Engine tune-up? Where to start? So many questions... (long)

[Kevin]

and I needed about 5 books

Oh am I not supposed to have not to have more than 5 no one told me that before

[JimK]

Oh am I not supposed to have not to have more than 5 no one told me that before

hehe, I did think that maybe 5 books for one car was excessive. I guess not, we've only had the car two months and we've already got three

[Packedup]

Although a thicker oil will reduce the piston movement and so be less free flowing, it will also increase the air velocity over the jet so more fuel will be pulled through (OK, pushed through if you want to get scientific). Hence you get a richer mixture even though the needle is maybe still further in the jet!

Plus the extra air speed results in greater port speeds, and so there should be an increase in volumetric efficiency. Certainly my experience is that a thicker oil, and/ or stiffer spring results in a much improved "pick up" compared to a thinner oil and/ or weaker spring in the same carb.

Could be that I've got those results from using incredibly tired old junk though!

[JimK]

OK, that's just great, I have several differing opinions each based on an unscientific survey of up to two cars. Marvellous

[Packedup]

If my experience was based on up to two cars I'd be much happier - Try something like 40 SU fed cars! I've had something like twice as many cars as I am years old!

But still, the science behind it makes sense for the various opinions. A faster rising piston will allow a greater airflow but with possibly lower fuel drawn through, a slower moving piston will restrict the airflow but increase port speeds and fuel amounts. The trick is to find the balance between the two so you get a decent wodge of fuel and plenty of air.

But whatever the case, I'm still right in saying it's an HS4 on there!

[Axolotl]

Perhaps the point is that the carburettor will work almost regardless of what oil you put in it, and different people have come to different conclusions about what they like on their engines.

Like most things, there is no single "right" answer. What the workshop manual says was probably the safest option BMC could come up with to cover almost any eventuality. They weren't after the absolute pinnacle of performance.

Why not try a few different oils and see which suits your set up best?

It is a fairly simple job to whip the cylinder off, clean it out with some meths or petrol, and put it back if you want to change the oil.

[Axolotl]

And yes, it does look too big for an HS2.

[JimK]

If my experience was based on up to two cars I'd be much happier - Try something like 40 SU fed cars! I've had something like twice as many cars as I am years old!

Sorry, didn't mean to put anybody down. I just like the fact that given the same piece of kit, I got as many opinions as answers
Just trying to work how old that makes you...

The trick is to find the balance between the two so you get a decent wodge of fuel and plenty of air.

Would you be able to say that one particular setup worked well for most of those? For instance, using the heavier oil in the carb? That would make sense to me, if they were all fed by the same make of carb.

But whatever the case, I'm still right in saying it's an HS4 on there!

I think you've won that one

[bmcecosse]

It's very definitely an HS4 carb - that's 1.5" inlet which is 'just' about ok for a 1275 in standard trim - but you will not be getting 60 bhp - 54 would be nearer the mark. HOWEVER - that standard air filter will be very seriously limiting the air flow - and that's assuming it has been modified internally to match the bigger carb inlet. If it has been clamped on without opening up the bore - well - you might as well have the standard smaller carb on there. I would remove the air filter and casing completely - and try the car like that. You may be surprised at the difference. I cannot get my car to run with that casing on - even with no filter inside - it's just too restrictive. Carb Damper - I use 3 in 1, but to do so needs a bit more choke for longer (and a bit of backfiring through the carb!!) , and the mix set up slightly on the rich side to stop it 'gasping' - but I feel it gives more rapid throttle response. Many use engine oil - and the Works Minis had EP90 in there on the rally cars - to stop the pistons bouncing about on the rough stuff and causing misfiring and loss of power just when it was needed most!! A really good upgrade for your engine would be to track down the larger HIF 44 carb and inlet manifold from an MG Metro. This makes a big difference - partly because the inlet is no longer being roasted by the exhaust heat - this alone is worth several extra bhp - and the bigger carb helps at the very top end , although this maybe doesn't bother you - in which case stick to an HIF 38 but still on that MG Metro inlet.

[JimK]

I'll check the airbox connection size, and maybe try it on the way to work without one.

As for the carb and manifold upgrades, do you mean this:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1
and this:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... %3AIT&rd=1

It was a bit dark to check inside the dashpot, so I couldn't see how much oil was in there. I'll do that during the day too, and see about putting some engine oil in there.

[Kevin]

Thats the right types but give the HIF44 you have listed a miss as its probably going to go for quite a bit as its heavily modified (in the best way) and you can normally pick a good up for around £20 give or take a bit.

[Packedup]

I'd be tempted to stick with what you've got, because it's the cheapest option!

Make sure the carb you have is in good condition, and if you really must then knife edge the butterfly and thin the spindle - That'll let a bit more air through.

What BMC says about seperating the manifolds is true, but I wouldn't go so far as to say it'll free up several horsepower on an otherwise pretty standard engine. In fact on it's own that mod will probably not yeild enough power to be noticeable, but it's another fairly cheap way of adding to the total increase. The MG style alloy inlet is good, and if you go for a 1.75" carb then it's a must (no point feeding a large carb through a small manifold IMO), but if you've got a grinder, a hacksaw and a spare manifold then you can seperate the inlet off one and exhaust off the other to remove the hotspot, once again cheaper than buying a new inlet.

That air filter casing may or may not be causing a real problem - I imagine the adapter that appears to have been made suits the carb bore, but how well the whole thing flows is another matter. If possible find a suitable filter casing off another car...

I'd be checking the carb for wear on the needle, weakening of the spring, wear on the jet, wear around the spindle leading to air leaks etc. Then maybe have a crack with a thicker oil in the dashpot (no real need to see the level - If when you remove the damper there's an oily "sticking feel" all the way out, and a definate resistance when putting it back in, it'll probably do. Though with carbs with the vent hole I just brim them and let the carb work its own level out

Also check the dizzy for wear in the bearings (try and push the shaft from side to side), make sure you can rotate the shaft a little by hand so you know the advance isn't seized, drop a little light oil down the holes in the plate to lubricate the advance weights/ springs.

Check the timing (I use the static settings myself), the dwell if you have a meter, and when you're happy the ignition is set up then make sure the mixture is about right. Easy done - Get the engine up to temp, then turn the adjusting nut one flat at a time in one direction till the engine runs quite roughly, turn the nut the other way till it sounds equally as rough, and then go back half the number of flats from each point. That's near as dammit, though with a colortune or sensitive ear you can probably get it even closer to spot on

Or, get a modded head, throw in a decent cam, whack on a tweaked HIF44, throw a good LCB manifold and exhaust system at it, and wonder where all teh money's gone!

[Rob_Jennings]

Jim,

I do love the fact it was your wife that wanted the car.... but you're slowly pimping your ride into some sort of sports car that you really wanted

I bet next on the list will be shocks and roll bar once the engine is up to speed!

I'm not sure how your travs performance matches up to mine, but I have a 1275 marina engine, larger carb and a modified mini airbox (air intake moved to the front near rad so not from directly over the exhaust). I guess that was all done to improve the breathing.

I'm not sure how it stacks up powerwise to yours? I'm used to driving a sport diesel, so tend not to look for loads of power at higher revs, it just won't be there.

[JimK]

Is there scope for a show called Pimp My Minor?

It's true that Wifey wanted the car, and I've never been a big fan of classics. But: I've had a load of fun driving it and I'm really getting into the whole old car thing. I am a bit of a fan of "sleepers" as well - I found myself thinking seriously about the black modified S2 in the For Sale section; it has potential. The idea of a trackday Minor that looks completely standard is intriguing...

I wouldn't do anything that fundamentally changes the car's character though; changing to a different type of engine, for instance. Some dampers that actually damp something and brakes that allow you to stop hard more than once are fair game though...
Maybe a bigger manif/exhaust. Then a 16V twincam head... The rollcage may turn out to be necessary

Are you around tomorrow evening? It would be interesting to compare and contrast our cars, both statically and dynamically.

[Kevin]

It would be interesting to compare and contrast our cars, both statically and dynamically.

That would be a good yardstick for both of you and if one pulls much better than the other you will be able to see what is making a difference hopefully.

[KirstMin]

If you do go for a larger bore exhaust and manifold etc then bear in mind that you lose one of the characteristics that most people associate with the Morris Minor - the farting exhaust. Don't go down that route and then be upset at it's loss - better to know it now!

On the original point - comparing with the fiesta - you'll be lucky to get 55bhp with your set-up if its all set up nicely. You'll be improving on the torque from the original 1098 but not too much power unless you change the breathing. So the results are exactly as expected when comparing a fiesta with 20 odd extra bhp!

[JimK]

If you do go for a larger bore exhaust and manifold etc then bear in mind that you lose one of the characteristics that most people associate with the Morris Minor - the farting exhaust. Don't go down that route and then be upset at it's loss - better to know it now!

I'm not too fussed, but Wifey likes the sound. She's wanted one for 25 years, and doesn't want its character changed.

On the original point - comparing with the fiesta - you'll be lucky to get 55bhp with your set-up if its all set up nicely. You'll be improving on the torque from the original 1098 but not too much power unless you change the breathing. So the results are exactly as expected when comparing a fiesta with 20 odd extra bhp!

A ~20bhp difference would explain the performance gap...

Is there any point in improving the intake breathing without changing the exhaust path? I'd guess not, but I've been mostly wrong so far...

[tickman]

Is there any point in improving the intake breathing without changing the exhaust path? I'd guess not, but I've been mostly wrong so far...


i like the attitude!
i am married too and am "mostly wrong" quite often not usually about the car though!

[Peetee]

I had a modified 948 that was putting out about the same as my standard 1275 (at least it goes about as well) this was on a standard bore stainless system. I would guess anything above 60bhp would need an oversized system. Vizard suggests that an LCB is only worth a couple of bhp at the top end which is good because it practically doubles the cost of an oversized system. As a rule, the larger the inlet the more power you produce at the top end and the more your mid range torque suffers. If you had a standard diff then a 1.75 cab and matching inlet would work well because you will spend a large proportion of hurried driving in high revs. A 1.5 with matching inlet would be good with a 3.7 or 3.9 diff to make the best torque with longer gearing.
On a 1300 the best £/bhp/character retention improvements go along the lines of:
alloy inlet+carb
flowed/large valve cylinder head
cam
Any of the above MUST be accompanied by a rolling road session. there are lots of cars out there that are loosing out big time because this has never been done (mine included) It can make a massive difference.

It would be interesting to compare and contrast our cars, both statically and dynamically.

You can count me in on that one too!

[Kevin]

Is there any point in improving the intake breathing without changing the exhaust path? I'd guess not,

It all depends on your final objective, when I ran a Midget engine I wanted to keep the standard exhaust so I used the 998 mini combined manifold as it flows better than the Moggie but still fits the standard exhaust so it retains the standard exhaust note. Then I removed the inlet half and cleaned up the exhaust half, for the inlet I used a seperate alloy manifold with an 1 1/2" HS4 rejetted to suit and it was surprisingly good especially up hills where the difference was quite dramatic hills that were almost 2nd gear could be taken in 4th so I was well pleased with the extra torque that was available, obviously if I had also fitted and LCB exhaust system it would have released even more oomph but I wanted to retain the exhaust note.