How to Adjust Intake/Exhaust Valve Clearances on a 308

Here a screencap from the 328 version of the 2 litre turbo manual
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Here guys, this is for the QV/328. Done from an actual profile, hence the slight discrepancy of the closing degrees.

Off to bed, ?'s answered later..

PDF for those wanting to print a copy.
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Thanks for this.

Its around 20 years since I did any cam timing (on Lotus engines) so I am really rusty on it.

So, the 123 degrees angle is from the point at which the valve is just starting to open to the point at which its just finished closing, assuming a 0.5mm clearance?
If so, surely you only have control over either end of this angle, as the angle itself is determined by the cam profile?

I seem to recall when I did this before I set the reference point at the point of maximum opening of the valve, by measuring a known amount of opening slightly either side of the max and taking the midpoint. Then, the clearance is cancelled out. Does this method not work on these engines for some reason?

 

The ~123* is the duration ~246* crank of the camshaft at zero lash and 0.5mm valve clearance. I have about a half dozen profiles, they all range around 122*~123*, most being ~122.3*

What's notable is that the notches in the cams are specific to the 0.5mm number. If one first set the running clearance of ~0.22mm and then checked timing by measuring a lift of 0.5mm the timing would be out. So either check it with zero lash or subtract the known running clearance from the 0.5mm and measure that, for example.

running clearance of 0.2mm;
0.5 - 0.2 = 0.3mm
check timing by measuring a lift (depression) of 0.3mm on the valve.

Fiddly tech point here, when checking lift the dial the indicator shaft needs to be axially inline with the valve or the measurement will be wrong.
Intake valve angle = 15*
Exhaust valve angle = 18*30'

Bear-in mind that the dwg above is based on a lift per 1* resolution file, in other words I have a spread sheet with lift at each degree of the cam lobe profile. That then is used to create the lobe curve in CAD I can then using tangents and contact points derive the lift on the valve based on the shim dia, the amount of contact face determines how much lift you have. The factory cams have very very slow ramps, the base circle is only ~160* so when you're checking clearance you need to make sure the center-line of the base is in line with the valve angle or your measurements could be off a hair. I've found that having a set of feeler gauges that are 'bent' or curved really help here. try and avoid brass ones as they deform over time and those are actually made to check reluctor gaps.

 

OK

So you mean the reference point of the cam for timing purposes is just that one point, ie 0.3mm of lift, or is it the center point between 0.3mm of lift on the opening and closing of the valve?
If the former, would it not be better to use the latter, ie a midpoint because that would not depend on the lift, you could use any reasonable figure as long as it was the same each way. Or is this not possible owing to asymmetry of the cam or some other reason?

 

The question I've seen posted many times is "how close are the factory 'tick' marks?"

Since I design new profiles for the engine builds I took the stock profile to find the timing data in simulations. Given that I wanted to have new grinds done where the 'tick' marks still line up vs having to time them it required changing the centerline, in order to that I needed to find where the 'tick' mark is in relation to the timing events. long story short, the profile data shows that the 'tick' mark lines up the timing based on zero lash and 0.5mm valve lift.

How one wants to measure or arrive there has many options. The total life of the will vary though as the factory marks are based on lift from the base circle.

 

Ha ha thanks Brian, I put the silly filter removal in as a bit of fun and to show what to do if you don't have a correct tool (which I do) It's better than sticking a screwdriver through it, which I've seen done also
And the hammer.....yes thought I'd put that in there too because the amount of damage people do to alloy engines with hammers and screwdrivers is unbelievable.
Anyway glad you liked it, Cheers!
Part 2 coming up as soon as it stops raining....
All the best, Bell.

Ps. Cheers SMG2 for the camshaft tech data, that's in my archive now, very useful.
It's interesting how car companies do things, on my Aston V8 Vantage the valve timing overlap is measured by valve depression at TDC.

 

Another interested viewer of your video. Thanks for taking the time to film and post. Great stuff & loving that U.K weather!

-Dave.

 

Great video! Thank you very much!

 

Indeed I have a 1/4" drive Teng torque wrench which happily covers the required range & which is certified/calibrated up to its eyeballs (and was about £30-40 I think)

 

As has been said (and as with Andy's car), my (328) exhaust valves were set in the 30-35 range by a leading Indi so its commonly done.

What you may not be aware of is that the shims come in (nominally) .05mm incremnents i.e. 4mm / 4.05/4.10/4.15 etc. so typically if you are at 0.3 on a vave, if you change the shim to the next one up it should go to 0.35

BUT the shims seldom mic out at the marked dimension.

So in order to alter the valve clearances what you really need to do the first time is take all the Shims out one at a time (and it helps to have a couple of spares to enable you to do this) and then measure them all & make a map of what you have & where they are.

You will then find you can correct/adjust a lot of your clearances by moving shims around & that will then leave you needing to source very few to fix the final few valves.

When you buy them then take a micrometer with you & check what you are getting. If you buy them via mail order then ask that they are measured because they can easily be 0.02-0.03mm out from what they are marked as.

Once you have made the map once & you know what shims you have & where they are then the next time through it should be easier if you ever had to do it again. Getting the shims out from under the cams is not that easy (you need special tools) & there is an argument to saying just take the cams out the first time so that you can get to all the shims easily.

 

Where can we order shims online? I know 2V and 4V engines require different diameter shims, I'd be interested in 4V shims?

 

2V shims are the same as in some Volvo engine I think, so easier to get.

For 4V shims, Superformance do them

 

Many thanks folks for your kind comments.
My cam covers and plenum are at the powder coaters to be painted matt red and will be back in 2 weeks, Bloody hell!!
Anyway there are other things to get on with, I enclose a picture for my engine bay inspiration. I have bought a plating kit to zinc plate in gold and silver factory finish all the injection fuel pipes and other fittings etc.
I'm also going to change out my camshaft oil seals which I can either do in situ or remove the shafts. Really it makes no odds to me. Removing would be better but for purposes of the video, I thought that leaving them in would be better for folks wanting to see how to do a seal change.
The thing is I'm really doing a cosmetic and mechanical overhaul at the same time and
I'm trying to do it in an order that will work for me and work for the videos too.
Also I don't want to take too many things appart as it will confuse the viewer and also make fault diagnosis difficult for me should something not work when reasembled.
ie. If you only tackle one job at a time you can trace a mistake more easily.

Iain, cheers for the heads up on the shims not being accurateI will just keep sending them back if they don't measure up until I get the right ones.
Gordon, I'm getting mine from Superformance.

Oh and finally...torque wrench! I'm trying to have fun with this and do things that are very accessible, my torque wrench is very, very, very accessible and accurate, I think you are gonna like it, can't wait to show you what I usually use ;-)

All the best, Bell.
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I got mine from an official dealership.

If you give your old back, I'm sure pricing will be (very) competitive.

 

You need to remove the camshafts to change the oil seals on a QV - the seal is held in a housing which is in turn sealed to the head with a large O ring - these themselves are often the cause of leaks. You take the cam out & then the housing comes off the back of the cam.

This would also give you a good opportunity to get to all the shims & measure them easily.

There has been some discussion about these seals/o-rings within the last year or so & also how to deal with sealing the gaskets in that area. You can buy a kit from Hill Engineering with Viton seals and O rings (they sell it for the 348 but they are the same parts). Andyww has recently found some X profile O rings which look like a good idea as well.

Many of us that have tried Superformance's cam cover gaskets have ended up buying the green ones from Ferrari not that long afterwards - even though they are 60 quid each. Draw your own conclusions!

If you want to change the cohline (plastic) FI lines that lead to the solid lines then I have the tool to do that (well, Andy has it at the moment I think!). If you are going to re-plate the hard lines then be careful not to block them in the process & you will really need to remove the plastic lines first.

 

Cheers Iain, I went for a walk today and quickly figured how to remove the cams but for video purposes make it look like I just changed out the shims with the tool. I guess I shall be doing a few video variations here. Regarding your gasket advice I'm going to do what you suggest regarding the O rings but the cam covers I will try something else, only as an experiment . Can you PM me your phone no for a chat? Cheers, Bell.

 

OH YES !!!!!!! The imprined thickness on new or used shims are usually off, many by a bunch.

I mic spec'd about 100+ sims at my Volvo and BMW dealer combined, to find the approximately 6 shims I needed to be within the middle 1/3rd of the acceptable range of valve lash and the four for cam timing to give me as close to exact as possible, the 0.5mm lash on 1 and 8.


I posted a handy little spreadsheet I developed sometime ago here that will run you all the calculations automatically in metric or imperal on what shim thinkness you need. It is color coded Green, Yellow and Red as you plug in your lash and original shim thickness numbers and then recalulates as you input your proposed shim's thickness.

Nice and real cheezy (read: Brain dead simple).

 

Any one know the actual torque spec for the cam cover nuts. The video said 5 lbs but also said not to bother with a t. Wrench at all. ???

 

Hi Allen, the actual torque is 6ft lbs and as long as you have a low range torque wrench ie one that goes upto 40ft lbs then the best way is to use that.
But as I said in the video if you use a torque wrench that goes to say 150ft lbs it won't be accurate down at 5-6ft lbs even though it may have it on the scale.
20 years ago before internet shopping in the uk low range wrenches didn't exist so the way I was tought was to tighten till you feel the 'pinch' and then add 20-25 degrees.
That method has worked for me on many Aston, Lotus and Lamborghini engines, I've never stripped a thread and I've never had a leaking cover even on a long 48 valve V12 motor.
However times have changed and the tools are readily available now, so the correct proceedure is best ie use a low range wrench.
I tried in my video just to for warn of potencial pit falls and how to get round them if the correct tools are not to hand. Like in this video here on how to make an accurate wrench from fish scales..

https://www.youtube.com/watch?v=lzrGJqZ5-Qg&feature=youtu.be

It's easy to forget that in WW2 our Daddies and Grandaddies built and flew most amazing aircraft without computers, a committee of suits to design it, without windtunnels or flight simulators.
These 2,000hp technical marvels of their time, were usually penned by one patriotic bloke, his slide rule and a vision or a need.
Test pilots wrote the flight manuals on the wing, then 'Boys' were told to go fight in foreign skies, many of whom would die in them.
In a digital age it's easy to forget these things I guess.

 

Well that came out a bit heavy, I really shouldn't write posts a 4am when I can't sleep.

 

I love that so much time was dedicated to the oil filter removal

And the hail: "Don't ever move to England: it is a horrible nasty place!"

 

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