Engine noise like a .22 rifle going off

[mogulmasher]

My truck is making a noise I haven't experienced before. It's a '77 K20 with a 355 built (poorly) by the previous owner. I know nothing of the internals, but have a eddy 600 electric choke, aftermarket HEI, performer eps intake, headers, aluminum water pump, electric fan. Last few days its running poor, like its down a cylinder or two. I've been fighting the #8 intake lifter for weeks....just won't pump up. Ever since running poor its been occassionaly with no pattern to the noise or when it occurs making this horrible knocking sound. Actually more of a crack then knock, like the crack of a .22 being fired. Its very tin-like sounding, not a heavy sound like internal engine noises typically are. I have had a slight ping under load, every since winter began I know I have been running truck pretty lean, just haven't had time to adjust carb.

Also few days prior to this happening truck was popping through carb (kinda sounds like truck sneezing.....when you push it too hard before being fully warmed up, I know likely from lean condition) during warm up.

 

[Chaddy]

Plugs/wires, cap and rotor? Timing? Bad gas?

 

[Mudstud]

That kinda sounds like a broken rocker arm. You adjust your valves right? If it'll run hold a stethescope or screwdriver to your ear on each valvecover. That aughta tell you which side to pull. Lettus know.

 

[mogulmasher]

Hmmm, that's sounds like a good possibility for sure. Yes I readjusted valves after I did new valve seals last summer. The rockers are crane roller tips....their stronger then stock, what causes them to break if it did?

Would explain why I feel a cylinder or two down.

 

[Mudstud]

I'm not much on an engine guy but I'd suspect age, miss adjustment, too tall of a push rod or not enough pivot of the rocker, big horsepower in cheaper parts. All these are guesses, will have to wait for an engine guru to tell you somethin definite. Good luck.

 

[Duntz00]

also sounds like a lobe is wiped off on the cam

 

[mogulmasher]

also sounds like a lobe is wiped off on the cam

You think maybe that one lifter that won't pump up is the one with the worn lobe? This motor wasn't built too long ago, probably doesn't even have 10k on it, but other evidence from this guys restoration has lead me to believe he was a moron and didn't know what he was doing. Probably never adjusted right from the get go and never broke in correctly. Thankfully it looks like a body shop did the body/paint and frame looks like it was southern or western truck...this is reason I bought it.

I have a '91 6.2 to go in truck, but have to limp it along until the 2' of snow on the ground is gone so I can be driving my Nova during the swap over.

 

[4X4HIGH]

Flat lobe on the cam is my best guess as well. Leaving a valve ticking without adjusting it quickly will ensure that this will happen. Pull the valve cover and have someone crank the engine over while you watch all the rockers to see if any don't move very far. If you find one that doesn't move as far as the rest then that lobe on the cam is flat. At that point you need to replace the cam and lifters to correct that problem. Also there are (were) certain chemicals in engine oil that helped prevent cam/lifter wear on new cams and most oil manufacturers have remove a good portion of it from engine oil which on a flat tappet cam can be very dangerous for a new cam break-in. You should look at some of the diesel oils for cam break-in if you find that you indeed need to swap the cam. Valvoline VR1 racing oil still has the chemicals that are needed.

Running an engine lean will also burn holes in pistons real quick.

Stop being so lazy and fix your problem(s) before they cost you a ton of money.

 

[mogulmasher]

Flat lobe on the cam is my best guess as well. Leaving a valve ticking without adjusting it quickly will ensure that this will happen. Pull the valve cover and have someone crank the engine over while you watch all the rockers to see if any don't move very far. If you find one that doesn't move as far as the rest then that lobe on the cam is flat. At that point you need to replace the cam and lifters to correct that problem. Also there are (were) certain chemicals in engine oil that helped prevent cam/lifter wear on new cams and most oil manufacturers have remove a good portion of it from engine oil which on a flat tappet cam can be very dangerous for a new cam break-in. You should look at some of the diesel oils for cam break-in if you find that you indeed need to swap the cam. Valvoline VR1 racing oil still has the chemicals that are needed.

Running an engine lean will also burn holes in pistons real quick.

Stop being so lazy and fix your problem(s) before they cost you a ton of money.

I know...I know...just been so cold and snowy and seems as though I've had other people's sleds in the shop every weekend since before xmas (part time sled mechanic). Anyone know how it feels to work on other people's stuff so much you don't feel like touching your own??? Oh well this one will probably cost me for my laziness.......oh well off to change the cats on the wife's Yukon....my truck waits another day.

 

[4by4bygod]

Also there are (were) certain chemicals in engine oil that helped prevent cam/lifter wear on new cams and most oil manufacturers have remove a good portion of it from engine oil which on a flat tappet cam can be very dangerous for a new cam break-in. You should look at some of the diesel oils for cam break-in if you find that you indeed need to swap the cam. Valvoline VR1 racing oil still has the chemicals that are needed.

Be very careful here - the ( new since january 07 ) CJ 4 diesel oils have the same decreased amount of anti wear additives ( zinc, sulfur, phosphorus ) as the passenger car oils. If you buy a diesel oil, make sure the bottle says "meets CI - 4 specifications" - those have the additives in there, but they're getting harder to find.

The VR1 should work, I don't know what's in it, so make sure it says "contains zinc and phosphorus"...your real racing oils will have that in there..most of your over the counter " high perf" oils have switched to moly as an anti wear additive.. it's not really an effective substitute, but it's cheap and the EPA doesn't want it gone yet.. once you rebuild it, it's worth the hassle to find a real racing oil to use for break in..

 

[blazin_blazer]

hmmmm...i've always used rotella for break in/run in, then swap to castrol...i did it cause rotella is cheap...didn't know it was actually better to break in with....good tip...thanks

 

[dcubb]

Comp Cams actually recommends Rotella for breaking in a flat tappet cam.
This is from their site.


Adequate Lubrication
Another major factor in the increase of flat tappet camshaft failure is your favorite brand of engine oil. Simply put,
today’s engine oil is just not the same as it used to be, thanks to ever tightening environmental regulations. The
EPA has done a great job in reducing emissions and the effects of some of the ingredients found in traditional oils;
however these changes to the oil have only made life tougher on your camshaft. The lubricity of the oil and specifically
the reduction of important additives such as zinc and manganese, which help break-in and overall camshaft
life, have been drastically reduced. In terms of oil selection, we recommend Shell Rotella T oil for the break-in
procedure. Most often used in diesel engine applications, this higher lubricity oil works in gasoline engines
as well.
11-28-05
Research & Development Dept.

 

[4by4bygod]

Comp Cams actually recommends Rotella for breaking in a flat tappet cam.
This is from their site.


Adequate Lubrication
Another major factor in the increase of flat tappet camshaft failure is your favorite brand of engine oil. Simply put,
today’s engine oil is just not the same as it used to be, thanks to ever tightening environmental regulations. The
EPA has done a great job in reducing emissions and the effects of some of the ingredients found in traditional oils;
however these changes to the oil have only made life tougher on your camshaft. The lubricity of the oil and specifically
the reduction of important additives such as zinc and manganese, which help break-in and overall camshaft
life, have been drastically reduced. In terms of oil selection, we recommend Shell Rotella T oil for the break-in
procedure. Most often used in diesel engine applications, this higher lubricity oil works in gasoline engines
as well.
11-28-05
Research & Development Dept.

Not trying to be a smartass, but look at the date - 11/28/05 - they're referring to CI - 4 diesel oils, which still had the higher levels of zinc, phosphorus, etc.

Back when they wrote this, passenger car oils were just starting to change for the worse, which is why they were recommending the diesel oils, oblivious to the fact that diesel oils were reducing their anti wear additives too - the diesel oils having a more hard and fast deadline, with the advent of the tier III engines in 07. ( the zinc, phosphorus, etc, will poison the exhaust treatment devices )

the hot rod magazines still advocate diesel oil - but they should still make the distinction between CI & CJ oils, and tell you what to look for, which is my only point.

 

[dcubb]

Yes I realize that the bulletin was issued in '05. The point is, even with the newer CJ-4 Rotella, zinc and phosphorus levels are still more than double than in most automotive oils on the market currently. And it's still good enough that Comp Cams and many engine builders still recommend it as a break in oil in flat tappet engines.

 

[4by4bygod]

Yes I realize that the bulletin was issued in '05. The point is, even with the newer CJ-4 Rotella, zinc and phosphorus levels are still more than double than in most automotive oils on the market currently. And it's still good enough that Comp Cams and many engine builders still recommend it as a break in oil in flat tappet engines.

My only point is that I want guys to read labels and know what they're buying, so the project is successful.

I've seen rotella bottles with an SM designation - that would be for passenger cars..SM oils are limited to 800 - 870 PPM of the zinc, phosphorus, etc.. not good for break in, obviously, so that's one to avoid.

now, for an oil to have "more than double the amount", you're talking over 1600 ppm of zinc or whatever.. and 1600 PPM of anything isn't a CJ - 4 oil - it's a CI -4, which is what one would look for if you wanted a diesel oil for break in. CJ - 4's are limited to 1200 - 1400 ppm zinc & phosphorus..

is that enough for break in? I don't know. doesn't make me comfy enough to issue a blanket guarantee. If I'm building something I care about, I'm looking at a racing oil myself, just to be sure I know what I'm getting.

Remember, CJ - 4 limits on metallic additives are upper limits, not minimum standards..formulas are subject to change at any time and without notice, and if the EPA can make GM pull their EOS (a zinc - laden engine oil supplement ) off the shelf, (for too much zinc ) they can put a gun to shells head anytime they want.

 

[dcubb]

What's a good alternative to the no longer available gm EOS?

 

[4by4bygod]

What's a good alternative to the no longer available gm EOS?

Just to be clear, I should have finished my thought and said that the EPA made GM pull EOS off the market due to high zinc levels, but it supposedly did come back under a different part number, and with much lower zinc levels, in line with ILSAC GF - 4 ( same as SM ) specs. I have not seen any bottles for sale at a dealership myself. I brought it up to point out that what the EPA wants, the EPA gets.

As to your question, if I were installing a new cam and wanted something for break in, I'd use whatever goop that came with the cam, and would dig through the bottles at my local parts store or wally world and find any " CI " diesel oil..if I couldn't find that, I would go with a racing oil from somewhere like agip or joe gibbs, making sure that what I was buying was a high zinc oil..

 

[mogulmasher]

Just an update. This morning I pulled the valve covers and no broken rockers, push rods, etc. Spun motor over by hand and everything looked to be moving up and down as it should....although #8 intake rocker still loose.

While I was under there I returned my eddy 600 to stock calibration, so should be running a little richer now. Found one problem while switching out metering rods. Driver's side rod retaining spring had popped off and was all bent up. I'm sure this was keeping the rod from functioning as it should. Not convinced it was the problem, but certainly was a problem needing fixing.

Only other thing I noticed was couple of plug wires look like they are catching hell from the headers, so I will do a plug wire swap in a day or two and see what happens. They didn't seem to be arcing though.

Truck was very low on fuel, topped it off with fresh and drove into work. Truck still made the funny noise a couple times, not quite as loud as before, more of a light pop or crack now. Wonder if I'm getting or have water in my fuel or bad fuel as this is very similar to popping I often experience working on 2-stroke sled motors when gas has water or contamination in it.

Long story short...truck is running a little better, but still very rough (especially in top gear at about 55 mph....not power and rough). Maybe junk fuel, maybe something in the ignition system, or bad fuel pump maybe????