2 door VAE 306H

[kevin s]

we'll keep our eye out for one, at the very least we should be able to use the 1098 one to keep things sealed while we are storing it etc.

The backplate I am using is a 1275 marina one which has been modified to take a minor starter position and MX5 gearbox bolt pattern I didn't even realise the 1275 ones were different because it fits straight on the 1098 but now I look I realise the oil pump hole is larger as well so I will need to get a 1275 one of those.

The other thing will be the flywheel, the current one is a 1098 which has been drilled to take mx5 1.6 clutch, I believe the PCD of the crank holes is the same so hopefully I can just mount it on the rotary table and drill the 4 additional holes.

[kevin s]

Last of the parts arrived today.

rps20210428_201643 (002).jpg (101.56 KiB) Viewed 6486 times

while I have been waiting I made a gearbox mount for the mx5 gearbox to mount to a minor crossmember.

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Also looked at the piston rings, none seem to be marked for the top surface (I'll have a closer look with my reading glasses tomorrow), the top one seems flat so that should be fine, the second two are stepped, from what I can gather this is a napier type and the step goes to the bottom, amazingly for this day and age they are made in the USA not china so hopefully decent quality.

rps20210428_201751 (002).jpg (80.53 KiB) Viewed 6486 times

I've now cleaned up most of the old parts we will be using getting rid of all the fragmented rubber from the shredded timing wheel damper ring, hopefully we will start putting it together later this week, mind you I also have block paving to lay and 2 windows to fit this weekend too.

[philthehill]

In most piston ring applications the stepped piston ring is fitted to the top ring groove so as as to allow for any wear ridge.
The step or larger diameter of the ring is at the bottom of the piston ring groove.
Piston rings should be marked 'top' or 'T' as the piston ring outer face is normally not square to the top and bottom faces of the ring. The ring usually tapers to the top of the ring and so acts as a scraper to remove oil from the cylinder walls as the ring travels down the bore.
The taper of the ring is not usually discernible and that is why the rings are marked to indicate top. Se schematic below.

Piston ring schematic 3.jpg (383.24 KiB) Viewed 6483 times

[kevin s]

I've come across the stepped ones for the top on a worn bore before, but these are in the packet for for the second and third grooves, one is as per your diagram, 4 is a normal oil control type ring.

rps20210428_211343.jpg (114.28 KiB) Viewed 6479 times

needs a bit more investigation I think.

[philthehill]

Have had a look on the web re Hastings piston rings and very interesting.
https://www.hastingspistonrings.com/piston-rings/

[kevin s]

thanks for the link,

Got the glasses and a bright light out, they do indeed have a dot on the top and they go with the step facing down, first time I have ever seen ones like this, with a name like Napier they might be quite an old idea though....

From the hastings site

"Wiper Napier
This reverse twist ring along with a taper-machined ring face duplicates the OD bottom side scraping edge of a positive twist torsional ring. Reverse twist promotes side sealing that prevents oil from being forced under and behind the ring resulting in better oil economy—a very common second ring profile in modern gas engines."

It will be interesting to see how they work.

[kevin s]

Checked a couple of the rings today, the gaps seem a bit on tbe big side (0.45 mm / 18 thou) but I can't see it being a problem, many engines run similar gaps and I would rather they were a bit on the wide side rather than too tight. I only checked a couple of the top rings, I'll have a look at some of the others later.

[kevin s]

Checked all the rings today, all have between .40 and .45 mm also the same in all the bores, so they can all go on the pistons next, then I need to balance the rods and they can go on the pistons.

It will be a while till we really get stuck into it though, I have loads of building work to do and Andrew has uni exams in a couple of weeks.

[kevin s]

Slowly going through a trial build of the engine, fitting the cam an oil pump, both 1275 items highlighted some issues, firstly the pump needs a spacer which is a part which was widely available Phil pointed me towards one on ebay which is now on it's way. Secondly the the oil pump is one of the modern steel backed 2 bolt ones, this requires an additional hole to be tapped and drilled in the block.

Once the Tap arrived I drilled and tapped the hole using the oil oump as a guide to keep it square.

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The thread is 3/8 deep which is clear of the water jacket, in the photo the bolt is bottomed out, with the 6mm spacer it should be perfect.

Next up will be to finish polishing the crank for a test fit and balance the con rods.

[kevin s]

Lightly Polished up the crank with some 1500 wet and dry.

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rps20210506_130413.jpg (132.13 KiB) Viewed 6321 times

Came up fine, all I really did was remove the surface discolouration from years of storage.4

Put it in the block with new bearings and plastigauge, clearances were a bit on the big side though, 3 thou for the centre and 2 for the end ones, the plastgauge did seem to sqeeze into the centre oil channel of the bearing though so I may try the micrometer to see what that gives (I have done it once but I only really checked they were round)

[kevin s]

Pump spacer plate arrived, fitted with 2 gaskets, and the cover fits ok.

rps20210506_203742.jpg (130.06 KiB) Viewed 6303 times

Also a couple of pictures of the crank, taken at 90 degrees, both identical so it's round but according to the scale they equate to 3 thou.

When we stripped the engine it had what looked like new shells, wonder if someone has had the crank lightly ground in the past.

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rps20210506_203839.jpg (131.41 KiB) Viewed 6303 times

[kevin s]

Contemplating a re-ground crank and possibly a strap for the centre main to help with durability as well.

[kevin s]

Just been out and measured the journals, used a micrometer checked with the 50mm gauge block first, the centre main comes out at 44.45mm whichever direction you measure it in, the front and rear somewhere between 44.45 and 44.46, this is I believe virtually unworn, so it looks like we are good to go, bearings are new, and a tight fit in the caps and block, I don't have an internal micrometer but I do have a set of mitutoyo callipers so I have measured the journals with this which come out exactly the same, then measuring the internal diameter of the bearings I also get 44.46 mm so I am confident the parts are OK but the plastigauge readings are the issue.

[kevin s]

Small steps, today I balanced the con rods, used a fixture to hold each end, one on the scales, one on the bench.

rps20210510_205215.jpg (212.76 KiB) Viewed 6223 times

Got them all to 721g with a equal big end mass.

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Used a flapwheel to carefully remove the metal.

rps20210510_205114.jpg (138.29 KiB) Viewed 6223 times

Next step is to fit a piston and check they don't protrude too far above the skimmed block for the gasket to accomodate.

[kevin s]

Been doing some measurements and calcs today, fitted a piston minus it's rings and measured where it sits relative to the skimmed block face, firstly found tdc with the dial gauge.

rps20210511_221203.jpg (136.72 KiB) Viewed 6201 times

Then used the depth gauge to work out where it sat.

rps20210511_221229.jpg (121.95 KiB) Viewed 6201 times

Turns out the piston is a tiny amount (0.04mm) or about 1.8 thou. Below the block.

Crunched this with the rest of the data and it seems with the 60 thou skimmed head we have we will have a static CR of around 9.45, with some work in the chamber to reduce the valve shrouding hopefully we will end up with around 9 which should be fine, still need to measure the piston and head to be sure, need to find a bit of perspex first though.

CR calcs.JPG (90.97 KiB) Viewed 6200 times

[kevin s]

cut up an old CD case today and got a syringe and the vaseline out, result is the piston bowl is 7cc and the machined head is currently 23cc.

Crunching the numbers through the spreadsheet gives a compression ratio of around 9.2, with a bit of head work to the combustion chamber we will probably end up not far off the original 8.5:1, I would have liked it a bit higher but I think improving the flow around the valves (I'll concentrate on the inlet) will give a better result than the increase in CR.

Also checked the valve clearance, the cam quotes a valve lift of 8.8mm and the combustion chamber is 10mm deep so we should be fine there. (as it's a 1275 cam that is probably quoted on 1.27 rockers rather than the standard 1.23 ones we are using so in reality its a bit lower than 8.8mm.)

[kevin s]

Spent my lunch hour today having a go at the combustion chamber with the die grinder, this is the result

rps20210513_181209.jpg (44.29 KiB) Viewed 6144 times

Comparred with a standard one.

rps20210513_181242.jpg (178.95 KiB) Viewed 6144 times

Probably twice the clearance around the valve and measuring it I have only increased the volume by about 1.5 cc which gives a compression ratio of 9:1 which is a good number with a relatively mild cam.

Also had a go at cleaning up around the valve guide in the exhaust side, aim being to get a roughly constant port x section area, not easy with such tiny valves! I'll do the same on the inlet when I have got round to making a punch to change the guides.

[Sleeper]

I think it must be the photos , but , apart from the sharpness of the " nose " , there seems to be more clearance in the "before" shot...

John ;-)

[kevin s]

This probably shows it more clearly, both valves are roughly at max lift, you can see the one on the left has far more space around the valve, unfortunately there is nothing much you can do to the side because of the head gasket .(the black line drawn on the face)

rps20210514_111700.jpg (103.95 KiB) Viewed 6112 times

[kevin s]

Been away for a week, but got an hour on the minor today.

I think aside from checking the cam endfloat and cam timing everything else is ready to assemble on the bottom end, So I moved onto the head.

First thing i needed to do was fit the new inlet valve guides. As I didn't have time to go round my parents and make a punch on the lathe I knocked the old ones out with a punch about a mm smaller than the outside diameter. To get the new ones in I made a punch out of an old valve guide and the stem off on old valve

rps20210523_153224.jpg (108.33 KiB) Viewed 6383 times

Worked a treat and they knocked in with no problems.

Next up was having a go at the ports, given we are keeping the standard valve sizes there is no point going mad, so based on vizards book the plan is to clean them up around the guide and just behind it where the port is at it's narrowest and ìncrease the small radius behind the valve seat.

With the new guides fitted they looked like this.

rps20210523_153012.jpg (75.72 KiB) Viewed 6383 times

So after some work with the die grinder I had this.

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rps20210523_152939.jpg (149.29 KiB) Viewed 6383 times

Could still do with a bit of refining, but already it's looking far less restrictive than it did to start with, I've roughef out all the exhaust ports and one inlet just need to do the other 3 and also the other 3 combustion chambers.