8 replies to this topic

[ferritt]

Can anyone shed some light on something for me, i have read somewhere that all A+ 1275 cylinder heads were of the large valve type (29, 35mm) and the were all unleaded. Is this true?

[pikey7]

no to the unleaded part.

[joakwin]

the valves are 35.6, 33 and 29.4mm

35.6mm dia is 1 13/32, inlet and part number TAM1059
33mm dia is 1 5/16, inlet and should have a part number of TAM1058
29.4mm dia is 1 5/32 exhaust, and should read TAM1061

and the valves will have a tripple groove collector at the top
and the lead ones have a single 1/4 groove

ive heard the rule of thumb is to not mix the leaded valve train parts with the unleaded head parts
because it causes the parts to wear out faster and whatnot

should be 90 on mini's and 84 on metro cylinder heads with the facotry unleaded parts in them

but i have personally seen a 83 metro 1275 with unleaded head form the factory, so it could have been built later in the yr or something

and the 84 up 998 unleaded head valve numbers are
TAM1062 inlet, 27mm and TAM 1770 exhaust, 25.4mm
with the tripple groove

Edited by joakwin, 19 October 2010 - 06:34 PM.

[ferritt]

cheers

[Cooperman]

I discovered an error in the Haynes Manual. It lists the head for the 1990-ish 1275 Mini engine series as 35.6 mm inlet, whereas it was 33.5 mm. It was the MG Metro which had 35.6 mm as standard, which is why the MG head is sought after for the later Mini.The MG Metor had bigger inlets and a much better cam, so that's why it gives a bit more power as standard.

[ado15]

The same also applies to post 1990 Minis. There were two performance specs. Low spec engines had the smaller inlet valves. While fitted with carbs, these were the ones with HIF38's.

There are also low and high performance Spi's, but not sure if these had different valve sizes.

[Cooperman]

It's all a bit odd really. The cars with A+ 1275 engines seem to be either the lower power ones like the Sprite, Mayfair, etc, and the Cooper 1275 with the nominal 63-ish bhp engines which had the HIF44 carb. With regard to heads and cams, however, the Cooper still had 33.5 mm inlet valves unlike the MG Metro which had 35.6 mm inlets. Then there is the issue of camshafts. Some claim that the late Coopers with a carb had the MG Metro cam. Maybe some did, but I've never seen one. A friend who worked in Purchasing at Longbridge, said that at that time they just fitted whatever cam they bhad in stock as their suppliers were sometimes reluctant to supply because they had not been paid for the last batch. That could be true as when I used to deal with Longbridge it took them 180 days (6 months!) to pay my company. I ended up refusing to do any more work for them.
That is why it is so easy to improve the performance of the 1990-1 carb Cooper. Just fit an MG Metro cam and a cleaned up MG Metro head, put the comp ratio up a bit, clean out the inlet manifold, fit a decent twin box RC40 exhaust, flow the carb a bit and, with a bit of careful assembly you can get c.80 bhp at the flywheel. I fully 'blueprinted' such an engine with that spec and got 84 bhp at 5700 rpm.

[ferritt]

thankyou all for the information, i am trying to identify if a 1275 A+engine i have aquired will be unleaded or not without having to take the head off. I have checked the engine number on the guesworks site and it comes back as been from an 1985 metro. Joakwins reply says 1984 onwards so hopefully it should be ok to run on unleaded. The engine number starts 12HC01AA, from the previous replies by cooperman etc i presume it will have the larger 35.6mm intake valves. Will there be other differences between my head and an mg metro one and would anyone have any idea which cam my engine will have in it and if its any good power wise. Trying to get the sort of power cooperman mentions (80bhp ish), but dont want to be buying different heads / cams etc if the ones i have already will be ok. What sort of bhp would my engine make as standard, i have read about all sorts of std power outputs for the 1275 engine and am now confused. Sorry about the rambling post, new to mini engines

[Cooperman]

Don't worry about being confused, ferritt, we all are when it comes to the Mini output from Longbridge from mid-80's onwards. They were in such a state there that even they didn't know the true specifications of their cars!
Unless it has had a different head fitted already, the inlet valves are most likely to be 33.5 mm and if the carb is an HIF38 you could expect aroung 55 bhp. If it's a Cooper engine from 1990-1 it should be giving around 65 bhp as the carb, inlet manifold and exhaust manifold are so much better.
The 80 bhp+ I mentioned was for a well-built 1330 cc 1990 Cooper with an MG Metro head and cam, plus some light head improvement inc. a raise in compession ratio, a slightly modified HIF44 carb, cleaned-up inlet manifold and an RC40 twin-box exhaust system of 1.75" internal diameter. The distributor was also changed for one with a better advance curve and a slightly lighter flywheel.
It's easy to get to around 80-ish bhp, but to get more than that requires some serious cash injection for better parts.