Bent push rods

[David Morris]

Hi Rodger, Thanks for the photo. Yes, I can confirm that you have hydraulic tappets. I have never had to remove the body of the hydraulic tappets, having assumed that they are similar to the mechanical ones, that easily slide out. Perhaps someone else can advise? However, I don't see why you need to take them out completely, just replacing the bent push rods should be sufficient? I don't think there will be any new ones, but JCS should be able to supply good used ones. Just ask for hydraulic rods, as they are completely different to the rods for the mechanical tappets. As for the reason for the bent rods, I suggest this must have been caused by sticking valves? When rebuilding the engine, you will need to make sure the valves are a nice sliding fit in the guides. If you are re-using the existing valves, you need to polish the stems to remove a build-up of carbon around the stems, that might have caused them to stick before., and hence bend the rods. You can test the clearances in the guides by putting your finger over the end of the guide which is away from the combustion chamber, and sharply withdrawing the valve stemshould get a good sharp 'pop'. If it's a dull sound, the guide is worn and needs to be replaced. THey can be knocked out with a suitable drift, which needs a shoulder to get the re-insertion depth correct.

I have never had the need to set hydrawlic tappets, when rebuilding an engine, but there is a procedure in older versions of the Javelin Handbook. I seem to remember you need to assemble them dry, with quite a lot of initial clearance. Which then gets taken up with the oil in the tappet cylinder when first starting the engine. The technical notes on the website should have this data?

As Keith mentions, if the engine was suffering from water in the bores, caused by a leaking head gasket, this might have also caused the valves to stick and hence bend the push rods. Also, if the engine had been standing, water might have got into the combustion chambers and caused the problem?

Anyway, an engine rebuild is going to be necessary, so you can check all is ok before attempting to re-start. Obviously, replace the head gaskets, using the NZ ones and no gasket 'goo'. But a smear around the liner shims is a good precaution, when setting the 0.006" projection. Don't even think about the 0.015" projection given in the handbook, this will almost certainly crack the crankcase! Also, only aim for a max torque setting on the head nuts of no more that 35lbs/ft. Any more will cause similar failure!

Hope this helps,

David

[Rodger]

Thanks for the help and advice chaps. All very much appreciated. Watch this space!

Regards

Rodger

[Rodger]

Hi David

Just following up on your previous post. I presume you don't think there's any point in replacing all the cam followers with mechanical ones and appropriate push rods. As there seems to have been a shift towards mechanical ones in later models I wondered if it would be advantageous to switch whilst the engine's stripped down.

Also, could you send me a photo of the page in the handbook showing the 0.006"/0.015" projection you referred to. I just want to be sure I'm looking at the right thing. A page number might suffice unless there are different versions.

Many thanks

Regards

Rodger

[Nick Webster]

Sorry you haven't had a quick reply to your last question.

In the Jowett world hydraulic tappetts have become strangely sought after! If you have a properly working set I would be very tempted to use them. There are advantages, especially with the nice clean oil we use these days. Also, I think the cam shaft profile is different for solid tappets.

Attached is a photo showing checking liner height. Actually, it is stage one and measuring how low the bare liner sits in the block. You can then calculate the copper shims needed to bring the liner up above deck height and measure again of course. Note also the gasket support tube between the liners has to be set correctly too.
Nick

2023-08-18-f.jpg

[David Morris]

Hi Rodger, sorry I hanen't replied before but we have been away on holiday to China. What a fantastic country! They are keen to be the No.1country! Back to Javelins. Firstly, the camshfts for an engine with hydraulic cam followers are materially different to one with mechnical tappets. They have different profiles. So, my advice is to stick with hydraulic cam followers. I am sure JCS will have some used but acceptable push rods. If not, try asking Chris Spencer, he may well have some? My guess is that the push rods became bent due to incorrect valve clearances, or stuck valves. The bent ones shouldn't be straightened, they will bend again.

Hope this helps, All the best, David

[Rodger]

Many thanks Nick and David for all the advice. Extremely helpful as always. I'll get hold of the necessary parts and let you know how I get on. Thanks again.

Regards

Rodger