57 replies to this topic

[klivins]

dear Mini guru's,
I am in need of an advice.

My engine got rebuilt using new 1275 block, standard crank and pistons, 266 Kent cam, worked-on head, bigger inflow and out flow manifolds.

In June, when the guy who built my engine gave it to me, I already saw the problem, when engine was a bit hot, it started to sort of lose momentum, and have noises from top end. After I found out that there was no oil pressure and no warning light about it either, I had a big word with this guy, and stripped engine in my shed myself. The problem turned out to be a jammed and broken oil pump, probably wasn't primed before !!!

Anyway, now using weekends and some longer evenings only, engine is back in the car, but the symptoms continue! There surely is plenty of oil everywhere now.

please see the video here as this is easier then my written words...



Have to mention the head - it was a cheap ebay find. Can be not properly assembled? Any other thoughts?

Here in Latvia we have a total of 40 Classic Minis around, so I dont have a friendly garage just around the corner:)

[jaydee]

Sounds like something catching somewhere, check the fan and if the rattle comes from the timing gears..
Check also the ingition timing which sounds waaaay out.

[klivins]

its deffo not catching somewhere. The judder starts when revving for some time, as if there is not enough fuel, then comes back to normality if dropping revs.

Are Mini heads known to stick valves in when not properly assembled and when hot?

[Neildanks]

have you got double valve springs or strenthened springs. usually when you change the cam you change valve springs.

[klivins]

yes the head came with double springs when I got it

[Neildanks]

was the cam correctly shined for end float

[klivins]

that may not be done as I just put it all back as it were with original cam. What would the problems of excess end float look like on a running engine?

Worth mentioning the cam change I did only now, the first unsuccessful attempt described in post Nr 1 still had the original cam what came with the block in. Same result.

[jaydee]

How did you set the fuelling? carb, needle, spring, etc..

[klivins]

well, the carb is a refurbished SU4. I got it from a company in England and said to them I need one for Stage 3 1275 engine. There they had put ABB needle in, and I had before that an AAV needle as well. I tried them both. They both perform the same regarding these noises.

Initially I thought there was not enough fuel in the carb. Now this can not be the issue either, I have Facet electrical pump lined in.

[jaydee]

ABB and AAV are too lean for this spec. The noises you ar earing come from underfuelling.
You need an HIF44 carb.
If you're keeping the HS4 you need a custom profile as no off-the shelf needle will provide the correct fuelling for your engine spec.

[klivins]

thanks for advice!
However, how will you explain that initially for 2 - 3 minutes the engine works very nice, responds to throttle without any delay. and only then starts to lose power and make noise?

[jaydee]

If you have the problem when 'stationary' i'd say you have a dashpot oil problem (level or too thin) or a too weak carb spring, but if you can drive the car then above 3.5k rpm the missfire comes, i can guess you enriched mixture by twaeking the nut.. the result is running too rich midrange and too lean top end.

I see you got no SU friendly rolling road, but you can try by yourself..
I'd start from zero, check all ignition components and replace where necessary, stick a lean needle in the carb (the AAV should be perfect) and then reprofile each station to the correct mixture using a gas tester or a lambda or a colourtune whatever you can find handy..

Have a read here:
http://www.terryhunt.../picsb/pics.htm

Then report back any question

[klivins]

cheers!

Will try! it will take me some while looks like next weekend job!

[chris1275]

Hello
Cant be certain but guess from the picture your running with normal distributor and points setup. I would start by taking off the distributer cap and putting a piece of card between the contact points. Use a multimeter (electric tester) between a good earth point on the car and the moving(left hand bit) of the points. If you get a reading it might just be the condenser needs replacing. (the little round barrel silver thing with one orange and one black wire which runs back to the coil.

I had a problem just like this in my car which is a mildly tuned 1275 MG metro engine. Worth as try before you start ripping the engine to bits again and best of all it only cost £2.50.......

Good luck friend.

[klivins]

thanks Chris, this was tested together with other ignition components on the first attempt. Now I think I have to follow jaydee advices and try to determine is my needle in need of adjustments.

I will have accessible gas analyser giving me the idea of % of CO2, am I right in thinking on the RPMs above idle the mixture should become leaner, but what figures on CO2 meter should I be looking for when revving the engine? Any ideas where to look for this information?