Built 351 windsor has sudden knock?

gearhead351 · #1 (**permalink**) 10-15-2007, 09:38 PM

This is my first time posting in this forum so I hope somebody can tell me somthing here! Check my gallery I have some pictures of my motor in there.

I have a 1984 Ford F250 4x4 with a built 351 windsor in it. The engine has 500miles on it since the rebuild. This knock started yesterday. At first I thought it was rod knock but, It doesnt make ANY knock when its cold to 130degrees water temp. As soon as its ran for about 5 minutes a knock appears. The engine has been kept under 3000rpm for its entire life so far. I had everything machined and turned. I put in ALL brand new bearings in the engine and torqued everything to spec.

It rises with engine speed and falls with it. But at Idle none that I can hear. Im running 8degrees at idle so its not to high of ignition. Im running 10-30 GTX in it but my oil pressure has varied. Im using a HV oil pump and When I changed the oil 2 weeks ago I was pulling about 30lbs at idle (700 rpm). Now Im about 19lbs.

That isnt a substantial loss for me to suspect it being a rod. What could this knock be!?!?! I can only hear it when My head is directly in front of the water pump in front of the grill. The only other spot I can hear it is slightly below the balancer. When I stick my head to the pan I can hear anything except when next to or in front of the balancer. I cant tell where its coming from. It seems to be louder over the top of the dist.

The only thing I can suspect it being is when I swapped the ignition and put a duraspark dist in. I didnt have my truck this weekend so I cant exactly tell when it started. I ran the old TFI ignition with the truck so I had a worn dist gear and the cam was new. When I put the new dist in it had a brand new gear on it. Could this at all cause a knock? Please help!!!! The Truck runs AWESOME! But knocks are bad.....

I tried unplugging one cylinder at a time at the plug wire to see if it would stop the if any rod knock and it didnt change. Im going to change the oil again and never use GTX again. After an oil change I run 30lbs of pressure and then after a few days it goes down. So im not using castrol GTX anymore. My engine kills it, not burning or dripping it. It just kills the oil. HELP!

dragogt · #2 (**permalink**) 10-16-2007, 09:01 AM

what about that timing chain? if it got stretched, it could have jumped a tooth or be slapping the side of the cover.

gearhead351 · #3 (**permalink**) 10-16-2007, 02:23 PM

Quote:

Originally Posted by dragogt

what about that timing chain? if it got stretched, it could have jumped a tooth or be slapping the side of the cover.

Not to sure on that one. I put a new one on it when I rebuilt the eninge 500miles ago. Ive jumped a chain before, but that could be likely.

wayneF250 · #4 (**permalink**) 10-16-2007, 03:08 PM

Do u have a roller cam????????

wayneF250 · #5 (**permalink**) 10-16-2007, 03:14 PM

If u do , that gear on ur Dist. is probably the wrong one for that cam, U have to have a "harden steel" gear not a "cast iron" gear.

gearhead351 · #6 (**permalink**) 10-16-2007, 05:12 PM

Its a hyrdalic cam. The dist is for an 81 F250 cause I needed the duraspark ignition. It is for a 351 windsor. Did they use a different type of cam then? Also I tried using a screw driver and I think I chased down the knock. On the block and oil pan very faint knock. When I stuck the screw driver on top of the water pump (had belt off) That knock was LOUD! so it must be that new dist. But where? Why does it knock when its hot? Could the gear be expanding and hitting somthing? Also could my fuel pump do this?

96sherm · #7 (**permalink**) 10-19-2007, 11:57 PM

a shot in the dark, but how about your rad fan... if the sound only appears when the truck is warm...the fan cuts in...bearings?? warped fan?? just a thought...

gearhead351 · #8 (**permalink**) 10-20-2007, 12:03 AM

sorry forgot to tell you guys. I found my knock. The fuel pump arm wasnt staying full contact with the ectentric. It got hung up when the arm was on the way down. It would stay up and the ectentric would whack it back up. So relativley easy to fix. But im gunna run the pump till it dies. Also.

I had a little bit of a low oil pressure with 10-30 castrol GTX. I was only running 19lbs engine hot. I switched to valvoline racing 20-50w cause the GTX was literaly turning into foam in my engine for some reason. Im running 25lbs now and thats pretty darn good. How ever...... With the GTX my oil pressure at 3000rpm was about ooooo 50lbs. Now I dont go above 45lbs.

Could my oil bypass valve in the pump be opening from the thicker grade oil? I have a HV pump in it. I know a good rule of thumb is 10lbs for every 1000rpm. Im good. But it seems a little low. I have the EL CHEAPO plastic tube gauge.

96sherm · #9 (**permalink**) 10-20-2007, 12:19 AM

good to hear ya got her fixed!!!

BEWOLD · #10 (**permalink**) 10-20-2007, 12:57 AM

Quote:

Originally Posted by gearhead351

I had a little bit of a low oil pressure with 10-30 castrol GTX. I was only running 19lbs engine hot. I switched to valvoline racing 20-50w cause the GTX was literaly turning into foam in my engine for some reason. Im running 25lbs now and thats pretty darn good. How ever...... With the GTX my oil pressure at 3000rpm was about ooooo 50lbs. Now I dont go above 45lbs.

Could my oil bypass valve in the pump be opening from the thicker grade oil? I have a HV pump in it. I know a good rule of thumb is 10lbs for every 1000rpm. Im good. But it seems a little low. I have the EL CHEAPO plastic tube gauge.

Kinda sounds like you have a aeration or windage problem

1pump · #11 (**permalink**) 10-21-2007, 11:50 AM

Quote:

Kinda sounds like you have a aeration or windage problem

I agree. Possible overfill or the wrong oil pan, or maybe a suction leak.