Checking for a bent rod.

[f_inscreenname]

Well as the old saying goes “sh** happens”. Got my new motor (360 mopar) put together and had a gasket leak in a exhaust manifold. Sucked up water in #6 cylinder. Did a compression test all were good except #6. There I had no compression “0 psi”. Having to find how bad it was I pulled everything off the motor including the heads and found a bent valve (at #6). The question is how do I make sure I did not bend a connecting rod without pulling the motor? Everything is new in the bottom end so I would like to avoid pulling it apart if I can.

 

[KennyKenCan]

Re: Checking for a bent rod.

With the head off, just measure the distance from the top of the piston to the top of the block.<br /><br />Do this for all pistons on that bank.<br /><br />If # 6 cylinder's measurement does not match the rest, then the rod is most likely bent.<br /><br />Hope that helps ya, without tearing the whole motor down.

 

[f_inscreenname]

Re: Checking for a bent rod.

I tried a straight edge laid across the deck an used a feeler gage. Couldn't find a difference in any of the pistons height. Of course this a backyard operation. I would think there would be a noticeable difference. For the little time I had it running I didn't hear any “ hard knocking” only the taping of a piston kissing a valve and that was only for a short time. I am crossing my fingers. What do you think the chances are of bending a rod? It didn't hydro lock for that matter it didn't even shut down. Just ran like poop and got worse as water sprayed back into the intake and soaked the other plugs.

 

[Peter J Fraser]

Re: Checking for a bent rod.

f...<br />Water in the cylinder shouldn't have caused a bent valve. Water in the cylinder will create hydro lock - that bends conrods real easy. You are prob OK on the rod if you can't measure any difference in height.<br /><br />Mis firing yes but bent valve is more than likely from a valve train problem. <br /><br />My Thoughts.<br /><br />Peter

 

[Walt T]

Re: Checking for a bent rod.

Its possible the rod and the bearing is damaged. I would pull the engine if only to check. The rod bearing may have been smashed. Pulling the engine is a lot cheaper than buying a new crank and possibly a new block. The rod may be very slightly distorted and can cause catastrophic failure down the road. Then again, it might be okay...............

 

[f_inscreenname]

Re: Checking for a bent rod.

Humm.... Everything new with valvetrain. Now you got me thinking.......dam....do you think. Everything is very tight in there flat top pistons 10.5 to 1 comp, 1.6 lift roller rockers, mild HP cam, add water. Besides bending a rod or blowing a new head gasket I would think the next thing would be bending a valve????

 

[MooseHootie]

Re: Checking for a bent rod.

My brother and I race at the local strip. Our car cracked a cylinder head and filled the cylinder up with water when it started it made the rod U shaped. When we pulled it apart the rod bearing was smashed enough that you could feel the play in it. If you blow a head gasket water will exit fast enough not to cause these problems.

 

[crazyray]

Re: Checking for a bent rod.

i would almost bet your rods ok...small block mopar have very stout bottomend....the head gasket would almost certainly push too if you had that kind of pressure....the valve was most likely hit by piston when it hung.....what work was done to heads...guides tight etc.....exhaust valve? what springs you r you running<br />can you see any marks on piston?

 

[f_inscreenname]

Re: Checking for a bent rod.

Heads are about a year and a half old (new swirl port design) they are tight but broke in. I will have to get back to you on exactly valves and springs used. A friend with a job title of “head specialist” built them (cant get a hold of him today) but I am sure they are stout. It was a exhaust valve. There is a “kiss mark” on the piston top. No dent but you can see where it hit it. I did change from a 1.5 stamp rocker to a 1.6 roller rocker but like I said I used a mild cam so the lift should not be that bad. Then there was the water ingestion, that had to be a factor? I would like to be sure though. One more thing to check out before I put it back together.