7.3 Banging noise

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May 19, 2006 | 10:53 PM

427-Shelby

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7.3 Banging noise

Well I got my engine running thanks to this board but now have another problem. Engine runs and idles great, good oil pressure etc. Rockers and valves all seem to be working correctly but as it sits and idles it is making a very loud, kind of popping/banging noise. When you put a rag over the intake hole it sits there and pops up in the air, kind of reminds me of a gas engine backfiring through the carb, Can anyone shed some light on this problem? What comes to mind would be a valve seat problem.

Dave

May 19, 2006 | 11:06 PM

PLC7.3

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Normally a wooofing noise at the intake indicates a bad intake valve and compression is firing back into the intake. I would do a compression test.........

May 20, 2006 | 02:51 AM

olgold

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oldgold89

Similar sounding to my '89 with 144,000 a year ago. Turned out a retainer had broken on a lifter and the lifter fell down and chewed up the cam. Spent 1300.00 to replace all lifters and a new cam....

May 20, 2006 | 07:25 AM

427-Shelby

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It is more a banging metallic noise than woofing /sucking noise. Do you check compression on one of these in the same manner as a gas engine? Thanks for your help.

Dave

May 20, 2006 | 07:26 AM

427-Shelby

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And what should the compression be on one of these engines?

Dave

May 20, 2006 | 07:54 AM

PLC7.3

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Lowest is 195 (bad) up to 440 in Ford book. It is not uncommon to see up to 500psi on a rebuilt engine. The difference between cylinders, the lowest must be within 75% of the highest.