| Moderated by: Greg Fletcher | ||
| Author | Post | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|
|
SimonD Member
|
I have recently started up my JH for the first time in 23 years. However crud has blocked the oil supply to the head. All is well except the front journal of the exhaust cam seized. I have replaced the cam housing and smoothed of the existing cam which now turns sweetly by hand. Thoughts on whether I should put it back in or replace it would be much appreciated. Picture attached I hope. Attachment: Cam damage.jpg (Downloaded 132 times) |
|||||||||
|
Esprit2 Member
|
Simon, There's no standard for how badly damaged a journal can be, and still be useable. IMHO, this one shouldn't be used as is. But take it to a machine shop and see if they can restore it welding metal back onto it, then grinding it to the correct diameter. If you go that way, then take the following specs to the shop. These are un-published specs you won't find anywhere else. I got them from a Lotus engineer. Cam Bearing Journal, OD Front, #1 = 49.746 - 49.759 mm (1.9585 - 1.9590 inch) ........ #2 = 49.492 - 49.505 mm (1.9485 - 1.9490 inch) ........ #3 = 49.238 - 49.251 mm (1.9385 - 1.9390 inch) ........ #4 = 48.984 - 48.997 mm (1.9285 - 1.9290 inch) Rear , #5 = 44.412 - 44.425 mm (1.7485 - 1.7490 inch) Cam Carrier Bore, ID Front, #1 = 49.835 - 49.860 mm (1.96201 - 1.96299 inch) ........ #2 = 49.555 - 49.581 mm (1.95098 - 1.95201 inch) ........ #3 = 49.301 - 49.327 mm (1.94098 - 1.94201 inch) ........ #4 = 49.047 - 49.073 mm (1.93098 - 1.93201 inch) Rear , #5 = 44.475 - 44.500 mm (1.75098 - 1.75197 inch) Running Clearance All ......... = 0.0508 - 0.0889 mm (0.00200 - 0.00350 inch) Cam carrier bores are to be straight, and all working surfaces (machined bottom) are to be parallel to the cam bores (ie, no bent/ warped cam carriers are allowed). Side Note: When a cylinder head warps, the whole thing warps like a banana. Simply milling the bottom flat may leave the top side seats for the cam carriers warped. When the cam carrier is bolted to the warped seats on the head, it may be pulled into a matching warp of it's own. That's not acceptable. At the least, getting a leak-free seal between a straight cam carrier and warped head seat will be an exercise in frustration. Good luck, Tim Engel |
|||||||||
|
SimonD Member
|
Tim, Thank you so much for all of that. So much detail. I have opted for a replacement. Simon. |
|||||||||
|
Jensen Healey Super Moderator 
|
The 7’s around the end of the cam indicates it is a 107 profile. Your engine seems to have received an upgrade from stock. Cheers, Kurt |
|||||||||
|
SimonD Member
|
Thanks for that Kurt. I have ordered a 107 cam from Lotus Bits in Nottingham. In the meantime I have taken the engine and gearbox out due to a massive oil leak through the front of the gearbox, which is now with my local gearbox specialist to check it over and replace all seals and gaskets before I put it back in next weekend. |
|||||||||
|
Esprit2 Member
|
Rubber seals and O-rings don't age well in static storage. If it has been 23 years since your car was last used, then plan on most of the seals being toast. Take the opportunity of having the engine out to replace them all, or as many as you can. Don't wait until after the engine is back in the car for them to start leaking, because they probably will. The following is also covered in another current thread, but it's worth repeating. Also see the "Transmission Leaks 4 Speed 13556" thread. The flywheel bolts should have Loctite AV (or 275/ 277). Apply it to the threaded holes in the crank flange (a Q-Tip swab helps), then mount the flywheel and run the bolts in. Torque to spec. If you have a Mk II engine with the rear lip seal, then the housing bolt threads need sealant... not threadlocker. Something like Permatex PST Thread Sealant. Both the flywheel and seal housing bolts use through holes into the oily engine interior. With clean, dry threads, oil can wick through the threads and cause an oil leak inside the bell housing. It's a similar situation with the front seal housing, except the holes 'can' (not always) break into the water jacket, and anti-freeze can wick out past the threads. Use thread sealant, not threadlocker. Regards, Tim Engel Last edited on 02-09-2018 05:37 pm by Esprit2 |
|||||||||