valve clatter under load

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My engine has an obscene amount of valve clatter and loss of power under load, such as when the car is accelerating fastly or when going up an incline. it also has been running a little how lately,

I know advanced timing will make it run hot but will it also cause the valve noise, and how do I check to get these issues resolved.

I have messed with the timing and not sure I have it right, the car idles great and sounds good at low rpm but as soon as the rpm goes up in comes the clatter,

please help
mike
 
It's not "valve clatter", which is not affected by throttle opening.
That's knocking - fix it.
 
Another probably cause is an exhaust leak. Doubel check that. People somtimes confused valve tapping for a small exhaust leak.

Slade
 
Mike, what year is your vehicle,what engine do you have, what is the piston type,dished or flat top,what head gasket are you using, what are the cc's of the combustion chamber, what camshaft are you using & is the vehicle an automatic or a stick shift???? Do you know how many degrees of mechanical advance do you have? also how many degrees of vacuum distributor advance do you have???
I'm trying to be helpful, but unless all the above is known your problem is a mystry. your condition is before the computer age & you need the expert advise from someone with gray hair to even begin to diagnosis your problem. respectfully william :!: :!: :D
 
I agree with Panic. That knocking needs remediating quickly. Your engine is trying to reverse its crank rotation one cylinder at a time, basically. Not good!

Rule of thumb here is once the idle speed and mix are set, dial the dizzy back until it's 2° retarded from the last setting where knock was heard on a warm engine under load.

Slight knocking may not be audible, and bad fuel may predispose with heat or other stresses. That's the reason for the 2° margin.

Regards, Adam.
 
mike, with spark knock, it can destroy an engine. if you want some real very technical advise, need the basics i asked for in a previous post.
A bandaid fix is just retard the initial advance.
If you give the specifications of your engine i will more than happy to help you with your problem. in the time you find a fix, i suggest you use premium fuel. william :?: :?:
 
okay, it's a 66 200 with auto matic transmission.

it's bored over .040 and has dished pistons with a stock cam and crank is .010 over as well. I''m using a felpro gasket and I'm not for sure the cc's on the head I've never had any head work done except for general inpection and cleaning from the machine shop.

the knock did not start right away, I have about two hundred miles on the rebuild and then the wiring went. so now that the wiring has been redone and the car is running again. I drove another 50 to 60 miles put two half tanks of gas in and on the second half tank the knocking started a couple miles down the road. I did use regular gas not premium (my mistake i'm use to driving my van)

I appreciate all the concern so far.

mike
 
sir knoxalot, the way I check for exhaust leaks is to have a friend stuff and hold a rag up the tailpipe while the engine is idling. This seems to build up enough backpressure to force the leaks. The I carefully listen the length of the exhaust for telltale pfft, pfft, pfft sounds. Not sure if this is the best way, but it has worked for me.
 
mtpony;
with the FelPro head gasket and no head milling, your compression ratio is likely less than 8:1. It would take a LOT of spark advance (like 15-18 degrees) to make it knock, if at all. When I had my engine set up that way, I could put 22 degrees of static advance on it with no sign of ping.

BUT - that same head gasket added .035" to the effective "height" of the head where the pushrods are concerned: they are loose. If the rockers are worn (as in, 'not new'...), then they will rattle quite a bit. Worst case, they can actually fall out of the rocker - mine did!

There's a couple of things you can do; here's the solutions I used, from cheapest to most expensive:
1. Get new pushrods. Your lifters are probably worn, but without pulling the head, you can't replace them. Pushrods are available from NAPA in .060" overlength, too. For example, a worn pushrod-rocker-lifter set will be about .020" undersize. When you add .035" extra head gasket height, this becomes (.020"+.035")=.055" too short! The lifter itself, when new, will compensate for +/-.040" difference. So, at least get new standard length ones, or, like I did, .060" overlength ones.
2. If you're not going to pull the head and mill it to remove that extra .035" height, you can mill off about that much from the bottom of the rocker shaft stands instead. This will "lower" the rocker shaft back into the original geometry, and is cheaper than pulling the head. However, if you later mill the head and/or use a thinner head gasket, you will have to use the .060" UNDERSIZE pushrods in that new setup.
3. Pull the head and get a thinner gasket. I have 2 of the FoMoCo composite (.027" thick) gaskets left: if you want one, PM me and we can talk about it. I'll give you more info about the whole head gasket thing then, if you want. Get new lifters and pushrods at the same time while the head is off: it's worth it for the extra power and smoothness this brings back.
 
when the engine was rebuilt it already had a composite gasket on and I also put new lifters in. and there was no problem before with the push rods.

but I'm going to pull the valve cover and check the push rods anyway and check for one not in the roker assembly

would one of the pistons not firing cause this as well, I think my #6 wire is broke, the end is pulling out as if it were not connected to the spark plug.

mike
 
I've been following this post because I was experiencing the same thing until I changed the oil. I had too much oil in the engine and finally got around to changing it and the noise is gone. It used to sould like rattling pocket chacnge when I got on it hard or went up a steep incline.
 
How can you tell if the pushrods are too short? Last time I had the valve cover off, I recall being able to wiggle some of them - this is just because of where the cam is rotated at the moment - right?

ski
 
I recently ran the engine for 5 minutes (per the directions) with an oil detergent and then changed the oil. During the 5 minutes, I noted a little more noise than usual from under the valve cover....it went away on its own...while idling @ ~ 900 rpm the whole time. Since changing the oil, I hear the valve noise more often, but not as loud (ticking vice tapping). The ticking will come and go. If I put the car in neutral and rev it up above 2500, the ticking will usually go away. Hopefully, the more I drive it, the less I'll hear it. After the oil change, I added some cleaner fluid that is supposed to stay with the oil - and replinished with the next oil change as needed.

Ski
 
Slade,

Thanks for the thread. Did you get your lifter noise to go away? My engine only has ~ 10,000 miles on it (probably closer to 5,000) since the rebuild. New cam, lifters... I have a non-adjustable rocker arm assembly, so I can't go that route. The car was ticking again last night. More consistently than before - but definitely quieter. It goes away at high rpms and then comes back when @ idle - sometimes. I used 10W40 this oil change. I think in the past I've used 5W30.

What are the pros and cons with changing between grades of oils? Plus, I use to understand the numbers (10W40, 5W30...). What do they mean, again?

ski
 
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