Sudden Knock, then Gone

I

Ianrig

New member
I have a 72 Scout II, 345, 4x4 with 727 tranny. I have been reviving it after a 14 year sit in a barn. Replaced all hoses, fuel line, fuel tank, new plugs, wires, dizzy cap, added pertonix, rewired bumper to bumper. Had the carb rebuilt by carbs unlimited. New exhaust and had carbs unlimited rejet carb, set timing and recurve dizzy. Rolled it out for the first time and it ran great. Quite, smooth and I saw an improvement from 6.7 mpg to 9.33 mpg. Ran about 80 miles over a mountain pass, rolled around offroad and again, ran great. Coming back over the pass about 60 mph, 3000 rpm into a head wind and maybe 3% grade, the engine started knocking horribly loud, pulled over to check. The knock was driver side, I checked oil levels, perfect, pull oil filler cap, oil visible. Set a bit, then started to nurse it home, maybe 50 mph and 2500 rpm. Knock disappeared. Drove another 70 miles, never to be heard again.

Any thoughts of the cause, is there a hidden issue waiting to blow? Would a strong headwind and grade cause a drop in oil movement? 10w30 full synthetic oil being used with wix filter.

Just picked up oil pressure gauge but haven't installed so I don't know my oil pressure.

Any help would be great.
 
It has been running and driving for the last year, it just hasn't seem to run perfect and the mileage was horrible (6 mpg). A few electrical gremlins sparked me to do a full rewire and I figured since I was rewiring, I should upgrade the coil, spark plug etc. Since I was going to have to re set the timing after changing that I figured I would install new exhaust and get rid of the old constricted and loud system that way I would only have to rejet and set the timing once.

Is the warning sign of impending doom or just a slow down and take care of me.
 
Your mileage is horrible, even your improved figure is nothing to write home about. I can get 12-13 from my 392 powered Scout with a 4bbl Holley carb. That sumbitch is fuel crazy, so your 9 point whatever from a 345 is atrocious. I'm always curious about the accuracy of the instruments and scientific controls involved whenever folks discuss their mpg findings, whether they're claiming 25 or 5 mpg from a v8 powered Scout. Reports of low to mid teens I tend not to bat an eyelash over, 'cuz that's where they generally tend to be in most real world scenarios. So, what did you set your timing to? What's the average elevation where you do most of your driving? Without knowing your location and climate, I'm going to step out on a limb anyway and say that 10w30 is too thin for these engines, unless you're running at or near freezing temps year round where you live. If you're experiencing 80's and 90's as most of us are at this time of year, you should be running 20w50. The wix filter is a solid choice. Pulling a three percent grade at 3 grand is nothing for these engines. They were born to do stuff like that all day long every damn day. What they weren't built for was to turn high revs even for a split second. Finally, did the noise sound anything at all like pinging or dieseling?
 
Thanks scoutboy,

I agree on the mileage, my goal was 11-12mpg but when the last year I have only seen 6-7 mpg, seeing 9.33 just as well could have been 20 I was so happy. I expect more driving and some time to average out my true mileage should see better numbers. My figures could be off a small percent based on how full I fill the tank but I try to bring the gas up to a viewable level. I have tracked every fill up and recorded mileage and gallons added since I bought the rig 1 1/2 years ago. Most of my driving since I got it was around streets, not much highway driving but some. This trip was freeway from seattle (sea level) over snoqualmie pass (4600ft) down to cle elum. I drove up dirt roads to about 4500ft. Temps were in the mid 70's to low 80's. I wondered about the oil viscosity because it was mid afternoon driving into a stiff headwind, uphill. Once we got to the pass, the knock was gone.

It was a knock. It sounded like a gremlin was inside the driver valve cover with a hammer trying to get out. It was coming from the area of the rear 2 cylinders on the drivers side.

I'll change the oil today, should I add an extra quart as well? Any checks I should do while I'm in there such as remove valve cover and check lifters etc. The oil that is in there has maybe 120 miles on it.

What about lead additive at fill ups. I've read do's, no need's, just use higher octane fuel. Any suggestions for a new, always wanted one and now will likely always be, a Scout owner.

What worried me was it has never knocked. It did have a ping and if you started it in the garage with the door open, within seconds your eyes were burning from gas fumes. The carb rebuild and rejet fixed both issues.

Thanks again!
 
Do a search on our forum for hi rpm oil starvation. IH had a tsb in the early 70's about this condition happening in Scout's due to the design of the pump and pan. Basically at consistent rpm's above 3000 the engine will starve itself of oil as all the gets pumped up and is too slow to return to the pan with almost a quart getting trapped in the front sump. IH's temporary fix was to add an extra quart of oil. After that IH redesigned the oil pump so that any bypassed oil would get redirected into the oil pump instead of the pan. Your Scout being a 1972 more than likely has the older style oil pump. For now I would do nothing more except add an extra quart of oil and retest.
 
My first thought was just that. I drove maybe 20 miles at 60-65 (3000-3200 rpm). It sounded just like a startup after setting for 6 months. I thought maybe the oil was low but nope.


I'll change up to 20w50 and add an extra quart, then monitor closely.
 
No need for lead additives. Some other engine makes of similar vintage May need it, but it does not apply to the IH sv8 engine family. Octane above 87 in these engines is really of no benefit and May possibly make the engine run worse. In proper tune they do great on regular. Save the $$$ for other things, like marine stabyl for preserving and combating the effects of the corn-sqweezin fuel we have to burn. You May consider installing a wet op gauge so that you can see some meaningful numbers at various operating conditions. A horizontal bar between the h and l isn't much to go on.
 
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