7 replies to this topic

[haveyoubooked]

Hello,
I just finished the build on my '79 Mini 1000. Its 998cc standard bore/crank/pistons block. Piper 255 cam set to 16 deg and new followers, 12G295 Head skimmed down 100 thou, HS4 carb with richer needle (E3 and blue spring if I remeber correctly), small bore lcb into janspeed 2 box exhaust, and electronic ignition pickup in the 25D4 distributor. Its also got a 2.95:1 ratio diff to make motorways comfier

I just did a 500 mile drive to Scotland, and it was very reliable, no overheating, pinking etc, however it seems to lack power (its been a while since I drove one so It might be rose tinted glasses), pulls away on the flat well enough, but you have to rev hard to get anywhere, and it slows to 50 ish going up moderate hills. I reckon the ignition timing is out as I ran out of time on the build after the engine was in and pretty much threw the dizzy in the hole and turned it until it ticked over ok. What static and dynamic timing figures would I be looking for do you think?

I was guessing 34 deg (ish) advance at 4000 rev's and haven't dug the book out yet to check the static and and idle dynamic timing.

So recommendations please on

1. Static figure
2. Idle dynamic figure
3. 4000 rpm figure
4. Anything in the spec I ought to change?

Thanks, Rory

[bmcecosse]

The 2.95 final drive is a killer for a 998......not the best choice - 3.44 would be MUCH better. Just advance the timing until you DO hear a bit of pinking and then take it back till it's 'not quite' pinking. It's the best you can do without doing a RR run. Then do a plug colour check after a good hard run. You would probably do better with an HIF 44 carb - certainly on the limit for a 38. But really -the FD is what's killing it on hills - your engine spec is not a 'slogger' - it needs to be able to rev.

[jaydee]

Whats 16 deg???????????????
The piper 255 have to be dialled in at 108°, you're probably confusing camshaft timing and ignition timing.

Regarding your questions, i quote every single word from bmcecosse.

[haveyoubooked]

Sorry, the 16 deg... I was half asleep writing that after an 11 hour journey in the min after a 5 o'clock start to change the clutch master cylinder... To explain better my timing dial was segregated in 90 deg markings so 90 plus 16 was 106 degrees which seems to be optimum for the engine according to Mr Vizard.

Well thanks for the replies, I agree on the diff, its fine in first and second gear, but from third to forth you have to rev to 5000 plus in order to keep in the power band into forth, although once past 65 miles an hour in top it starts picking up again into the 80's (i haven't dared anymore just yet as the car's fairly newly built)

You reckon the carbs a little on the small side then? I have a HIF 44 in the garage but opted for the HS4 as I believe that it should give more torque lower down.

So I'll have a go with the pinking method and see what it feels like then.

[jaydee]

106 deg sound perfect to allow chain stretch/wear.
I've been using both HS4 and HIF44 on a similar spec and the HIF44, once tuned correctly, provided a lot more low down torque, if you can gey one cheap, try it and make your own conclusions.

[haveyoubooked]

I certainly shall, any needle recommendations to go with that to start with?

[bmcecosse]

The beauty of the SU carb is that has a variable choke area - so the larger 44 carb will still maintain a good air speed across the jet bridge at lower revs. You are on the edge of needing a larger carb - the 38 should be fine most of the time - just may not give the absolute ultimate full revs power. Change the final drive !

[haveyoubooked]

Ok, well I have both 3.44 and 3.7? (can't remeber 2nd decimal place on the 3.7? diff) diff's sat in the garage, which would you say. I am hesitant to change it as it'll need half a day's worth of engine pulling out and replacing.

The reason I put the 2.95 diff in was because the commute to work and back of 50 miles is 60-70 mph stuff all the way and I was trying to get away from the screaming its nads off all the time. Like you say though, probably best to give it a go.

I'll have a go at the timing tomorrow with the "pinking method" and see what difference that makes, then report back.

One final thing, its four years since I last did a mini engine build and i'm unsure if the following is normal or if my oil pressure relief valve is playing up, but at cold tickover there is 75-77 psi indicated oil pressure, and 50 ish hot idle, 70 ish hot at 2000+ rpm. Is this normal or does the valve bear another look? It's a '68 riley elf 1000 block on original bearings (they were perfect when I stripped it, and a new minispares standard oil pump. Running unipart 20w50 oil. Sorry its a little off topic.