Recommended engine bores

[rgh0]

Commnets below are what i would think about and consider doing assuming all the measurments have been correctly done by the shop you are using. As a general comment though I would trust the QED advice. Lots of options depending on use and money available to spend but initial comments below are my interpretation of your sitiaution from what you have said

1. Get the block wall thickness surveyed to confirm OK and worth spending money on. If it has been running for years at 84mm and has no cracks then should be ok for a hone to fit new pistons but i would want to confirm this.

2. New pistons and their required clearance will vary from manufacturer to manufacturer. You may be able to find a set and clearance requirements that enables you to hone and fit new nominal 84 mm pistons the QED recommendation appears to meet that need. Dont rely on the orginal Lotus clearances but use what the piston manufacturer recommends. You can get custom psitons made that will be slightly oversize if you need to match the bore diameter after a hone if no standard pistons avaialble to suit if required at a cost but this will be cheaper than new block. It does not surprise me that the size of the nominal 60 thou oversize psitons from Burton and QED are slightly different, I never bore a block until i have the actual psitons I will fit to confirm actual diameter and clearance to determine how much i need to bore.

3. Potentially you could fit sleeves and go back to original 82.5 mm bore and standard pistons. Sleeve OD for a standard bore is normally around 85 mm diameter so you would not need to do much to the block to fit them but would need the ultrasonic thickness survey data to confirm they could be fitted ok.

4. You can fit a speedy sleeve to repair the seal areas on the crank

5. 40 thou undersize on the crank is pushing the limits for a crank but is Ok for normal road use. I dont now much about the quality of bearing available for this size but again for road use you should be able to use whats available OK. The alternative is to build up the crank journals by plasma spray welding and regrind then to standard size which will be cheaper than new crank and again OK for a road engine.

6. Oil burning will also be coming from the valve guides - have you dismantled and measured up the head components to determine what is needed there also as part of the rebuild ? It sounds like you engine has had a lot of work over the years, maybe 2 or 3 major rebuilds and the head could be in any state also.

cheers
Rohan

cheers
Rohan

[carlt]

have the block and head pressure tested for leaks/cracks
if you say there are no wear ridges on your bores you could glaze bust them and try a new set of piston rings for your pistons
-gap test them fitted down the bore

get the head overhauled

could be not too expensive

all this assuming your not going racing !

[robertverhey]

Time to consider cylinder liners and some new standard pistons and rings?

[marode]

I have bought a used .010/.010 crank. This will be crack tested prior to use.
I could possibly reuse my pistons, if I would find a set of new rings to fit. The ring gaps are 1.2mm at the oil control ring and 0.45mm at the compression ring. Way too much. Piston to bore clearance is ok, .060 pistons (ASSO-W 339) measure 93.93mm, bores are 84.03. So 0.10mm clearance, that should be ok. Don?t ask me why the ring gaps are so big, maybe someone before used a wrong piston ring set.
Piston ring to piston groove clearances: oil control ring is >.002'' , compression ring (1st) is between .004'' and .006'' (could not measure more accurate with my feeler gauge). Compression ring (2nd) is between .002'' and .004''. Elan manual figures are oil control .0018'' to .0038'', compression ring .0016 to .0036. I would reuse the pistons and bores, if I would find someone to check the block for remaining thickness and cracks.

I could possibly go for liners and standard pistons. Seems like the safest option. I have not measured the remaining wall thickness of the block yet. The block is quite rusty inside, someone must have driven the car with pure water for a while.

The head has been pressure tested and is leakproof. But there is a lot of corrosion at the waterways which will be repaired by welding. New valve seats, guides, valves, springs at spring platforms will be fitted. All in all about 1.500 GBP to get the head done.

Thanks for your thouhts, I?ll keep you informed about the process. Weather it getting better here, I have to hurry a bit not to miss the season...