'New' old Javelin

[Keith Andrews]

Best way to advoid Valve recession on older carsis to make sure the carb is jetted right and butterfly bushes dont leak, and no inlet manifold leaks.
Run lean, runs hot with very high exhaust temps...burns valves, recession, pings, melts pistons...etc etc
Get this right and and there is no need to screw up the intended cam profile, reducing economy and power and running a noisy engine.
Keeping valves in contact longer is a concept long disproved.
If one insists to have higher contact, do it right , re profile the cam, dont 'patch' to compensate.

[David Morris]

Hi Tim and Ben,

On your question about additives, I play safe and add the necessary measure of 'Superclean Zero Lead 2005' made by Morris Lubricants to tankfulls of normal unleaded. It adds about 6% to the cost of the fuel but gives me peace of mind.

I suppose that if the normal tappet rattle started to get less, then this would be indicative of vave recession. So far, ours just seems to be the same as usual!

You will notice my choice of additive supplier. They claim that their product met ( by 8 times ) the MIRA tests, but I suspect that having the same name as mine had more to do with my choice! Just an old softie really!

All the best,

David

[Tim Neville]

It's wonderful how experts can differ (or appear to differ!)
All comments and sugestions are most welcome. At our early stage I must say that a good additive seems the best bet, to begin with anyway.
Ben and I have just spent an hour or two checking all the electrics on our Javelin and most things seem to be working. At his young age Ben was enthralled at the sight of 'trafficators'! Only the clock appears not to be working. Anyone know a clock expert?? ( considering all the work to be done I don't rate the clock as urgent!!!).

[Tim Neville]

Hi there, Ben here.

yes, the trafficators where an interesting sight! Quick question, our Javelin is a 1950 De luxe model, as such it has the wooden de luxe dash, did the layouts change i.e. positions of trafficator switch, heater switch and what not. As all the photo's i have seen of the De Luxe dash have the wooden dash yes, but switches in various different positions, with the trafficator switch on top of the dash etc. Was this just a later alteration?

[Robin Fairservice]

I also have a 1950 De Luxe Javelin, number 10010, which is left hand drive and shipped from England to Canada on August 21, 1950. It is very close to yours. It alsohas a wooden dashboard and the trafficator and knobs are all in the same place as in the Owner's Instruction manual.

[Keith Andrews]

There was a lot of hype and build up when lead was removed from the petrol...just like there was to the yr 2k bug in computers.
The petrols did not just have the lead removed, they where re forumated with aromatic hydrocarbons.
Sure the oil companies protected their Ass&^s..by telling use to use additives etc.
Now the yrs have rolled over, older engines now being rebuilt, and valve resection is being measured in machine shops.
The result is sure there is marginal valve resessition on engines without hardened valve seats...but the amount is only very slightly more than if lead was used...not enough to warrant any concern or to resault in a situation a rebuild would be required due to resession.
Even with additives there is still marginal ression over leaded.
Now throw in to the equation that our classics are not high milage cars (10,000 plus miles per yr) are additives realy needed?

opening tappets resaults in a cam with and artifically lower duration, in particular opening the inlet vave later and closing earlier. This has the valve opening too Far after BDC and to soon before tdc...not allowing a full charge of mixture...this resaults in under powering (noticable on hills)..it also creates a higher exhaust valve temp, regardless of how long the valve is in contact.
Depending on the flow charactoristics of the heads, to get around this problem when opening tappets, the cam lift canbe increased.
Changing things resaults in a chain reaction thru the design of the engine, something boy races dont understand...
Now a higher lift is on the cam, the cam ramps and the springs will now have to also be changed, along with dizzy curve and carb jetting.
Sure the pool fuels where different close to kero with a octane rated(based on modern method of measurements) around 6.2 to 7.4 compared to about 91 for modern fuels...this is not important unless one wants to redesign the engine with higher dynamic compession ratios (cylinder pressure) opening the tappets in effect lowers the dynamic comprssion ratio creating and even worse situation.

Quote from Harry R Ricardo, F,R,S. an exhaust valve can get rid of the bulk of its heat only through the valve seating.

Increasing tappet clearance by 3/1000 with give a total of 1 to 2% increase in contact time with insignificant resaults