 99GT, with right on 300rwhp, and he is able to trap 110 in the quarter. He says that GT's weigh in around 3200 lbs, so nothing to sneeze at for sure.

Like I said in the original post, the dyno runs were made through VERY free flowing headers and mufflers. Now the engine is bolted up to a set of 1 7/8" Hedman headers and 3" exhaust through Flowmaster 3 chambers, and 2.5" pipe over the axle, so that is another key factor.

Basically, I'm taking my engine dyno #'s with a grain of salt.

Originally posted by Big Block Dave:
O.k...something is definitely wrong here, OR, that mustang had some serious dollars invested in it.


If your motor dynoed 557 hp, your car should be MUCH quicker than a low 12 second car with correct gearing (3.90-4.10), more like a low 11 sec car.

BUT.....did you keep everything from the dyno? Same Distributor? Same timing curve? Same Carb and jetting? Same fuel pressure? Same size headers?

A new 305 hp mustang is NOT going to turn low 12s out of the box, and quite frankly even with two big dudes in the car, you should have still pulled on him. Yes te extra ballast is hurting you, but he shouldnt have pulled on you.

Go over your whole setup He is saying a stang with 305 REAR wheel hp, nto 305 sae net at engine, so we are talking a 375ish hp stang that weighed more than half a ton less with better aero from a roll.

FYI I did the calculations and it takes roughly 500 rwhp for a 71-72 chevelle to hit 200mph...

Originally posted by doggy69:
He is saying a stang with 305 REAR wheel hp, nto 305 sae net at engine, so we are talking a 375ish hp stang that weighed more than half a ton less with better aero from a roll. [/QB][/QUOTE]

O.k....so regardless of all these numbers, this is still the same current car that goes low 13's right?

Just like all those Camaro SS cars with 320 REAR wheel hp that go low 13's out of the box.

I would still expect that big inch Chevelle to pull away at 50 mph, and unless he has a giant billboard on top of the car, I seriously doubt aerodynamics are playing into this.

Originally posted by Big Block Dave:
</font><blockquote>quote:</font><hr />Originally posted by doggy69:
He is saying a stang with 305 REAR wheel hp, nto 305 sae net at engine, so we are talking a 375ish hp stang that weighed more than half a ton less with better aero from a roll. </font>[/QUOTE]O.k....so regardless of all these numbers, this is still the same current car that goes low 13's right?

Just like all those Camaro SS cars with 320 REAR wheel hp that go low 13's out of the box.

I would still expect that big inch Chevelle to pull away at 50 mph. [/QB][/QUOTE]

SAE net hp is basically the same as rear wheel, it is measured at the end of the driveshaft with the car set as it would leave the dealership. its probably within a few percent of what a good chassis dyno could read.
This reply goes to the remark that a 557hp/540 ft-lb motor should really cruise past the low 12's into the 11's. It would with some slicks, but just to show how 'just a number' dyno's can be, in the three "versions" of my engine, I have made 560-565hp on *three* different engine dynos, but always turned a different MPH with each "version." Thats why dyno #s need to be taken with a pretty big grain of salt. This current 560hp is about 3.5mph faster than the last 565hp, but on the surface that makes next to no sense...
Chevelles are heavy cars, I think people tend to overlook the weight of these cars. A mustang to a (basically) fully loaded chevelle isn't really apples to apples. 305 rwhp in that mustang is probably good for a 12.7-13.3 on street tires if the guy practices alot, so fast but not blazing. With the added weight, the chevelle in this scenario is at a big loss.

Here's my .02 cents. If any weight or hp loss is a reality in a TH400, and it is bothersome, Just drop an aluminum 4 or 5 speed in the monster and watch it launch. With a manual you control your weight and your own "stall speed", you just have to get good at power shifting and watch it fly...

Could be just a matter of gearing. What speed did you race up to. I would assume you were probably in second gear. What gear was he in? I have had a few cars that were very quick at the right rpm and speed if you got onto them from a rolling start. They probably weren't all that quick in the quarter, but then it wasn't really a quarter mile contest. He just may have caught you at the right speed/rpm for a really impressive burst of acceleration. Your weight disadvantages I'm sure didn't help. The only way to settle this is to lose the buddies and race balls out and then you will really know whose car is fastest.

[QUOTE]Originally posted by jakeshoe:
[QB] Harold,
I disagree with the .1 second loss anmd 1.5 MPH difference being typical on a TH350-400 swap.

Jakeshoe, Both of these transmissions had been worked over and the T-350 ran a tenth faster in very much the same weather. The T-400 is 140 lbs without the lightweight drums as measured on a very accurate set of scales and the T-350 is 119 lbs. on the same scales. My sons car had a 481" BB when we first compared the two trannies and the 350 was just plain faster and quicker with the very same torque converter. The car ran 10.26 with a T-400 and the next weekend it ran 10.15 and the trap speed increased 1.5 MPH with the T-350. (130 vs. 131.5) A friend of mine has a T-400 with all the lightweight parts which is almost as light as our T-350 at 123 lbs. It ran much better than his stock type T-400 (10.40 vs. 10.28). These are actual weights, not guesses.

No the new cars have 305 hp maybe 260-270 rwhp....You might not think aero is a big difference but its huge. I have no clue what the drag coefficient of the stang is depends on the year. But for a 71-72 it's something like .4 or .41 whereas the new corvette's are like .28. What I am getting at is that there are too many variables. aero, weight, power, gearing, driver, did they both leave at the same time or is the stang getting a better r/t... From a dead stop with just drivers no doubt he'd pull away unless the guy has crazy suspension work.

Originally posted by doggy69:
No the new cars have 305 hp maybe 260-270 rwhp....You might not think aero is a big difference but its huge. Didnt you just say in your last post that the car has 305 REAR wheel horsepower? Im a little confused here.

I still really doubt that aerodynamics are going to play a serious role at 50mph regardless of drag coefficient numbers. If we were talking above 100mph Id buy into it, but at 50mph Id say weight is significantly more important than aerodynamics.

I he said the car we was going against had 305 rwhp...the new cars have 305 hp but thats not measured at the rear wheels so it is less something like 270ish...so 305 rwhp stang has mid 12 sec potential.

It's all in the weight. Too many Bubbas in your car. The '70-72 Chevelle has a drag coefficient of .420 and 25.52 square feet of frontal area. You can all go to Smokemup.com and check out wind resistance to see how much aerodynamics affect some cars. You can't possibly put an extra 520 pounds in your car and expect it to "run the number". Your talking about running about 5 - 6 tenths slower for the extra weight. I'll gaurentee it will take more than 500 H.P. to run 200. My son's car has 672 RWHP and no way would it go 200.

Harold,
I've been to WELL over 160 (approx mid 170's) in a 2nd Gen Camaro with probably well less than 500 HP...

461, T56, 3.73's..

Probably had over 550 lb/ft but it was a relatively mild 461.

Jake, That Chevelle is a lot less aerodynamic than that Camaro your talking about. Here is what the Smokemup site says it takes to push the Chevelle through the air. (150-242 H.P.), (160-293.5), (170-352), (180-418), notice the trend. It's really a moot point because the Chevelle becomes unstable at about 160 and just might go upside down and crash. As i don't have the figures on a early seventies Camaro i don't know what their safe limit is. These horsepower figures are drag only so no telling how much additional horsepower is required to get one there. I had my old Chevelle about to about 143 at almost 7000 RPM so either that Camaro had more than 500 H.P. or the speedometer is way optomistic. My sons car has been a little over 147 @ 7800 RPM. It's geared back down to 3.50 now for the juice, i'm sure a T-56 overdrive would change how fast one could ultimately go but not 200. A local Camaro guy has a goal of hitting 200 but has only managed 186 so far with near 800 H.P. This Camaro can be seen in the August 2004 issue of Hot Rod Magazine and is the 8th fastest without nitrous but geared to run the quarter. He changes gears to run top end.

Going to make a couple of assumptions here. First, 557HP did not occur at 5000 rpm?? Probably more like 6200=6300??. This is where the big debate of HP vs Torque comes to play. Flat out drag racing, the BBC torque really comes into play, but I have found that running from a roll like you did, the motor with more overall RPM and wide powerband would be quicker. And no matter what, do not discount weight. THe '68 Mustang Vert I did had a nice .030 over 351W with a good set of heads, intake, headers, (the usual), most likely somewhere in the 375 - 380HP range, 2800 Stall, 9" w/ 3.55's, C-4 trans. I never ran the car in the 1/4, but can tell you this, the car was a handfull. Car had subframe connectors to stiffen it and some tricks in the suspension. Car also had a glass hood and trunk lid. Factory wt for the '68 vert was about 2800-2900 lbs. As built with the glass hood/trunk it probably didn't weigh all of 2800#. Needless to say, it flat out was quick. One of those cars I should have ran just for the see what it can do factor. That weight factor does it everytime.

I am sorry that I lacked clarity on that. 500 rwhpI actually beleive it was 503 was aero drag only. This doesn't include rolling friction etc. I got a drag coeff of like .41-.42 and checked my work several times. And that number is to a top speed im not talking bout 3/4 mile straight. So for our practical purposes, to achieve 200mph on any reasonable short distance i.e. a straight mile we would like to have the greatest excess of power possible.