Morris Minor Owners Club

Out of interest folks, what's the red line point for a standard 1098 engine? And what do people think the red line should be for a rather tired 1098 engine with reasonable compression but about 230k on it?

Cheers:)

Nikki

Well, the book says for a standard 1098, the maximum power is at 5100 RPM so it's pointless to go over that.

In practical terms I would not either, especially if you are unsure of the state of your big ends!

5000 RPM will give you a terminal speed in 4th of 81.5 MPH, so you really don't need to go faster than that.

As for revs changing up though the box, I always do it by ear and it depends on the engine and if I'm driving normally or not.

I guess I'd keep it under 4000, but basically rev until you feel happy with it (as long as it's under 5000!).

Cam wrote:Well, the book says for a standard 1098, the maximum power is at 5100 RPM so it's pointless to go over that.

Well, it is useful to go a little over that, depending on gear ratios. You might find changing up the moment you hit peak power drops the revs outside the power band so much that holding onto the gear for a couple of hundred more would've been better

In practical terms I would not either, especially if you are unsure of the state of your big ends!

Seems some people are put off checking them - It's only a matter of dropping the sump and then whipping the caps off quickly! And at the price, might as well throw new shells on anyway if they haven't been done before.

I've only ever broken one crank, and that was a 1098 A series. Although we did estimate it was doing twice the redline at this point, from the extensive damage I'd say as the 1098 is a long stroke torquey motor, it's probably better to use the low end grunt instead of hunt the red line, other than where gaps in the ratios make more revs more useful. As a rough guide, I'd agree much over 5k is just stressing things for little gain

I used to take 5.5k as my redline on Rebecca, but as a real red line. The only time I went beyond it was experimental, and the valves started to bounce at about 6k, so...

Cam wrote:5000 RPM will give you a terminal speed in 4th of 81.5 MPH, so you really don't need to go faster than that.

ello Cam, how come this differs from the factory spec for a top speed of a 1098?

Is your factory spec for an LCV, with the different axle ratio?

no, it's a 1966 convertible. I thought the top speed for a Morris Minor 1000 was 77Mph. I was just wondering where the 81.5 MPH figure comes from?

Mines a 1966 four door and it'll do 70 reliably but can trundle on to 80 without too much hassle (just lots of revs) provided there's no wind!
This is all relying on the accuracy of the standard speedo of course.

I really miss not having a tacho, I used to drive by them rather than the speddo.

The factory limit takes 'normal' wind resistance into account, so the engine is not actually reaching maximum revs, just topping out on torque at 78 MPH. If you were going down hill with a wind behind you It's very possible to exceed the factory specified maximum. The 81.5 MPH figure is calculated from the engine RPM, gear ratios, standard wheel/tyre size etc, and corresponds to and engine speed of 5000 RPM.

oh right, so theoretically, if I was going down hill and with the wind behind me then @ 5000 RPM I would be doing 81.5 MPH? If I/one could reach 5000 RPM that it!

Or thereabouts depending on tyre tread & pressure, but you get the idea...

I've had Hebe (accidentally of course) 46% faster than perhaps she ought to have gone legally, but that was downhill. Of course, I'd never be so naughty to do it all the time.

Coincidentally, the reason for my question was:

at about 4,500 rpm Hebe's developed a rather large resonant rumble. Big end? (would tie in with the broken pully)... or perhaps something gone in the clutch (like a loose/broken thrust bearing)

Any ideas???

Nikki

(oh, and it happens in all gears and in neutral...)

I've had Hebe (accidentally of course) 46% faster than perhaps she ought to have gone legally

102 mph?!

blimey Nikki!

Erm... No... Seee... I was never good at maths...

Let's see... that's supposed to be 88mph

Doesn't sound like (ha!) clutch to me. *wipes sweat from brow and hopes he's covered himself...*

Erm... Cam? Since you've obviously got your maths head on, can you answer these questions?

1. What are the engine revs for a standard 1098 at 70mph
2. What are the engine revs for an Austin Metro with the 998cc A-series, also at 70mph?

I'm just interested... Ta ;)

1. 70 MPH = 4292 RPM in 4th, 6060 RPM in 3rd, 9321 in 2nd and 15570 in 1st!!
2. Can't calculate without knowledge of the wheel/tyre spec, gear ratios and diff ratio... If you let me know these, I can work it out.

Oh I see. I thought you might have a little magic book somewhere... Obviously not. I don't know the Metro gearing, or the diff ratio, presumed it would be the same as the 998cc Mini, but then it's a heavier car, so they could have fiddled with the gearing. Again, this was based on my erroneous assumption that you had a crib sheet. I see now you're doing it all by 'head.'

Anyhow, I just wonderd. So I'm looking at 4k at 70... not that Phyllis goes up that high usually... Ta.

So I'm looking at 4k at 70... not that Phyllis goes up that high usually...

does she ever get to 4.3K? If not I'll give her a run for you to burn off some of the carbon deposits ....

Gareth, yes, working it out the 'old fashioned way' I don't have a 'crib sheet' nor can I find any gear ratio info on the Metro on t'internet!