Clutch messing with performance at top end?

[wreckit]

Need some of yalls help!
My 03 cobra has been having an issue on dynos. Near the top end (after 5,000rpms to be exact) the car displays signs of "belt slip."
Well, after Stiegemeier and My performance shop consulted with one another, they have determined it may be the stock clutch causing this issue.

1. What are your thoughts on this issue?
2. What is a highly recommended clutch that will have a VERY soft pedal feel?
**Looking for soft clutch pedal so my wife, who has had 6 surgeries on her left ankle, could be able to enjoy our dream car!

 

[JuStAkId]

How many miles on the stock clutch? Stock clutch cable? What are the current mods done to the car? Usually the stock clutch starts to slip at 600rwhp/550rwtq (given that is if your stock clutch is in good condition)

Also for your power level I would look into the mcleod rst

 

[wreckit]

Car has 33k miles. Stock clutch and cable.

Was also looking at swapping the 10 spline for the 26 spline whiles its out.

 

[JuStAkId]

Car has 33k miles. Stock clutch and cable.

Was also looking at swapping the 10 spline for the 26 spline whiles its out.

what hp mods do you have?

 

[wreckit]

JLT RAI - Stage 8 Steggy port with ported plenum and throttle body - 2.90 upper - 4lbs lower - 90mm aux idler - Borla Stingers - Bassani catted x - 60lbs injectors - and new pumps to support gas flow

 

[Bdubbs]

Could it be spark blow out? What plugs and gap. Just trying to address little stuff first.

 

[P49Y-CY]

2. What is a highly recommended clutch that will have a VERY soft pedal feel?

twin disc. will feel like you're driving a Honda civic

 

[wreckit]

twin disc. will feel like you're driving a Honda civic

Any twin disc?

Plugs are ngk 8 race plugs I believe. gapped .35
The Shop gapped them for me when i brought it in to get tuned a month ago.

 

[P49Y-CY]

Any twin disc?

personally I have had great experience with the McLeod RXT for my street cars, but i believe others have tried different brands with success.

 

[Bdubbs]

Any twin disc?

Plugs are ngk 8 race plugs I believe. gapped .35
The Shop gapped them for me when i brought it in to get tuned a month ago.

Not familiar with ngk 8, is that the stock heat range? With a ported blower I'd tighten the gap to .030-.032 and try ngk tr6's.

If you think the clutch is on it's way out, go on the highway at like 40 mph in 4th or 5th gear and put it to the floor. See if the rpms flash up like what a loose converter would do.

 

[wreckit]

Not familiar with ngk 8, is that the stock heat range? With a ported blower I'd tighten the gap to .030-.032 and try ngk tr6's.

If you think the clutch is on it's way out, go on the highway at like 40 mph in 4th or 5th gear and put it to the floor. See if the rpms flash up like what a loose converter would do.

Do you think the clutch would have anything to do with it acting strange at high RPMs?
When i get the car back tomorrow morning ill see what it does with the pull test you mention. What do you mean by flash up?
they are gapped at .032 my mistake. I was going to get tr6 but bob suggested the TR race plugs bc the blower is ported and the higher airflow.

 

[15PSI]

I think NGK 7s are one step colder. Try .028-.032. The 7s work well in just about all conditions.

 

[wreckit]

they are ngk 7 sorry for the mix up

 

[Bdubbs]

Do you think the clutch would have anything to do with it acting strange at high RPMs?
When i get the car back tomorrow morning ill see what it does with the pull test you mention. What do you mean by flash up?
they are gapped at .032 my mistake. I was going to get tr6 but bob suggested the TR race plugs bc the blower is ported and the higher airflow.

Typically a clutch is bad, doing the test I mentioned will cause the rpms to flash up but the car isn't pulling. Many people including myself are running tr6 plugs. I'm currently at 19 psi, but plan on trying them even at 21 psi.

Edit, are they tr7ix? I had spark blowout with tr6ix gapped at .030, ended up going back to tr6.

 

[Riddick]

Did your tuner log boost? If you have belt slip the log will show lower boost in the upper RPMs. Do you have an aftermarket boost gauge? You can always go out to a safe open area and see what the boost gauge is saying over 5000 RPMS. The Eaton will fall off a little but if its slipping you will see a drastic loss in boost.

Also, I saw you have a 90mm snub idler..... any chance you have 100s in place of the other idlers. If so slap on a 100 up top to see if it solves your problem. Any chance you can go out and take a pic of your belt tensioner, if you took a pic of it showing the tensioner tab we could tell you if you need a tighter belt or not.

 

[Bdubbs]

Riddick has another good suggestion. I've had both belt slip and blowout on the dyno. They both look similar.

 

[wreckit]

Once i get the car back tomorrow morning i will take a photo of the belt tensioner.
No, I do not have a boost gauge. .
I will ask the tuner if he logged the boost and try to get everything i can from him before I leave.
Will also try the clutch test tomorrow and see how it goes.
Also, will ask if they actually gapped the spark plugs correctly.

 

[wreckit]

Alright. Picked the car up this morning and spoke with my tuner.
He said the plugs were not the problem and are gapped correctly.
The boost wouldnt drop to much when past 5k rpms, maybe by 1-2 psi. So its not the belt slipping.
I tried the method (Bdubbs) suggested, the rpms did not flash way up so the clutch may not be completely on its way out.

But the clutch has been known to lock me out of 2nd, 3rd, and reverse from time to time.

 

[hotcobra03]

I run stock clutch. .have single hook quadrant with heavy duty cable..

my pedal falls to floor vs stock quadrant and cable.


I would try plugs gapped tighter. ..many threads on that..



age could be issue also...oem coils can weaken and not show on test but will show in drive ability

 

[wreckit]

I run stock clutch. .have single hook quadrant with heavy duty cable..

my pedal falls to floor vs stock quadrant and cable.

That is very interesting. Something I am definitely going to look into asap! thanks
What are the brands of the cable and single hook quadrant? where did you pick these parts up at?