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A horsepower question.

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regularman

regularman

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With some of the posts on here it got me to wondering about horsepower. I'm sure many of you are much more familiar with this than I am. I have fooled around with little british cars for many years but mostly what I have done is try and get them roadworthy and trustworthy. My brother had a midget when I was a kid and I helped him on it and that was about my total experience until I went in the Air Force and ended up on a 2 year tour in England. I helped people keep their cars running and the most common "beater" car that you could pick up for a few hundred bucks was the mini. No body wanted to buy a new car for a 2 year tour and then try and sell it before leaving the UK. So I worked on all kinds of minis and austin allegros, and such. The cool thing about those cars was most things were interchangable, but I never really got into making any real horsepower out of one of the a series engines. I saw 2 or 3 minis that were smoking hot with all kinds of power but I don't know what all had been done to them. Anyways, my question is this, what is the approximate hp of a stock 1275? What can be done to add horsepower? What gives the most bang for the buck? What can be done without pulling the engine? I did a re-ring job on my midget when I had the engine out. There was almost no wear on anything and I went back with all standard rings, bearings, etc. The engine had 52,000 miles on it. If everything else works out well then I might think about a few mods for more power. I am just curious whats out there. Thanks guys. Kim
 
Other folks with more smarts than me will post, I'm sure, but a good place to start is with David Vizard's book Tuning the A-Series Engine (available from Amazon and such). This is the bible of sorts for A-series tuning. Much of it was over my head, but it did get me thinking along the proper lines. I'm at least a bit more knowledgabel know, so when I am finally ready to call Hap and get the specifics worked out, I'll be able to have an intelligent conversation.
 
Proper head and valves 10 HP.

Cam another 10 HP

How's that for starters. Lots of things to do both inside and outside all the way up to 130 HP for those who wish to race.

Seem to remember that a 1275 is about 80 HP stock but more experenced folks than I on this engine will have more info for sure.
 
Original 1275 was listed as about 65 HP, I think (pre-smog). Of course, that's in 1960s - style ratings, so the actual HP at the wheel as rated today is a bit less.

My remembrance from our discussions here is that a true 70 - 80 is a straightforward process.
 
I should have told what I have. I have a 71 midget with a 1275 with stock exhaust manifold and one of those "monza" mufflers to go on it. I have a weber carb conversion as well. I don't know if that hurts or helps as far as HP. If my test out works ok and then I finish up the car this year, I might be willing to pull the head back off and do some work on it for more power, but I would not want to take out the cam, because that means pulling the motor for most people. Although it is possible to change the cam out in a 1275 without pulling the motor. I have seen it done. This british guy had these 8 little electromagnets on strings tied to a wooden stick that ran on a battery and he used to pull up and hold each lifter so they would not fall once the cam was removed.
 
To get real HP you got to go inside. Oh you can get a couple with carb modifications, the exhaust is good as stock, but a tuned one will give another couple, otherwise in you go.
 
One thing Vizard's book will tell you is that very little HP is made in the block (well the cam, but that is part of the valve train, and a little with the rings, higher max rpm, and of course compression ratio with pistons and such)

But mainly it is all in getting more air in, and out, and doing that faster. This means better flowing carbs, exhaust, valves, ports. Better valve flow can also come from the cam and rocker ratios. Proper timing and good mixture control are also a must. Then it has to hold together with all that extra power. Then you want to make sure you can transfer that power to the ground. Then you want the engine to be used within the power producing speed range.

I know, it's a lot, but small steps work well also.

Bang for the buck! I remember reading it in Vizard's book, but I can't find it right now. It would be really neat if it were available on .pdf that way I could just search it. Certainly a starter is the exhaust and air filter. A good ignition system is next. Good carburation and manifold next. Maybe interchange the last two points, or just do them both. Then 1.5 ratio rockers. That's probably all for bolt-on hp. Then it starts getting more expensive.

And you know what, Hap probably knows a lot more about this than I do.

One thing for sure. The old saying is right.
HP = $
and conversly
$ => HP
 
It's like Phil @ APT asked me: "Speed costs money, how fast do you want to go?"
 
Here is the real world values that my stock (but worn) 1275 put out when I put the car on the dyno. This is even with the stock air cleaner covers on.

69_Sprite_Dyno.jpg
 
Now that's slick indeed. Yep, I think you are right, that engine is tired. Thought they were like 80 stock?

Just looked at your pics, nice clean up. That was a good find.
 
jlaird said:
Now that's slick indeed. Yep, I think you are right, that engine is tired. Thought they were like 80 stock?

Just looked at your pics, nice clean up. That was a good find.
Click to expand...

Well Jack, you, without a doubt, know MUCH more than I do about these little guys. However, wiki says the 1275 produced 65 HP @ 6000 RPM. I think I've seen this in other books too. Judging from that dyno graph I saw higher up in the thread, I wouldn't say that engine is tired at all, given that it's putting out almost 58HP at the wheels. If that 65 from the factory was measured at the flywheel (which is common in current cars), you're only losing a little over 10% of your total power in the drive train. I've seen figures for other cars which list well over 20% (I think my Jeep cherokee is one of those beasts).

Regular,

I'm waiting for that book to show up on my doorstep, along with a couple other engine building books (from a thread I started about a week ago). I'm shooting for the low 80's, but would love to hit 95-100. One thing you should find out when looking at increases is if they are at the flywheel or rear end. Obviously you can lose alot of power there. My goal figures (which I didn't say in the original thread) are at the rear wheels. Let's be honest, why brag about HP increases if they're being lost before you can use them.

Keep up the ideas guys! I'm loving this thread.

Ben
 
What about a turbo charger? I have a turbo off a 1.8 Subaru engine and thought about trying it somehow. I would have to make up my own exhaust manifold and intake arrangement to have it work. Has anybody done it? I would think that with a solid copper head gasket that the head might be able to handle the extra compression.
 
Well not a turbo, but this is the site I've been poking around regarding a supercharger. If you click on the "shorrock" links there are a bunch of PDF's with good information about general supercharging info, which is close enough to a turbo to start.

A turbo has three main lines, oil in-out, exhaust in-out and intake. You've only mentioned 2 of them; the oil lines don't seem to be any small feat (Note: I've NEVER jury-rigged a turbo onto a car, I've only worked on my old Saab 9000's turbo). You might need to increase the total oil sump capacity, pump capacity, etc. Additionally, I'd be concerned with the amount of boost you could run without doing some major work (which is sounds like you don't want to do?)

There are a couple guys who run superchargers on their race spridgets. Maybe one of them will chime in.

Ben
 
Great sites. That gives me something to think about. The turbo that I have off the subaru has water intercooling as well. It would be a real trick to hook all that up. I have all the pipes and everything from the subaru because the crank shaft broke and I put a different engine in the subaru and gave it to my dad. I need to find another A series head to play around with and see if it is even possible to rig up. A turbo itself is really pretty simple. I never fooled around with a blower before, I remember there were some antique bolt on blowers for A series that ran off of a v belt but I have not seen one of those in a long time.
 
Jack, according to Horler: 65 hp at 6000 rpm for the 1275.

For comparison, the 1275 in a Mini Cooper S of the same period made 75hp at 5800 rpm. Spridget engine was in a very different state of tune for reliability reasons.
 
Intresting, guess I learned something about 1275s today.
 
jlaird said:
Intresting, guess I learned something about 1275s today.
Click to expand...

Hey, I'm just thrilled we finally broke him of calling it a 1296 /bcforum/images/%%GRAEMLIN_URL%%/smile.gif


Drew's advice is solid, you wanna know more about the A-series engine, read Vizard, then come ask questions /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
So an engine swap is just about 25 HP well that's about a 1/3 increase in HP over the 948.

So then 85 HP should be rather easy to do and that's about a 100% increase.

Double the HP double the fun, weeeee.

I only have one question then, do BEs do burnouts, hehe.
 
Jack:

I have always been gentle on first, but 2nd and 3rd chirp nicely. /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

Pat
 
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