I swapped in a different set of heads this winter on my 350. After a half hour or so of run time, I discovered these heads are cracked. I trusted the guy that I got them from when he said they weren't, and it back fired on me. I ended up with some coolant in the oil, but it wasn't that terrible. The oil was still closer to a dark shade than white. At the end of the last time I ran the motor with those heads I developed a really bad shake coming from the motor. The motor still reved ok, but I didn't drive it with the shake. There also wasn't any real audible miss to be heard from the exhaust. I thought it may have been loose or bad plug wires so I replaced them when I swapped my set of heads that I know are good onto the car. Started the car up, and the shake was still there. I check the mounts (solid moroso's) converter, and flexplate and all checked out ok. Also checked for vaccum leaks, which didn't turn up anything. When I went to start the car again ~2 hours later the starter would spin for a second, then stop, like the motor wouldn't spin over any more??

My thinking led to a bad bearing that was siezing the motor up. So I pulled it last night and took off the main caps. All of the lower halves of the bearings looked fine. I haven't checked rod bearings yet, but didn't really suspect anything from them since there was no noise coming from the motor.

What is causing this?? There is no metal in the oil pan, and everything looks great in the bottom end so far. I really dont want to tear the whole thing apart and have to put in new rod bolts (I've heard you shouldnt' loosen used ARP's and re-use them, is there any truth to that?)

Need some big time help here guys this really sucks, the bracket season is going to be starting up here soon.

Thanks!

 

If you have known leaking heads, and cannot crank the engine over, remove the spark plugs and try it again. You may have a cylinder hydro-locked from coolant leakage. You'll be lucky if you didn't really damage some of the rotating assembly.

That miss could easily have been from the coolant contamination of the plugs in the wet cylinders. It's all inconsequential now, since the heads have to come off again.

 

The vibration was there when I started the motor back up with the good heads, but it could have been that there was still a small ammount of moisture in the cylinders causing the shake.

I took off one pair of rod bolt nuts, but didn't remove the bolts. Is it ok that I put the nuts back on and torque them the spec?

Right now it looks like I'll just put the pan back on the motor and go again. Hopefully this clears itself up if it is the tiny bit of moisture in the cylinders.

 

The original con rod bolts are not TTY design, so you should be able to re-use them with no concerns, provided they are inspected for flaws. A little thread locker and correct torque should take care of it. ARP fasteners are evidently NOT QS9000 qualified, ISO or FQA compliant, and may or may not meet OEM design standards. Because of this, they may be TTY, and shouldn't be re-used.

I inquired directly directly to ARP several years ago (back when I thought I might give a damn about them), and got no reply. I suspect they could provide no traceability certs about which I was inquiring, so I couldn't be sure they are the same design. If they're ARP, replace them just to be safe.

BTW - When is the last time you heard of a rod cap bolt failure in an SBC that wasn't caused first by a rod failure?

 

Dont rod bolts have to be pressed in? I SHOULD know this, but I had my short block put together by a shop, so I didn't really have my hands on it. I guess I don't even know which bolts they put in. All I know is they are ARP.

 

Anymore on the pressing in rod bolts?

Anyone have odds on what the chances of the ARP's letting go are if I re-torque the 2 bolts? I know its risky, the only aftermarket parts I'd loose is the cam, and its a $80 summit one.

 

Yes, they are pressed in. Heat up the big end of the rod with a torch, and then a tap is all it should take to get the bolts out.

Then, just use the nuts to press the new ones back in place. Just be careful not to heat up the rod to much, or concentrate the heat all in one area, and then let it air cool.

I don't think the ARP rods are torque to yield, but you'd better contact ARP direct to make sure of it.