500hp Valve Springs ????
 

Have 96, 35' Fountain with 500 hp's. 200 hours. Was told I should immediately replace valve springs and exhaust valves. Anyone have info on what I should put in for springs, valves, retainers..etc. Thanks in advance!

You definately should put Inconel valves in the exhaust side. I believe Manley is the brand most commonly used. I'm not sure what springs are correct for your application, but they are due for replacing @ 200 hours. I have two sets of new Comp 929 springs if they will work for you. I'm sure someone here will know exactly what you need.

I would not worry about replacing the exhaust valves until after a leak down test. It is the springs that the problems around 200hrs.

I beleive Isky makes a nice set that are actually coated,and the valves just need to be checked,pretty hard to screw up an Inconel valve unless theres water intrusion or valve guide scoring!

I thought Merc used inconel exhaust valves as part of the stock HP500.

Thanks guys for your help! I appreciate the input. I think I'll do a leak down test and go from there.

I would change the spring regardless of what the leak-down test shows. The Comp springs mentioned above are a great choice over the Crane springs. Isky has a line of springs (a lot more money) that are supposedly one of the best available.

The Merc HP500 uses Inconel exhaust valves and has had some reversion issues (risers) from that era.

With that said we have a friend in the area that had the springs changed and ran the engines with well over 500+ run hard trouble free hours:cool:

The springs are a "maintenance item" as far as I'm concerned! You will probably see a slight increase in performance as well.
As far as going any further, I would do the leak & a compression check and if all looks good, run it!!
I have had very good success with Comp valve train parts, best performance for the $$.

P.S. Chuck is that you??

RedDog382:

I'm at the 200 hour mark on my HP500 as well. Might be interested in your springs if I can confirm those are the right springs and the price is right. Drop me a note as to what you want for a set. Also, just curious, how did you come to have two new sets of springs?

Mike
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Boatnick,

I just did mine with Comp 929 springs. My lesson learned was because its a double spring, you have to use the lever-type spring compressor. I originally bought the spring compressor which has jaws that engage the spring and screw clamp to compress it. The jaws weren'y deep enough to grab and compress the inner spring.

Don't forget, you need the spark plug adapter to hook up to an air hose...so you can keep the valve shut while you're changing the spring.

I put new new Crane valve locks and retainers in as well. You need 3/8" valve locks for the 500. Got everything from Summit.

Pulling the exhaust was the worst part of the job. I don't think you can get the valve covers off without doing so.

Bill