Hi all
Running a NF 5.0 and it has fitted to it a set of GT40P's and a set of 1.7 Roller Rockers. It is still running the standard HO cam.
Its also on Injected LPG with a Crane Hi6 box.
I have found that when getting up it , around 4000 RPM it has develloped a bad miss fire. Pops out the exhaust and all. Rest of the time its fine.
Missfire is much more obvious on gas but still there on fuel.
It wont stop reving its just miss fires that bad there is no point reving it.
I was thinking along the lines of an electrical problem because its worse on gas but then I remembered the springs in GT40P's are only slightly tougher then cream cheese and Im now wondering if I have pushed the friendship far enough with them.
They were standard ones when I put the heads on and I have done around 30000km on them driving it fairly hard. No idea what KM were on them when they went on.
Have never had a valve spring issue on any car before so not sure of the symptoms.
If indeed my springs are stuffed what are the recommendations for replacements? I will most likely buy them from Summit unless someone has a good recomendation in Oz.
Cheers for the assistance.

sounds like the same issue I had with springs in my EF beforeI upgraded them. I used {DESCRIPTION}

but a quick check of my toolbox suggests the last individual who borrowed it has not returned it.

There is quite a few different ones out there, but I found this one worked well and was easy to use.

Which GT40P heads do you have? If you have 1.94/1.55 (AU 220kw) valves then intake/exhaust retainers are the same. If you've got the normal 1.84/1.46 valves then intake/exhaust valves have different retainers. I got the Crow Cams 7738-16 springs which are a direct easy fit without having to grind stems and much stronger than stock. From tuffcarparts I think it's $250 from memory for retainers and springs which is pretty good and keeps $ in the country