davy5

I bought a secondhand 455 '70 engine with bad crankshaft. After replacing bearings and crankshaft build this engine in my TransAm '79. At about 1500/1700 rpm valvetrain starts clattering. I replaced valvesprings but problem remains. Does anyone have suggetions? Dots on camshaft and crankshaft I placed in line.

Oldsguy

Provide some more info. Did you rebuild the engine completely or just the bottom end? If you replaced the cam and valve train did you pre lube the cam and the lifter surfaces? Stock rocker arms? etc.....

Deltarocket

If you're using adjustable rockers, how did you adjust them ?
If not, did you measure the preload on the lifters before tightening down ?
What's your oil pressure ?

Oldsmaniac

Heavy pre-ignition or spark knock can sound like valve clattering....actually valves dont clatter....lifters and rockers can tap. Run premium fuel and make sure timing is not advanced too far.

davy5

I only replaced the bearings and crankshaft. I do not have any information about what the previous owner has done with this engine. It has stock rocker arms. I did not measure the preload of the lifters. Oil pressure is OK. Ignition time was set whit little advance. If run idle engine sounds fantastic and smooth but as said before with 1500 rpm a real naisty metallic clattering occurs in the valvetrain area. Is it possible that the dots on cam and crank do not must be exactly in line? I read this in the technical bulletin on this site.
Or is this a problem with the lifters?

Deltarocket

I would go back and reset the rockers. This time check the preload. The preload should be around 40 thousands.

Oldsguy

If the alignment of the camshaft was advanced by say, 4* then you might get pre-ignition but backing off on the timing would probably correct that at the expense of low engine speed performance. What I mean is, it might be a way to verify what you suspect about the timng chain but not a permanent fix. If after checking pre-load and you still have that problem you could loosen the distributor a little, hold it in place and have a partner start and bring the engine speed up for you, when it begins to clatter you could then back off the timing a little and see if that corrects it. If it does that might be an indication that the initial camshaft angle is set at the advanced point. It might be worth a try anyway.

Deltarocket

Being that the stock rocker configuration has no adjustment, if a smaller than stock base circle camshaft was used, and the aluminum bridges were not shimmed properly, this would be one of the possibilities. This is what I'm referring to.

88 coupe

Hi all,

Deltarocket: If a smaller than stock base circle camshaft was used, lash would be increased on all valves, and the sound would be present at idle. His "clattering" appears at 1500 RPM. If the problem was in the valve train, shims under the trunnions would only make it worse. Lifter preload only needs to be less than zero, and can exceed your .04" by as much as the plunger can travel.

davy5: Did you check all clearances on the crank/bearings? Did you inspect the rest of the engine while you had it apart? Did you tighten the TC bolts when you put the engine back in? Why did you replace the valve springs?

Does the noise appear only under load, or also in neutral? Cold or at normal operating temp?

To check valve lash:
Remove both valve covers.
Start the engine and let it idle.
Place a finger on the #1 intake rocker, where it meets the push rod, and put a small amount of pressure there.
If it is loose you will feel the slack.
Repeat on all rockers.

Norm

Deltarocket

88 Coupe, I meant to put the +/- on the shims. Bottom line, if a camshaft was used, that has a different base circle than what came with car. The stock push rods will no longer work.

Above the 1500 rpms, the lifters would be pumped up with more oil, making the sound less obvious. The fix would be to get the proper lenght push rod, or to go with adjustable rockers.

88 coupe

There are no shims on the stock rocker assemblies, and you do not know the dimensions of the cam. Reread my previous post.

We do not know that he has such a cam. Problem with your theory is, as I said before, the ticking (clattering) associated with improper valve lash, would show up at idle. OP says there is no problem at idle.

And the OP said, it gets louder (not quieter) at 1500 RPM

A fix can only work, if it addresses the actual problem. I have seen nothing, so far, that points to the cam as a problem.

Norm

Deltarocket

Seen ? you've seen his engine ? As for shims, they are available, they do exist, and I have used them in order to correct a similar sounding problem on a friends engine. Please keep in mind, that it's all speculation at this point, since it is rather hard to diagnose a problem over the internet. I was just giving my .2cents.

88 coupe

Did I say I did?

No, I still do not see it.

Yes they are. Did I say they were not?

I said, they did not come on the stock Olds trunnions. I said it is impossible for them to do, what you said they would. I did not say they were not available.

Similar sounding? On a friends car? Does that mean both problems are the same, and both cures will be the same?

It is always in my mind when I’m troubleshooting any automotive problem. Doesn't that make it rather silly to suggest that the OP buy adjustable rockers, pushrods, and/or shims?

It is. Because it is, there are many “experts” who immediately give the OP a list of parts to change, “because it’s how my buddy fixed a similar problem”.

It never matters, that the OP bought and installed a thousand dollars worth of parts on that list, before he discovered the culprit was a vacuum leak.

Yes, you were, along with a little misinformation.

Here is mine: I do not randomly throw parts at a problem until it repairs itself. Moreover, when someone is led in that direction, I will do my best to get him back on track. As I have, in this case.

Norm

Deltarocket

Sad way to exist dude.... later

bennymac

I have the same clatter noise and can't figure it out. It seem to get worse when the timing is advanced, but does not go away when i retard it. Davy5 did u ever get the problem resolved?

Deltarocket

Too much compression for the fuel you're burning.