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Posted By Discussion Topic: horrible engine noise -- page: 1 2     trimboulster 06-13-2013 @ 2:34 PM reply profile send p.m. Member Posts: 12 Joined: May 2013 Bob, If you are running a pre '49 flat head V8 engine, you probably have a rod knock. These engines had "floating" rod bearings, one set per throw and two rods per throw. The reason the noise is only heard in low gear on fast take off is because it is under a load at the fastest rpm. If you have a tach, you can check this out. Watch the tach as you go up through the gears. A good way to check for a rod knock is start the engine, put it in gear, hold your foot on the brake and slowly let out on the clutch part way at the same time, and you will hear the knock. Usually flat head engine knocks are caused by low oil pressure or a low oil level. You can get a correct oil pressure reading by removing an oil passage plug and connecting an accurate 60 psi gage. Most of these engines run about 30 psi oil pressure and below. I had a 40 Ford once that only had about 5 psi pressure when cold and about 15 psi when hot. The rod bearings would only raddle when the oil was low though. I think you have an oil pressure problem and you shouldn't have to do anything to the engine if you get the pressure problem corrected soon. At this point, you can't trust the dash oil gage. Lowell trimboulster 06-13-2013 @ 2:32 PM reply profile send p.m. Member Posts: 12 Joined: May 2013 Bob, If you are running a pre '49 flat head V8 engine, you probably have a rod knock. These engines had "floating" rod bearings, one set per throw and two rods per throw. The reason the noise is only heard in low gear on fast take off is because it is under a load at the fastest rpm. If you have a tach, you can check this out. Watch the tach as you go up through the gears. A good way to check for a rod knock is start the engine, put it in gear, hold your foot on the brake and slowly let out on the clutch part way at the same time, and you will hear the knock. Usually flat head engine knocks are caused by low oil pressure or a low oil level. You can get a correct oil pressure reading by removing an oil passage plug and connecting an accurate 60 psi gage. Most of these engines run about 30 psi oil pressure and below. I had a 40 Ford once that only had about 5 psi pressure when cold and about 15 psi when hot. The rod bearings would only raddle when the oil was low though. I think you have an oil pressure problem and you shouldn't have to do anything to the engine if you get the pressure problem corrected soon. At this point, you can't trust the dash oil gage. Lowell trimboulster 06-13-2013 @ 2:28 PM reply profile send p.m. Member Posts: 12 Joined: May 2013 Bob, If you are running a pre '49 flat head V8 engine, you probably have a rod knock. These engines had "floating" rod bearings, one set per throw and two rods per throw. The reason the noise is only heard in low gear on fast take off is because it is under a load at the fastest rpm. If you have a tach, you can check this out. Watch the tach as you go up through the gears. A good way to check for a rod knock is start the engine, put it in gear, hold your foot on the brake and slowly let out on the clutch at the same time, and you will hear the knock. Usually flat head engine knocks are caused by low oil pressure or a low oil level. You can get a correct oil pressure reading by removing an oil passage plug and connecting an accurate 60 psi gage. Most of these engines run about 30 psi oil pressure and below. I had a 40 Ford once that only had about 5 psi pressure when cold and about 15 psi when hot. The rod bearings would only raddle when the oil was low though. I think you have an oil pressure problem and you shouldn't have to do anything to the engine if you get the pressure problem corrected soon. At this point, you can't trust the dash oil gage. Lowell trimboulster 06-13-2013 @ 2:26 PM reply profile send p.m. Member Posts: 12 Joined: May 2013 Bob, If you are running a pre '49 flat head V8 engine, you probably have a rod knock. These engines had "floating" rod bearings, one set per throw and two rods per throw. The reason the noise is only heard in low gear on fast take off is because it is under a load at the fastest rpm. If you have a tach, you can check this out. Watch the tach as you go up through the gears. A good way to check for a rod knock is start the engine, put it in gear, hold your foot on the brake and slowly let out on the clutch at the same time, and you will hear the knock. Usually flat head engine knocks are caused by low oil pressure or a low oil level. You can get a correct oil pressure reading by removing an oil passage plug and connecting an accurate 60 psi gage. Most of these engines run about 30 psi oil pressure and below. I had a 40 Ford once that only had about 5 psi pressure when cold and about 15 psi when hot. The rod bearings would only raddle when the oil was low though. I think you have an oil pressure problem and you shouldn't have to do anything to the engine if you get the pressure problem corrected soon. At this point, you can't trust the dash oil gage. Lowell joe b 06-13-2013 @ 1:08 PM reply profile send p.m. Member Posts: 389 Joined: Oct 2010 I think Tom O and Stroker might be onto something. I had a similar noise after duals and Smithy's were installed. The pipe on the right side was hitting just behind the steering box. Remember the engine torques over a bit on hard acceleration. TomO 06-13-2013 @ 9:22 AM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 Before I would drop the pan, I would start looking for spots where two parts are making contact. If I could not find any, then I would start disconnecting easily removed objects, such as the electric fan and alternator. If you did not have the noise before the duals were added, look at the installation of the duals for possible interference points. Tom Stroker 06-12-2013 @ 8:55 AM reply profile send p.m. Senior Posts: 1460 Joined: Oct 2009 Fenbach: This may be a "stretch", but is it possible that one of your recently installed head-pipes (between the headers and mufflers) is tapping on the frame under hard acceleration? These usually pass through the oval holes in the frame, and if your motor mounts are soft, contact is possible. I'd look for any evidence of contact, such as a shiny spot on the pipe. fenbach 06-12-2013 @ 8:41 AM reply profile send p.m. Member Posts: 227 Joined: Dec 2009 thanks to both tomO and supereal for more suggestions. of course, i have to hope it's just the belt and not a rod bearing! i did snug the belt with no apparent difference, however. and the sound is really more metallic. even so, i'm puzzled that i basically only hear the sound when accelerating rapidly in low gear. i thought LB stood for "loose bearing" or "late block" [with insert bearings]. regardless, that is what i have. now i have to ask if the pan can be removed by just raising the engine. and if i could identify a bad rod [or main] bearing without removing the caps. thanks again. i'm glad you fellers don't have better things to do! TomO 06-12-2013 @ 6:41 AM reply profile send p.m. Senior Posts: 7250 Joined: Oct 2009 Could the horrible noise be your alternator belt slipping? Tom supereal 06-11-2013 @ 9:24 PM reply profile send p.m. Senior Posts: 6819 Joined: Oct 2009 That is the first time you mentioned oil,pressure loss. The noise is likely a spun rod bearing. It usually happens so quickly you don't have time to shut it down. If your LB is a poured block, it is probably toast.

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