How do you find a spun rod bearing?

rojam18801 · Post by **rojam18801** » Wed Jan 21, 2009 6:50 am

malcolmv8... you said it made some noise, not to much at first at first. then you got on it and went away. puter sounds are not good. but my guess is a colasped or weak lifter. when you got on it oil pressure went up pumped up lifter and sound went away. starting cold again would make that clattering sound. sounds to high pitched for rod or main bearing...the old trucker

cgrey8 · Post by **cgrey8** » Wed Jan 21, 2009 7:34 am

I can see that being a stronger design if the bolts come in horizontally to the cap or at an angle like outside splay bolts on some SBC 4-bolt mains. If that's the case, the threads wouldn't have to be the main "holding force" keeping everything together like they are with standard engines. The bolt itself would take on the sheering load so the threads wouldn't have to.

MalcolmV8 · Post by **MalcolmV8** » Wed Jan 21, 2009 9:24 am

rojam18801 wrote:malcolmv8... you said it made some noise, not to much at first at first. then you got on it and went away. puter sounds are not good. but my guess is a colasped or weak lifter. when you got on it oil pressure went up pumped up lifter and sound went away. starting cold again would make that clattering sound. sounds to high pitched for rod or main bearing...the old trucker

I'm not as familiar with the 4.6 mod motors as I am with the old school small blocks, do they have lifters much like the 302 OHV motors? Don't the cams ride right on top of the valves? Or is there a little lifter between cam and valve?
I guess the next question is, if possible how can I tell it's a collapsed lifter? and if so which one?

rojam18801 · Post by **rojam18801** » Wed Jan 21, 2009 11:32 am

sorry malcolm, never been into a 4.6. i am old school and big block to boot. it's just that sound to me is like the old big blocks made when a lifter colasped or even when a pushrod bent. clatter like hell..i've seen people pull the engine out and junk it or even give the car away. it was a $2 fix and 10 min to do it for the pushrod. i would love to have your cobra... hey maybe you would like to give it away because it's blown up...ha ha. wish i could get my oilpan off without pulling engine like yours. i like 88ranger306's saying if it has wheels or tit's...the old trucker

MalcolmV8 · Post by **MalcolmV8** » Wed Jan 21, 2009 9:00 pm

OK I pulled every single rod bearing cap tonight and checked both upper and lower. I pushed rod and piston assembly up to free it and checked wrist pin end for any play. Nothing. It's all good. It's not a rod bearing or wrist pin.

Bazowak · Post by **Bazowak** » Thu Jan 22, 2009 1:04 am

Malcom,

Your 4.6 does have lifters or rather lash adjusters and a set of roller rockers or rather cam followers. The lash adjusters are hydraulic and take up the any slack between the cam. I just did a quick look at AutoZone.com and found the replacement parts.
Lifter JB-2271 at 7.99 and the rocker MR-929 at 20.99.

The rockers themselves are "wedged" between the cams and valves. Nice thing is that the cams on the DOHC's is that the cams have journal caps, so once the timing chains are removed you could remove the cams. However, there is also another tool that will need to be added to your tool box. The cam alignment tool and some other tools such as good friends, cold beer, a grill, some burgers, and of course time. This could very well be your problem.

I normally check the site at work and we can't go to youtube so that I can listen to the sounds it is making but the lifter deal sounds like it could be the issue. Another place to check about the problem would be the corral.net. I really don't like dealing with some of the guys there as they can be snooty if that's a real word and some of them don't really like to pass on any real helpful information but it is another avenue that you could use.

I hope this helps some and I hope you get your car up and going again.

v8ranger · Post by **v8ranger** » Thu Jan 22, 2009 5:21 am

MalcolmV8 wrote:OK I pulled every single rod bearing cap tonight and checked both upper and lower. I pushed rod and piston assembly up to free it and checked wrist pin end for any play. Nothing. It's all good. It's not a rod bearing or wrist pin.

Thats a plus. I know someone else has said its possibly a colapsed lifter. I still think its in the flywheel area. Its hard to say tho with trying to listed to it over a computer. We cant centralize where the noise appers to be coming from. I guess anything is posible. Let me ask of this, If it is a lifter can checking the headers on each cylinder with a temp gun narrow down which one may not be working right? or a compretion check? I think you said pulling the valve covers is going to be a real pain in the ass. I would think tho if there is a bad lifter wouldnt it run ruff?? Just a thought.

87sc302 · Post by **87sc302** » Thu Jan 22, 2009 7:39 am

I had a lifter go bad in first 302 (pre 5.0) I built 30 years ago.The noise was very similar but with the cam and lifters in the block it sounded like a rod. I took engine completely apart before finding out.

Very little experience with 4.6 cammer motors.

Hope you find it soon I know this is driving you crazy.

MalcolmV8 · Post by **MalcolmV8** » Thu Jan 22, 2009 8:51 pm

No progress tonight. Not sure what to tear apart next. Someone posted on the cobra forums that they had a chip tear off the top of their piston from detonation and their motor made the same noise as mine. I'm not sure how to check for that without pulling the heads. Wish I had a scope like doctors use that I could put in the spark plug hole and look at the pistons.

Bazowak · Post by **Bazowak** » Fri Jan 23, 2009 12:17 am

Another option that may have been mentioned already is to use an automotive stethescope (SP) just like the ones used to listen for pulse/heart rate/or used on date night (only kidding). You could also use a piece of wood or even a long screw driver.

Along the lines of the bore-a-scope, do you know any aircraft workers? Or for that matter any jet engine mechanics? I work on aircraft and have access to one but that doesn't really do you any good at this point b/c I'm in Wichita.

Anyway the stethescope(SP) can be had at AZ for about 15 to 20 bucks. Great tools to have, I've used mine to pin point out of adjustment rockers in the past and also finding bad bearings in water pumps and alternators. You might give it a try because you don't have to tear anything apart to use one.

Hope this helps some.

Warpig Racing · Post by **Warpig Racing** » Sat Jan 31, 2009 10:05 pm

any new news? Did out what the deamon is?

MalcolmV8 · Post by **MalcolmV8** » Sat Jan 31, 2009 10:27 pm

Not yet. Can't find anyone with a borescope to look in spark plug holes for a damaged piston so I figured I'll checkout the fly wheel and clutch in the mean time, it's free except for the oil I'll need to put back in the tranny.
So I got the motor closed back up on the underside and wrestled that kmember on my own for a while and finally got it back up in place. Got stuck there due to lack of torque specs on the bolts. Hopefully through the week I can get back on it and pull the tranny and take a peak.

broncobowsher · Post by **broncobowsher** » Sun Feb 01, 2009 10:46 am

I got a scope, but can't say the when the next time I will be in KC. Don't want to wait that long.

MalcolmV8 · Post by **MalcolmV8** » Sun Feb 01, 2009 12:26 pm

broncobowsher wrote:I got a scope, but can't say the when the next time I will be in KC. Don't want to wait that long.

I appreciate the thought. As useful as they appear to be I may just buy one and considering how much they go for on ebay I'll have no problem reselling it if I decided to.

broncobowsher · Post by **broncobowsher** » Tue Feb 03, 2009 7:01 pm

I just saw a Dewalt one at Home Depot this past weekend. Home Depot will take just about anything (except paint) back.

V8-Ranger.com

How do you find a spun rod bearing?

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