UPDATE: IDLE CLIP ADDED

ENGINE RUNNING GOOD NOW


Help guys!
Mods in my sig,

New Tick LS1 SNS stg 3 cam.
I am having trouble with my engine falling on its face at 5800rpm during tuning on Dyno

When cam was a 222/222 which was meant to rev to 6500rpm but only ever managed 6200rpm before falling over, I had Patriot Gold dual springs fitted.
Changed springs to Pac 1518s due to small cam, engine revved to 6000rpm.

I am now running Patriot Gold Duals with the Tick cam, Ti Retainers

I am looking for possible causes of what seems like valve float.

Could my H/S rockers be causing this?

H/S rockers & patriot Gold springs were fitted when I was cam only TSP 231/237 & engine revved to 7k & I changed at 6800rpm.

Solution: I am giving my standard rockers to the workshop to fit & see if that helps, if so will use the trunion upgrade.
Any help here is gratefully appreciated guys. My car has been down now for 9 weeks.

Cheers

 

Are you talking about different sets of springs or the same set?

If so they are likely worn out.

Could also be the heavier rockers. Different cams have different lobes and some might be more prone to float than others...hence being fine with the rockers on one cam but not on another.

Are you sure it's valve float and not fuel starvation?

 

Either put the stock rockers back on or you need a spring with 180/420+.

 

Roller rockers=Prc eht .675 springs
Stock rockers=btr .650 springs

 

No theory, just proven facts.

 

I have personally seen roller rockers cause valve float at higher RPM on a few applications. It would cause the dyno graph to look "wavy" on the top end and wouldn't allow it to make power over ~6200. I'm not sure if the springs couldn't "keep up" with the heavier roller tip or not, but I found one of two things fixed the problem. 1) go back to stock rockers (i recommend doing the trunion upgrade) 2) Get a spring with higher pressure ( we use BTR Dual springs for everything!)

Hope this helps!

 

It's not a fuel issue, tuner is good at what he does & tells me everythings fine untill 5800rpm.
This has happened with a mild low lift cam & now the Bigger Tick cam, I believe by me having the Pac 1518s springs put on it kind've masked the real problem before with the small 222/222 cam.
Springs are not worn.
This is happening with the Pac 1518s & the Patriot Golds, with the pacs it revs to 6200rpm, the Patriots to 5800rpm


I am taking my set of stock rockers this morning to the tuner



I haven't seen the dyno graph but believe that it was making power all the way to 5800rpm then just dropped.
If the stock rockers work, then yes I definitely will do the trunion upgrade.

 

Yeah let us know what you find out! If stock rockers fix the problem, feel free to contact us and I can give you a good price on a trunion kit! Good luck!

 

Did you check spring pressure before you installed them? Maybe they have lost a little pressure.

 

This has been an on going issue over a number of years since my engine build, with the previous cam which originally I had Patriot Golds fitted, engine would fall over at 5800rpm & it should've gone to 6500rpm.
I had then gotten Pac 1518s installed, engine went to 6200rpm, I had assumed it was a spring issue being that the Patriots were to strong for the baby cam etc.
Obviously the tuner I used then also thought the same thing.

Hense now with the Tick sns stg 3 fitted & Patriots installed it is doing the same as before.

I dropped off the standard rockers to the workshop this morning & was told definite valve float was noted at 5800rpm to 6200rpm with a base run on the baby cam & Pac 1518s before Tick cam install, then after Tick cam install with the Patriot springs fitted it revs to 5800rpm then just nose dives.

 

At a minimum you should have someone check the seat and open pressure of those Patriot springs. Even if they are fairly new they could be off or possible not the right springs for your cam.

 

It's not the springs!
It has been happening with different springs & different cam

 

Okay, sorry, when I read it I interpreted that it went away when you had changed to the PAC spring.

That said, I would get a new set matched to the cam even if it isn't the issue. Good luck in your quest.

 

Patriot Golds are trash. They lose spring pressure quickly and don't have enough open and closed pressure to control a heavy roller rocker: they are all wrong for HS roller rockers.

Go for 150+/380+ spring pressures and OEM rockers. You'll rev cleanly past 7k with that camshaft. Also, fit the biggest pushrods you can in there to avoid deflection.

 

Ok, I will also look into better springs, in saying that, years ago when engine was cam only & fitted with a TSP 231/237 it ran perfectly up to 7000rpm with the H/S rockers.

Does anyone know if Texas Speed fitted their 5.3 stg 2.5 heads with bronze guides or not!
Without having to wait till the workshop opens Monday & they have a look themselves.
I understand the Trunion upgrade won't work with the bronze.

 

I'm 99% sure the TSP 5.3 heads are powdered metal guides (stock)

 

Thanks for that. Was starting to get a little concerned in case I do need to go back to my OEM rockers

 

how much lifter preload do you have ?

 

I haven't set it up so am unsure.
But it's not lifter preload, this has been happening for to long now with 2 different sets of lifters, comp & the current LS7 Caddi,
with preload being set on 3 seperate occasions when engine work was being done by 3 different mechanics.

 

Put the stock rockers on and don't look back.

It will fix your issue indefinitely.