JUP and Targa Tasmania

[paul byrne]

Hello all,
Just to let you know that my Jup, with Veronica and me, has just completed the 2000k of Targa Tasmania and 30 closed road stages with no problems, apart from heavy oil cosumption. We were in the Tour section and thus did not have to try to achieve base times, but we had to move along to avoid being pulled out if the competition field caught us. We found we could fairly easily keep up the pace and teamed up with a 356 porsche, Targa preparedVW, and MGB.
Had newly rebuilt (by me) motor which performed well although I didn't have time to fit Scott's webers and had to run on Javelin Zeniths- out of puff at 4000 with the 2mm bigger bore. I used Mike's technical notes carefully in the rebuild and there are NO oil leaks. I used 1mm Al plate and O rings for the rear timing cover with apparently perfect results, Oil pressure is a steady 75psi.
We used pistons from JP in South Australia (74.5mm and little dish in crown) and I can't understand the heavy oil consumption--over 1 litre per day under fast touring plus Targa stages. An suggestions welcome.
Clutch slipped immediately on start up and was replaced although new. Slipped again 24 hrs before scrutineering! Eventually traced to the flywheel being dished slightly- perhaps after lightening machining from the engine side released cast-in tension? Hurried replacment with an old but flat flywheel cured the issue at expense of loss of carefully balanced engine.

Cooling was marginal and I would like to refit standard fan to augment electric one. Does anyone know where I might pick one up?
It's the 5/8 in tapered shaft.

[Forumadmin]

Well done. Next year how about trying to compete? Wouldn't mind having a go myself!

[Andrew Henshall]

Congratulations Paul & Veronica - a splendid result! Good to hear that your engine rebuild held together despite a few teething troubles.

The excessive oil consumption needs diagnosis to determine if it is coming up the bores past the rings, or down the valve guides, or through the balance pipe due to a leak at the pesky o-ring, or due to some other PCV valve issue.

Are you running the standard oil level? Did you do anything to stop oil surge in cornering and braking? Did the liners distort excessively when overbored 2 mm? Did you replace the felt filters in the covers? Are you using a suitable grade oil?

Sorry, can't help you with a standard Jupiter fan.

Cheers,

Andrew

[paul byrne]

Thanks Andrew,
I ran HPR 40 during the event and will use HPR 30 over winter. Balance pipe seal tested ok and I was very careful during assembly. Also there is no smoke at idle when vacuum would be strongest. At 2mm overbore there is still a lot of meat in the liners so I doubt they are distorting. The Padman engine that came out has 76mm bores (I think) and was fine.
Valves are new of course. Misubushi and Mazda! and original guides were bored to suit. Oil is turning black quickly and there could be quite a bit of raw fuel going into the engine, and hence the sump, from the tired Zeniths, although I have fited a fuel pressure regulator set to 2 lb/sq in.
I suspect the piston/ ring/ bore combination but have no real evidence. Pressure in cylinders is even at about 115lb/sq in. When the engine was first started blue smoke was prominent at all speeds , but this declined to invisibility after one day of Targa. Unfortunately oil consumption did not follow suit!
I'll keep looking for the problem and meanwhile I'll fit the Weber ICT34s that Scott kindly supplied and then perhaps it will develop some useful power above 4000 RPM!
I'm very happy with the oil tightness and I can thoroughly recommend the RTC aluminium sheet/o' ring gasket replacement.

[Mike Allfrey]

Dear Paul,

Well done indeed! I tried to send some clutch information to you via E-mail the day you rang. The message was 'Server Not Known'. Has your E-mail address changed?

Based on my experience with the Zeniths, oil became black very quickly. It improved a bit when I set the fuel pressure to minimum pressure. Now I have the Solex carburettors fitted the situation has improved somewhat, but the oil darkening is still there. I never had an oil consumption problem though. It did take the piston rings a long time to bed in properly.

I have had a balance pipe 'O' ring cut through on assembly, pass the test and then cause a heap of smoke. Did the vacuum test and again it held for more than half an hour.

Re the clutch: Jupiter uses light blue springs. Morris Minor of similar period, uses blue springs. I have tried to find a Borg and Beck spring chart on the Internet, but was not successful.

It seems you have found a logical cause for your problem.

Regards,

Mike Allfrey.