mypolonga sunday 16th jan

[Greg]

We're getting there.

Now, we've just got to get the width up to between 600 and 800.

Greg

[rumbles]

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they are rollers with a 65 stamped on them.
finally figured out the pic sizing!

[rumbles]

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before and after showing the offending valve....

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20140226_083529 (590x443) (330x248).jpg (97.64 KiB) Viewed 7303 times

happy days are ahead im sure

[screwit]

I think that they are 1.5 standard.

[The Spook]

Holden rocker arms are 1.65 to 1 standard, Chev are 1.5 to one. If you are having problems with valves hitting the pistons then you need to get someone who is experienced with Holden V8s to have a look at it. In my Holden V8 which is now 357 cubic inches I have a .600 inch lift camshaft with 260 degrees of duration at .050 thou lift, inlet and exhaust and nothing touches. Even before when it was a 308 with flat tops it had 250 degrees of duration at .050 and .560 lift inlet and exhaust and nothing touched.

The only times that I have had a problem with valves touching pistons is when a conrod lets go or the camshaft stops turning. The only other possibility is that you don't
have enough valve spring to handle the camshaft which will allow the valves to float, commonly called valve bounce, if this is bad enough it could allow a valve to touch a piston.

In a Holden V8 if you are running an after market hydraulic camshaft you should be running about 300lbs of spring pressure at maximum valve lift. If you are running a solid lifter camshaft then you need to start looking at 350 lbs of spring pressure at maximum valve lift and depending on the revs you are pulling maybe even more. Be aware that you wont achieve those sorts of spring pressures with a standard Holden 308 valve spring set up. You will need to use something a bit more robust. In my engine I am currently using 380 lbs at full valve lift (600 thou), titanium retainers and ten degree valve locks, 100 thou longer valve stems and have also sunk the valve spring seat .050 into the head to give an installed spring height of 1.900 and am using big block Chev springs. In all the time that I have been using Holden V8s I have yet to bend a pushrod. Damn I've just put the mocca on my pushrods.

Oh by the way if you're still using standard holden push rods throw them away and talk to crow about some heavy duty jobbies.

Spook

[rumbles]

thanks for that info spook.
whilst I have a great mechanic on my payroll, he has an older mate who cut his teeth on this old stuff, who is coming to pick up the motor tomorrow. he works from home and has extensive machining equipment etc.
im sure once he gets it apart he will work out whats wrong. he already mentioned yesterday when he called in that it would need heavier valve springs, so I think hes on the right track.
thanks again

[The Spook]

Rumble

There are other things that need to be thought about as well. I didn't talk about installed spring height and valve spring solid height as well. These things also affect valve spring selection.

Every valve spring package has what is called a valve spring solid height. Think about putting a valve spring set in a vice and doing up the vice, at some stage you will reach a point where the valve spring cannot be compressed any further by the vice. This is called the valve spring solid height, also called valve spring coil bind height. If the camshaft lift causes the valve spring to reach solid height you will bend a push rod.

I will try to explain and use my current valve spring setup as an example.The valve spring installed height of my spring package is 1.900 inches. This means that when the valve and spring are installed in the head, the height of the spring from its seat in or on the head to the underside of the valve spring retainer is called the valve spring installed height.

The difference between these two figures is the valve spring free travel distance. Once again lets use my spring package:

Installed height 1.900 inches
Valve spring solid height 1.100 inches

Which leaves a valve spring free travel of .8 inches

If I put a camshaft in the engine which produces 850 thou of lift I will reach valve spring solid height and bend all the push rods.

I have however a camshaft which produces 600 thou of lift at the valve. From the free travel figure and the lift figure we can calculate the valve spring duty cycle

Which is valve lift 600 thou
divided by
Spring free travel 800 thou

Which gives a duty cycle for the spring of 75% of free travel.

In general terms the duty cycle of the valve spring as a percentage of free travel should not exceed 80%. You can use higher duty cycles but this increases the stress levels of the spring and increases the prospect of spring failure.

So when deciding upon the overall spring package you first need to know the valve lift of the camshaft. Ie 600 thou
Then you need to know how much free travel you need to give you an acceptable free travel to cope with your valve lift. In my case I chose a 75% duty cycle and went for 800 thou of free travel.

With those two figures you figure out approximately what installed spring height you need to give you that free travel. The spring solid height and installed spring height pressures are found on the spec sheets of valve springs from various valve spring manufacturers.

Next a decision needs to be made as to what spring pressure you require at maximum valve lift as this will determine whether the valve train will cope with the camshaft/valve lift and proposed revs of the engine. In my case I determined from previous experience that I would need 370 to 380 lb of spring pressure at maximum valve lift to cope with 600 thou of valve lift and as much as 8000 rpm.

The next thing we need to calculate is the height at which we need the spring to produce the 370 to 380 lb of spring pressure at:

so Installed height of 1.900
minus valve lift of .600

equals a compressed spring height of 1.3 inches. This is where you need to start looking at valve spring spec sheets to find a spring set which will give you your valve spring installed height of 1.900 and your spring pressure of 375 approx at 1.30 inches compressed.

This turned out to be a set of big block Chev springs and to get the installed spring height I had to use 100 thou longer valve stems and sink the valve spring seat .050 into the head.

Spook

[rumbles]

thanks for all your help spook.
we loaded the motor into ol'mates ute yesterday with him saying the first thing he was going to do was pull the cam out to find out what we are really dealing with and then sort out what valve springs and push rods to use. im pretty sure I am in good hands.
I might at this point say I bear no malice towards the previous owner. he acquired the engine from a related 3rd party who claimed it was built some years ago with all the good gear, and left unused until recently. upon inspection it certainly has been built with the good gear and to a very high standard, perhaps with just a minor miscalculation somewhere.
anyway, it will be quickly and easily resolved and I will have had the benefit and pleasure of seeing whats really been done to it.
I like to know these things! as we no doubt all do.
the first thing I did when I got the boat was to get my boys to strip everything out the hull, floor boards, fuel tank seats etc., so I could see everything was in order. they then put it all back together with new hoses, clamps, filters so the marine inspector for the insurance company could ok everything. ( which he did ). now the only remaining grey area of the boat has been laid bare I am comfortable and happy.

thanks again,
mark

[The Spook]

Rumbles

Good,good, once you and your mate know what camshaft is in it then you can start to work out what the rest of it needs to be. When I got my first boat it had a Holden 253 in it and I didn't have a clue about all this stuff. I have long ago left the 253 behind and built a 308 which lasted about 3 years, then the second 308 and I've now converted my second 308 to 357 cubes. Along the way I've learnt about all this stuff so that I can understand how it all works. That way when you are talking to an engine builder it evens the discussion up a bit.

I'm a bit lucky in that I have a good mate who is a bit of an engine guru and I pick his brains a lot. He and I also know and use the same engine builder. Our engine builder recently made a comment to me; "that he had never seen a Holden engine with the amount of gear in it that mines got".

Anyhow I hope all the info about valve train stuff was of some help to you.

Spook