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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
Ok turns out the '82 beater has a pretty loud engine knock only under certain conditions and hoping someone knows the noise before I dig in too deep. Feel free to toss out ideas or let me know why mine are all wrong!
Knock situation:
- Engine under load (brake stand OR hard acceleration)
- Only over ~2500rpm
- Warm or cold
No knock situation:
- Neutral or park with gradual throttle up to any rpm
- Gentle driving around
- Brake stand under 2500 rpm
The simple things I started with:
- Separated plug wires (especially 5 and 7)
- New cap and rotor
- Fresh fuel
- Oil change (no metal)
Current Ideas:
- Rod knock
- Head gasket
- Broken motor or trans mount
See video below of brake stand from 1000rpm up to ~3000rpm:
Hi Vincevs. Sounds like a rod knocking. Missing and knocking. Determine which cylinder is missing, pull the valve cover and see if it has a bent pushrod or jumped out from under the rocker. If you don't find a bent pushrod, then you probaby have a rod knocking (spun or stacked bearing). Don't spend any money on that engine until you determine what the knocking and missing is.
It's my understanding that rod knock is all the time and not just under load at mid rpm... is that wrong? Maybe this is the start of it?
Also, this car is only for a 1000 mile car rally so no worries about spending money on the motor. Max budget is $700 including the car. Ha ha. This is a find the problem only question.
Hi Vincevs, if it is a bottom end knock then the damage is done. You need to determine that and stop running the motor before it grenades. A lower end knock can come and go a little but the crank is already damaged, *if it is a rod*.
You should check the cylinder with the miss as it is most likely the rod with the spun or stacked bearing. Confirm the push rods are properly seated under the rocker. This can cause noise similar to yours. It would be nice if were only a pushrod jumped or bent , then you could easily replace it.
bent pushrod as mentioned above would be the first port of call, if its not a bent pushrodrod, retension the rockers, make sure they are all rocking. If after verifying the pushrods are straight, you come across a rocker that isnt lifting, you may have wiped a lobe off of the cam. - new camshaft
being under load there is another option. i had an exhaust header leak that only appeared under load initially, after a couple of hundred km it developed into all the time but would increase in severity. a set of copper header gaskets for the exhaust fixed it up.
is there any metal in the oil after running a few minutes?
a mechanics stethascope or long screwdriver to your ear could help isolate where the noise is coming from?
could be a badly stretched timing chain jumping around to?
hopefully not a rod knock.
Ok i am alone tonight to harder to diagnose but here is what I came up with... so long screwdriver gives me no noise from the top end or manifolds other than a pretty good whine from the distributor. Pulled the valve covers and the push rods are straight and everything else seems to be in place. Also seems like when i put it under load every knock lines up with a little puff out of the carb.
Looks like bearing material to me. No need to "drop the pan" for that.
Knock w/puff out of the carb under load = head gasket; blown between, most likely, #5 & #7.
Time for a new motor; or at the very least, unless it's a 267 or a 305, a crank kit. If it's one of those, then the only "correct" answer is a new motor with a 4" bore.
This is a 305..
So if it's indeed a head gasket can I not just fix the head gasket or do you think it caused further damage? No evidence of coolant in the oil but if so a 4" bore sounds like a great plan... just won't fit my $700 car rally limit.
A head gasket CANNOT POSSIBLY put bearing material in the oil.
PERIOD.
Sure, you can swap head gaskets; That might fix the "puff" issue; just don't expect it to do any good in the longer run about the knock. Might run a bit better for a day or 2, but in the end, that won't put the metal back onto the bearings. Might even tear em up the rest of the way faster.
You can P&M all you want about "budget". Best to, instead of attempting to adjust your needs to your "budget", adjust your budget to REALITY. Things cost what they cost. PERIOD. Getting on here and P&Ming about "budget" isn't going to change what's wrong with your car, or what it will take to fix it.
Do what you can to be absolutely certain about it; don't necessarily take my word, or anybody else's, for that; believe ONLY what you see with your own eyes. Take photos if you don't know what you're looking at and post them here, we'll be happy to help you interpret.
My guess would be that there's some abuse in the past of that motor that you're either not aware of or not admitting to. Coming here and beating us over the head about "$700" isn't going to undo the damage. Either you want to fix it, or you don't; "$700" BS isn't going to magically make it all right again.
What is P&M? Just tying to have some fun figuring out what's wrong and if it's over $700 I'm driving the old girl until it blows up. As for following the advise... it looks like I have some major cam failure! Ha ha. Any good posts on doing a cam swap and is it the consensus that it's both cam failure AND rod bearing? Or (with any luck) could the metallic supstance in the oil be cam only?
Videos in next post.
cam failure in your case was likely caused by your primary issue in the bottom end.
either way do not delude yourself into thinking that the missing metal from the cam lobes somehow 'disappeared' and hasn't flooded throughout your oil passages.
although my bet is that bearing failure in the bottom end increased tolerances so much that the cam bearings ultimately starved for oil.
any money, time or effort into doing anything to that motor that doesn't start with a tear down and interior cleaning is wasted.
Ok thanks guys... on the hunt for a cheap 305.
Or maybe just do the Summit K1102 cam for the fun of it and see how it runs because, according to this thread and probably my X wife, I suck at listening... if it ends up that I am still having an issue in the bottom end I'll toss it in the replacement 305.
If the metallic substance in the oil is in fact the cam & lifters, it's some of THE HARDEST metal in there. I.e. the most destructive to everything else.
Motors with a flattened cam tend to have gotten that debris and metal chips all in the oil passages and therefore the bearings. They tend not to last long after that. Furthermore, the single most common reason the cam goes flat in the first place (apart from improper break-in, or just, bad luck at that time) is lifter bores that don't point straight at the cam. Meaning, even if you put in a new cam and do everything right, the odds are very high that the same lobe will fail on the new cam for the same reason the old one did.
You can try it though if you don't believe me... you can do it in the chassis, you'll have to remove the radiator and A/C condenser (cond & comp can fold over and sit on the strut tower without unhooking any lines). Then you'll need to remove the vertical brace in the center, under the hood latch.
Time to start looking for a 4" bore block. Installing a 305 is a waste of perfectly good gaskets & fluids, not to mention time and effort.
Hate it, but I'm in with the engine swap/rebuild crowd. To repair an engine with a wiped out cam lobe correctly, requires a complete tear down to clean out all the oil passages in the block.
Update:
Replaced the cam, lifters, pushrods, and timing chain and she runs well. New bottom end issues may show up (due to the metal from the cam lobes) but this should get me the 1600km I need to drive for the Great Beater Challenge! Put in the summit racing sbc #2 cam and it sounds great!
03-20-2017, 05:06 PM
