GT/KA ? What class?

[Adger Smith]

No. The 327 275 carries more HP(299). That is based on the 1966 327 300 HP(285), via the GT calculator.
I have personal experience with a couple of GT cars & the runs missed the GT Calculator a little. One I had on my dyno, the other went into the car with out a dyno session.

The list below is from the 70 Chevelle as it fit on the GT calculator in GT/JA
Mike,
I'm not sure about your dreamers HP figure comment. If you figure .060 overbore & + .013 stroke on the 327 it comes up 338 Cu In.
If you divide the Required index HP(478.3) by 338 you get 1.412 HP per cu in.
If you take the 1.2 under required HP (663.6) divided by the 338 cu in you get 1.96 Hp per cu in.
Just how far out of line do you think those numbers are. On the one I did my Dyno numbers only missed the 1 second under by a little. I know my dyno well enough to know it is calibrated on the conservative side. I feel it is best that way to work with simulation programs, torque converter companies & customers.

GT/JA
11.60 index
10.80
10.60
10.40 1.2 under

3732.50 min weight



478.3 HP to run the index
592.6 to run .8 under
626.8 to run 1. under
663.6 to run 1.2 under

[Mike Voth]

Here's another possibility to consider - If the car has been back-halved, and done right, you could drop between 100 and 200 pounds. If you put disc brakes on all four corners, you could drop another 150 pounds, or more. If the 327 is build right, it has the potential of making more torque than some 350 combinations, but still short. It has been my experience in the past that dropping weight and moving up in class gives you the potential of running further under the index with the 327. Our 275 horse 327 liked to get the weight out from under it. If you play your cards right, you might be able to drop under the GT/FA minimum, and be able to control the weight up via the weight box (up to 100 pounds). We have our car set up to adjust weight with the amount of fuel in the cell, and run 15 pounds over the 3120 limit. It works good, and the car responded better when the weight was removed. You might find that you like being a little quicker (ET), and not have to leave first all the time.

Just a thought. Since you've chosen to run a GT class, I believe your options for carbs are greater, too. But mainly, it's all about what weight you'll end up at, and what year engine you claim. A q-jet will cost you HP, and without looking, I think in the 299 range, depending on the heads. I think that Holley carb Adger was talking about is a 580cc carb (I'm sorry if I'm wrong, trying to go off memory), and an early style q-jet is 720-750, I think??? The Holley would be the way to go if you can make similar numbers compared to the q-jet.

I hope this helps a little.

[Mike Voth]

Adger, I know dyno's are all different, and you'll get different numbers on any given day of the week, but the last time we dyno'd, the shop had an exhaust ventilation problem, and we kept blowing the tubes off the collectors, so we didn't see the numbers that we should have. But what we did see is right at 600 HP, and not to the tires, which would be less. We're still the fastest GTE in the country, and have a ways to go, but come on, if we had 675 HP or more, we'd be running in the low 9's! It just doesn't compute. I made a statement in another thread that I thought we made as much power as any 327 in the country. Maybe I'm way off base. But we must be doing something right to be running 9.73 with our heavy Monte Carlo.

On second thought, the dyno we use is very old. Maybe there's a difference that is not being calculated in the process, and we're not seeing actual numbers. Who knows. I just know we're happy with the power we're making, and it seems to be translating to the track.

[Bill Harris]

The HP calculator is just a ball-park since there really is no way to do an accurate estimate of the peak HP for a racecar. The Chrysler estimates were developed back in the '60s and are roughly based on a constant acceleration model that would give an estimate of power at the flywheel. The equation uses basic Newtonian physics to determine the power needed to accelerate a given mass to a given speed in a given time and then padded to account for observed performance. Anyone who has a data aquisition system can see at a glance that the acceleration of a racecar is anything but linear which makes a constant acceleration model a rough estimate at best.

There are other ET estimators out there that use similar equations but with some variation of the "200" constant. For example, the TCI website (www.tciauto.com/Products/TechInfo/Calculators.asp) has a calculator that is the same as the Chrysler estimates except that the constant is 193 instead of 200. It goes though the intermediate step of calculating the MPH and then the ET, but the end result is that the estimated HP is weight*193/(ET^3). These results are of course lower than the Chrysler results, but not by a lot. The difference is around 15 to 20HP for various weights and HP ratings.

The spreadsheet was originally developed to allow me to figure out which GT classes I could run with various engine/body combos when I was planning my adventures into the realm of super stock competition. The HP stuff was added to give a relative measure of how much power I would need to make at the different weights. It is more of a measure of which legal class is more attractive from a power standpoint than a target to shoot for in the dyno cell. I found it useful and thought that others trying to decipher the GT class mess might also benefit, so I shared it with the forum.

I am pretty certain that the classes that the spreadsheet reports are accurate given the NHRA indexes, rules and user input, but there are no guarantees. The HP stuff is for entertainment purposes only.. if you get my drift.

Enjoy, or not....

[Mike Voth]

I don't want to give you a bad impression. My apologies. I think the calculator is great! It IS very imformative, and very helpful if a guy wants to play around in different classes. I appreciate that you shared it with the forum!

[Adger Smith]

Mike,
I think you are right on about pulling the weight out. The GT calculator was showing the same thing. I'm far from an expert with GT class cars. When I was running Comp, Esp in the old Gasser & Modified days, running a low HP combo light ran better. I know it is true with my current V-6 car that I run in 4 classes by weight/carb changes. Seems like there is some physics law that applies to that. Too may birthdays to remember. :~)

[Mike Voth]

Our combination hasn't been beat to death, yet. Our 327 is still factored at 295.

[Bill Harris]

Mike, No apologies needed! I'm glad that others are getting some use out of the tool. There are so many different combinations that it helps to have something that will do the math.

Just for grins, I added the "293" factor calculations to the spreadsheet and put it up on my shared drive. Feel free to check it out at
http://www.employees.org/~bhracing/g...ulator_1p2.xls

Might be a bit more realistic.. but again, your results may vary. Ya'll git whut ya payed fer......

[Mike Voth]

That's more like it! I can live with those numbers. I think these are closer to realistic, but like you said, there's no way to accurately "guess" what actual HP would be.

I guess my 2 cents didn't get much, huh? LMAO

[trmnatr]

Originally Posted by Adger Smith

No. The 327 275 carries more HP(299). That is based on the 1966 327 300 HP(285), via the GT calculator.
I have personal experience with a couple of GT cars & the runs missed the GT Calculator a little. One I had on my dyno, the other went into the car with out a dyno session.

The list below is from the 70 Chevelle as it fit on the GT calculator in GT/JA
Mike,
I'm not sure about your dreamers HP figure comment. If you figure .060 overbore & + .013 stroke on the 327 it comes up 338 Cu In.
If you divide the Required index HP(478.3) by 338 you get 1.412 HP per cu in.
If you take the 1.2 under required HP (663.6) divided by the 338 cu in you get 1.96 Hp per cu in.
Just how far out of line do you think those numbers are. On the one I did my Dyno numbers only missed the 1 second under by a little. I know my dyno well enough to know it is calibrated on the conservative side. I feel it is best that way to work with simulation programs, torque converter companies & customers.

GT/JA
11.60 index
10.80
10.60
10.40 1.2 under

3732.50 min weight



478.3 HP to run the index
592.6 to run .8 under
626.8 to run 1. under
663.6 to run 1.2 under

Dyno numers? You had one on the dyno? How much HP will the 327/300 {285} make on a dyno? 550hp?