You can easily get 90 horsepower out of a 1380, you have to be good to get that out of an 1100.

Now, to be fair, a supercharger would not look out of place under the hood of an ADO16 car.  Just saying.

I bet 1098's would be pretty popular if you could EASILY get 90hp out of them.

If you think you're going to get 85-90hp from the 1100 then you will need to start considering an LCB. Since 90hp would be close to double the stock hp of a 1098 it's probably not going to be a very streetable engine. Of course, everyone has their own definition of streetable.

Kelley

From the above mentioned article on MM's site:

"  1. Cooper FreeFlow: The best all rounder for all road cars where up to 85-ish bhp’s expected. Only slightly restrictive up to 90 bhp. Mid range/drive-ability benefits usually out-weigh slight loss at top- end. Supplied in the better, properly developed stage one kits for most engine sizes

 3- LCB Medium bore: Engines where 70-110 bhp’s expected. Best used on longer stroke type engines like 1100 and 1275cc units. Gives good over-all performance on race 1000s. Contrary to popular opinion, isn’t best suited to engines where less than 70 bhp’s expected - in fact can be detrimental to power, consequently not recommended.  "

So I guess it all depends on how much HP you think the motor is going to make. I would think that the more cylinder head flow would lead to the need of the med LCB. If the cylinder head is going to be left un-touched then maybe the FreeFlow would be better.

The Cooper freeflow manifold might be a better choice for your application than an LCB. See this link:

//www.minimania.com/part/C-STR816/Freeflow-Exhaust-Manifold-Header---Mini--Mini-Cooper

There is a good explanation of the choices in the article attached to the page above.

Kelley

rick, I sent you an email using address in your profile

I;ve not yet tried the stock Cooper and S exhaust manifold.
Would the front pipe clear a mechanical fuel pump?

They LCB header can work but you have to 'releive" some metal from the balance pipe on the bottom side (not visible) on the twin HS2 set up. I know of a 1275 Mini that runs the 998 Cooper stock 3 into 1 exhaust header and it pulls good with plenty of low end torque.

The MG 1100 weighs a bit over 1800 lbs. An MG Midget, also with a 1098 engine weighs a bit over 1600 lbs. This may give you a good starting point for comparisons. It may also be easier to find comparisons between the 'B' and the Midget.

Since you're looking at doing canyon runs rather than racing, I would think that you would find power across a broad range of RPM more useful than a big power peak within a narrow RPM range. If this is the case you probably want to look at raising the compression ratio and keeping the intake velocity as high as possible across the RPM range. Sizing the intake manifold/ports and the exhaust ports/manifold is crucial. They should not be too big.

Kelley

For an uneven comparison, I have a 1320 in my MG1100, twin 1 1/4", SW5, 3:65 final drive.I have installed a bunch of sound deadening and have a full set of Austin Princess leather seats, so she weighs more than a standard 1100.

That said, I understand that a worked 1100 would make similar outputs to a stock 1275, the "heavy" 1100 with the tuned 1275 keeps up to the "B's" without any trouble at all.

Thanks, I should point out that it is an MG 1100 and not a Mini.  I am trying to keep up in club canyon runs.

 It use to be said;'there's no substitute for cubic-inches.' I don't know what the 'power-weight ratio' is between a 'B' and a 'well sorted'out' Mini. Pretty sure others here do. My`70 'B'  w/a V8 weighed about 2,100 lbs-as the standard 'chrome-bumper' MGB's, but put out double the h.p.[200] & torque, compared to the [std] 'B' 1.8 ltr. 4 cyl.[100 h.p. max]. The V8 alone weighed 45 lbs. LESS than it's orig' 4 cyl!  I found shedding lbs. from our 'LBC's' pays in available pwr & handling.    The late `74 -`80 'rubber bumper' 'B's' are heavier [the front bumpers weigh around 63lbs!]. These 'rubber 'B's, [especialy N.American] are 'cat' fitted & 'de-tuned [65 h.p].

So, Rick unless you come accross say, a 'Killer 'B,' I'd not be too fearfull, even if one 'slamed you' in some 1/4 mile run, you'd  give 'em a hard chase on the twisty-bits! And THIs IS where the Mini excells and your 'skill' & 'finesse' [or lack of it] will quickly become manifest.  -John

I just want to have a reliable car that will keep up with MGBs. 

Over the years I have found a medium bore Maniflow LCB, or (Australian) Perry LCB to give more torque & HP than a freeflow, on 1098s. They really seem to like the extra secondary pipe length.
I have never used Graham Russell's Supa pipes, but the engine dyno numbers show they are better.

Yes, I think Graham aims for velocity into and out of the chamber, thus the Supa Pipes and his own design intakes for both SU & Weber...together with head and cam.

I thought too big of a exhaust manifold on a small bore motor would loose torque? It was my understanding that the smaller manifold like the cooper manifold or free flow were more beneficial than a lcb on a small bore motor. I thought I read that in a Russell Graham article. 

I will look into the pipes.  I already have a set of new oversized pistons so I think I will get a good cam, have the head worked with larger valves and hard seats, rebuild the dual SU 1.25 carbs, and get an extractor exhaust.   I heard that the MG1100s have clearance issues with LCB headers but I hope it is something I can fix. 

We ordered some .60 over pistons from Russell and shipping was no problem. I don't think I would worry too much about the exhaust, any damage would have to be covered by the shipping company.

I am pretty sure I will be going with a set of 1 1/4" carbs on my build.

Rick, the Supa pipes are the best for HP & torque, the Maniflow med bore LCB was 2nd best I believe.
[edit] There is another article in this series from Graham concerning exhausts, but I cannot find it on this site.

Graham has exported pistons etc to Don before, I'll ask him about the pipes. My concern would be possible shipping damage.

DRMINI how important are Graham Russell's Supa Pipes (exhaust extractors) in the power build up of modified small bores?

And, does he export the same to North America?