Crazy About Mini's
Posted 29 March 2019 - 09:46 AM
It does look to have damaged the thread on some of those bolts - helicoils may be required.
The domed nut is the oil pressure relief valve cover - at the other end of that spring is the bit that comes under great debate - ball or cup!
The two holes near the core plugs are for the engine steady bracket.
Up Into Fourth
Posted 31 March 2019 - 06:32 PM
It does look to have damaged the thread on some of those bolts - helicoils may be required.
The domed nut is the oil pressure relief valve cover - at the other end of that spring is the bit that comes under great debate - ball or cup!
The two holes near the core plugs are for the engine steady bracket.
No ball and no cup, maybe it's still in there?
Up Into Fourth
Posted 31 March 2019 - 06:35 PM
Well I finally managed to get the pistons out:
Lined up left to right, chamber 1,2 3, and 4
Worst one is No 1 but I knew that would be the case as there had been some coolant left sitting in the bore for a long time.
Then they get progressively better from 3 to 4.
None of the bores are scored or marked really.
Up Into Fourth
Posted 31 March 2019 - 06:35 PM
Journals look good:
One Carb Or Two?
Posted 31 March 2019 - 09:11 PM
Did you mark the conrods ? so you know which one came from where
The journals look ok but get the carnk checked out
Up Into Fourth
Posted 31 March 2019 - 09:38 PM
Aha yes, I scratched on I, II, III and IV with a scriber but need something that won’t polish off.Did you mark the conrods ? so you know which one came from where
The journals look ok but get the carnk checked out
Up Into Fourth
Posted 01 April 2019 - 06:30 PM
It does look to have damaged the thread on some of those bolts - helicoils may be required.
The domed nut is the oil pressure relief valve cover - at the other end of that spring is the bit that comes under great debate - ball or cup!
The two holes near the core plugs are for the engine steady bracket.
GraemeC - what kid of bracket and what size bolts, these obviously weren't used in the Metro that it came from?
Crazy About Mini's
Up Into Fourth
Posted 01 April 2019 - 07:30 PM
For those of you who have advised before please don't think I am going around the bush again I just want a final confirmation before I order the pistons that I need.
I took the engine, head etc to the machine shop today for their assessment on what re-bore to go for.
The bores measured 2.782 which was said to be about 2 thou wear so a +20 thou bore was recommended.
Using a rather large old Piston Manual the machinist tried to identify the Pistons that were removed, they had 20142 on the inside, having no luck he measured the compression height and found them to be a close match to 21253's.
The machinist suggested getting some advice on what pistons to get as that was not his area of expertise and told me to go and speak to our local classic car restoration garage (Very reputable reputation).
My local classic car specialist said they use the Minispares Evolution Low Drag Pistons or the P21253's. I said that I had been told that I needed a CR of 9.75:1 and would not be able to achieve that with these pistons and said I had been advised to get 10cc Omegas. The response was that, with todays fuel, a CR of 10:1 or even slightly higher would be fine? They also said to flush the pistons with the deck?
Piston Choice - Confirmation Needed
So to be sure I get the correct pistons and get the correct machining done, can anyone advise on the pistons and CR.
MG Metro Cam, MG Metro Cylinder Head (21.4cc chambers), standard inlet 35.6mm and exhaust valve 29.2mm, standard MG Metro Rockers. I will have a Stage One Kit fitted.
Using this calculator for a 1275 +20, standard gasket, 10cc dish, 0.010 Deck Height, 21.4cc Chamber, I get 9.93:1 CR, this would mean sticking with the Omega 10cc Dished Pistons. If I were to use the P21253s from Minispares I'd have a CR of 10.45:1 which would be too high?
Based on my intended setup:
1. Please confirm the correct CR
2. Please advise on Pistons and supplier
Both ACDodd and Kieth Calver have said get the Omega 10cc Dish Pistons, AC Dodd opted for 0.016 Piston Deck Height and Keith has said set them 0.010 down the block to get a better burn?
If I opt for a new Cam will using either of these Cams make a difference to the CR required?
(a) Kent266 Cam
(b) Evolution 001 Cam
Thanks again for the help
Edited by JonnyAlpha, 01 April 2019 - 08:44 PM.
Up Into Fourth
Posted 05 April 2019 - 07:16 AM
Up Into Fourth
Posted 05 April 2019 - 07:31 AM
Up Into Fourth
Posted 05 April 2019 - 10:45 AM
Aim for a compression ratio of 9.75:1 with either of those cams. Chamber the head to suit. 0.010" deck height is fine as long as the head is chambered to suit.
Ac
Thanks AC, and for the MG Metro Cam would 9.75:1 be OK?
Up Into Fourth
Posted 05 April 2019 - 11:28 AM
Aim for a compression ratio of 9.75:1 with either of those cams. Chamber the head to suit. 0.010" deck height is fine as long as the head is chambered to suit.
Ac
Just check the calculator again. Using the P21253 pistons with 8cc dish increasing the the chamber to 24.1 gives 9.76:1 and with the 10cc Omega's increasing the chamber to 22.1.
So thats adding 3cc or 0.4cc to each chamber depending on which pistons I choose.
Up Into Fourth
Posted 05 April 2019 - 12:25 PM
Up Into Fourth
Posted 11 April 2019 - 08:31 AM
Can someone point something out here.
Where the original pistons in the MG Metro 8cc, e.g the ones in this engine, seem to be equivalent to 21253's (I could measure the cc in these ones I guess). If so does that mean the original engine ran at a higher CR than we are aiming for with this refurb at 9.75:1?
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