deboatmon

Twin Gen V 502 EFI with several very reasonable mods including cams, rockers, lifters, head work, Paccaloy springs, Inconel exhaust, stainless intake, computer work, Stainless Marine exhaust. I have broken valve springs all over the place. Starboard engine dead from it. Pieces everywhere. Several valve guides and valves to be replaced.

These are good springs. No over revving ever. Cruise 3500 RPM.

200 hrs use and springs are dead in both motors but starboard totally dead.

Any suggestions as to what might have happened ? Any ideas on helping avoid this happening again ?

stevesxm

the person that "designed" and assembled the valve train didn't have a clue what he was doing. there is no single cause of failure here. get someone that understands the geometry rquirements in a dimensional sense and start over.

Budz Motorsports

Wow could be several things that could do this. But this valvetrain was not happy. Like stated above get the heads to a good engine shop.
www.budzmotorsports.com

deboatmon

Actually the motors as described have 450 hrs. At 250 hrs all springs were replaced and there were no broken springs. On the advice of original builder, I replaced the springs @ 250 hrs whether it looked or sounded like they needed attention. He said @ 250 hrs do it. So I did it. When the springs were replaced my local Merc guys did the work. Therein may lie the problem. While very good overall they may lack the experience with this particular type setup.

At the very end of last season the starboard motor made a bad noise. These motors have performed beautifully for several years so I find it very difficult to discredit the original builder.

I simply was asking for input as to where to start looking for possible problems.

The heads are off now with 5 guides being replaced and 5 new valves as well as new springs. The head work guy is a competent performance marine engine builder. I do have confidence that he has the ability to rebuild these heads to new or near new condition. Perhaps the mistake was mine in not taking the heads to him @ 250 hrs. The heads never came off on the 250 hr maintenance.

Thanks for the input. I'm anxious for my first boating of the 2008 summer.

MM1

Maybe the springs that replaced the originals were not the correct ones. I personally have had very good luck with Isky products the 8205 plus is a great spring for 500 efi or 502 replacement. Just my two cents Good Luck

lake speed

I had a similar problem and found out that the installed spring height was wrong and causing coil bind. Bottom line is that it was the wrong springs.

barry d.

I build cylinder heads for a machine shop, and if I had to guess, I'd say your problem is coil bind. I just set my own heads up with a good set of comp springs, titanium retainers, etc and no problems so far. What you need to check (or have a local machine shop check) is install height and then check the springs. Say your springs are in at 1.975"...that is the height the spring sits at while the valve is resting closed. You need to put the spring in a spring tester (machine shop will have), see what the seat pressure is at 1.975" to make sure it's sufficient for the application (hydraulic roller, solid roller, etc). They will check the spring at 1.975" and THEN start compressing it to the point of max valve lift. So, if you have a .650" (valve lift) cam, they will close the spring up that much (if it will) and check the pressure and then it needs a MINIMUM of .050" more movement before coilbind. If it doesn't have that much beyond max lift, you'll run into the exact problem you have. Perhaps the springs that went back on just don't have the available lift of what was on it. I've seen newer springs vary even with the same part # as an older one so if the application was close already, it becomes a problem. Anyways, they just need the install height and max lift and they can check to see if you'll have problems with coil bind. Like I said....050" after max lift is needed. Hope this helps.
Barry
www.ProLineRaceEngines.com

Budz Motorsports

Barry very good info. I agree with your thoughts on this one. Springs not correct or installed height not correct.

barry d.

...just curious if there was any follow up on this, or have you not had a chance to mess with it yet?

Carder

Any signs of water reversion?