1970 Cuda 4 speed 60 ft problem

[raffaplymouth]

The one thing that bothers me, and it might just be the picture, but those slicks look awfully close to the leaf springs.
So when will you be trying the new mods out?
How about some fiberglass for the front end, like a hood and bumpers?

i have fiberglass hood .. im looking for fiberglass bumper ..i have found on ebay at 70 $, i will buy!

[raffaplymouth]

Raffaele,

Ok, so it just occurred to me...

You're running full street exhaust on the track, right ?

I see you've welded your crank evac tubes into the exhaust outside the collectors so this might pose a problem, but I would drop the exhaust & mufflers and run with open headers with maybe 12 inches or so of extension stubbies to provide a little back pressure for low end torque, but for sure drop the muffler set up.

Weight = HP, right ? And HP = ET

On my little blower car it helped on my 60' and was worth 2 tenths at the top end...

this is a good idea .. i can buy another header flange ant tube long 12" and drill for put another evac and lambda nipples , only for races ... you think will make power ??? or only much noise ??

[wikd69]

this is a good idea .. i can buy another header flange ant tube long 12" and drill for put another evac and lambda nipples , only for races ... you think will make power ??? or only much noise ??

It's my understanding that what you want is the right amount of back pressure for the best bottom end torque. Part of the benefit to tweaking back pressure is to help increase exhaust scavenge at the heads. You get back pressure from your street exhaust, but maybe too much and you most certainly get the weight penalty of all those tubes and mufflers.

Mine seems to run best with about 12" of extension - it just has more grunt and pulls better over the curve. An easy test for you would be to fab up some 18" extensions and make one run with full exhaust, one with the 18" extensions and one with just open tubes. Aside from the noise aspect, you'll be able to feel the difference. If the extensions are an improvement, you’ll need to determine how long they need to be.

The trick I used on mine was to start with 18" extensions and use a heavy crayon to mark the extension all the way down its length. Then, make a run. The point at which the crayon stops burning is where you cut it. There may be better ways to get the right length (on a dyno, for instance) but the crayon trick is supposedly the best way to figure it out on the track. Mine doesn't perform as well with straight open headers, and, the induced harmonics makes all the screws in the interior back out and drop on the floor

Also: You're running 2" primaries, 3 1/2" collectors and 3 1/2" tubes. I have close to the same, with 2 1/8" primaries and 3 1/2" collectors. With mine however, I neck my extensions down to 3" out the back. That ensures I get good back pressure and doing the crayon thing lets me figure out the right extension length to level it out. If you can afford it, you might want to try both 3" and 3 1/2" extensions. Again, as I understand it, the idea is to get the right scavenge effect at the exhaust ports - the amount of back pressure needed to help that along will be purely dependent on your intake air flow, intake/exhaust runner size, cam profile and compression ratio. You're running enough displacement to maybe need the bigger tube size all the way back, but it might be worth trying the slightly smaller tube size just to check.

Note that I'm running a lot smaller motor (434 ci / .030 over 427) but I'm also running a bunch of boost out of the blower, so that changes the mix, when looking at overall tube size and flow, etc. With your much larger displacement you would think you'd need much larger tubes in back but (in my opinion) you're using relatively small primary tubes (2") for your displacement. Add to that the fact that (according to your first post) you're pushing a healthy shot of nitrous into the motor. That increases cylinder pressures and delivers a corresponding increase in exhaust flow and volume. I'd prefer you had bigger primaries (2 1/8" to 2 1/4") but again, that’s a personal opinion (they may be just perfect as is ). I think tho, the 2” primary size makes tuning your exhaust even more important. Getting the right level of back pressure to balance primary tube flow and the resulting scavenge effect at your exhaust ports will help a lot overall.

I'm also running a TH400 with a brake. I launch at 4000 and shift at 7400 so I have a nice long power band to play with and only 3 gears to worry about. You don't have the benefit of the transbrake and all that raw grunt at launch (I launch with full boost out of the hole )

This aspect of tuning is as much voodoo as science so you'll just need to play with it a little. Like I said tho, same day, same track, same tune - I made one pass with my street exhaust and the next with my extensions. 2 tenths difference at the stripe and a big diff with my 60’s.

If / when you get to the right length of the extensions let us know the weight difference between the extensions and the full exhaust. I'll bet you're looking at least 35 pounds difference, weight wise.

However, like everything else in this business, your mileage will vary I tend to build all this stuff in my head while I’m puzzling out what I want to put together and it all seems to make sense to me . If you asked any number of the guys on the forum here you might get a completely different view of things.

It'll be interesting to find out what you find in playing with this part of your build.

[Bruce69Camaro]

Here is something to think about, I just looked up the Moroso crankcase evac system and there was a footnote that said you shouldn't run this system if you run mufflers, which you do.

It's probably due to the back pressure????

There is a reason why they put these footnotes on the instructions.

I'd remove the 5/8" hose between the check valves and the breathers and just run the breathers if you didn't want to drop the exhaust or you could just leave the hose hang, but route it so that it doesn't touch anything hot.

[Bruce69Camaro]

Hey Raffa,

A friend of mine is an administrator on a Cuda Challenger site and he let me post a question about chassis modifications for your car. One thing that was brought up, if you plan to use leaf springs, then switch to a setup using housing floaters and ladder bars.

[John_Heard]

Hey Raffa,

A friend of mine is an administrator on a Cuda Challenger site and he let me post a question about chassis modifications for your car. One thing that was brought up, if you plan to use leaf springs, then switch to a setup using housing floaters and ladder bars.

I'd debate that one all day, no need to switch to ladder bars. There are plenty of very fast cars running leafs out there. Now a good quality set of shocks is a heck of a lot better investment than putting ladder bars on it.

[Bruce69Camaro]

John,

I think you read into this wrong, the guy was stating that if he wanted to use housing floaters, he had to use ladder bars with them.

[John_Heard]

Sorry, missed that wasn't following closely along with this discussion.

[Bruce69Camaro]

No argument here, can't mess with the guy that gives us this place.....

We'll just blame it on looking at too many diodes and flashing led's

[raffaplymouth]

Guys ...all your information, including those of wik69 are very important to me ... I will make a treasure, I think I delete the muffler and put 2 long tubes 18 " and then do the test marker, but my engine has too much power ... but now we must work on 60ft !! now we have 1.99, I'd like to 1.65-1.70, my goal is 10.80- 10.90 ET ,is a half second !! now my best ET is 11.49@138 ...i would like to make 10.80 with my leaf spring , i know that with ladded bar will make 9.50 -9.80 , but remember that car i use sometimes on the street ..and also a crime to destroy enough original car...then in the future will buy 'a rolling chassis , and i will put this engine ... now my goal is 10 high !!

when return to italy i have in my mind this work :

1) exhaust removing 40 lb
2) heater removing , hifi, speaker..35 lb
3) pinion allignement

the weight become around 3500 lb ...

i have some questions

why when i make burnout the rear euspension go up-down ... up down .. up down ???
where is the right time of burnout ?? 5 seconds ??
rear suspension adjust ?? now is all soft
yesterday in the third test my friend told me that the front left wheel wheelie of 1" ... in the track with glue this wheelie can increase ???

thank you very much for your help

RAF

[clutchdude]

Your 10 sec expectations are easily obtainable! And you dont need ladder bars to do it.

You are simply just overpowering the tires off the starting line and the chassis needs some help to minimize this. And if you are going to use a street clutch in the car you have to try and bog the engine a little, leave at a lower rpm, i have seen some street clutch big block cars leave as low as 3000 rpm. And even then they had to slip the clutch a little as well as feather the throttle.

On my car when i had a street clutch in it i was able to leave at 5000 rpm, but the chassis was working. Get your car to transfer weight in a controlled manner with shocks and springs and i see no reason why it cant be a 10 sec car with 1.50 60's

Here is a old video of my car with a street clutch.
http://www.youtube.com/watch?v=5BURGEF0v30&feature=plcp

[Bruce69Camaro]

why when i make burnout the rear euspension go up-down ... up down .. up down ???

To me, it sounds like your describing wheel hop, here is some info on that and let us know if this is what your talking about?

http://www.competitionengineering.com/a ... assis2.asp

where is the right time of burnout ?? 5 seconds ??

I was told 3 seconds is long enough

[clutchdude]

Get some good video's !!!!

[raffaplymouth]

Your 10 sec expectations are easily obtainable! And you dont need ladder bars to do it.

You are simply just overpowering the tires off the starting line and the chassis needs some help to minimize this. And if you are going to use a street clutch in the car you have to try and bog the engine a little, leave at a lower rpm, i have seen some street clutch big block cars leave as low as 3000 rpm. And even then they had to slip the clutch a little as well as feather the throttle.

On my car when i had a street clutch in it i was able to leave at 5000 rpm, but the chassis was working. Get your car to transfer weight in a controlled manner with shocks and springs and i see no reason why it cant be a 10 sec car with 1.50 60's

Here is a old video of my car with a street clutch.
http://www.youtube.com/watch?v=5BURGEF0v30&feature=plcp

WOW , I SEE NOW THIS LAST PICS .. IM AT KINGMAN AZ , TOMORROW WILL GO TO PHOENIZ AZ.. YOUR CAMARO IS VERY IMPRESSIVE ALSO WITH STOCK CLUTCH !!YOU HAVE A GOOD TRACTION , I THINK FOR LIGHT WEIGHT ... I THINK HAVE A LOT OF TRACTION PROBLEM ON MY CUDA ... GUYS WHAT DO YOU THINK OF TIRE COUMPOUND ?? IF I PUT A SET OF DRAG SLICK MORE SOFT ??

[raffaplymouth]

why when i make burnout the rear euspension go up-down ... up down .. up down ???

To me, it sounds like your describing wheel hop, here is some info on that and let us know if this is what your talking about?

http://www.competitionengineering.com/a ... assis2.asp

where is the right time of burnout ?? 5 seconds ??

I was told 3 seconds is long enough

YES BRUCE LOOK LIKE MY PROBLEM .... BUT I HAVE CAL TRACS !! IS VERY STRANGE THIS WITH CALTRACS ... I DONT KNOW IF DEPEND FROM MULTILEAFSPRINGS ....