1098 tuning

[sowden]

Hi everyone,

I have been thinking/researching about how to modify my 1098 for maximum power in the easiest way, and keeping things as standard as possible. I have arrived at the following:

1098 head with some gas flowing (inlet short bend radius smoothed, valved guides pencil-tapered, exhaust ports polished, Cyl head combustion chamber recesses polished, exhaust port throat constrictions enlarged)
Hi lift rocker gear

with

either
combined mini inlet/exhaust manifold (is the 998 one the best or is there a better one?) with a 1.5 HS4 SU carb
or
midget 3-into-1 exhaust manifold (non-LCB) + cast iron metro manifold or MG metro turbo alloy inlet manifold or aftermarket alloy alternative, with a 1.5 HS4 SU carb

pushing a 3.7 / 3.9 diff.

I would value comments / critique / potential improvements from our experts or anyone wishing to express an opinion.

Thanks to all,

Russ

[bmcecosse]

Don't waste your time on the 1098 head, it will make no noticeable difference! Either use a 12G295 head, which will need skimming by 60 thou (and are expensive!) - or get a 12G940 head from a 1275 engine and use that. Sink the exhaust valves into the head by 40 thou - or grind 'pockets' in the block below the exhausts for clearance. DO NOT use high lift rockers. Change the cam for an MG Metro cam - but that does mean engine out, so otherwise just keep the 1098 cam. !.5" carb - HIF38 is best (but HS4 will work) on MG Metro alloy inlet. Unfortunately the Midget exhaust won't fit past the chassis - larger bore Marina single cast exhaust can be used - with a large bore exhaust system - I think JLH do one, or make up your own . The MG Turbo inlet is hopeless - it's designed for a Turbo and is intentionally poor flowing to mix up the air and fuel - and therefore hopeless on an aspirated engine. Diff of your choice - I've just fitted a 3.7 but 3.9 will be good too and possibly less expensive.
Better of course to fit a complete 1275 engine if you can find one at a good price - and be sure to improve the brakes ! See the 'Wolseley' thread for that.

[Peetee]

Brakes and suspension first. That way you can drive within the capabilities of a 1098 for longer, not just whey you are on a straight, even, empty road - of which, lets face it, there are very few.
I'd go along with BMC but add that up to 70mph the standard diff is fine. A 3.9 or 3.7 will give you a higher top speed but will blunt the acceleration.
You could feasibly get 60bhp from a healthy modified 1098 with good mid range pull. More radical tuning will push the power further up the rev range and won't suit daily driving, the gearbox or the crankshaft!

[Kevin]

combined mini inlet/exhaust manifold (is the 998 one the best or is there a better one?) with a 1.5 HS4 SU carb

Nothing wrong with that combination as it will go straight on the standard exhaust however it will be restrictive but you will keep the exhaust note, but it would be best to seperate the two halves to get rid of the hot spot or just keep the exhaust side and fit an alloy inlet as you have mentioned.
If you do decide to do your head yourself don't go too far with the polishing aspect as a ground type of finish is preferred for the airflow.
To get more ideas you could always get a copy of Vizards book unless you already have one.
http://cgi.ebay.co.uk/Tuning-BLs-A-seri ... dZViewItem

Another small point unless you are going to change the air filter for a K & N you will need to adapt the orignal housing if you want it to look standard with the larger carb.

[sowden]

Hi guys,

thanks for your responses. Its a great forum for expertise, this one!

What lead me to start thinking about modification was the stunted top speed - mine will do more, but 55 seems to be the speed its happiest at. The engine seemed to be able to give more than the final drive allowed - which lead me to thinking about a diff swap. This diff idea was moved forward in my thinking when I nearly melted my diff the other week (no oil), it's now singing like a bird.

The head's in good nick as I recently decoked the engine and head and relapped the valves (and that made a noticeable difference!!). Thus, I started wondering what I might easily do to my spare 1098 head to ease a few more BHP out of the situation. To be clear: I dont want massive gains, just as much as I can get. And as easily as possible. This lead me to thinking about bigger carbs, best manifold, better breathing. I dont really want to swap the engine you see, or mess about with the cams, at least not yet. (re brakes/suspension: My brakes are in good nick, and stop the car very well - they could handle a modest power hike. Will tele shocks front and back do for a suspension upgrade?)

It is within my capabilities to do a little metal grinding, if that helps improve things. Also I can afford a 2nd hand carb and manifold, and if it looks standard, so much the better. (is the combined mini one better?)

In a nutshell, the above thinking was what lead me to my suggestions in the original post. I'd rather tinker with what I have but I dont want to flog a dead horse!

Cheers,

Russ

[Kevin]

Also I can afford a 2nd hand carb and manifold, and if it looks standard, so much the better. (is the combined mini one better?)

Yes it flows better than the Moggie one especially the exhaust side according to Vizard I am sure someone can quote from Vizards book as to the 1098 head limitations which I cant at the moment.

[linearaudio]

BMC is right- Don't waste your time working on the standard head, it's far too much work to get a noticeable improvement, valves are far too small. Also by the time you have reprofiled the combustion chambers you will need a good skim to get the compression ratio up again. Find a cheap 940 head, all the porting work and much bigger valves already done for you! It will probably cost you more than the price just to get your old head skimmed! Don't know about raising the gearing on a standardish engine. It may sound busy on the flat, but when you get on an uphill drag the power fizzles out quick enough on standard gearing, especially with any weight on board!

[wanderinstar]

Find a cheap 940 head, all the porting work and much bigger valves already done for you!

I wouldn't say all the porting is done. You try putting a finger down the exhaust port. Very restricted. Whip the guides out and remove the guide boss, certainly on exhaust and possibly on inlet. As recomended by you know who.

[linearaudio]

Find a cheap 940 head, all the porting work and much bigger valves already done for you!

I wouldn't say all the porting is done. You try putting a finger down the exhaust port. Very restricted. Whip the guides out and remove the guide boss, certainly on exhaust and possibly on inlet. As recomended by you know who.

Granted, but not more than a couple of minutes work to slim the boss down, and even without doing it, still breathes far better than the 1" valves on the 1098!

[sowden]

Gang,

I've been mulling your comments over; if the 1098 std head is really that untunable, it might be best to pitch for the 1275 instead and getting it machined as suggested by BMCEcosse.

Thanks for all your coments.

Cheers

R

[linearaudio]

Gang,

I've been mulling your comments over; if the 1098 std head is really that untunable, it might be best to pitch for the 1275 instead and getting it machined as suggested by BMCEcosse.

Thanks for all your coments.

Cheers

R

IF you're lucky ( I was) you won't have to sink the valves/relieve the head. It seems to be a touch and go thing. Worth doing the calculations first before sinking the valves, remembering the thickness of the head gasket, which you can use as your minimum clearance factor (app 0.8mm) Years back I did a 1098 head to the book, ended up with a huge pile of filings and had to take 120 thou off the face to bring the compression up, which then meant brazing up the oilway that had broken through. Made the car sharper and about 5mph at top end, but what an effort!

[bmcecosse]

Yes - we-ve all been there modifying 202 heads in the past! I've still got one somewhere that we skimmed so much - the deck moves under finger pressure - although it's still not into the oil way. Concentrate on finding a 12G940 head - and an MG Metro inlet manifold, and an HIF38 SU carb. That's the cheapest way forward for a good 10 bhp increase.

[bmcecosse]

This is the head to go for -this one is at the top of the price range I would pay! http://cgi.ebay.co.uk/1275-Cylinder-Hea ... 240%3A1318

[sowden]

Hi BMC,

I'm watching this head! Its my kind of price too, I have to say (my alterego is called Dr. Stinge).

I dont want to get my hopes up though, as ebay is a bit crazy and unpredictable at times; so we will see what the fates have in store.

Good news on the diff front - I won a 3.7 diff in good nick tonight.
V. chuffed about that. I hope they are not too hard to fit!

All the best,

Russ

[bmcecosse]

Easy to fit - normally quite expensive, so well done on the auction. Be aware it will throw the speedo out quite badly! I 'think' you will need a speedo with ~ 1250 tpm.

[sowden]

BMC - the head went for £35 - must have been the double valve springs!

[bmcecosse]

Yes - I was watching it. See the Oselli head that's on now - nice head - but it will go for daft money!

[alainmoran]

I dunno ... its the third week of the month - traditionally the time when people are skint and dont bother with ebay, plus with christmas coming up and the credit crunch, if you have the spare £ (and I do - i just got a raise) then there might be a bargain to be had ;)

[sowden]

I've just had a quick email conflab with the vendor (seems like a really nice guy, and an A+ nut to boot!), to buy-it-now, I confess; but he's keen to let the auction run. I imagine it will fetch good money but I've had a punt on it just in case the fates deem that its got my name on it.

The good news is that in the interim, my 1098 is running lovely (touch wood)!

[MikeNash]

Sowden,
Can I offer a sideways view? I'm not against the search for power, but you say yours feels happy at only 55 mph - why so low? My standard 63 Trav, although worn and loose, will cruise happily at 60-65 (true) for literally hours, even when towing a light trailer. It might then burn oil at only 150 miles per pint and have only 40 psi when the oil's hot (210F -and then only 8psi on hot tickover) but like all minors if its got good compression it should pull all day.
I don't think it worth increasing the power if you can't use the power you've already got to the full and be able to use it continously, and I think the real problem for minors is the noise and vibration, much of which comes from unbalanced wheels and brakes.
Its not good enough to just have the wheels balanced. After a suggestion from bmc, I tried balancing them myself on a scrap hub which I'd desealed and degeased - and found to my astonishment I found that the hub itself would need 10g at the wheel rim to balance and the brake drum alone another 40g! With all wheels sorted and matched to their drums the car was transformed, going to 70 -75 with untold smoothness. With a fully adjusted steering rack and new front suspension bushes together making the steering pin sharp, it was a joy.
And does your propshaft make a light "ting" as you pull away? (like mine). If so you'll gain more smoothness by replacing the spider bearings.
Finally, I set my carb slighly rich and run with NGK BP6E plugs, far colder than normally recommended - but when I've the foot to the floor on a long motorway rise and punching upwind, pre-igntion is what I don't want. (One day I'll try the effect of bmc's favorite timing method - but he'll explain that.) Regards, MikeN.