6 replies to this topic

[Ant@BackyardRacing]

hi all, i recently purchased a 1275 A+ engine from a member on here, with the intention of re-building it and swapping it into my 1971 850 auto.


i bought the engine as faulty, "oil light on". this is my first mini, and have never worked on one prior, so i have a few questions.
i have stripped the engine down, and it seems to be modified, the oil pump is buggered, scored to hell, and is a "powertune" tune, i assume this is not a standard pump?

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secondly the crank looks to of been balanced as there is clearly grinding marks and notched cut out of it, its marked "cam 6232" again, im unsure if this is standard or not.
thirdly, the head is a 12g940b, is this standard, and is it any good, i.e can anyone tell me the valve sizes, and if its a decent head to start with, i would be looking to fit the hif 44 carb and aiming for 75hp or so for a fun road car.

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the rocker assembly looks brand new and again looks after-market, its chunky, but i cant seem to find any markings on it for a part number etc, but the same with the vales springs, they look new, so looks like maybe a recon head has been fitted, and i filled the ports with parafin and valves didnt leak a drop in 2 hours, so the seats seem to be good.
the bores are scored though sadly, so a rebore will be needed, im just unsure what casued the initial failure, i.e did the pump fail, or has something else failed and the pump has injested some swarf and its that what killed the pump?

is bottom end failure a common problem on A + motors?

if so, is it usually the oil pump itself at blame, or worn rings leading to oil burning, then low oil, then bottom end failure?

i would just like to be sure i have found the culprit of the initial failure before i re-build and have have the same problem a month later!


sorry for the long post, cheers guys!

[Shifty]

What are the crank bearings like?

[Ant@BackyardRacing]

not too bad really, i was expecting the big ends to be really bad, but there not too bad.

they are damaged for sure, but ive seen much worse. there does however seem to be some end-float to the crank,
i can move it in and out by hand and make it "thud", id say maybe .5mm of end-float

[Badboytunes]

I think the markings on the head indicate its a "big valve" head.

Im sure I will be corrected if im wrong.



cheers

[Ant@BackyardRacing]

Just an update, pulled the main caps off, and the mains are trashed!
Crank is heavily scored. Bit odd in my experience its usually big ends go first and mains
Are usually the better, not in this case!

[freshairmini]

in regards to the rocker assembly to me it looks like the factory sintered type, which is supposed to be not the best kind of rocker assembly. But anyway its not an aftermarket one I dont think, I have the same one on my 1990 carb'd mini (RSP).

[Doz1971]

Did you get the gearbox with the engine? Maybe something failed there first sending shrapnel through the motor before getting filtered out?