Thread: new noise after V8 cam install

hi peter thanks for reply.

agree best figures to work off are real world.

$6m dollar question - so how do you check lifter preload once full of oil? pull lifters back out and drain then test?

just trying to build enough circumstantial evidence to get mechanic to check it.

the heads were exchange so I'm only guessing about thickness. gasket thickness was in the rimmers parts catalogue. composite came off so that's what I wanted back on.

just can't afford time to fly over and check myself lest the problem be deeper in the motor and car is undriveable. this sounds straightforward to check.



brett.

G`day Brett ,

Yes no oil is the way , there`s no free movement with oil inside .



If i put an engine together today and it makes a noise i have a fair idea what it may be or at least a posssible cause as soon as it`s heard but the norm would be to find it when checking bits on assembly .

I know this sounds simplistic but it`s as it should be in my opinion .


If the heads are within factory thickness and the valve stem height is within factory and the pushrod ends are good and rocker arms/shafts are good , the cam and lifters are you said new and spec , then there sound be no noise .

If there`s a noise your man should know or discover what it is and fix it , you shouldn`t even come into it .

The tin head gasket in theory will give it a bit more preload , if the valves have been ill fitted and are also high that would also give it more preload .

I can only offer theory because there are many things that could be wrong but eyes used to looking at such things automatically see , then it`s measured and rectifled .

Too little preload is more likely to give a noise , too much may mean the valve geometrys not correct as in the stems not being pushed straight into the guides but again theory and i`d think unlikely unless the heads aren`t factory spec .

Without the details of the new noise , the things that are the replacments are checked against what was replaced and the difference will be the noise as i suggest is part of the proceedure .


Peter

Look, IMHO if the engine has not been started for a day or so or the lifters just primed a bit then enough oil leaks down that the preload figures are accurate.

I have always checked mine on an unstarted cold engine after soaking the lifters in oil , or more correctly injecting oil through the hole with a syringe.

I have never found lifters to have no clearance or a reduced clearance with this method. The alternative is to put in dry lifters, then check the preload , then disassemble the rockers etc AGAIN then assemble them again with danger of scuffing the cam.

As it was I had to disassemble and reassemble a couple of times as mine were still too wide even with 15thou shims and I needed 30 thou.

So IMHO, as long as the lifters have had a good long time unused to leak down, you should get a fairly accurate reading. AND there is a noise there so something obvious should be wrong, and any pumped up lifters should show as an anomaly.

The problem SHOULD be too wide a gap, although I do not still know with any certainty from your description what the final profile of the heads , gaskets and cam is, and too much preload within reason should not really be an issue that causes noise. Too little preload however causes noise but from what you say this is unlikely .

Regards Philip A

Originally Posted by PhilipA

Look, IMHO if the engine has not been started for a day or so or the lifters just primed a bit then enough oil leaks down that the preload figures are accurate.

I have always checked mine on an unstarted cold engine after soaking the lifters in oil , or more correctly injecting oil through the hole with a syringe.

I have never found lifters to have no clearance or a reduced clearance with this method. The alternative is to put in dry lifters, then check the preload , then disassemble the rockers etc AGAIN then assemble them again with danger of scuffing the cam.

As it was I had to disassemble and reassemble a couple of times as mine were still too wide even with 15thou shims and I needed 30 thou.

So IMHO, as long as the lifters have had a good long time unused to leak down, you should get a fairly accurate reading. AND there is a noise there so something obvious should be wrong, and any pumped up lifters should show as an anomaly.

The problem SHOULD be too wide a gap, although I do not still know with any certainty from your description what the final profile of the heads , gaskets and cam is, and too much preload within reason should not really be an issue that causes noise. Too little preload however causes noise but from what you say this is unlikely .

Regards Philip A

Phillip, i agree, I have done/ checked lifter preloads after bleeding them down, never had an issue with inaccuracy. I got my pedastal shims from Rovacraft years ago, I would say try TRS also as they build RV8's a lot.

JC

Morning .

Well you live and learn , my suggestion of doing things before the fact must be outdated and you should have no problem getting your mechanic to check your preload .

If both Philip and Justin consider it the norm to check preload after assembly maybe i have the wrong opinion of your present mechanic considering Justin runs a workshop , he`d know .

Takes me a while to remove an inlet manifold and related but i only do it every now and again .

Peter

Originally Posted by PLR

Morning .

Well you live and learn , my suggestion of doing things before the fact must be outdated and you should have no problem getting your mechanic to check your preload .

If both Philip and Justin consider it the norm to check preload after assembly maybe i have the wrong opinion of your present mechanic considering Justin runs a workshop , he`d know .

Takes me a while to remove an inlet manifold and related but i only do it every now and again .

Peter

Hi Peter,

I have had to do this once with an assembled and run (2000km) engine after it had developed a miss, which i was concerned was a pumped up lifter. It turned out the cam the owner had fitted had a lot of lift (.500" exhaust!), and did require pedastal shims to correct. The others i have done during initial assembly. They are a lot easier to measure as you say. Bleeding down an oiled lifter just takes a bit more grunt and is easier if left overnight.
I must mention that it isn't something we get to do much anymore, most people don't want to repair their V8's for cost reasons, we seem to have become mostly a diesel repair shop nowadays. Which is fine by me

JC

I'm a little naughty and didn't do the preload check after a cam, chain and rocker gear change over. Used standard spec parts so I didn't think it would be needed. Quiet as a mouse )

typing on phone so shall be succinct

with valley gasket off motor turned over on starter for 30 secs and oil visibly being pumped upto rockers. wait 10 min and take measurement of 50 thou preload on lifter.

i assume the lifters would not have bled down?

will this more likely require shims to be added or removed to correct?

apologies if incoherent!