Hi my slant 225 was rebuilt about 8 years ago, in that time it has not done many miles, so the motor is still great. Recently i removed the tappet cover and adjusted the tappets, while i was at it i heard you should check the tension of the head bolts. So as per my manual it says to set them at 65ftlb and i was doing it in the sequence in which the manual said, then one of the damn bolts snapped on me, it is snapped deep down to the block and no ways of getting to it with out removing the head which i really do not want to do. My question is, if i fill the hole with high temperature sealant, will the motor run fine still, as its only one bolt out of the 14? I know i should pull the head of, but another part of me is saying it still may run fine. If i remove the head i know things are going to snow ball, i will end up buying arp studs, then shaving and modifying the head and the costs are going to be a fair bit which i don`t really want just now. If i do drive it as is and the head gasket fails because of the broken bolt well i am just going to have to do it then. Has anyone else had this happen to them??

It takes more torque to snap those bolts then 65 ft-lb.... be weary of whatever torque wrench you used.

8 years is a long long time to check head bolt torque. Maybe a few months / hundred miles after a rebuild, then it's good..

I say run it until it breaks, what have you got to lose? If it holds it holds, if it doesn't the failure won't be catastrophic. Keep an eye out on coolant level and check compression occasionally.

Filling with sealant won't get you anything besides a mess during the repair.

Hi Pierre, i think you mis-understood me. The motor was rebuilt about 8 years ago, car was of the road being restored for a few years, lucky if its done 10 000 miles all up, and when it was rebuilt after the first 1000 miles the tappets were re-adjusted and head bolts were re-torqued. The motor hasn`t been touched and recently i adjusted the tappets now and checked head bolts. Yes you are right, my torque wrench was set at 65ftlbs and is a kinchrome brand, all the other bolts it clicked like it should, and that one that snapped did not torque up and click like it should have. I am really annoyed this has happened but yeh im thinking i should just drive and it see what happens, as we know the slant motors are very tough and just keep on going.

Does the fractured end of the bolt show any sign of an internal defect like an inclusion or lap, it will probably take a micro examination to be sure, but it would be good to at least look.
Agree with the above post, it would take a lot of overtorque to break a good slant six head bolt.
And consider there are only 4 head bolts per cylinder and two are shared between two cylinders.
If you choose to run it you will blow the head gasket.
I would rather fix it a my convenience than living in “wonder when it will be undriveable” scenario.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

With modern head gaskets, they basically never need retorquing. I always overtorque mine to about 80 ft lbs and then forget about them. I have never broken or stripped a bolt, so that is curious. I agree you will probably blow the gasket, although it might be OK for a while if you do not drive it hard.

I wonder if your torque wrench "clicked" right when you started pulling, and so you were already over 65 ft-lbs when you started and went up from there... I do not like click torque wrenches and never use them. I use the old beam type, which gives you a continuous scale to interpret as you pull.

If this is a "weekend cruiser" that you do not take far from home, then I might leave it for a while. If driven more, then you should pull the head. I would not personally drive far from my house like that, or without another car/backup to get home.

Best wishes,

Lou

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Home of Slant6-powered fun machines

Try to get the threaded end of the bolt out, with-out removing the head...

The good news is that the threaded head bolt holes and bolts stay pretty clean so the stub may be pretty loose down in there.

First use spry carb cleaner and compressed air to get any crud out of the deep hole.
Then try a rubber tipped probe (pencil eraser) to reach down, push and turn to see if the threaded bolt end unscrews, then use a magnet "on a stick" to pull it out.

If that does not work, get the top of the stub dry and use a very small dab of 5 minute epoxy on the end of a 7/16" wooden dowel, slide it down the hole, let it set and try to unscrew the broken piece out. The key is to use very little epoxy, just a small dot on the center of the dowel so it does not hit the surrounding walls.
You owe me a beer if it works.
DD

Good thoughts, Doug. You could also try a 3/8" bolt with JB Kwik on the end...

Lou

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Home of Slant6-powered fun machines

Hi well the car is just a weekend cruiser if that, sometimes i only get it out once a month. The bolt snapped and whats left behind is about 3 inches down into the block, its so small i don`t think i can get anything in there to try and spin it out. I think i am going to drive it and see what happens, i really don`t want to be pulling the head off.

You'll probably be pulling the engine instead of the head if you do that.

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There's no such thing as too much cam....only not enough engine!

Damn you guys aren`t making me feel confident.

Slant six motors are very robust for:
Crank shaft construction and engine bearing diameters,
Block and head wall thickness,
Connecting rods,
Engine cooling
Lubrication path

Four bolts per cylinder is adequate, but certainly nothing over engineered.
You will have 3 bolts for at least one, prossibly two cylinders providing the clamp load with approximately 25% of the piston gasket circumference not fully loaded. I am not aware of any IC engine with 3 bolts per cylinder.

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Doo Ron Ron and the Duke of Earl are friends of mine.....
https://www.youtube.com/watch?v=uX8Nj8ABEI8

As a last resort before pulling the head, I would try a left hand drill bit. I would try for a bit about half the diameter of the bolt. If you can make a "sleeve" to keep the bit centered things will go much easier. I have had pretty good success with LH drills on other things. The key is to get a GOOD bit, this would not be the time to go harbor freight shopping.

Well, with that same logic, if you bent a push rod, would you just leave it in the engine because you couldn't get it out and hope for the best too? This is a pretty major issue that can lead to other more serious problems if not corrected. Were not trying to give you a hard time. No doubt this isn't an easy fix, but it's well worth the effort to try.

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There's no such thing as too much cam....only not enough engine!

I know its not a good thing to happen, looks like i might not have much choice, think im going to have to remove the head. Is there any where i can buy new bolts from that you guys might recommend? Only replacement i have seen is to buy Arp studs. At the moment its smack bang in the middle of summer in Australia, today is 40 degree Celsius which is 104 Fahrenheit. But if i do a bit every day it wont be too bad. How should i go about it? Drain coolant, remove the intake and exhaust manifolds, all the vacume lines ect, drain coolant, remove top radiator hose and alternator bracket, remove the remaining bolts and it should come of? Or do i have to remove all the rocker gear before i remove the head? I have never done this before but feel i am very capable of doing it. Once i get the head of if the bolt is above the block which im pretty sure it is, i will weld a washer and nut to the bolt and unscrew it if it doesn`t easily come out with vice grips.

Well, look at it this way. The bolt is broken. To repair you will be pulling the head and hopefully be able to remove the broken bolt. If you drive it, well perhaps, just perhaps if you take it easy it may hold for a while, then it will blow a gasket and you get to pull the head and fix it. So really the question is not “IF” but likely “when” you will pull the head to do it right. I’d personally pull it now. As to why the bolt broke, it’s possible the wrong bolt was fitted and it was too long, bottomed out in the hole and it snapped when you tried to torque it. Maybe a dud bolt but it’s unlikely, maybe you overtightened as mentioned? Who knows. Bolts shouldn’t be too hard to get. I’d get to the bottom of it and see what else is not right. That way you get peace of mind cruising, especially in the summer heat.