Bending pushrods

[aspoors]

During my re-build I've turned the engine over manually a number of times while making various adjustments - tappets, distributor fitting etc - and I now find that some of the pushrods have bent - to various degrees, some quite dramatically!  Is there a procedure for re-fitting pushrods that I have missed?  I'm sure they are the correct length and are seated correctly in the cam followers.  Any thoughts?  Thanks

[Tom Fremont]

Is it possible the cam is out of time with the crank? Don't know what could bend the pushrods except valves contacting the pistons. I would worry about the condition of the followers and the cam at this point, too - having lost a couple of sets myself I have the sense they are relatively delicate...

[Richard Crawley]

Tom,

sounds to me like you’ve got something rather seriously wrong there. I can’t imagine the pushrods bending unless the valves have come up against something immovable i.e. the pistons but I would have thought you would have felt the resistance when turning over by hand. Sounds to me as if there could be something radically wrong with the valve (camshaft) timing.  It could be the springs binding but I don’t see why this should happen, unless the cam somehow has too much lift; I don’t know if fitting similar components from one of the other members of the Triumph family engines (i.e. pistons or head etc) would cause such problems, perhaps others may know. What’s the history of the engine?

[Andy Moltu]

There can be one of a number of causes for bent pushrods

1) **** pushrods

2) Incorrect valve timing (Piston hits valve)

3) High lift cam fitted to valves with standard valve spring so that coils of valves bind at max lift.

These tend imply that things need to have been apart in the engine department at some stage.

[Guest ron]

Tom

I hope I'm right, but I think the springs would bind before the valves met the pistons, only thing I don't understand is how you didn't feel anything when turning the engine over by hand?

Ron

[squeezer99]

Hi,

 

Did you rebuild the rocker gear? Some of the rockers have spacers/washers between themselves anf the posts. If these aren't correctly located the pushrods can rub against the casting of the head! Worth a look anyway...

 

Regards

 

Jim

[marvmul]

Like Ron I think that the combustion chambers are too deep to make contact between valves and pistons possible.

Valve spring binding is possible, but one of the rules is that you don't apply brute force when turning over the engine but investigate instead. The pushrods can be bent when something went wrong with the engine?

[aspoors]

Thanks very much for your replies to date.  The engine has been re-built recently by a local specialist (and Register member) who assured me that the cam/crank timing was set up accurately.  Certainly, I feel no resistance when turning the engine.  The rocker gear was also re-built, and I'm pretty sure that's o.k. too.  When the engine was dismantled I found that about half of the original pushrods had bent, so I replaced them.  Of course, I don't know if the rods which have bent now are original or replacement.  I wonder if the "**** pushrods" theory is perhaps the best.  I'll replace, I think, and let you know.

[Guest ron]

I still think you have a problem somewhere even '****' pushrods are unlikely to bend without considerable force, try slackening off the tappet adjusters completely before installing new pushrods, and make sure you set them to the rule of 13.

Ron

[Guest ron]

I did a check on a spare cylinder head, screwed one of valves open with a clamp until the valve springs were binding and it looks as if you will probably get away with it although if you have a high lift cam or different valve springs [mine are doubles] there might be a different result.

Ron

[simon iregbu]

If any of the pushrods were replaced did you get the correct ones because the early CP models have shorter pushrods than the later CR models (8.11" to 8.3")

 

Another thing for you to check.

 

Simon