My friend has an OT engine (it is. Hemi though) but the subject matter should pertain to HAMB friendly engines. So, if a cam was wearing a lobe down, would it be noticeable at idle through the RPM range? I’ve never had a cam go flat, only had engines bought that had a flat cam. I’d ***ume there would be a lifter tick,etc as it was getting worse. Next question, what happens with a collapsed hydraulic lifter? If the engine was rotated to where the valve (s) in question were fully open, will there be slop on the rocker arm? I’d think there would be, but never had a collapsed lifter before, so I don’t know. Would a collapsed lifter be noticed at idle through the RPM range? I’d think it would be. Thanks.
Yes, if the lifter actually collapsed, there's going to be quite a bit of slack between the rocker arm and the pushrod. I just reread your post, and with the valve in the fully open position, all slack may be taken up, depending on the actual lobe lift vs. the dimension of the lifter plunger travel.
A wiped exhaust lobe will cause a sharp backfire or rapping sound through the carb when revving the engine under no load. From the fuzzy part of my memory, I think a partially wiped lobe will still idle OK but show up as a miss under load.
Yeah all of those 305's we used to buy because we were broke *** hot rod guys, had wiped lobes, noted by the popping through the carb. I've never had a collapsed lifter though. The best part of the cam vs lifter battle has always been getting the lifters out lol...
Google the cam/lifter failures of the Ford Godzilla truck motor. Actual delamation of the contact surfaces. Lots of videos you can listen to running engines with bad lobes.
Helped grandson on his off topic 454 today. Pulled valve covers off and #8 intake rocker barely moving up & down. Popping through carb. We think his engines toast. We'll pull intake later to confirm.
When a cam goes flat, it's a sound you NEVER forget! Doesn't matter which lobe, it's unmistakeable...
Yup, popping back through the carb or fuel injected intake is most likely. Some Chevy engines of the '50s and '60s, for example, were pretty bad about cams going south. Got a free '51 Olds one time because no one could diagnose a flat cam. Don't be fooled, though. A burned valve can produce the same symptoms. A compression test should reveal which it is. Also check for a lot of slop in the timing chain.
I had a 440 that wiped a lobe. At first it would just carbon foul that cylinder's plug. It was strange and I didn't know what was happening so it cleared up for a while with a hotter plug in just that cylinder. After a couple of months it got worse and started that that sharp backfire mentioned by others. Then I checked the rockers and discovered the rocker on the lobe didn't move much.
The slack in the valve train might not show up on a collapsed lifter with the valve fully open. It would most certainly show with the same valve fully closed. There will be a lot of slack in the rocker arm to valve stem at the fully closed position.
"I knew a guy who used to put a quart of straight 90 weight in his Falcon 289 every so often" Yeah, when I came back to "the world" after military service, I discovered the original engine in my 57 Pontiac had rattles, tics and blow by. Thinking I was a know-it-all I let the oil level drop down [didn't take long] and topped it off with 90 weight gear oil. Some of the little tics lessened but the blow by was still there. That 90 weight gear oil stink found any little holes in my firewall and filled the inside of the car with hot gear oil smell! It was STRONG TOO! A few weeks later I replaced the engine and trans. I put new "blue trees" in the car every 2 days.
Confirmed. Cylinders #2#4#6#8...Grandson’s 454 results. I ran out of steam after removing this much. Here’s the carnage
Well, I don’t think it was oil, but ya never know. That engine will be coming out I hope and apart. There’s some chunks of the lifters missing as well.
I busted a lifter fighting it out with vice grips. It was a wrestling match getting these out. I had to explain to him this is the result of the “ Cheap oil he gets at Costco.” His words not mine. He also hates Quadra jets to his core. His favorite carb installed on this boat anchor had no Choke hooked up. Again I explained that GM designed the Q-Jet with a automatic choke with a fast idle feature for reasons he never thought of. Keep raw fuel from washing the rings away...speed up warming the engine...and here’s the big one...allow the engine to throw oil up to the camshaft to avoid this s**** metal he created. Allowing your engine to sit at a low idle after you fire it’s cold *** up is a death sentence!!!! Don’t get me started on the destruction caused by not using a thermostat.....
Maybe I am wrong(if so offer an explanation) I have thought,heard,read that a primary cause of a cam/lifter going bad is directly rated to its non abilty to spin in the hole causing rapid wear. I think a lot of it is spring pressure excess. Having dealt with flatheads(mostly modified, but a few stockers) have never seen a flat lobe on a cam. Since the flats have no pushrods or rockers, the spring pressure is minimal and a stocker valve can be pushed off its seat using hand pressure only—no mechanical device is required!! Yes, I am also certain that a proper oil should be used, however I run spring pressures near 85-90 lbs on my flats and use regular everyday motor oil with no destruction in 60 years of building and racing flatheads. My engines are run up to 5500 rpm quite often. Flatheads Forever!!!
I’m a firm believer in lighter spring pressure. When built my first LSR engine, flat tappet, I installed what the cam people advised which was 125-130. My engines were 5500 rpm and I never lost a cam or follower but it bothered me. I read in manuals that solid lifter Chevrolets recommended less than 70# stock and they reved to 7000 so when I had roller rockers made I lowered the pressure to under 100# and went to a single spring. I’ve used as low as 85 and and-set records with the engines. With the use of longer valves and LS beehive springs I don’t have a concern any more. With rollers, especially hydraulic, cam problems can be in the past but for us old traditional guys it’s tougher.
That damage is a lot more than cheap oil! The oil also had to be extremely diluted to allow that much wear! And likely not changed very often either! Betting the lifter bores are bad too, and might be best to toss the whole block. Wonder what the rod and main bearings look like?
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