mkulikow

Background, '99 7.4L MPI

Engine has overheated twice and is defintely suffering from slight water intrusion. I blow steam and get some plug steaming as well but get zero milkshake, oil always looks fine. I took the risers off last night and you can see a little puddle in the port side. My guess is a cracked manifold, since riser gaskets looked OK. Had already decided to replace exhaust this spring as well as head gaskets since I have a month to work on her and for a little piece of mind.

Once I got the intake plenum and intake manifold off I was poking around looking at the intake ports and I see some surface rust on some of the intake valves and the ports but overall it looked very clean. Would this be a concern or is it more due to condensation and lack of fogging oil in the intake system combined with 8 months of sitting? I can snap some pics of it tomorrow if it helps.

- Mike

Wobble

If you haven't pulled the heads yet, I would check compression and do a leak down test. If that checks out then go from there.

Depending on where you store your boat (humidity) it seems that a little superficial rust on the intake side is probable

Big Block Billy

Beware of rusted valve springs, they get the least bit of pitting they break.
Also look at exhaust valve stems, where the stem joins the head. They also break if rotted in this area.
Otherwise from what you stated you should be fine.
BBB

mkulikow

Under the valve covers everything looks very clean. I didn't see any signs of rust on any spring or valve stem (above the guide). I think at this point after seeing a puddle of water in a manifold that I am more worried about rusted exhaust valves and seats then the intake side of things. I won't see this until the heads come off this weekend.

offthefront

iTrader: (1)

mkulikow .... did you have to completely dissasemble the plentum and Intake ? or can it be removed as a unit ? I have a cpl of 502's that need valve jobs ......m

mkulikow

In my case I had to remove the plenum first. Half of the bolts are covered up by it. I believe you will have to as well, assumin it is an MPI and not carb.

And in another feet of engineering marvel you also must remove the throttle body (easy but a waste of time) because there is one plenum bolt you can't get to because a socket won't slide down past the throttle body.

offthefront

iTrader: (1)

Yea 502 MPI's ..... How manys hours your 7.4's got ? These are at 350 hours ...I got them from a repower job and we ran em checked all the codes and it was all clear ... there was some compression issues and leakdown showed valve leakage ...

mkulikow

I have ~300 hours on mine with 2 bad overheats. I lost an impeller the first time and lost an alternator pulley (therefore the belt) the second time.

I am doing 99% of this just so I feel better about it after a low compression reading, no leakdown available. With the heads checked out, new top end gaskets and new exhaust I am hoping to be trouble free for another 2-3 seasons. That way I can concentrate on the other things I want to do to the boat. It is probably overkill but I'm an engineer and a mech-head so this just gives me a reason to tear $hit apart.