Export thread

My ~17-year old Craftsman lawn tractor (917.275760) with a 18.5 hp OHV Intek engine (engine model 31p777-0299e1 040910ze) is now burning about 1 oz per hour when grass cutting. You can notice very light blue smoke going up hill (presume under load) and smell it all the time.
This seems to have started fairly recently; within the last month or so.
It gets used about 45 minutes/week grass cutting at my home. Since April of this year, it has about 10 hours of use. Our cutting season is roughly April/May-Oct/Nov (I'm near Philly) so that is ~ 24 cuttings @ 45 mins = 18 hours/year. I change oil and filter each year so I don't think a maintenance issue is the cause.

I don't see any leakage on the block or drips beneath on the floor after it being parked.
I'm assuming it is a ring issue and they need to be changed.
Any other suggestions/thoughts on what to check before I order parts and take the engine apart?

I've done a rebuild on a 1960 BS 8 hp. I assume this one not too much different in difficulty?

Thanks!

With that engine I would say there is a very good chance that you are dealing with a blown head gasket.

I agree with IL. Best thing to do is to find someone with a leak down tester and preform a leak down test on the engine. This will give you a better idea of where your problem lies.

How does that increase oil burning?

Oil would be sucked into the cylinder from the valve guide chamber, which is the most common place for the gasket to blow.

Crank the engine with the valve cover off.

Thanks! I'll give that a shot. Head gasket is a better repair than rings!

I assume I'll see oil squirting into the chamber on cranking?

Pull the air filter and make sure there is no dirt residue in the carburetor intake. If there is, the air filter was not seating properly and you might need new rings. Otherwise check the head gasket.

Never use any added sealant when replacing head gaskets.

Rivets said:

Never use any added sealant when replacing head gaskets.

Click to expand...

Thanks; I found this on Permatex site for this after I posted (duh):
"Not recommended for use on head gaskets or parts in contact with gasoline."
So much for a posting on another place.

Intek head gaskets are dirt cheap

Click to expand...

I use the Stens ones where possible as they are a lot stronger than the OEM ones
After that I have some solid copper ones from Coppergasketsus because some heads just don't want to seal even after lapping.
I put that down to bad castings or bad post casting heat treatment it is possible to get aluminium to be harder on one side than the other,
BAck in the old days when you were doing a run the first 2 to 5 revolutions of the casting machine would all be considered as scrap because it takes that long for everything to get to full operating temperature ,

I assume I'll see oil squirting into the chamber on cranking?

Click to expand...

No it will be sucking oilly crankcase vapour but you will see a gap hole or discolouration on one or both of the sealing faces.
Some of the tell tale signs of a blown head gasket are
1) White smoke coming out of the dip stick tube after the engine is turned off
2) knocking when the blades are turned on or drive engaged that smooths out
3) oil in the carburetter or air cleaner
4) oil dripping out the fuel pump brass vent
5) Plug oiling up / carbon fouling

Head is off:

and with gasket removed:

Arrows show where I think gasket failed. Agree?
Is this enough to cause my oil burning or do you think I need to go to the rings?

Thanks!

Ouch. Has that actually eaten into the block?

Yes that is the typical intek blown head gasket
I there is a deep groove it will need to be filled with your favourite liquid metal goop then the whole face smoothed & lapped.
I use a coarse stone followed by a sheet of wet & dry glued to a sheet of glass cut to the size of the wet & dry then flame smoothed on the edges .
The head needs the same treatment, but it is a lot easier to do.
B & S rough finish the heads & blocks deliberately so it grips the gasket like the teeth of a vice but some of them are just too rough and lead to a leak.
I have polished then dead smooth only to find the gasket blows out so I had to fit a solid copper head gasket.
OTOH this particular engine blew a head gasket every season or two so I had to do a couple of gasket replacements under warranty as a head gasket has a full 12 month warranty.
Coppergasketsus have intek head gaskets in a few thicknesses

bertsmobile1 said:

Yes that is the typical intek blown head gasket
I there is a deep groove it will need to be filled with your favourite liquid metal goop then the whole face smoothed & lapped.
I use a coarse stone followed by a sheet of wet & dry glued to a sheet of glass cut to the size of the wet & dry then flame smoothed on the edges .
The head needs the same treatment, but it is a lot easier to do.
B & S rough finish the heads & blocks deliberately so it grips the gasket like the teeth of a vice but some of them are just too rough and lead to a leak.
I have polished then dead smooth only to find the gasket blows out so I had to fit a solid copper head gasket.
OTOH this particular engine blew a head gasket every season or two so I had to do a couple of gasket replacements under warranty as a head gasket has a full 12 month warranty.
Coppergasketsus have intek head gaskets in a few thicknesses

Click to expand...

WHAT liquid metal goop? JB Weld will melt out. An old wrench once told me that lead wool (used for obsolete plumbing) would work. Never tried it.

I only use Devcon or POR 15
Both will make a suitable repair to heads
As for JB weld, 99% advertising hype 1% performance So I never use the stuff.
The trick is to buy from shops that engineers go to not the shops that DIY's go to .

Thankfully there is no groove or erosion of the head surface; that mark is just discoloration.

Is the recommendation to have the head and block surfaces smooth as possible or roughened similar to brake rotors are when new?

Just a light lap to flatten some of the high spots

bertsmobile1 said:

I only use Devcon or POR 15
Both will make a suitable repair to heads
As for JB weld, 99% advertising hype 1% performance So I never use the stuff.
The trick is to buy from shops that engineers go to not the shops that DIY's go to .

Click to expand...

JB Weld is awesome, in the right application. I have a power window switch still in service that I JB Welded 19 years ago, and some bicycle handles that get heavy, frequent use have served for 12 years now.

What's it's NOT is anything like a substitute for welding. It's nowhere near as strong as metal, can't stand any heat, and will only adhere to clean surfaces. It also takes at least a week to reach full strength, and will keep flowing for hours after mixing if you don't contain it. It's the advertising that's at fault, not the product. Which is just epoxy.

Back together; started right up.
I don't like the valve adjusting; a bit finicky for me.
Fingers crossed on how long it lasts.
Any comments on potential benefit of retorquing the head bolts after an hour or so of running?

Thanks to all for their help and comments on this.

"retorquing the head bolts" meaning checking to see if they are at the 220 in-lbs level; not loosening and redoing it.

FWIW, I rechecked the head bolts after running it for an hour. No change; they hadn't loosened a bit.