The Dodge Challenger Message Board

Hi guys.
Last week y try quarter mile first time against other powered cars.
I told you few months ago about my engine but I want to show you again my last upgrades.
Original 440 '70 block, original forged crank and rods.
Bored 0.030" with 10.34 forged domed pistons.
Edelbrock performer RPM aluminium heads, edelbrock performer RPM intake, 750 speed demon carb with 4" height k&n filter.
238-246 cam with .495-.495" lift.
aluminium roller rockers 1.5:1 ratio
Hughes 3000 rpm stall converter, 727 hughes transmission.
MSD ignition
1-7/8 headers to 3" tube and 2.5" exhaust.
Milodon race oil pan 7 quarts.
Hi volume oil, fuel, water pumps.

Now I try to get more HP.
What do you think about continue from 3" headers tube to 3" exhaust and 3" cutout to race. When cut out will be closed the rest of the line 2.5" until rear flowmasters like I have now.

Now I have this units before cut out (always in 2.5")

http://store.summitracing.com/partdetai ... 304+1005+0

Is better only 3" inch without restriction to race?
Is better use x-pipes
http://store.summitracing.com/partdetai ... toview=sku
H-pipes
http://store.summitracing.com/partdetai ... toview=sku

or idependant lines?

Now car has 3.23 rear 8 3/4 sure grip and I do not want to changer this ratio because sometimes I need to drive about 150-250 miles to arrive to the track and i drive 3000 rpm - 120 km/h.

A lot askings may be?

Have a nice day. Alfred.

Please, do not recommend me 1.6-1.7:1 ratio rollers, I bought this set not much time ago...
I know is one of the ways to get more hp...but there are other ways? Or not?

Thanks again.

I know you don't want to hear this but it is the rear gears that are killing the performance.

You need a 4.10:1 - 4.30:1 rear gear for the track. It would make a HUGE difference. But as you say the driving to the track will be a pain.

However. I also have to drive 150-250 miles to the track (depending on which track) and I used to do it with 3.91:1 gears no problem.

In fact if you are driving at only 3000rpm you are probably not getting best mileage from the engine. Best mileage is at the same rpm as peak torque on your engine. Which i guess will be around 4000rpm?

I will bet when you drive at 4000-4500rpm the engine "sounds" and "feels" sweeter? That is the engine telling you where it wants to be.

Of course there is one expensive answer to your problem. That is to fit 4.30:1 rear gears and an overdrive like me.

With the exaust. An x-pipe is said to be best. Very close second is the H-pipe.
How well they work is dependant on exactly how far from the headers they are fitted.

I am told if you paint the exhaust with interior house paint and watch it as you run the engine from cold at a mid-range rpm you will see the paint burn off at one particular place faster than the rest. That is where you put the X or H pipe. Or if it is a race car that is the length of the collector extension.

They increase the amount of torque at lower rpms. I don't think they increase peak power much (if at all) on the track when run with an open exhaust.

Use a 3-inch system and run it open at the track.

Thanks dave.
I'm sure that is the way at the track but I'm searching to get more popwer on the engine, then I will decide if I shorten the final end ratio, probably 3.55 or 3.91, may be like you.

dave-r wrote:I will bet when you drive at 4000-4500rpm the engine "sounds" and "feels" sweeter? That is the engine telling you where it wants to be.

Is this really true?

Of course there is one expensive answer to your problem. That is to fit 4.30:1 rear gears and an overdrive like me.

Have you gear vendors installed, right? How many HP and torque is maximum allowed with it?

I am told if you paint the exhaust with interior house paint and watch it as you run the engine from cold at a mid-range rpm you will see the paint burn off at one particular place faster than the rest. That is where you put the X or H pipe.

Is a hand made way to know it. But you know that chally hasn't a lot of places to do it, about 20-30 cm from the end of headers.
They increase the amount of torque at lower rpms. I don't think they increase peak power much (if at all) on the track when run with an open exhaust.

Use a 3-inch system and run it open at the track.

Only a 3 inch totally open to race is better? With X-pipes installed?

To make more horspower you need to either make more torque or loose less in mechanical losses. The higher up the rpm scale you make the extra torque the more HP you will create.

I can think of three ways off the top of my head.

1. Increase engine efficiency and friction losses.

2. Make more torque (burn more air/fuel)

3. Move the torque you make higher up the rpm scale (HP = Torque x RPM divided by 5252).

Chances are that any extra power you make will be higher up the rpm scale. If you do not use all the gears and rpms you have because of too high a rear gear then you will never "see" that extra power.

Your engine has to operate in the rpm band you have designed it to run in. I doubt you are using all the power your engine is making right now.
You can only do that with the right gears. Also the amount of torque at the rear wheels is directly proportional to the gears.
Going from 3.23:1 gears to 4.10:1 gears will give you over 20% more torque at the rear wheels.

To answer some of your other questions.

A GV overdrive (actually made in Britain we suspect) will take up to 2000HP.

Yes you can not always place an x-pipe or h-pipe exactly where you want it but fit one anyway.

On the track with an open exhaust I am not convinced a x or h pipe makes a huge difference but you want one for street use anyway and it will not hurt on the track.

Hi again

3. Move the torque you make higher up the rpm scale (HP = Torque x RPM divided by 5252).

This is HP at dyno?
Because my engine is something like that : http://carcraft.com/techarticles/116_0111_mopar/

The main difference are the MSD distributor and 1.6 vs 1.5:1 roller ratio, and cam vary a little bit. 230-236 vs 238-246 and comp. ratio 10.23 vs 10.34. (Mine are the second on each case)
If I do this formule 582.9 x 4100 / 5252 = 455 I think is real HP, not at crank.

What is the way to know the right rear end I need to get maximum power from this engine?

How much is gear vendors cost? I suppose I will need to short the driveshaft and balance it again.

I try to get more info about the efficience of x or h pipes at the track, because on the street i prefer the sound without them. PROPA-PROPA

How RPM have your idle? I love the sound of your exhaust and the quick way to get RPM on video.

As soon as i will have videos I try to put them here, we must wait until realisator of the video weekend make copies for each one who ask for it.

Thanks.

plum-crazy wrote:Hi again

3. Move the torque you make higher up the rpm scale (HP = Torque x RPM divided by 5252).

This is HP at dyno?

NO! This is how HP is calculated. It is what HP is! It is the definition of HP. How else can I put it?

Horsepower CANNOT be MEASURED. You can only measure TORQUE. Horsepower is calculated from torque.
If the torque you have is measured is at the crank then you use that formula to calculate horsepower at the crank.

What is the way to know the right rear end I need to get maximum power from this engine?

By using my various spreadsheets found on this board in this section and
in the transmission section you can work out what mph your car should be doing as it crosses the line at the track. From that you can work out what gear you need so that you cross the line at that speed with the engine at peak power rpm in top gear.

How much is gear vendors cost? I suppose I will need to short the driveshaft and balance it again.

About $1,000??? You will have to look up their prices on their web site. You driveshaft will have to be 14" shorter if I remember right. They also supply a different front slip yoke to fit the output of the OD unit. I have the full story about fitting one on this board.

How RPM have your idle? I love the sound of your exhaust and the quick way to get RPM on video.

About 850-900rpm I think? I can't remember how I set it the last time. Less than 900 for sure. Refer to my thread on carb tuning.

As soon as i will have videos I try to put them here,

Can't wait to see them.

I need enough time to check all that you say.
Thursday i will go to the mechanic (with closed door) to check roll brake.
I will be back!!!

Yesterday I was playing and checking the spreadsheets.
I think the engine is ok, I want to change 2.5" exhaust for 3" until cut outs only to race. after cut outs i will let the 2.5" lines , I think is enough to cruise.
Probably, when I have more budget I will get the 1.6:1 ratio rollers.
First I think the better chance is look for Gear Vendors unit, I was playing with ratios in the spreadsheet and I think for me 4.10 gears is the best, with GV the final ratio is the same like I have now, 3.23 to cruise and the rpm limit is around 110 miles.
This may be good to make 12's?
3800 pound car/400-420 RWHP = 12.1-12.3ET @ 110-112 mi.

Today go to public scale to weight my car with me inside and half tank.