Javelin engine.......sever vibration

[Len]

Having taken too long to rebuild the Javelin engine, I finally thought I had made in March this year when it was installed. After a few teething problems I finally got it running. Elation.
Tweeking the carbs made it run pretty well, though only at tickover and low revs.
On road testing the car I found a vibration/shuddering coming through the whole vehicle which got worse as revs increased.
Thought it was drive train orientated but problem was still there with vehicle at standstill. As no rev counter I estimate the vibration/shuddering is eye blurring at about 2k revs......getting worse. Feels like engine will shake itself to bits.
Have tried the trick of taking out each clutch cover plate bolts in turn and running engine. Did not seem to make any difference.
Have checked valve timing, set ignition timing so many times could do it blindfolded, valve clearance is ok. Has new set of plugs.
Work done on engine:
Club exchange crank
Conrods matched for weight.
New piston rings
Bores honed
New mains and big end shells
New tappets
New valves and New guides
Seats recut and lapped
Combustion chamber capacities matched
New clutch plate
Recon gearbox
New contact points
And various others can't remember

I am flumaxed. Stumped. Mystified.
Has anyone any ideas of where the problem may be? Where I might look? What can I try next?

I live on the borders of North Lincolnshire and Lincolnshire, 6 miles from Brigg......just in case you wondered what this vibration feels like.
If I cant sort it then the car gets put out in the field.

[David Kemp]

Have you started it at night with lights out & looked for electrical arcing?
Sounds very much like an electrical problem to me, faulty leads, cracked coil, faulty distributor cap or faulty plug cap.

[Len]

Thanks David. Good ideas. I will give that a go asap. I did fit a new distributor cap too. Leads and caps all look ok....but you never know.
Cheers

[TedAllen]

-I suspect dizzy cap as well. I came across many cases when working on the road rescue where there was a tracking spark between 2 terminals in the cap. That meant the car was only running on 2 pots. Take out the HT leads one by one with the engine running and see if it improves at any stage. If it does, it means it is now running on 3. New cap will sort it.

[Nick Webster]

Is the fan and water pump mounted correctly? Remember the upright support legs should not be tightened right down, but allow for movement.

Nick

[Forumadmin]

Check the two front engine mountings and the rear one making sure the gearbox extension tube can rotate in the rubber ring. Loosen 4 small bolts and insert washers , if it does not.

The vibration you describe is possibly coming from the flywheel. Was the whole assembly balanced and put back correctly?

Normally a misfiring gets better at fast revs. However it could be a distributor problem with the advance weights not working correctly. Has the dizzie advance curve been checked? This should affect all cylinders equally so should not give a bad vibration. Does the engine seem to have power and rev freely up to 3000 rpm.

But do not rev too much as this vibration may be a major issue. Something may not have been torqued up correctly.

Take out plugs and see if one or two are blacker than the others, thus showing which one is misfiring. If you have a strobe light then you can use that on each cylinder in turn, but this will not show a faulty plug or arcing plug cap.

Check spark at each lead by using a spare plug earthed to head. This may also show that polarity of ignition coil is correct but you can check using the pencil trick.
Check timing of spark is at TDC on all cylinders. Check dwell is 60 degrees or set points to 14 thou,if you do not have meter.

Use about a metre of hosepipe and listen around the carburettor base for any hissing sound. Also around vacuum pipe to oil filler cap. This shows leaking gaskets.
Also use hose to check balance of carbs by putting in same place at top of air inlets. This in absence of proper balancing manometer.

Check idle mixture as per book.

If roughness is throughout rev range then check tappet clearances again and make sure all the valves are travelling up and down correctly. It could be a sticking valve or broken spring.

You could put rear on axle stands and see if vibration changes when you let the clutch out. This will isolate before or after clutch. From what you say it is an engine issue at high revs. You could take off fan belt to check it is not fan assembly.

[Len]

Thank you all for those suggestions. Lots to try.
Have tried running in the dark and see no arcing.
Have done the long, chunky screwdriver trick against the ear and listened everywhere I can reach. Can hear a thudding noise but cant tell where from. Sounds internal though. Difficult when your arm is around the back of the carb to work the throttle linkage.
The vibration builds with revs. It doesnt just appear which makes me think it is mechanical.
No I didnt get the flywheel/crank assembly balanced........am I kicking myself...you bet.
Thanks again. It will take a while to try out and eliminate your suggestions.
Watch this space.
Cheers

[David Morris]

Hi Len,

I totally sympathise with you. You have obviously done so much during the rebuild and are sadly faced with this vibration. Yes, it might be a balancing problem but I doubt this would cause such a severe problem. It's something else... First, let's make sure she is actually running on four? Remove the plug leads in turn and see if removing one makes no difference? Are the banks of cylinders totally out of balance? I recommend the use of a Syncronmeter. ( £35 from Amazon ) It simply can be sat over the air intakes with the bonnet open in turn and will show how much air is being 'sucked' by each side. My engine, on tickover, shows a reading of 7 and this is normally a useful tool for balancing the carbs. In your case it should show if one 'bank' is completely out of balance.

I know you may have already done this, but try just turning the engine over on the handle. Are the compressions reasonably even? Keith's idea of running without the fan belt for a couple of minutes is a good plan too. Finally, invest in a new set of NJK B6HS plugs. I had a spate of problems with Champions and other random makes. Just don't risk anything else than NJKs. There is a set of new 4 on eBay for £5.99!

I hope you soon find the cause! It will be there and obvious when located!

All the best,

David

[Forumadmin]

Oil pressure 75 + when cold?
As David says you must check it is firing on all four. Taking a lead off each cylinder in turn with some well insulated gloves or pliers is the quickest way. Loosen each plug cap first then start the engine. But be extremely careful you do not put your hand near the fan. If you can, take the fan off. If, like me, you have converted the distributor cap to the push on variety then this is easily and safely done. It is preferable to earth the spark so as not to cause tracking in the distributor or rotor arm using a wire stuffed in the connection.

Also check the firing order ! I have seen a Jav run on two cylinders with two leads crossed.

Before you buy a carb synchroniser , buy a decent strobe light with advance adjustment and dwell capability, and a compression tester. They are valuable in doing quick diagnosis.
Always check flywheel runout when assembling. The thudding sound would not be caused by this but would be a big end or more likely misfiring if oil pressure good.