I recently broke a couple of pushrods on my Sunbeam Alpine V8. The engine is a 6-bolt 289 with Hi-Po heads that was rebuilt less than 10k miles ago. This post is intended to (1) warn others about the failure mode and (2) seek repair advice.
Failure Analysis:
Upon disassembly, I noted significant wear on some of the pushrod guide slots in the head. This wear coincides with the two broken pushrods on one cylinder and loose rocker arms on another cylinder. The rocker arms that were at the worn pushrod guide slots showed signifcant wear on the tips, and the valve stems were more or less chewed up at those locations as well. This is a known issue with the flat tappet rocker arms as detailed in the following article:
http://www.mustangbarn.com/boss289.html
Apparently the fellow who rebuilt the engine for a previous owner didn't notice the wear in the pushrod guide slots and he and the previous owner were unaware that it is advisable to upgrade the valvetrain of the early 289 engines for higher performance applications. The failure could have been avoided by installing pushrod guide plates under the rocker arm studs at a cost of less than $100. Note that this type of failure can result in a dropped valve, so if you are running stock rocker arms, you might want to consider an upgrade. The lessons learned here are (a) have an engine rebuild performed by someone who is very familiar with that type of engine and (b) don't go cheap and upgrade as necessary to reduce or eliminate known failure modes.
Repair Options:
Both heads are out. My basic options are (1) rebuild the heads, or (2) swap engines.
(1) Rebuilding the Heads
My main question here is how feasible is it to re-install and torque the heads with the engine in the car? One professional Tiger mechanic told me it couldn't be done with the engine in the car, and another told me it could be done with the engine in the car with the right mix of sockets and extensions. Obviously leaving the engine in the car is preferable.
(2) Swap Engines
A friend has offered me a complete 289 in very good running order (still in a car that can be driven around to test) at very low cost. If I can't install the heads on my current engine without removing the engine, I would probably just buy my friend's 289 and swap engines.
My question here is how difficult is an engine swap assuming a couple of mechanically inclined folks (one of whom has done engine swaps on other vehicles) with an engine hoist, a couple of weekends, and good attitudes?
Of course my other option is to just pay somebody to do the swap for me, but I'm on a tight schedule to make a vintage driving event in a few weeks, and none of the local Tiger guys are available between now and then.
Failure Analysis:
Upon disassembly, I noted significant wear on some of the pushrod guide slots in the head. This wear coincides with the two broken pushrods on one cylinder and loose rocker arms on another cylinder. The rocker arms that were at the worn pushrod guide slots showed signifcant wear on the tips, and the valve stems were more or less chewed up at those locations as well. This is a known issue with the flat tappet rocker arms as detailed in the following article:
http://www.mustangbarn.com/boss289.html
Apparently the fellow who rebuilt the engine for a previous owner didn't notice the wear in the pushrod guide slots and he and the previous owner were unaware that it is advisable to upgrade the valvetrain of the early 289 engines for higher performance applications. The failure could have been avoided by installing pushrod guide plates under the rocker arm studs at a cost of less than $100. Note that this type of failure can result in a dropped valve, so if you are running stock rocker arms, you might want to consider an upgrade. The lessons learned here are (a) have an engine rebuild performed by someone who is very familiar with that type of engine and (b) don't go cheap and upgrade as necessary to reduce or eliminate known failure modes.
Repair Options:
Both heads are out. My basic options are (1) rebuild the heads, or (2) swap engines.
(1) Rebuilding the Heads
My main question here is how feasible is it to re-install and torque the heads with the engine in the car? One professional Tiger mechanic told me it couldn't be done with the engine in the car, and another told me it could be done with the engine in the car with the right mix of sockets and extensions. Obviously leaving the engine in the car is preferable.
(2) Swap Engines
A friend has offered me a complete 289 in very good running order (still in a car that can be driven around to test) at very low cost. If I can't install the heads on my current engine without removing the engine, I would probably just buy my friend's 289 and swap engines.
My question here is how difficult is an engine swap assuming a couple of mechanically inclined folks (one of whom has done engine swaps on other vehicles) with an engine hoist, a couple of weekends, and good attitudes?
Of course my other option is to just pay somebody to do the swap for me, but I'm on a tight schedule to make a vintage driving event in a few weeks, and none of the local Tiger guys are available between now and then.
