77' 351M Engine noise
Thread Starter
|
New User
Joined: Jun 2007
Posts: 10
Likes: 0
From: Virginia
77' 351M Engine noise
I have a 77' F-100 351M with a C-6. I just bought this truck because it supposedly had the engine and tranny rebuilt together 46,000 miles ago. Engine supposedly has R/V cam, I know it has a brand new Holley 600 cfm carb and Weiand dual plane intake. Tranny has B&M slap shifter and shift kit. Seems like low mileage. Sometimes when first started it makes a chattering sound for a minute or less. Also makes this chattering noise when in third gear and accelerating, sounds like a deisel. It seemed at first that the oil pressure was low when started (10-15psi at idle), (20-30psi drive). I thought main bearings. I changed the oil, now the pressure runs about 40psi driving and 20psi at idle. I haven't heard any more noise at idle, just when accelerating at low speed in third gear. If I get on it or manually shift to second gear rpm's rise and noise goes away. Could this be Top end noise, or timing?
Junior User
Joined: Jun 2006
Posts: 68
Likes: 0
Sounds like it is pinging to me. Retard your timing a little and see if it goes away. Stock distributors are not set up for the new intake and carb changes which eliminated the smog equipment so the timing curve is off. You need to have your timing curve match your engine to get the most out of it. Usually you can get by with retarding the timing but you lose some performance when you do that.
Posting Legend
Joined: Sep 2001
Posts: 30,255
Likes: 37
Adjust the vacuum advance unit to reduce pinging at part throttle cruise.
Adjust base timing to reduce pinging under acceleration.
There is always the possibility the engine was improperly rebuilt with excessive compression.
Make sure your vacuum advance is hooked up properly to the proper ports thru the temperature vacuum switch.
Adjust base timing to reduce pinging under acceleration.
There is always the possibility the engine was improperly rebuilt with excessive compression.
Make sure your vacuum advance is hooked up properly to the proper ports thru the temperature vacuum switch.
Thread Starter
|
New User
Joined: Jun 2007
Posts: 10
Likes: 0
From: Virginia
I finally got around to playing with the timing. I have no degree indicator on the balancer. I just have a line someone marked with a white pen or something. Facing the front of the engine it spins clockwise. I adjusted the timing so that the line is just after the pointer. The idle went down to between 700 and 800 rpm originally it was around 900-950rpm. I beleive this is After TDC. Other than the idle being slower I am not sure there is any difference. It may have been slighly slower to accelerate than before. I didn't notice any chattering. However even before I messed with the timing, at times the truck made no noise until I had been on the road for a while. So I am not certain that the noise is gone completely. Should I have went the other way? Before TDC? I have been told that the chattering is nothing to worry about. But I am a perfectionist and I want my truck to run great, not just O.K. What can I do if the noise comes back? Where should the timing be for the best performance and economy without noise? Thanks for your help thus far.
