ctadams21

On a carbureted HP500 how can you tell if the stock springs have been replaced with the Comp or Isky springs?
Also do the Comp or Iskys last longer than 200 hrs?

Mudball

I redid the top end of mine late last year and went back with the comp 929-16's. The color stipes on them were different from the old Cranes, but I don't remember what they looked like!!

The Cranes were weak at 180 hours.
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The question of life for the comp and Isky's is a great one! I would like to know, too!

cstraub

No matter what spring you use if the engine sees valve float then the springs will see severe harmonics. Once a spring takes a harmonic set then it is down hill from there.

Chris

ctadams21

Did stock springs have an inner dampener? Any visible difference from aftermarket springs?

Thanks

HOTTZU98

What is valve float and what is severe harmonics? I think I know what valve float is but need a better description?

HOTTZU98

Are there any other problem areas on hp500's? Also what is the cost to redo valve springs on these engines?

Mudball

There was no visible difference with mine, other than the paint markings.

I didn't mention, but my HP500 is a 1999 carb.

Mudball

Hottz, there are NO other problems with the HP500 other than the valve springs.

From everything I've read, only the carbed versions and very early EFI versions were affected by inferior valve springs.

Later EFI's are supposed to go a lot longer than the magic 200 hour mark for the carbed versions.

You can replace the springs without removing the heads. It's not a big job. I did pull my heads and they were perfect, other than the weak springs. The lifters and cam were also perfect. Everything else was perfect! It didn't even need a valve job, but I did one anyway... There have been a few others with leaking head gaskets at higher hours. Mine were not leaking. I also believe the Merc head gaskets are not as good as Felpro's or Cometic's. I went back with Felpro's.

These are wonderful engines, IMO!!
Kent

Mudball

Valve float is when the valve springs can no longer overcome the mass of the rest of the valve train and follow the curve of the cam properly, so the whole mass floats above the cam on the down slope, slamming against the cam in some cases later in the cycle.

Overrevving and weak springs can cause this.

Harmonics are a resonance created by certain rpm's of the valve train. The resonance involved I don't understand, but it can cause the springs to weaken.

Ever look at the cam profile of the HP500? That sucker is steep!!
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Chris knows far more than I about these things!!
I'll be contacting Chris when I go through this motor for MORE POWER, in another couple hundred hours!!
Kent

HOTTZU98

yOUR dONZI MUST BE A ROCKETSHIP WITH A 500 IN IT SOUNDS LIKE A BLAST!!!