The V8 Owners Forum -

Hello, i have a problem. I finished building my engine over a week ago, put it in the car and it wouldnt start, on investigation found all of the exhaust push rods very bent!! The engine is a 3.5 with 9.75 pistons with cut outs, crowler 50232 cam with rhoads lifters, late 4.6 heads which have been ported and fitted with the larger valves and bullet guides and 1 less coil springs and comp head gaskets. the engine was turned over by hand at each stage to check the insides. the only difference would be oil pressure to the lifters causing to pump up. Anybody any ideas?

I think they are bent for a reason. If the lifters had no oil in when you turned everything over then you wouldn't be seeing maximum lift.

Have the valve guide tops been installed at the correct height? It aint the spring holder thingies hitting them is it?

i had the same thing but with a crower 50233 cam,
it turned out my springs were not the less 1 coil as i was informed,
i ended up buying the correct springs from Real Steel which cured my problem,

It is either valve spring bottoming, retainers hitting the guides or if all these check out, valves hitting the pistons.

The springs are the 1 less coil type. I did prim the lifters as the instrustions, the guides are the shortened type as brought from V8 tuner. As i filled the lifters with oil when building it, shouldnt it have touch when turning over when testing? whats best to do, pull a head?

Both heads off is the first thing I would do - something has fouled so need to see the damage.

Are the valve pockets the right size for the larger valves?
Only other thought is the cam timing being off.

Cheers

Andrew

yes I would say head off and check valve clearances with a light spring to make sure your not too close to the pistons. Sounds like cam timing if everything else ok. the clearances of a running engine is different from hand turning if its close to start with. Are the shortened guides installed at the proper hight?

I don't know this for sure but I would have thought if the valves hit the pistons the valves would be more likely to bend than the pushrods.

I agree that it all needs to be checked though.

You can make a really good set of weak springs by cutting in half the springs from an old set of rocker shafts. You also need to measure the compression that the valve spring will under go at full lift. You can then compress one of your proper springs this amount in a vice and work out if you have a coil bound issue. You can also push the valve past full lift whilst it is one full lift to see if there is a valve guide issue.

I would not trust that the lifters are not compressing to a degree during the tests, I used an old one and fill it with candle wax before re-fitting the inner cup. You need to make sure that the up is right against the retaining clip and does not move away from it during your tests.

I have some old rocker springs and lifters that you can have for free if you need them.

Doing all the tests will take a few hours and is bit of a pain in the bum but then again so is having a load of bent pushrods!

Do you want some pushrods? I've got loads!

Pete

just a thought,
are the piston reliefs big enough for your larger valves?

As said above, if it is bent push rods I think it is most likley coil binding or valve spring retainers hitting the guides, if it is valves hitting the pistons you end up with valves stuck partly down in the head. I still would strip the heads off and check everything.
Mike

Mike,
on one build i did i had the valves hit pistons on cranking, the pushrods bent but valves went fully home each time, thats why i asked regarding the reliefs mate.

Right, ive spent the last few hours taking the engine out and got a head off, can see where the exhaust valves have hit the pistons, have removed the timing cover, the timing is ok, so i can only think its the pockets in the pistons not big enough. Any thoughts??

did you do the reliefs mate? or did you buy the pistons already done?

when i did mine i used a valve bigger than what was fitted to the inlet and used it for both doing the inlet and exhaust reliefs,

I brought it from V8 developments about 2 years ago, the pistons came with the pockets, only had the problem since fitting this cam.

sorry all I was wrong! not the first time won't be the last. Previous time I did it it was because I increased the lift on a C70 motorcycle engine, and it was the valve springs. I shall go stand in the corner.
Do I have to pull another Chevy valve out of a head now?
Mike