I hate to bad mouth the competition but the OSCO manifolds have some pretty poor flanges between the manifolds and risers. Take a file and draw it across the flanges a few times (to make sure they are flat) before putting it back together. Using the latest design Mercruiser gaskets will help considerably (they had so many problems they've changed the design of the gaskets a couple of times).
Dennis Moore
www.mooreperformance.org

Thanks Dennis,

Actually, I cleaned the paint off the flanges and checked the flatness with a straightedge before I bolted it all together. Everything seemed ok (i.e. .001 feeler could not slide under). Maybe something loosened up. Come to think of it, I never re-tightened the riser bolts again after the first time out. I figured one heat/cool cycle should do the trick.

I hate to say it too, but the last OSCO riser setup I had used gaskets similar to what Merc is using now - teflon/graphite over SS shimstock. The riser gaskets that came with my current setup were light green and had no SS core. They seemed like a rubberized fiber stock that had me think for a second that they may not be the best material for the job. I guess I'll find out soon enough.

Looks like the rain stopped for awhile and I am getting ready to work on it now. I'll stop by again later with any info I have.

Thanks for your help!

-Larry

I even took my spacers and riser to work and milled the machined surfaces flat to make sure. Resulted in more leaks and more problems. The problem with mine was not the surface finish, but the amount of cast iron (weight) the long threaded studs had to handle. A little side load from some rough romping, which I do often, will result in a puked gasket/seal. Take my word for it. Not sure which risers you have though. Some risers are not like mine and have short studs with the nut only 1/2" or so above the manifold surface. Do you have a pic lj?

BT

Well....The verdict is in.. UGH!

Did a compression test first:

#1 140 psi
#3 140 psi
#5 45 psi
#7 125 psi

#2 125 psi
#4 130 psi
#6 120 psi
#8 130 psi

As you can see cylinder #5 is kinda lowww..

Pulled the riser off and saw rust/water inside the manifold. Gasket looked ok, but I replaced it with a new Merc gasket.

Pumped out oil and changed filter, put plugs back in, and started her up. Ran ok, but a little rough - especially at idle. Then stopped motor and immediately pulled #1,#3,#5, & #7 plugs again. Imagine my amazement when I see water pouring out of the #5 cylinder! #1, #3, & #7 plugs were dry this time.

So, here's what I think happened:
Head gasket let go on cyl #5 and when engine stopped or slowed to idle, allowed water backup through the exhaust valve and into the manifold, thus wetting other plugs on the same side.

I hope the head isn't cracked. So, this week I am pulling both heads off, and at a bare minimum, getting a valve job. Hopefully, I will be able to get away with minimal expense. I blew out all the water and fogged the crap out of it so the cylinder won't rust. I also drained the block again and the oil.

Thanks for all the advice. I appreciate it.

-Larry

Well, it's bad enough that the head gasket let go and the inside of my engine looks like cream cheese. It's even worse when all you have is one more headbolt to loosen and the head is so rusted that not one socket, metric or otherwise, will grab onto it.

Does anyone have a suggestion as to how I am to get this bolt out? It is recessed a bit so it is impossible to grab with any vise grip. I thought about welding a grade 8 bolt to it with my MIG welder, but the weld is unlikely to be very strong.

Is the only solution to use an oxy-acetylene torch to cut it off?? I don't want to ruin the head if I can prevent it.

Arrgh!

The bolt in question in the picture is directly above the engine mount.

Hellllpp...

-Larry

Cream Cheese anyone?

ttt

If you want that head bolt out.
Try the Craftsman 'Bolt-Out'.
They really work.
You have to buy an entire kit for $49.99
Item # 52162
Good Luck!

There are special duty sockets availabe on the market which are designed to cut into the head and grab harder the more you pull. They come in various sizes for wheel nuts etc. They work on dam near anything as long as you buy the "good" ones which are real hard and have very sharp flutes forged into them.

That is some fugly stuff lj. Maybe the special bolt remover tool along with some heat to stretch the bolt before applying torque. A wack with a hammer never hurts either.

Any pics of the exhaust manifold chambers?

BT