My buddy called me over the other day to listen to his Dodge truck's 230 flathead. He said that it was newly rebuilt (which really doesn't tell me much..... ). It purrs like a kitten at idle, but when he revs it up just above idle (say around 1200=1400 rpm,hard to tell without a tach), there is a tap tap.....tap.....tap tap..tap tap knocking noise coming from the lower front end, around the front timing chain cover/lower pulley area. It is definitely not coming from the pan, but the lower front of the engine. It goes away at idle and returns at the above idle speed. He said it is definitely louder when cold, but is alway there, even when warmed up. Any ideas on what this could be? I told him I would research the issue and get back to him (this post is my research )
Could this be a worn timing chain thing? Any suggestions would be most helpful. He is little discouraged that he has issues with his "new engine."
Any dents in the front cover? I have seen a few instances where the cover got bumped and dented during engine installation resulting in the timing chain rubbing it.
One other issue with some engines, #1 rod cap will actually hit the oil pan slightly when revved up. I've seen a bunch of pans that this had happened; you can always tell from the slight buldge in the bottom of the pan directly under the #1 rod. The first few times the engine revs, the rod cap will bump the pan of some engines creating the buldge. Once the buldge is firmly in place, it's all over and doesn't give further trouble. Never saw this cause any major issue. It really happens frequently when installing a new oil pan. If you are hearing a tapping when it revs up and not at idle RPM; this is exactly what will happen as the rod cap bumps the pan; doesn't do it at idle. Revving it up higher a couple of times will cure that, but I'm reluctant to give that advice unless I could actually hear it myself to know that is the issue. I don't want to offer advice that may cause further problems. If you can lay your hand on the pan directly below the #1 rod, speed up the engine just enough for the tapping to start, you will feel it hitting if that is what is going on. A couple of good revs, the problem will be solved without further issue has been my experience every time. BUT, proceed at your own risk; I'm not there to diagnose, just sharing past experiences.
There is also a passage through the front support plate that goes from the valve cover opening into the timing chain cover. Seems that I recall seeing a couple of instances where small bolts, nuts, washers, etc got dropped through the opening and were getting tossed around by the chain.
I would get to the bottom of this issue if it took pulling the front cover back off. Most likely you will readily see what is causing it once the cover is pulled. 1 other thought just came to mind; if the old style front cover oil seal was used, the one that requires the oil slinger, the slinger could have been installed on the crank backwards which will allow it to rub the crankshaft timing sprocket and chain. If the late style oil seal was used, that requires that the slinger not be used and it must be left out of the assembly. If the slinger was installed with the new type seal, it will rub the seal case.
Thanks for the advice and benefit of your experience. There is no better instructor than experience. I looked all around for anything that may be hitting the pulley and belts...no luck. I'll go back over there and get him to rev it up a bit while I feel the oil pan. I hope that's it, but not too optimistic as he has had it running for a couple of trips around his neighborhood and it still knocks as described. So my advice for him will be "pull the cover off and take a look, and please don't ignore it" as he has suggested.
Is that issue with the oil pan interference a design defect? I can't imagine that Dodge would have continued to produce oil pans without making a slight modification, unless the retooling costs exceeded the benefits.
Cost, benefit weighed out. Likely not worth it for Chrysler. Like I stated, a few good taps with the engine revved up will reshape the pan and it never gives any more problem.
I would guess if we did a poll on forum member's engine oil pans; the vast majority would have the slight buldge directly beneath #1 rod. While we do see engines with straight pans under #1, by far most we have seen here do have that buldge indicating the rod cap has bumped it. Never saw a pan with any significant intertior surface damage as a result of this, so it is minor in nature, but will scare the heck out of you if you aren't aware that this issue exist with some engines, especially when first starting up a newly rebuilt engine.
I'm not far away from where you live, I'd be happy and interested to take a look and listen if your buddy would like me to do so. I would do the feel check on the pan first though like I explained in the above post, easy to diagnose if rod bumping is in play.
Rick Hoffman from Tucson, also a forum member here can atest too and maybe upload a picture of a buldged pan. I sold him his current engine that we installed a new pan on back in '94. I don't know why that particular one sticks in my mind, but it tapped like crazy the first time it fired up and went above an idle. #1 rod reshaped the pan slightly, issue over.
Take a long rod or screwdriver and put it against your ear. Idle up the engine and probe around to different points while listening. It magnifies the noise and pin points where it is. My 327 chevy engine had this same type noise. When I touched the fuel pump boss, it about broke my eardrum . After re adjusting lifters etc. it ended up a weak fuel pump spring letting the rod clank. 16.00 later, fixed. Don't let your hair get caught in the fan belt if you are a Hippie! , I'm bald and safe! John
Water pump? On my M151, which I know is a different motor than the M37, but when ever the water pump would start to go bad it made a knock sound that could fool some into thinking it was a rod knock. So I'm just throwing that possiblity out there since you say it seems to be coming from the front end.
We took the fan belt off to isolate the generator and water pump. Still made that darn noise. Got under the truck and felt the oil pan where the bump was formed by the number 1 con rod... no vibrations other than the usual engine vibration. I used a tube like a stethascope and listened around, paid particular attention to the file pump...hoping that was it. Nothing there. The sound still is coming from the lower pulley area. So I guess the next step is to take the timing chain cover off to get to the suspected source. We're going to attempt this without taking the engine out.....
jordankjcm wrote:We took the fan belt off to isolate the generator and water pump. Still made that darn noise. Got under the truck and felt the oil pan where the bump was formed by the number 1 con rod... no vibrations other than the usual engine vibration. I used a tube like a stethascope and listened around, paid particular attention to the file pump...hoping that was it. Nothing there. The sound still is coming from the lower pulley area. So I guess the next step is to take the timing chain cover off to get to the suspected source. We're going to attempt this without taking the engine out.....
Possibly the chain oiler tube could have been left out, or maybe installed slightly out of position so the oil isn't directed correctly.
Another tech tip, on Willys Jeep flatheads, if the camshaft has too much end float, it will tap tap like a lifter with too much clearance. Since you will expose the end of the cam, check that. You seem convinced it's coming from the timing chest, hopefully it will show itself to you. Keep us informed on what you find! Thanks, John
Solved....we hope!!! When we took the front cover off, we discovered that cup shaped oil slinger was installed along with a seal that protruded from the case (National Seal # 6186-S). This protrusion allowed for the slinger to rub along one section of the seal. We removed the slinger (which had obvious signs of fresh wear on it) and installed National Seal 6636-S. Hopefully this will do the trick. We'll know tomorrow when we put it all back together and fire it up. Even with minor rubbing as such, I recommended that he change the oil. Cheap insurance!
Pay close attention to the cover to be sure it didn't get bent or warped in the seal area, as it doesn't take much. If it's warped, the seal won't be square with the crank hub and can cause a leak.
I imagine you found the noise issue, I've seen it before. Not enough clearance in there for the slinger if the late style seal is used.
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). It purrs like a kitten at idle, but when he revs it up just above idle (say around 1200=1400 rpm,hard to tell without a tach), there is a tap tap.....tap.....tap tap..tap tap knocking noise coming from the lower front end, around the front timing chain cover/lower pulley area. It is definitely not coming from the pan, but the lower front of the engine. It goes away at idle and returns at the above idle speed. He said it is definitely louder when cold, but is alway there, even when warmed up. Any ideas on what this could be? I told him I would research the issue and get back to him (this post is my research 
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, I'm bald and safe! John