kathycool

Just did a compression and then leakdown test on port engine.....'90 merc. 525sc. #2 cyl. showed 120 lbs., rest were 140 to 150 lbs. Leakdown obviously indicated bad intake valve.

Anyone have this happen? Approx. cost to fix if no other problems?

All spark plugs looked fine. When checked timing, it was at 19*(idle). Stbd. engine was at 15*. Started looking for problems when rpms were 400 less than stbd engine @ wot. Looks like to much timing may have caused problem.??

I guess it's off to the shop next week.

rjcardinal

Hey George,

Sorry to hear of your problem. Where are you going to take it? I hope you get her back in the water before the Shakedown Cruise on the 29th.

I just finished installing CMI headers today. Went off without a hitch. But when I fired it up to check for leaks I noticed the engine water pump dripping out of the weep hole. I guess it never ends!

Good luck,

Ron

Griff

If it just a valve job and you replace all the intake valves, it should run somwhere in the $500 range + $100 for gaskets. this is doing all the labor yourself.

Griff

BTW, timing should be set at 13* at idle and 35* total. This assuming you have 22* advance modules like I have on my '96 525SC.

kathycool

Thanx for the info Griff.

Vinny P

What % leakage did you get? Did you hear air leaking through the intake to determine a bad intake valve seal?

tripps

Ill bet that valve is tuliped a little from detonation,or a spring is weak tripps

kathycool

Had about 20% leakage through carb.......was pretty obvious.
Gonna pull head off tomorrow.

bobby daniels

Detonation or to little timing which causes the intake to super heat ,be sure to use wide seats when you put it back together and the best valves you can ,if you haven't replaced springs lately do it now and save trouble later

kathycool

Thanx for all the replies.
Pulled the head Tue. and found intake valve w/ a dimple on the seat, probably from the 1/2" piece of the piston missing!!
Looks like it has been that way for awhile.........doesn't appear to have damaged the cyl. walls. Going to have it taken down and looked at. Also do both sets of heads while down. Will post pics later. Also considering new rings while down. 240 hrs. on mtrs.