Nice to see the build in progress Daz,i will say this though mate after looking at the bearing pictures.
The slight wear marks and colouration chamge i can see would make me change them especially with all new parts going back in and the silly power level your running lol.
Not worth the risk imho mate but up too you at the end of the day.

 

^^^ I must say, esp. for the sake of £100-150 quid - or whatever a new set of ACL Race Series bearings cost - I have to agree with Ryan!

It'd be the ONE area of a rebuild where I would always use a new set, regardless of the subjective perceived condition of the existing ones!

 

I've since found out that the big end bearings do need replacing so I'm just going to order a full set.

 

Good man! Mains too?

 

I thought a full set meant big ends and mains ll

 

lol, my bad. Obviously.

 

I'm going to reuse the mains. I plastigauged them tonight and they are pretty much all a uniform 0.0015in or as near as dammit.

So ideal considering what the car will be used for. I couldn't get a new set anywhere near as perfect as that.

 

Yeah, it's not is if the mains suffer in the same way as the bigs too. i.e. uniform radial forces verses non-uniform eccentrc forces (more stress), repsectively.

 

Just thought I'd post these up. The reason for the failure.

This is the worst of the bunch but all of the exhaust valve lifters had started to do this.

 

I would presume they where machined to thin then Daz?

 

Not too this as such but it took the hardening off the top. The cams have then ground their way into the buckets thus causing masssive valve clearances. This meant that the valve was clattering against the seat instead of just touching it when closing. The valves have fatigued as a result of this and eventually one has had a head drop off and killed the engine.

Thankfully the engineering company that carried out the work for me have met the ost of the new parts

 

*idiot alert*

what am i looking at here? whats the problem with them?

 

Hang on a minute ! The valve will close as it closes, it will not close any better or worse 'cos the valve to bucket clearance is wrong. The valve and spring and upper and lower spring seat are a fixed length and that doesn't change when the shimmed bucket wears.

The impact of the valve to seat is governed by the strength of the valve spring, which if fitted and measured to its correct dimension is also a fixed value.

The dimensional difference is between the bucket and cam. That is where the ' clattering ' is going to occur.

Skimming or grinding cam buckets is a very bad idea and unless you are talking a clean up of say; one or two thou, is always going to be a disaster. The only variable is WHEN it is going to fail - never IF. The correct way is to tip the end of the valve stem to gain clearance or re-cut [ within limits ] the valve seat to reduce clearance.

I'd be very surprised if the cams aren't knackered too, as they will have re-profiled themselves to that bucket shape. They will need specialist measuring to see if they are re-usable.

The machine shop are not at fault for grinding the buckets, the person who asked them to do it is at fault. [ for asking a too large dimension to be taken off ] I am surprised that any machine shop have accepted that as a responsibility as it clearly isn't their fault. They must not understand engine dynamics and dimensions or they would have said exactly what I have said.

David APi

 

Are you really sure about that David? The cam defines how hard the valve hits the seat, (unless your engines run with the cam not in contact with the follower), as it controls the motion of the valve, and by having a very large clearance the valve is opening and closing on the main ramp instead of the take up portion of the cam profile. Resulting in the valve hitting the seat at high speed rather than in a controlled manner.

Also if you read Daz's posts, he instructed the material to be ground from the pip of the follower.

 

Course I am sure, There is no change to the valve spring fitted length no matter what you do to the valve clearance. Once the spring is tensioned that is it as far as valve closing pressure is concerned. The actual correct clearance of say 6 or 8 thou is not enough for the acceleration rate to increase substantially to clatter the valve into the seat. The noise is bucket hitting the cam lobe, which might be thought to be the valve bashing the seat, in fact is not.

In any case - machining the pip inside the bucket is almost impossible to do, most grinding is done in a lateral plane and to do it end-on is very tricky. All shim grinders I have ever seen, are a type of surface grinder ideal for doing bad things to buckets.

The valve head fell off sure - probably because at some point it had clouted a piston. not because the buckets were ground badly.

David

 

David, to be blunt here you're making assumptions and talking nonsense.

I had one over rev incident (9600rpm according to the Syvecs log at the time) and the engine went on to do 3000 miles, 10 1/4 mile runs, and a 600bhp mapping session after that.

I've had an over rev of that nature happen before on a previous engine and that let go spectacularly at the time (not 3000 miles later). All four pistons showed signs of valve to piston contact and a couple of the other valves had bent as a consequence. When I stripped this engine there was no sign of any valve to piston contact on any of the other three pistons and all 12 of the other valves are straight.

I'm absolutely certain the cause of this failure was due to the wearing of the lifter because the hardened layer had been machined off. The engineering company I used have held their hands up and have paid for replacement parts. They sent the lifters away for hardness testing and even compared the subaru lifters to some Renault ones which incidently much much harder than the subaru ones. The results showed that the machining process had significantly weakened the lifter. The company used have a fabulous reputation and this just goes to how what a decent reputable honest company they are. I will happily use them again I just wont be asking them to machine any lifters.

 

No nonsense and no assumptions.

You will never have a proper engine if you machine the top off the buckets, it simply cannot be done with any level of success.

But it has been done and you have a failure.

Clearly you won't agree with common sense and well meant advice. l will leave you to your superior engine assembly skills......................

I hope the next one lasts a bit longer.

David

 

David, now you're just being an arsehole and clearly havent read what I have written properly. I'm not saying that machining the buckets was OK, quite the opposite infact. I totally agree that it shouldnt be done and as Paul has quite correctly pointed out that wasnt what I had asked them to do.


I'm disagreeing with what you say is the cause of the failure.

I'm also disagreeing with you saying that excessive valve clearances wont cause a valve to fatigue and break off due to hitting the seat at high velocity.

It would appear that some engineering federation does too as this is on one of their posters. It was incedently on the wall of the engineering firm I used and made me first realise what had actually caused the failure.



Now, get back in that box of yours there's a good chap.

 

You're quite right that the spring seat pressure is constanct, but that's purely the static force holding the valve closed. However if the control of the valve is not good, the valve will impact the seat at high speed, and the peak force on the valve will be many times higher than the seat pressure. This is why valve bounce (which can happen near peak lift or zero lift) damages cams, the evidence of which I'm sure you've seen in the many years as an engine refurbisher.

The spring is there to keep the valve on the cam (via the follower) and then provide enough seat pressure to keep it there once shut. As to whether or not it caused the failure is not my point, but a significant change in cam clearance will have an effect on the load on the valve.

As for grinding the inside of the bucket, I've done plenty and I can assure you it's not impossible!

 

Lol

 

This rates alongside East Enders

 

Popcorn at the ready

 

Was thinking more like gardeners world myself.

 

Would that be because you're an uphill gardener?

 

Turned into a p1ssing match between experienced engine builder and the young upstarts

 

That one went straight over my head Daz.

 

You should ask your bf's to improve their aim then

 

which do you class and which?

I am with Paul and Daz.. sorry David..

 

who cares it was meant in jest...

 

either I have drunk too much or your camera skills need work chap

Simon