'72 OMC 165 - blown head gasket?

[southkogs]

Howdy all:

I'm starting a new thread because the problem is a little different than the header on my OTHER one suggests:

The 165 Stringer is a Chevy inline 6 (250), and I'm getting zero compression on cylinders #2 & #3. Under load on the water the boat has no power, runs way rough and makes a pretty consistent popping noise while running. I'm guessing at a bad head gasket ... does that make sense, or should I be checking something else?

If it is a head gasket: is that something that a novice, and not that good, mechanic can tackle?

 

[Silvertip]

Re: '72 OMC 165 - blown head gasket?

The diagnosis is reasonable. Yes -- a novice can replace a head gasket IF (note that I said IF) you have the service manual that is specific to your engine. Some of them are downloadable from this forum. If you have never adjusted hydraulic valve lifters and decide to try and do this repair yourself, you need to at least make a trip to the library and check out a Chevy service manual (one that contains info on the 230/250 six cylinder motors). That will also describe in detail how to adjust the valves. Do that wrong and you create more problems than you can imagine. Use marine parts in the repair. You can get those from NAPA or possibly right here on iBoats.

 

[Bondo]

Re: '72 OMC 165 - blown head gasket?

Howdy all:

I'm starting a new thread because the problem is a little different than the header on my OTHER one suggests:

The 165 Stringer is a Chevy inline 6 (250), and I'm getting zero compression on cylinders #2 & #3. Under load on the water the boat has no power, runs way rough and makes a pretty consistent popping noise while running. I'm guessing at a bad head gasket ... does that make sense, or should I be checking something else?

If it is a head gasket: is that something that a novice, and not that good, mechanic can tackle?

Ayuh,..... How big's yer toolbox,.... It's abit more involved than changin' the spark plugs....

 

[southkogs]

Re: '72 OMC 165 - blown head gasket?

Toolbox is above average - but nothing that a pro would be impressed with. I also have a couple of friends that are very capable auto mechanics that I think I can get help from.

My assumption that hiring the job out is nearly $1k. If I do this myself is it reasonable to expect parts and service on the head to come in under $500? (I've only looked at a couple of gasket sets online.)

I'm trying to sort out my options and decide what to do ...

 

[Silvertip]

Re: '72 OMC 165 - blown head gasket?

You don't need an entire engine gasket set. Valve cover, manifold, and head gasket.

 

[southkogs]

Re: '72 OMC 165 - blown head gasket?

I'm leaning toward taking it on right now ... stay tuned for more questions!

 

[southkogs]

Re: '72 OMC 165 - blown head gasket?

I've been assuming that there are different gaskets for marine applications vs. automotive. Is that true? The boat runs normally on fresh water, but there are a few places on the coast I might (maybe) someday take it.

Thanks again.

 

[southkogs]

Re: '72 OMC 165 - blown head gasket?

As I'm gettin' ready to get into this engine (collecting parts and information right now) a question popped into my head: I read somewhere a while back that running an older (used to run on leaded fuel) engine on unleaded fuel was no problem. So, I've been running on straight unleaded for the last two years. Is there any chance that I goofed and shouldn't have done that? Or, is it true that typical unleaded shouldn't have hurt anything?

Thanks as always.

 

[427amx]

Re: '72 OMC 165 - blown head gasket?

have head magnafluxed for cracks then surfaced on a mill , not a sander type mach. Have done many and never had a come back using this way .

 

[427amx]

Re: '72 OMC 165 - blown head gasket?

Heads from those years do not have hardened valve seats. Lead in 70"s fuel was used as a seat lube as well as octain booster. Have stelite valve seats installed and no more head or lead substitute additive probbs again. glad to pass it on.

 

[bruceb58]

Re: '72 OMC 165 - blown head gasket?

So, I've been running on straight unleaded for the last two years. Is there any chance that I goofed and shouldn't have done that?

Not unless you have put close to 1000 hours on your engine in those two years.

 

[427amx]

Re: '72 OMC 165 - blown head gasket?

obscure hr. guess without knowing valve spring pressure. Since allmoast full thrd moast of time spring rate hight to keep lifters to follow cam profile. Raced one in pro gas in 70's. Just a lesson learned.

 

[southkogs]

Re: '72 OMC 165 - blown head gasket?

Not unless you have put close to 1000 hours on your engine in those two years.

Nope, not quite that many

Thanks guys. Stay tuned ... should get interesting.

 

[bruceb58]

Re: '72 OMC 165 - blown head gasket?

In any case, you need to get the head gone over so new seats and guides should be put in.

 

[southkogs]

Re: '72 OMC 165 - blown head gasket?

One last question, and I'll start a new thread if any pop up after this: Do the valve seals need to be marine specific? Or will auto part valve seals do the trick?

I've gotten a quote to have the head machined and included they'll do the valves and reseat everything. They're an auto shop, so the only thing I'm concerned about is specific application (marine seals).

Thanks again.

 

[Bondo]

Re: '72 OMC 165 - blown head gasket?

One last question, and I'll start a new thread if any pop up after this: Do the valve seals need to be marine specific? Or will auto part valve seals do the trick?

I've gotten a quote to have the head machined and included they'll do the valves and reseat everything. They're an auto shop, so the only thing I'm concerned about is specific application (marine seals).

Thanks again.

Ayuh,.... Like 99.9999% of All the motor's internal parts,...

They're Exactly the same....

Go for the cheap umbrella seals, insteada the fancy metal bodied spring backed seals...

The ole umbrellas might fail from old age, after another 20 years or so,...
The fancy seals aren't much of any kinda Improvement...

 

[southkogs]

Re: '72 OMC 165 - blown head gasket?

...The ole umbrellas might fail from old age, after another 20 years or so,...

"Father in Heaven, please let my OMC Stringer last 15 of those 20 years. Amen."

Ayuh,.... Like 99.9999% of All the motor's internal parts,...

They're Exactly the same....

Go for the cheap umbrella seals, insteada the fancy metal bodied spring backed seals...

Thanks Bond-o. Helps me a bunch.