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Broken Pushrods ==> failure analysis and repair options

Discussion in 'Sunbeam Tiger' started by ducsingle, Aug 9, 2011.

  1. ducsingle

    ducsingle Donation Time

    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.
     
  2. RootesRacer

    RootesRacer Platinum Level Sponsor

    Is it possible that your cam went flat?
     
  3. ducsingle

    ducsingle Donation Time

    All of the cam followers are in primo condition with shiny follower surfaces and no noticeable wear. So I don't think the failure was due to a cam problem.

    I recently chatted with a local Tiger expert who recently had a major cam follower failure (flat tappet cam), and I've seen a few similar issues with vintage motorbikes with flat tappet cams. That's why I use Brad Penn or diesel (Rotella T, etc.) motor oil in my vintage vehicles as those oils retain the zinc anti-wear additives.

    I mention the above oil info only because it is related to the question about cam damage. Please do not turn this into an oil thread!
     
  4. mikephillips

    mikephillips Donation Time

    Since you call it an Alpine V8 I'm making the assumption of a conversion. The biggest problem with advice in that situation is I can't see where its the same and where its different.

    What I can say is that the remark about having the right angles, extensions, etc is correct. It can be done in the car, the exhaust and rear bolts being the tough part that might require putting a coulpe small dings in the firewall to have enough travel.

    As for removing the engine there's mixed opinions. I personally think it's easier to drop the front crossmember and drop the engine/transmission out the bottom. I put mine in that way after trying from the top like the manula says and found it much easier. Depending on how fast you work could be started one day and finished the next.
     
  5. pdq67

    pdq67 Donation Time

    I replaced the heads with the engine in the car many years ago and decided afterwards that it would have been easier to pull the motor. If you want to try it, here are some tips. Remove the motor mounts and let the motor drop as low as possible, Install the rear two pushrods in the heads before you drop the heads onto the motor using some tape or wire to hold them in place. There is not enough room to drop them in after the heads are on the car. You will be able to torque the head bolts but not the rear bolts on the intake. Also, the rear valve cover bolts are a pain.

    If you decide to pull the motor, plan on about 1 1/2 hours to get it out and 6 hours to reinstall if you have a helper. Do yourself a favor - Pull the motor. It gives you the opportunity to detail the engine bay, inspect and/or replace the clutch, and if you pull it from the bottom you can do a thourough inspection of the front suspension while it is off the car.

    I used to have problems with bent pushrods when using Rhodes lifters. I now use stock lifters but I also have pushrod guide plates, screw-in studs, hardened pushrods, and roller rockers. No problems in six years.
     
  6. MikeH

    MikeH Platinum Level Sponsor

    Is this a solid lifter engine?
     
  7. ducsingle

    ducsingle Donation Time

    Thanks for all of the helpful comments.

    My car is a converted Alpine, but the conversion was done by grafting parts from a crashed Tiger, so mechanically the car is the same as an original Tiger.

    The lifters are hydraulic, not solid. The cam is a flat tappet cam, not a roller cam.

    My engine had screw-in studs and hardened pushrods, courtesy the Hi-Po heads. Unfortunately, the engine builder and/or previous owner were either really ignorant or went cheap on the rocker arms (standard rockers, not roller tip) and did not install pushrod guide plates. Nothing time and money can't fix, but it's unfortunate that the engine wasn't built right to begin with.

    I've heard it's easier to drop the engine and transmission out the bottom. Can anyone point me to a write-up of that procedure?
     
  8. Duke

    Duke Donation Time

  9. MikeH

    MikeH Platinum Level Sponsor

    Just curious now. Is it possible that your issue was caused by a failed lifter, that may have not pumped oil up through the push rod to the rocker?
     
  10. cal44

    cal44 Donation Time

    You mentioned HiPo heads. True early Hipo heads not only have screw in rocker studs but cast in spring cups and narrow oblong push rod holes and of course they are cast iron. Is this what you have?
     
  11. ducsingle

    ducsingle Donation Time

    All lifters were found to be in good condition upon disassembly.

    Read the article from the link in my original post and note my comment about the worn pushrod guide slots on the affected valves. I've talked to several folks who are very familiar with the 289's, and they basically said mine was a classic failure of the stock valve train. The phrase "woefully inadequate" was used to describe the stock rocker arms when used in a car like a Tiger.

    There's a pretty good reason why so many companies make aftermarket rocker arm conversions for these engines. . . .
     
  12. MikeH

    MikeH Platinum Level Sponsor

    Interesting article, but the problems seem to attributed to wear. My '65 Mustang sports the original 289 4V and I've never had any valve train issues. I've had the car since 1995 and the odometer had turned over at least once and has turned over once since I've had it, so It could be nearing 300 or 400K miles, not sure which. I've had the valve covers off and have not noticed the type of wear mentioned. But I will definitely take a closer look.

    Another popular "fix" on the 289 is to swap in a 351 or 5.0 HO cam to change the firing order from 1-5-4-2-6-3-7-8 to 1-3-7-2-6-5-4-8 to reduce front bearing load caused by the sequential firing of 1 and 5.
     
  13. ducsingle

    ducsingle Donation Time

    Agreed, the failure probably would have been much less likely to have occurred if the Hi-Po head pushrod guide slots (and maybe the rocker arm tips) were not worn. Pushrod guides are cheap insurance against this sort of failure though, and the rocker arm upgrades are surprisingly inexpensive.

    My failure happened with no warning like unusual valve train noise. I was just chugging along at about 2500 RPM when the engine started sounding really bad, which was probably the engine backfiring through the carb due to at least one intake valve getting stuck open by a broken pushrod.
     

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