I’ve been on and off this forum for many years, having bought a basket case S3 FHC in about 2008 or so. Jobs, family and building a house have been getting in the way, but recently I got access to a garage relatively near my house for the first time in many years so am trying to re-energize the project again.
There are some great engine build threads on this forum and so many knowledgeable people - it is really inspirational. I’m hoping to use this thread to document my engine re-re-build, inspired by some of Rohan’s and Naury’s posts. Hopefully it may be use to others in a similar position.
I had originally rebuilt the engine to approximately Sprint spec (Q360 cams, big valve, head done by Paul Exon) but my uncle died earlier in the year and left me a bit of money, and he was a car nut, so it felt like he’d probably appreciate me spending it on pushing the project along, and building a more exciting engine, rather than something dull like the mortgage.
This was what the engine bay was like when I got it. I was worried (and still am) that I’d bitten off more than I could chew. When inspecting the car originally it was in some woodland and I couldn’t get under it to see well.
Skip forward a couple of years, and I had a rolling chassis. I hadn’t ever had the engine running so at this point, due to budget constraints, I decided to rebuild the front cover, replace the gaskets and seals and fire it up, to see what the oil pressure was like, and do a compression test.
This wasn’t a total disaster but it was smoking a bit and oil pressure was at the low end of acceptable, so I bit the bullet and sent the head to Paul Exon.
Another few years later the head was back from Exon after a complete refresh with new guides, seats, follower sleeves, valves, followers, studs and Q360 cams and then mated with the bottom end which had new bearings and rings. Cylinders were honed as they were ok but at the larger end of the range. Pistons were ok size-wise but a non-matched set, and I didn’t check balance.
This is effectively the starting point for the re-re-build. Since the head is now more or less as-new I will probably source another for this phase and keep this one as a spare/sell it (it has been built up but never run.)
great story… I would think the most time and possibly money is spent on the body for such a project, even if doing a lot oneself, so that is where your uncle may allow for a decisive move to keep the ball rolling.
I, too, am storing a freshly rebuilt, 40 years ago, head. I knew it was going in storage at the time so every
valve got greased up from the seat to the tip of the stem. No springs or cam followers are installed. I didn’t
want any corrosion on any mating surfaces. Still looks good today,
Thanks Mike. I got as far as getting some quotes a few years back, but I want to do a few more bits and pieces (for example, check the exhaust silencer doesn’t need a bigger tunnel) before biting the bullet. I think I’m leaning towards SMS as they seem to get good feedback but aren’t as expensive as someone like Option 1.
I’ve done most of the structural stuff and a bit of the tissuing but don’t have the skill or patience to do the epoxy primer, flatting etc. Getting the paint off was a big undertaking and not very enjoyable!
After stripping the block down it became apparent that it had been sleeved at some point. As mentioned above, the bores were at the bigger end of the range and since I plan to use the longer throw 77.6mm crank in this engine, and it will need new pistons anyway, a rebore or resleeve+bore was on the cards.
The block is a LB graded one, which according to the Miles Wilkins book:
‘min wall thickness 0.100" …
LB to be used for 1558cc only, unsuitable for 83.5mm rebore’
There has been discussion on here that with careful measurement and offset boring it might be possible to get away with 83.5mm in a ‘LB’ block. To take some measurements I bought a secondhand ultrasonic tester on ebay and did my best to take a set of ‘worst case’ readings. This was a bit tricky, probably caused by the liner/block interface, but after a bit of trial and error it looked like the liners are fairly well centered, and worst case thickness was 3.4mm, on the existing bore size of a touch over 82.5mm. Allowing for 0.5mm a side (targeting 83.5mm) that leaves 2.9mm, so a shade over the 0.1" recommended.
At this point I test-fitted the new long stoke crank, rods and old pistons using an old set of bearings and used a Dremel to open a couple of areas to give 0.060" clearance. You can see a couple of areas in the photo. There was also an area on the back of the engine mount lugs. It was a bit fiddly getting the feeler gauge in but I found that tying a bit of wire through the loop at the end enabled it to be dangled in and moved to the right spots.
Annoyingly I realised later that I had forgotten to check the jackshaft, so will need to do this later on. I have cut the jackshaft down to just two bearings, and faced off the end in the lathe to clean it up. It might be necessary to grind off some of the old push rod cam profiles.
That is a good point - I’ve been thinking the same thing. Doing the bodywork is quite unpleasant, and the previous time I tried spraying a car diy-style the finish wasn’t great… A lot of orange peel.
orange peel can be sanded flat and polished (actually quite straightforward with “direct gloss” paints, i.e. not requiring clear coat on top), this is not the worst part, but the preparation of the bodywork to get a good result can be very demanding, depending what you start from … and the beautiful paint not lasting very long if not done properly…
Regarding painting. SMS partner Paul Mason split from the rest of the SMS team and set up on his own as Paul Mason Autospray I believe working at or alongside Spyder Engineering. Paul was the sprayer at SMS who they’ve got now I don’t know, but their reputation was built on his work.
Most Lotus stamped “LB” blocks or standard non lotus 120 E and other blocks will take 83.5 mm bores with offset boring to achieve the best wall thicknesses. Sleeved blocks get a little trickier as you need to consider both the sleeve thickness and the total wall thickness and try to pick up both with the ultrasonic measurement which is not easy with the general type measurement devices.
A lot of blocks were sleeved by Ford from new to recover casting or machining problems. Hard to tell whats Ford original or if its been sleeved later now in many cases.
From your measurements t sounds like your block is Ok for 83.5 for road use for which 2.5mm / 100 thou is generally OK provided the thinnest areas are small and not on the thrust face. I try to have over 3mm / 120 thou for a race engine.
There is a big choice of rod and piston combinations with a long stroke 1600 crank in a 1500 short block but lighter is always better
Finally found some time to start measuring up. Checked the micrometer against setting gauge and measured new JE pistons from Dave Bean, 1/2" up from base of skirt. They were very consistent at 3.2840-3.2841", and within 1 gram.
The bores should be 3.287" (83.49mm), so 0.030" clearance per the piston data sheet. Set the micrometer to size, and then zero’d the bore gauge at 0.00mm. It is quite confusing working with a mix of metric and imperial tools. The bore gauge also turns anticlockwise as the bore increases, to add to the fun.
In the thrust direction the measurements were coming out at between +0.01 and +0.02mm (~= 0.0008") over spec, which I am a little surprised by. But I don’t know if Gosnays machined the bores with a plate clamped on to simulate the head. I will ask them. It also isn’t the greatest bore gauge, although I tried a few tests against the micrometer, which I trust, and it behaved as expected.
While I was at it I measured the new 77.6mm Farndon EN19 crankshaft journals. These were also very consistent at 2.1256-2.1257" (across 20 measurements at various orientations) and 1.9373-1.9377" (across 16 measurements.) This should be good to 8000rpm, although I am aiming for 7500rpm, based on crack tested and balanced 125E rods with new ARP bolts. The plan is to use a single dowel to the flywheel, but I’m interested to hear about peoples experience on this as it sounds like often no dowel is used.
The crank assy was balanced by Gosnays - crank, flywheel, clutch diaphragm, pulley and bolts, in total 25.5kg. This is a heavy duty road/competition Helix unit and lightened steel flywheel. I was hoping to get a lighter flywheel but couldn’t find one to suit the road clutch.
I took the opportunity to chase out all the threads in the block - I was hoping to fit the crank and check clearance to the block but found I didn’t have the right bearings so will have to order them. The 701m block is 35.9kg with the jackshaft bearings, coreplugs, and (square) caps and bolts.
I would not worry about the nominal piston clearance of 0.003 inch / 0.076 mm giving a 83.49 mm bore versus what appears to be an actual bore of 83.50 mm. If anything a little extra clearance is good in a modified engine intended to spend significant time at full power.
cheers
Rohan
corrected to get the decimal points in the right place
Yes you start talking in mixed units you confuse me. I am just a simple fellow and getting the decimal point a zero out is the least of my many problems
