21HP V-Twin Head Gasket Repair

[TwinL]

I just picked up a Craftsman LT1000 with a 21HP Briggs V-Twin, model number 407577-0283-E1. I believe it needs new head gaskets, I have ordered the gasket kits but I was just wondering if I need to order new head bolts too? In the past I have ran into issues reusing head bolts and them snapping in the block while torquing them down. I was also wondering what the torque specs are for the head bolts, and how many stages I should torque them down and how many foot pounds for each stage. I’m 18 and fairly new to this, so any help would be appreciated.

I know these engines are famous for the valve guides sliding up jamming the rockets and bending the push rods, usually the shroud over the fly wheel has gotten filled with crap, quite often caused by mice causing the engine to overheat, the head bolt torque is 220 Inch pounds, that's "Inch Pounds", I've done many and used the original bolts and never broken a bolt off.

 

[slomo]

I know these engines are famous for the valve guides sliding up

Also famous for OWNERS not doing maintenance of any kind. That is the real problem these engines face.

 

[GasGuzler]

So bit of an update. Tore down the motor, it appears that the exhaust valve guides had began pulling out, and on one cylinder it had lifted enough that it didn't allow the exhaust valve to open all the way, consequently bending the pushrod. It had fallen out and ventured down into a passage right next to the lifter, I was able to pull it back out. Now the intake valve on that side was also bent, though no signs of a reason why... I can only wonder if it had let air into the engine, and right after the guide popped out and didn't allow it to exit the cylinder, and then when next intake stroke came around the compression forced the valve shut and bent the pushrod. It wasn't horribly bent like the exhaust one was, but definitely noticeably crooked. Other cylinder was perfect, valve guide had began pulling out on that side as well but hadn't gotten far enough to cause any damage. I pulled both heads, the headgaskets were both perfectly fine with no burn-through marks whatsoever, so those had survived. HOWEVER... the cylinder with the bent pushrods had a puddle of oil in the combustion chamber when I initially pulled off the head. The other cylinder did not, and that worries me a little bit. Both pistons have ever so slight side-to-side movement in the cylinders, but I was told that it is normal as the rings expand when the engine heats up and seals up better. Felt equal in both cylinders so one was not worse than the other, a hopeful sign. But that puddle of oil is definitely something I am worried about. Any ideas what the cause of that might've been? I'm just about ready to throw this motor back together, have new pushrods for it and every gasket needed. Just want to make sure there isn't something catastrophically wrong with it before I do so.

 

[Tiger Small Engine]

So bit of an update. Tore down the motor, it appears that the exhaust valve guides had began pulling out, and on one cylinder it had lifted enough that it didn't allow the exhaust valve to open all the way, consequently bending the pushrod. It had fallen out and ventured down into a passage right next to the lifter, I was able to pull it back out. Now the intake valve on that side was also bent, though no signs of a reason why... I can only wonder if it had let air into the engine, and right after the guide popped out and didn't allow it to exit the cylinder, and then when next intake stroke came around the compression forced the valve shut and bent the pushrod. It wasn't horribly bent like the exhaust one was, but definitely noticeably crooked. Other cylinder was perfect, valve guide had began pulling out on that side as well but hadn't gotten far enough to cause any damage. I pulled both heads, the headgaskets were both perfectly fine with no burn-through marks whatsoever, so those had survived. HOWEVER... the cylinder with the bent pushrods had a puddle of oil in the combustion chamber when I initially pulled off the head. The other cylinder did not, and that worries me a little bit. Both pistons have ever so slight side-to-side movement in the cylinders, but I was told that it is normal as the rings expand when the engine heats up and seals up better. Felt equal in both cylinders so one was not worse than the other, a hopeful sign. But that puddle of oil is definitely something I am worried about. Any ideas what the cause of that might've been? I'm just about ready to throw this motor back together, have new pushrods for it and every gasket needed. Just want to make sure there isn't something catastrophically wrong with it before I do so.

If i

So bit of an update. Tore down the motor, it appears that the exhaust valve guides had began pulling out, and on one cylinder it had lifted enough that it didn't allow the exhaust valve to open all the way, consequently bending the pushrod. It had fallen out and ventured down into a passage right next to the lifter, I was able to pull it back out. Now the intake valve on that side was also bent, though no signs of a reason why... I can only wonder if it had let air into the engine, and right after the guide popped out and didn't allow it to exit the cylinder, and then when next intake stroke came around the compression forced the valve shut and bent the pushrod. It wasn't horribly bent like the exhaust one was, but definitely noticeably crooked. Other cylinder was perfect, valve guide had began pulling out on that side as well but hadn't gotten far enough to cause any damage. I pulled both heads, the headgaskets were both perfectly fine with no burn-through marks whatsoever, so those had survived. HOWEVER... the cylinder with the bent pushrods had a puddle of oil in the combustion chamber when I initially pulled off the head. The other cylinder did not, and that worries me a little bit. Both pistons have ever so slight side-to-side movement in the cylinders, but I was told that it is normal as the rings expand when the engine heats up and seals up better. Felt equal in both cylinders so one was not worse than the other, a hopeful sign. But that puddle of oil is definitely something I am worried about. Any ideas what the cause of that might've been? I'm just about ready to throw this motor back together, have new pushrods for it and every gasket needed. Just want to make sure there isn't something catastrophically wrong with it before I do so.

If you pushed a valve guide, you can’t simply tap it back down. It will work its way back out. Valve guides that have moved is usually caused by engine that overheated. Engine overheating is usually caused by cylinder head cooling fins and top of engine caked in dirt, oil, and grass. Long term you need a new cylinder head and gasket to fix the problem.

 

[GasGuzler]

If i

If you pushed a valve guide, you can’t simply tap it back down. It will work its way back out. Valve guides that have moved is usually caused by engine that overheated. Engine overheating is usually caused by cylinder head cooling fins and top of engine caked in dirt, oil, and grass. Long term you need a new cylinder head and gasket to fix the problem.

I am aware of that, however I am on a budget here. I’m also not going to be using this mower to cut grass, the deck will be getting removed and I’ll most likely just be fooling around with the tractor. I’ll replace the heads in the future if needed, and will make sure to keep the block clean.

 

[ILENGINE]

I am aware of that, however I am on a budget here. I’m also not going to be using this mower to cut grass, the deck will be getting removed and I’ll most likely just be fooling around with the tractor. I’ll replace the heads in the future if needed, and will make sure to keep the block clean.

Need to keep in mind that even if the cooling fins are kept clean and you push the guide back down, it will migrate back up and bend another pushrod in about an hour.