Another valve spring question....
 

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?

Re: Another valve spring question....
 

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!

Re: Another valve spring question....
 

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

Re: Another valve spring question....
 

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

Thanks

Re: Another valve spring question....
 

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

Re: Another valve spring question....
 

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

Re: Another valve spring question....
 

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

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

Re: Another valve spring question....
 

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

Re: Another valve spring question....
 

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

Re: Another valve spring question....
 

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

Re: Another valve spring question....
 

I think rocketship is relative, but it is REALLY FUN!!

I have hit 78.2 gps (Garmin eTrex handheld) so far.
Bravo 1 drive 1.5 gears, stock Bravo 28p prop, a little over 5000 rpm, maybe 5100. Hard to tell when you are going fast.
The 80mph speedo is almost buried, showing maybe 85. I have Gaffrig II gauges..

It's a handful above 75! I'm working on that. It needs 'something'...

I want to try to fix the handling before I play with props.

I have already installed a single ram full hydraulic steering (from the helm back), from XS Marine.
I am planning on some LOONNNGGG tabs at this point to try to help the handling.

We'll see....

Re: Another valve spring question....
 

Ctadams21
It would be difficult to determine the origin of your current springs unless they have external markings. You could check O.D./I.D, damper, or the rate on a Rimac. However if the springs have begun to sag that would be inconclusive. It is correct, there were some problems with a run of springs used in the 500 series of engines (due to improper heat treat) that have since been resolved Here are some options from a previous post of mine regarding springs.
Valve springs are a “read” component, similar to a spark plug, in that they contain a great deal of information relating to the operating condition of your engine. Not only are they responsible for returning the valves to their seats, they need to keep them there; a difficult task compounded by aggressive ramping and (in some cases) forced induction. In the process they are required to dampen and stabilize the harmonics created by the valve train and dissipate the resulting thermal buildup. Spring life has so many variables it’s difficult to put a cycle value on them. Because they are affected by heat, RPM (one “zing” can kill a spring), wire quality/heat treat, and camshaft profile, the degradation curve is not linear and varies greatly from application to application. Heat is generated in the spring from multiple sources. First by cycling the spring through compression and extension. Secondly the friction between the coils generates heat. Third is heat absorption.
I would suggest that you check your springs for current values at seat load and open load, compare that to spec and see if you are within tolerance. These figures will give you baseline references for future fatigue evaluation and alert you to other potential valve train problems. Many cam/lifter failures originate with the springs inability to maintain dynamic stability. Check springs for discoloration and/or cracks regularly. If you do find a break that is jagged, that is due to harmonic resonance. A clean break is a sign of improper heat treat. Monitoring your springs for degradation is cheap insurance. Below are links to on head spring test tools of various prices.
http://www.power-t.com/spring/pt-700.html
http://www.intercomp-racing.com/fr_springtorque.htm
http://www.intercomp-racing.com/detail.cfm?ItemID=121
http://www.jegs.com/cgi-bin/ncommerc...52&prmenbr=361
http://www.moroso.com/catalog/catego...?catcode=27105
http://www.lsmproducts.com/p3.htm
Bob

Re: Another valve spring question....
 

If it were me and I was unsure I would change them. I could get ugly if some break at 5000 RPM. Our boating season is short enough with out having a break down in mid season.