Morris Minor Owners Club

Hello gang,

have been gathering bits to improve horsepower output of my 1098 engine. These are the bits I've got together - can you suggest which bits to use (and why):

Marina 940 cylinder head
MG metro cylinder head (bigger valves; leaded)
mini exhaust manifold
marina manifold (could buy 1.5" exhaust to go with this if nec.)
Oselli torquemaster inlet manifold
Austin alloy inlet manifold
SU HS4 carb (from 1977 auto mini)
K&N-alike air filter
Marina rocker gear
Alloy rocker gear ( from more modern A series engine).


Thanks

Russ

PS - many reading this will have responded to similar requests from me; thanks guys, you've got me to where I am now!
I'm interested at this point in the 'best match' of what I've got. I want as much power as poss but without sacrificing torque. Also - any readers who offered me cylinder heads will wonder why I now have 2...it was a freak ebay incident.

The ignominy of having to respond to your own posts....aii !! I'd hoped the modification pundits would have relished the challenge I'd laid out above, but I guess you are all too busy with your Christmas shopping!

My main dilema with my engine upgrade is whether to use the MG metro leaded head over the Marina head. I will probably use the HS4 (with K&N type air filter) on the Oselli inlet and use the Marina exhaust (with the inlet chopped off) with a BMM 1.5" exhaust downpipe & boxes.

I want maximum power but with enough torque - which head please?

Thanks to all

Russ

i would go with the metro head, likely to be slightly better than the marina one, and also unleaded is a bonus. oselli inlet manifold will work well, but does your "mini exhaust manifold" also have an inlet cast as part of it? the inlet can be cut off with a hacksaw but it takes some time! if you want to go the extra hassle and cost of the marina exhaust then that will be better still.

I dont think you will see any improvement by changing the rocker gear, leave that as is. also the later rockers were sintered and are actually weaker, ive snapped one before which doesnt do the engine any good.

Picky

For maximum torque on a 1098 you would be better off with the Marina 1275 head as it has smaller valves than then MG Metro. However what would be a better suggestion would be to measure the inlet diameters of the componants you have and match them accordingly. Step changes in the gas flow can destroy any gains you could acieve from choosing the optimum valve size alone.

Hi sowden, in order to fit a 1275 head you need to have the block machined to allow a pocket for the larger valves to open into.
This problem is made worse by a high lift cam.Best head for a 1098 is a 12G295 head where no such machining is required.
I went down that route but a year later have a 1300 installed.I went for an oselli style manifold though.Just separating exhaust and inlet can give upto 5 extra horses with a good inlet and exhaust arrangement. Might be worth putting a fast road cam with these mods.

Hi again,

Picky - thanks for your response. I goofed - the head is actually leaded (which I think had bigger valves still than the unleaded) - I've amended the above posts. I have some Marina rocker gear and I will use that (the newer stuff looks whizzier but I suspected it might not be as strong).

Peetee, ta for your post - I'm keen to do as you say and try to match things, but is that just a case of maintaining the same bore of gas pathway all the way through?

If so it would be Oselli / Metro / Marina (chopped) with 1.5" system, as the Metro ports are bigger than the Marina - but then there is the torque question. I read somewhere that torque is reduced with larger ports, though the latter come into their own with higher revs. I cant find the post I read that in any more, though. My max revs will be as low as I can get away with really, I'm into quiet engines and I am not a racer (99% of the time!). The diff will be the 3.7, which I imagine needs as much power to it as you can safely achieve.

Cheers

Russ

PS - hi Longdog, just read yr post, it crossed mine I think. Thanks for your comments, will try the head first before bolting up...dont really want to machine the block, will sink the valves if necessary I think!

but is that just a case of maintaining the same bore of gas pathway all the way through?

Well in an ideal world yes, but that's virtually impossible due to the constraints around the valve and, that futher up, two cylinders have to share one port (siamesed). But you're right; make sure the interface between each component matches. For example, there are alloy inlets sized for 1.5 or 1.75 carbs. It follows then that one or the other will not ideally match (in terms of gas flow) to any given head.

I read somewhere that torque is reduced with larger ports

As it is with smaller ones! You've stumbled upon the paradox that is engine tuning. In basic terms there is a difference between torque and hp. If you liken it to a boxers punch. Torque would be like a heavyweight delivering a 'slow' uppercut, hp would be a flyweight sending in a fast right hook. Both impact your chin with the same force, it's the speed and weight that is different. Torque is a function of efficient and long cylinder filling (smaller inlets help here because the gasses flow quicker and are dragged into the cylinder through inertia even when the valves are closing). There is greater mass in each combustion and the piston 'punch' is bigger. Hp is a function of rpm. The faster you get the gasses in and out the faster the engine turns and the more power it is producing. You can see then that hp requires wide ports but torque requires smaller ones.

I would agree with pete and use:

Marina 940 cylinder head

marina manifold (assuming its the twin downpipe version)

Oselli torquemaster inlet manifold__
Austin alloy inlet manifold------------>Both very similar bore/pattern doesn't make much odds

SU HS4 carb - just make sure you have the correct needle

K&N-alike air filter - A proper K&N would be better I am dubious about the filtering ability of some others

Marina rocker gear - Alloy will almost definately be high lift - avoid at all costs if your using a '940 on a 1098 engine!

When using the 940 the valves may need to be recessed by 40 thou or so

Thanks Matt / Peetee for your posts.

Peetee - thanks especially for your lucid explanation - its a lot clearer now!

Matt - I think you are right about the Marina head - I'm going to get the valves out and check them for soundness then get them lapped back in (being sure to make a thorough job of the exhausts, so as to sink them & thus keep them clear of the block...I'm hoping it will go straight on with no mucking about).

BTW, the Marina manifold is a single, not a twin. Still a lot bigger than the mini one I also have...my intuition tells me this size increase will help me in my quest for power ('mighty evil one'-type laugh echos in the background).

Cheers,

Russ

For the 1098 engine - go with the smaller valved 940 head - and you WILL need to recess the exhaust valves 40 thou to make sure they don't hit the block. Don't machine the block - it's not necessary - the valve sinking is much easier and doesn't deface the block. Some manage to 'get away' without sinking the valves - take the risk if you like. I measured mine - and I HAD to sink the valves. Alloy inlet manifold with larger carb (ideally HIF38) - best exhaust you can afford or make up. For rockers - use any that properly alignes the rockers over the valve tips. The standard 1098 rockers are stronger - but you will need to re-align them on the rocker shaft so they accurately centre on the exhaust valves. Just save the larger valved 940 head for when you upgrade to a 1275 engine !

A couple of points- don't expect lapping the valves to do much in the way of increasing clearance- my factory unleaded head has seats as hard as diamond! With the greatest respect to bmc, it's not neccesarily a case of "risking it" with the clearance. You can calculate it scientifically easily enough, though it seems I am in a minority by NOT having to recess/pocket! I wonder if the original height of the valves is different with hardened head to unhardened, thats the only explanation I can put to my good luck, in which case you may also have similar luck (no harm hoping). If/when you do your checking- don't forget to factor in the thickness of the head gasket!
Finally with the port matching thing- it seems OK to step up on the exhaust manifold face, maybe even advantageous, so don't worry too much there as long as the step isn't down in size!
I still haven't woked out how to accurately align the inlet manifold if the locating rings and grooves are not there!

yes, unleaded seats are very hard (that's the point!), I can't touch them with my hand cutters, so I guess you're right, lapping will hardly touch them.

Normal leaded ones are easy to recess though.

Andrew

But not by 40 thou! You will need a cutter - grinding in the valves may drop them 1 or 2 thou - no more!
And yes - I measured mine (As said above) and i had to sink the valves. Not everyone has the equipment/facilities to do the measure accurately enough - hence - for safety, if in doubt recess the valves. It's only minutes in a pillar drill witha 45 degree cutter.