Cylinder Head

[alanworland]

I have just pulled out of the loft a sidevalve cylinder head which I salvaged from an MM about 35 years ago.
I expected it to be the same as the one fitted to my vehicle, and it is other than :-
Mine has Qualcast cast in the surface, the spare has MM in a diamond shaped outline (cast by Morris Motors?)
Mine has 25-11-52 cast in it, the spare has 16 L1
Both heads have the same number 31693 on them (part number?)
Just curious, any ideas? Mike?

[mike.perry]

I have just checked my cylinder head and it has the same part number 31693 and a 1951 manufacturing date. My parts book lists 31361 as the part no. for the early cylinder head but for some reason does not give a part no. for the later head which was fitted to engine no 77001 onwards.
See the topic "Lawnmower Engine" posted Jun 08

[alanworland]

Thanks Mike, do you reckon the 'MM' cast into the head mean its a Morris Motors casting? if it was manufactured in house?
Did the earlier heads not have the recess for fitting of a thermostat?
Incidently underneath the 'dirt' finish it appears to have been painted canary yellow!

[mike.perry]

I assume that Morris produced some cylinder heads in house but also had outside suppliers. My cylinder head does not appear to have a manufacure stamp on it. I have a couple of old ones but they are inaccessible behind a sv generator engine and a '47 Morris Vedette marine engine.
The early cylinder head had no provision for a thermostat and the dynamo bolted onto a bracket on the head. The distributor clamping arrangement was different as well.

[alanworland]

The head I have fitted (original) has had some material removed to raise the compression ratio - I can't remember how much but I seem to remember it was raised to 7.5 to 1 in an effort to squeeze a bit more performance out of it, have you any experience(s) of similar mods?

[mike.perry]

Getting late, I'm going to bed. Continue the conversation tomorrow.
Goodnight.

[mike.perry]

You can shave a little off the head to raise the compression but you have to be careful not to get too close to the water jacket or you will fracture the head above the combustion chambers. I know! Also if you take too much off you will affect the gas flow from the valves in to the piston area. The best s/v head design is probably the Derrington head.
Other mods include the usual blueprinting, polishing the ports and relieving the excess metal around the valve guides.
Also I have heard that timing can be improved by running a 1098 distributor which seemed to work on mine although I could never convince myself that the vacuum advance was any advantage. I intend trying the 1098 internals in a s/v distributor to see what happens. Whilst on the distributor it is worth checking the slack between the top of the jack shaft and the drive dog and replacing the drive and if still free play then welding up the slots in the top of the jack shaft so that the distributor is a good fit.
I have found that running the carb with a rich (M9) needle improves the acceleration but it is important to get the timing spot on by trial and error first.
I believe that you can fit slightly larger inlet valves but you have to be careful with the valve seat inserts.
The best way to get more power out of the engine would be to scrap the manifold and get a decent 4 branch exhaust system with maybe an H4 carb and inlet or a pair of H1s.
Also other mods are engine balancing (only of real benefit if you are going to rev the nuts off it), lightening the flywheel and reprofiling the camshaft (I have one in my spare engine).
With that lot it should go well. You could just fit an Alta head.

[alanworland]

I dont want to do anything too drastic or non-reversable!
I had for years a Mini Cooper S distributor fitted (no vacuum advance) and have recently refitted the original after rebushing the body and dont think I can notice any difference - better or worse!
I am in the process of finishing the fitting of a pair of H1 carbs on the Morris:-

http://i248.photobucket.com/albums/gg17 ... G_3370.jpg

This is using the original exhaust (rightly or wrongly!) to retain our lovely exhaust note!
Hopefully will have them running sometime over Christmas, these have at present got the original needle type fitted (EK) I did consider obtaining the M9 needles but decided a better comparison would be obtained by using the same needles initially.
I have a particular bit of road that I should come to some meaningfull conclusion on any improvement.
The installation will use the original air silencer which has actually ended up in the same position it even uses the original bracket! so at a glance all looks standard.
Although probably all sooted/coked up by now I have in the past given the ports a good workout to improve gasflow, with particular attention to matching the ports to gasket/manifolds which if I remember was not very good.

[mike.perry]

I'm not sure what the best needles would be for an H1 twin carb setup. The 1098 in single and twin carbs and the 1275 twin carb all use an AN needle in HS2 carb, whereas the 948 engine uses different needles for single and twin carb applications.
I use the M9 in a single carb because it has the same profile as the EK needle from tickover to mid range and then continues to taper whereas the EK needle is parallel for the top half of its profile, so theoretically it should give a richer mixture and better acceleration at higher speeds.
I know someone with a twin H1 carb system for an Alta head with a 4 branch exhaust so I will try to find out what needles he uses.
If you fit a 4 branch system and connect it up to the existing silencer you should retain the exhaust note.
I have heard from a couple of MM owners in Australia that they are working on producing a replica Morano (an Australian tuning firm I believe) twin carb setup with a 4 branch exhaust. I am trying to get some idea of the cost and availability dates.

[alanworland]

I found a website:-

http://www.teglerizer.com/suneedledb/index.html

which gives needle diameters and I have seen what you describe in that the last part of the EK needle being parallel, and I would agree that theM( would be the way to go but from a comparison of single to twin I wanted to stick with the same needle as originally fitted.
It would be interesting to find out what setup the Alta uses.
I saw on this site months ago a post about the twin carb setup (I think the name is Monaro) you refer to, which is what started my interest and is totally responsible for where I have got to with my setup!

[Keith]

Alan, I have a set of twin carbs that came with my Alta, I'll look them out over the Christmas period and give you the needle etc details. regards Keith

[mike.perry]

I have a copy of the SU Reference Catalogue, Needle Charts and Workshop Manual which provide interesting bedtime reading.
Keith, do you use the standard needle in your supercharged engine?

[Keith]

Mike, Yes I do, although the carb is a 1.25 inch SU. I tried all different combinations of needles, springs etc, and came back to the standard. regards Keith

[alanworland]

Keith, that would be great, thankyou.
Do we know if a supercharger has been fitted to a standard sidevalve? I must admit I was toying with the idea of experimenting with a charger from a MINI as they seem to crop up on ebay and some have had very little use.
Mike, are we sad to enjoy reading such matter! I found my Burlen catalogue quite interesting!

[tortron]

I am looking at running twin 1 1/8th su's through the above mentioned australian casting with the suggested 1 1/4 inch exhaust

i figure some custom 4-2-1 manifolds should really open up the breathing of the engine

Is your stock air silencer/filter the oil bath type? that is what mine is currently fitted with

i am considering making a replica shell of one and fitting a pod or mushroom type filter inside that to match the extra flow of the exhaust.
Hopefully the new system will blow out less than the standard im finding my downpipe flange gasket will blow monthly

[alanworland]

I ended upgoing my own way with the inlet manifolds because the Australian one seemed a long way off production.
The exhaust manifold sounds a good idea but wouldn't it be restricted from the silencer back it is after all rather small diameter?
My air silencer is standard and therefore has no filtering effect.
I have had a manifold to exhaust gasket blow in the past but only the one, so I wouldn't say it was a problem.
Does the joint come together squarely as it is pulled together?

[tortron]

i think the silencer has been replaced and put on slighly askew, putting a bit of stress on the join

my planned new system will be 1 inch collectors down to the 1 1/4 inch exhaust pipe

[alanworland]

1 1/4 right through from the silencer?

[tortron]

thats the plan (minus the silencer part )

[tortron]

well actually most likely a coby type straight through muffler. Looking at an all stainless system