Petrol Pump

[Forumadmin]

From Tech Notes Note early engine also there.

To Set The Valve Timing – Series III Type

121. It should be noted that the crankshaft sprocket can be installed either way round. The positioning of the keyway in the sprocket bore, in relation to the sprocket chain teeth, is such that half a half tooth radial movement can be achieved by reversing the sprocket on the shaft.

122. Any timing marks that may be found on the timing sprockets should be totally ignored.

123. There are two types of camshaft sprocket mounting, the later ‘vernier’ type is the most desirable; The two types are best described as:

Early type – simple one position mounting on a fixed position dowel.

Later type – a more complex mounting system with a multi-position dowel.

124. The later type, commonly known as the Series III, is described here. To set the valve timing, turn the crankshaft one full revolution so that it is positioned at TDC (1 & 2) again.

125. Mount an indicator pointer at one of the front timing cover bolt thread holes.

126. Mount the crankshaft sprocket and a new timing chain on the crankshaft nose.

NOTE: The camshaft timing dowel should be removed from the shaft or sprocket and kept handy for later use in the valve timing procedure..

127. Mount an accurate 360° engine timing disc at the front of the crankshaft. Make sure that it is held snugly, but can be moved to align zero with the pointer when the crankshaft is at TDC (1 & 2) position

NOTE: Use a pair of suitable fibre washers and a pair of plain washers to hold the timing disc.

128. Using the flywheel, turn the crankshaft back so that it is positioned 35° before TDC (1 & 2).

129 Again, using the flywheel, turn the crankshaft forwards until the pointer registers accurately with the 12° before TDC mark on the timing disc.

NOTE: Be sure that the disc has not slipped on the crankshaft nose bolt.

130. Set the number one cylinder inlet valve so that there is slight loading of the valve spring. Do not load too heavily, or the retainer cap could clash with the valve guide as the camshaft is rotated.

131. Mount an accurate dial indicator clock to rest on the pushrod end of the number 1 cylinder inlet valve rocker.

NOTE: The plunger end of the dial indicator must be longitudinally aligned with the pushrod. It is the actual movement of the push rod that will be measured by the dial indicator.

NOTE: The dial indicator plunger should have more than 0.250” of free travel after it is positioned against the rocker arm.

132. With the cam follower set accurately on the heel of the cam lobe, adjust the dial indicator to read zero exactly.

133. Carefully rotate the camshaft, in clockwise direction when viewed from the front, until the dial indicator has shown 0.014” movement (valve lift) at the rocker arm.

134. Hold the camshaft in this position, This position has been determined as the ‘point of valve opening’ by Jowett Cars Limited.

135. The camshaft sprocket can now be inserted into the timing chain. The two sprockets should be offered up to their home positions. There are two large holes in the camshaft sprocket for the setscrews to pass through. It is possible to slip the camshaft sprocket in the chain until the two large holes are positioned over the threaded holes in the camshaft nose.

Without moving the crankshaft, nor the camshaft, the sprocket should be oriented so that the dowel can be pushed through the sprocket into one of the camshaft vernier dowel holes without changing position of either shaft. The camshaft sprocket may require rotating 180° within the chain to achieve alignment. There is also the facility to reverse the sprocket on the crankshaft nose. Care must be taken to ensure that the crankshaft position is held while removing the timing disc to facilitate the changeover.

136. Once accurate dowel alignment has been achieved, push both sprockets fully home and install the timing dowel with the peg facing the camshaft.

137. Re-check the 12° before TDC and 0.014” push rod lift settings to ensure that no errant movement has taken place during the installation process.

138. Install the two camshaft securing setscrews, using a new locking plate. The plate should cover the timing dowel.

139. Rotate the crankshaft two full turns and check that the 0.014” push rod lift coincides with the 12° position on the timing disc. Use the flywheel rim to rotate the crankshaft.

140. Should the valve timing be correct, tighten the camshaft sprocket setscrews and fold the locking tabs against full flats on the setscrews

NOTE: Do not hammer the tab over against the setscrew heads. The tabs should be carefully bent against the flat using a pair of suitable vise-grips.

141. Remove the valve setting equipment and reset the number one inlet valve as described at Step 88.

[Keith Clements]

You might also observe that the procedure requires removal of the bottom clutch cover and is also made easier if the other push rods are not installed. This may also require removal of the tappet covers as frequently it is necessary to recover a cam follower that has been pulled out.
Note also that there are some modified camshafts in circulation that may require a different setting.
Philip Dingle did a good treatise on the subject and showed that the bending of the shaft and wear on shaft bearings affect readings on lift and its position on each valve.

[David Morris]

Hi Alexander,

I agree entirely with Keith that setting the valve timing is very complicated, as you can see from the previous posts. However, Jowett's did help with the Series 3 camshaft, with it's vernier peg adjustment. Much better than the BMC 'A' series engine where you have to shave a bit off the camshaft Woodruff key to set the timing...crude! Jowett's were far ahead!

However, I think we are delving into the details of engine initial builds. What I think you would like to do is to simply check the valve timing rather than having the engine practically stripped? Can I suggest what I think might be a simple test? First set the engine to TDC for No. 1 cylinder. The valve gap at the inlet valve for that cylinder will be very small, probably around 0.003" or so? Now deliberately adjust the gap to say 0.040" and record. Rotate the crankshaft nearly twice and stop at the 12 degree setting point on the flywheel, ( this will be the second time you will have seen the 12 degree mark ). Now remeasure the inlet valve gap. If everything is correct, it should measure around 0.019". I think this takes into account the x1.5 amplification factor that Keith mentions due to the rocker arm, plus the 0.014" initial lift from the camshaft at the camshaft setting point.

If you don't get anything like the reading I suggest, then there may be a need to delve further. However, as Keith says, the camshafts do wear quite a lot, so some variation is to be expected. The early camshafts for the hydraulic camshaft followers had a different profile and again as Keith says, there were probably different camshaft profiles for special engines. Over 70 years, things change! I believe Tony Grey in Tasmania even modified his Javelin engine to use roller followers, which is what modern engines use.

Now move the crankshaft onto the TDC point and restore the valve gap to the correct 0.003" point or where the push rod is just spinning, if that's what you prefer. As Keith says, it is easy to suffer from a bent push rod. This will rub against the channel in the head and cause problems and could even be the cause of your problems at higher revs?

I really hope this helps,

David

[Forumadmin]

This PD's treatise which also gives you a timing disk you can print. The camshaft setting is halfway through the pdf. Page 40 has a good diagram showing lift on each lobe versus cranshaft degrees. Page 59 shows the issue with movement of camshaft and bending of rocker shaft.
I am questioning measuring a 3 thou tappet clearance at TDC and the method of checking valve lift at 12 deg BTDC.

First set the engine to TDC for No. 1 cylinder. The valve gap at the inlet valve for that cylinder will be very small, probably around 0.003" or so? Now deliberately adjust the gap to say 0.040" and record. Rotate the crankshaft nearly twice and stop at the 12 degree setting point on the flywheel, ( this will be the second time you will have seen the 12 degree mark ). Now remeasure the inlet valve gap. If everything is correct, it should measure around 0.019". I think this takes into account the x1.5 amplification factor that Keith mentions due to the rocker arm, plus the 0.014" initial lift from the camshaft at the camshaft setting point.

On the start of the inlet stroke there will be no gap at TDC so you need to make sure you are on the end of compression stroke. Possibly a better method (as it only requires one measurement and checking is easy by rotating push rod) is to set the gap at 21 thou (1.5 x 14) rather than 3 thou and see if the inlet valve just tightens at 12 BTDC. I have not tried this, but will have a go this week. I have five working engines to test!

[David Morris]

Hi Alexander,

Yes, I agree entirely with Keith that setting the gap for No.1 inlet at 0.021" at the point where you would normally set the gap at 0.003" and then check at the 12 degree point on the flywheel BTDC for the push rod to just start to get tight would be a quick and easy method to check the valve timing.

Obviously, you would need to reset to 0.003" afterwards.

Best wishes,

David

[alexander]

Thanks both had to work today hope to get back on the Jowett Monday and will report back once I’ve checked lift.

[nigel jarrett]

It's just a thought as most things have been covered ,
The pump has been overhauled,but has the throw of the pump been looked at ,is the arm ,the pump pushrod or the cam lobe that drives the pump worn reducing the throw .
A few years ago I had problems with the car not going on anything over half throttle ,up to half throttle ok any more and it would just die .
Fitting an electric pump in the engine bay cured this .

[alexander]

Today I checked lift using the method of setting inlet number 1 to .021” instead of .003”.
Turned flywheel till I reached 10 btc for the second time. At 10btc I
I had .018” , by 5 btc I had .010” and at tdc .007”. Is this what I should expect?

Hi Nigel When I bought the car it did have an electric pump and no push rod so bought a new pushrod from JCS. I wanted to use a mechanical pump as I could not tell the pressure I was getting from the electric and it was very loud.

[David Morris]

Hi Alexander,

With regards the valve timing, I don't think the readings you have are correct?

At the correct 12degree BTDC point on the flywheel I think you should be getting no gap at all, assuming that the push rod will have moved out by 0.014" and the rocker gives an amplification factor of 1.5.

Also, I am wondering why you are mentioning the 10 degree point?

I believe Keith is going to use this new method to check the timing on the five engines he has in for test, so it will be interesting to hear his results.

All the best,

David

[Keith Clements]

In response to Nigel,
I asked Alexander to check the volume of petrol pumped by hand and by a couple of turns of the engine, as this might show if there was a worn lever or actuator issue.
In response to Alexander's timing check.
I have not yet checked my engines using the 21 thou method. I suspect that gap may not be correct as it was assumed a 14 thou at push rod would be 21 thou at the tappet. I would not read much into your result until I have checked all my engines. I expect a variation between them and suspect the average or most common to be different from 21 thou.
Certainly do not try altering the timing yet, but you might try verifying what the lift is using the book method (14 thou at pushrod)

My experience of lack of juice is stuttering rather than stable loss of power. I would also expect the same stuttering on hard acceleration, rather than a loss at stable speed.

My experience of wrong valve timing is popping through carbs or bark on exhuast.

Ignition coil breakdown is brought on by wrong dwell as not enough power is given to spark at high speed.
It could also be weak points spring. But all this should be visible with the strobe light and a sequence of checks such as an unstable strobe. It should be rock solid with no change of vacuum and vary slowly according to the speed advance curve.

[alexander]

Thanks for quick posts I should have written 12 not 10 , today I will redo just in case I’ve made a mistake and make a bracket to test lift with dial.

[alexander]

Just did the following and I have .018” which seems close.

First set the engine to TDC for No. 1 cylinder. The valve gap at the inlet valve for that cylinder will be very small, probably around 0.003" or so? Now deliberately adjust the gap to say 0.040" and record. Rotate the crankshaft nearly twice and stop at the 12 degree setting point on the flywheel, ( this will be the second time you will have seen the 12 degree mark ). Now remeasure the inlet valve gap. If everything is correct, it should measure around 0.019". I think this takes into account the x1.5 amplification factor that Keith mentions due to the rocker arm, plus the 0.014" initial lift from the camshaft at the camshaft setting point.

[David Morris]

Hi Alexander,

Wow! Well done! I agree that that all seems right and you can probably be reassured that the valve timing is pretty much spot on. As Keith says, it is tricky to get the valve timing right during an engine rebuild and this check you have just achieved looks to be a good way to get some reassurance without much trouble.

Still doesn't solve your problem though? With so many variables, perhaps someone else can suggest what is the cause? It sounds like the car just doesn't what to go over 50mph. Perhaps we should think outside the box? Are the brakes getting hot? Does she roll easily on a flat piece of road with the engine turned off?

Very curious?

All the best and well done again,

David

[Keith Clements]

I did my proposed check on an engine on the bench and Amy's SC which has an ex-rally engine with slightly modified camshaft. I will get around to doing the other three soon. Perhaps leave for the proposed Tech Day sometime in August! I recorded the process with a few pics. It only took 10 mins.
1. Take off both rocker covers and rotate crank so that no 2 Inlet is fully open.

20220726_161247.jpg

2. Adjust no 1 inlet to 21 thou. so that the rod can only just be rotated with fingers.

20220726_161256.jpg

20220726_161316.jpg

3. Rotate crank 1.75 turns till 90 deg before TDC, then slowly turn, feeling when rod starts to get tight. Then rotate until as tight as it was when you had the 21 thou feeler gauge in.

20220726_162122.jpg

20220726_162536_001.jpg

4. Check flywheel is at 12 deg BTDC mark.

20220726_162157.jpg

The bench engine was spot on
(let us say plus or minus 2 mm on flywheel)

The SC with probably a non standard cam was 7m +/- 2mm earlier so probably about 15 deg BTDC
The SC does have a bark on the inlet at over 3500 rpm. I run all the engines with hardly any tappet gap on the inlet. Thus giving more lift and earlier valve opening.

I will have a go at the SA, Javelin and other bench engine during the tech day.

Note it is very important the push rod is not bent and that you check the rotational feel precisely as the difference between starting to tighten and not being able to turn can be 5 deg.

[alexander]

Thanks Keith for the above .
Please dismiss my earlier post as I have just followed Your post and can not get the rod to tighten up a t 12 btc it does get tight again at tdc.
Tried to repeat the .040” at tdc method and can not get the result I had this morning, keep getting back to ..040” not .018. No idea what I did this morning. But it does seem that I have a timing problem.
Will check again Wednesday as I might be doing something wrong but I don’t think so as I’ve just done both methods twice with same results.