Lotus Elan

Mismatched Camshafts

PostPost by: type26owner » Fri Oct 01, 2004 6:15 pm

Just pulled the new buckets out of the wrapper I got from DaveBean and put two together touching face to face. There's no tipping and they are not convex or concave so they have to be flat. Not so flat that they will wring though. Gray coating comes off on the fingers so I'm guessing they are dicronited. The only surface which is not coated is the OD and it's been ground.
-Keith
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PostPost by: mike+2s130 » Fri Oct 01, 2004 9:14 pm

the early cast maufolds were inaducate for the engine and should be replaces with a fabricated one .this was common on all elans and plus 2s.getting the correct exhaust is paramount to performance of the engine .as for the cams.they came as follows.b type standard no groove,0.375 in.totallift c type s/e 1963 on wards,one groove 0.3498 in.total lift . d type sprint +2s130 two grooves 0.3600 in.total lift this was also used in super s/e. e type plain 0.3659 in.total lift. use in lotus cortina 1963 on. and now for pistons .originally all pistons were graded for each block.because of rebores and no new blocks availiable grading became obsolite.lotus pistons are c type with small cut outs.all powrmax pistons have large cut outs like the original a type.the are made of as follows, solid skirt,tin plated aluminium alloy,with fully floating machined seamless steel tube gudgeon pins .i hope this help kind regards
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PostPost by: type26owner » Sat Oct 02, 2004 3:12 pm

Hi mike+2s130,
Yes it helps, thanks for the info. My goal for my Elan is to keep it going on the road as a daily driver with a minimum of breakdowns. Have resisted pumping up the performance through the years to achieve this end. IIRC this blown head gasket is the second time I've had the head off. About 50k miles ago when my airbox would not seal up airtight I sucked something magnetic into #4 cylinder that bent the valves.

Greatly encouraged to find there is absolutely no ridge at the top of the cylinders after 100k miles. Can still see some of the cross-hatched honing scratches. Synthetic oil must have been invented for the twincam. :D
Best Regards,
-Keith
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PostPost by: type26owner » Thu Oct 07, 2004 2:00 pm

Had a chance to look at the interface fit of the stock cast iron exhaust manifold and the head. The fit and finish from the factory is horrendously bad. 3 of the 4 ports on the manifold were shifted off to one side by about 1/8" and all were undersized by at least 1/8". Could clearly see the interface by the soot pattern on the manifold flange face. Was easily able to grind away the material to smooth the flow of the escaping gas with a die grinder and stone.

The head required a little adjustment too. Couple of tall casting lines got ground off inside the ports and two of the ports had bumps to remove to make them round at the flange face. That's the end of my performance mods.
-Keith
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PostPost by: type26owner » Wed Nov 24, 2004 3:52 pm

New intake cam is actually quiet even though both ramp slopes appear much steeper and it opens and closes the bucket more abruptly. Pulls about the same at WOT so no blistering gain there. Listened to the clatter of the flattened top on lobe #2 of the original cam for 100k miles and now have to get used to a quieter engine.

Only errant noise is a new buzzing type noise on overrun above 3k rpms. It's not the gearbox cause I can't dampen it away by holding onto the shifter knob. Suspect it's the flywheel coverplate that is resonanting because I just modified it again. I cut it in three pieces wayback and now had to trim the offset center out of it to clear the aluminum bracket that holds the lipseal on the rear of the crankshaft. I'll have to add some bracing cause it now is buzzing away. :(
-Keith
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