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Realistic power expectations

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drooartz

drooartz

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Okay, I've been a bit power spoiled these last few days, riding my motorcycle around. Flattens hills and straightens curves, as the Dukes of Hazard would say. Got me thinking about LBCs and power.

I'm not looking for massive grunt, just the ability to hold decent speed (say, 50) on a hill. My daily driver, a 2003 Hyundai Accent automatic, seems to do just fine. Not the speediest around--probably one of the slowest new cars about--but passable. Is this kind of power reasonable to expect from a Spridget, assuming a swap at some point to a 1275?

I ask because I'm beginning to see that the Tunebug as is may not be the best ride for living in the mountains with lots of hill grades everywhere. The TR4 I just sold did fine, limited only by the lack of a functioning overdrive (and of course by the buckets of rust--though I suppose it lightened the car!). The Tunebug struggles even with small grades.
 
A 1098 head with mild work done to it, a mild cam, lightened flywheel and 1 1/4 carbs (or squared out stock ones, if you want to look original) should get you a bit more hp with a reasonable cost. This would probably add between 10 and 15, which translates to about a 25% boost in power with the engine looking fairly stock.

If you don't care about the stock look I would say a 1275 or adding to the above an intake manifold and header.
 
Right, it was made for england and you know how they drive. A straight 1297 would give you 1/3 more horse power in stock trim.

Oh, what's the rush it tops out at 73. But you knew that, it is in the corners where it shines. Suck em in and watch em go into the fields.
 
It's not the corners and straights here, but the hills/mountains that are the issue. I was down to 30 mph on US 40 between my house and my work. It's a divided highway, gaining about 1000' of elevation. That's almost slow enough to be scary on that road, and there's not another way to get anywhere--the downside of living in the mountains, I guess.

Top speed is not even the issue here. 55 in the Bugeye feels plenty fast! Just want to be able to drive the mountain passes without having to get out and push. /ubbthreads/images/graemlins/grin.gif

No real concern about originality, as long as changes are reversible. That's one reason I'm wondering about the 1275 option. That way I can crate up the original 948 and smooth case if I or a later owner want them (they're original to the car). Budget is the higher priority, as cash is always tight.
 
A fresh 1275 would be a significant gain in HP, but a fresh 948 would probably be a big improvement as well.
 
Well with a 1297 and a turbo you can prob get 130 HP or so, and that's a far cry from 42. But then why not a car with a bigger moter from the factory. Keep it stock.
 
A stock 1275 puts out 60 to 65 HP. After losses through the drivetrain, that translates to about 55 HP at the rear wheels. I would imagine a stock 948 puts down around 40 HP to the rear wheels on a good day.

Making the assumption that a Bugeye with driver weights about 1700 lbs, the stock setup drags around 38 pounds per 1 horsepower.
The stock 1275 should have numbers around 31 pounds per 1 horsepower....a noticable difference.

My old, stock 1275 box-Sprite could wind to redline (6300) in fourth, which is about 95 mph.

I co-drive another race-Spridget in enduros. That car, a 1275, has a mild cam, 10:1 pistons and a modest carb improvement. I would say it has about 75 or 80 HP to the rear wheels. In a Bugeye this engine would move 22 pounds with 1 horsepower. This would be a nice,speedy combo.

This hotted-up 1275 wil still run on 94 octane street fuel, but just barely.

With a 3.9:1 final drive, I've had it to around 6700 rpm in fourth, which works out to about 105 mph.
Our 1275 race-Spridget has a full windshield (so does my 1500 car), so the aero is about the same as a street car.

A 3.9 final drive (from a rubber bumper Midget) will help your cruising rpm, but you may lose a bit of "grunt" in fourth Your car should have a 4.22 final drive, if it's stock.
 
Hmmm, I forgot your car had a 4.22. I'd think you could pull that sort of incline a little easier than you described.

If it were me, I'd probably opt for a 1275 and rebuild/mothball the 948. It sounds like you want a fun driver rather than a showcar. The 1275 still retains the character of the car, but makes it more useable in modern traffic.
 
remember too that higher altitude lessons the power output. If a stock motor puts out 40 hp to the rear wheels, up were you live it may only be putting out 36 or 38. Go with a 1275 you will be much happer.
 
I have a atock 1275 in my BE, it hauled off nicely, could chirp the tires in second. I would not change to a 3.9 ratio in hilly conditions.

The mods that I am doing on the 1275 BE are equavalent to the enduro mentioned above by Nail. I am doing a little less with the compression, so that I should be able to run on pump gas and a little more on flow.

If you are not concerned about appearance and have a budgeted amount, I would recommend the 1275. IMHO
 
Yep, about 75-80 with 1275 at rear wheels is pretty close, with just a little work. It would ber a big improvement over the 948. One of the big things you will notice is the increase in torque in the 1275 compared to 948. Let me know if I can help, LBC motors are what I do and 1275s are my specailty.
 
I thought the rubber bumpers had a 3.7:1 diff. My 71 had a 3.9:1 diff but it seemed too low and I have changed it to a 3.55:1 gears so its better on the highway. I have not got mine back together to test it yet. With the stock 1275 and the 3.90 mine did fine here in these mountians, but the high mountians of the rockies might be different, but still as low geared as it was I could hit 3rd gear and take any grade at a pretty good clip. I'm sure you could get more power out of the 1098 but IIRC people started having bottom end problems when they did that. Something about the size of the rod bearings. I would go with a 1275, you can get all the power you want out of them with enough money /ubbthreads/images/graemlins/wink.gif When I lived in the UK, I knew a couple guys who had 1275 minis that were absolute terrors once they changed cams and went to flat top pistons and roller rockers.
 
Drew,

I've never driven a 948 powered car, but my 1275 Bugeye has plenty of grunt (though still not as much as the TR4). We have plenty of hills around here, and usually, the curves slow me down before the grades do.
 
Not quite ready yet for a new motor, but I'm definitely leaning towards the 1275 route. I've never been much of a power guy (my current largest motor is the 1.6L in the Hyundai), but the 948 in the car now is not adequate for where I live. Part of me says, well then get a bigger car, but I'm not quite ready to even see that as a remote possibility. The nice thing about the 1275 option is that the original engine is preserved and can be reinstalled later.

If I can get everything running smoothly, I might try to do a dyno run to see where the car is now. I'm sure the engine is tired, and that might be part of the problem.

I'll certainly let you know, Hap, when I get to the point where I'm ready to make an engine choice. I've got some planning to do first to see what I really want to do with the car.
 
Where did those 3.55:1 gears come from?

As an aside, only the latest 1500's came with 3.7:1. Perhaps only '79, or some '78's. Mine's a 3.9:1. I'd definitely be interested in a 3.55:1 gearset to make cruising at 65 MPH yield less than 4300 RPM ...
 
[ QUOTE ]
Where did those 3.55:1 gears come from?

As an aside, only the latest 1500's came with 3.7:1. Perhaps only '79, or some '78's. Mine's a 3.9:1. I'd definitely be interested in a 3.55:1 gearset to make cruising at 65 MPH yield less than 4300 RPM ...

[/ QUOTE ] I bought mine from Vicky Brit. Its supposed to be the same ratio as used in the lotus 7. Its all Mowog stuff so it will interchange. My old gears were 10 on the pinion and 39 on the ring. New gears are 11 on the pinion and 39 on the ring. I have also installed a Datsun 5 speed and its supposed to have a lower 1st gear so I'm hoping that works out good. With the higher diff and 5 speed I am hping for less rpms on the highway and better milage as well. I still have a long way to go though. I hope to test all the running gear within the next month or so. I want to give it a decent shake down mechanically before I go to putting fenders back on and start exterior bodywork and painting.
 
[ QUOTE ]
As an aside, only the latest 1500's came with 3.7:1. Perhaps only '79, or some '78's. Mine's a 3.9:1.

[/ QUOTE ]

Yep, GAN6 200001 on, starting in '78, together with the "safety" 4 spoke steering wheel, oil pressure gauge delete, and a few other things. /ubbthreads/images/graemlins/computer.gif

My '77 has the 3.7, but that's because I pulled all my running gear out of a '79...
 
Just for the record, all A-series engines have the same rod journal sizes, but the mains are different on the engines, The 948 and early 1098 had smaller main journals, late 1098s and 1275s have larger mains. The quality of the steel used in the crank and rods on the 1275 is much better than the 948s as well. The one thing for sure that gives me the creeps about a 948 is the pinch bolt on the small end of the rods, if I have to use a stock based rod in a performance/race 948, I like to switch to 1098 rods which do not have pinch bolts and of floating design. Make no mistake about the 1275 is not just a bigger motor, it's a much better motor as well.
 
Thanks for that info, Hap, though I know so little about the internals of engines that I caught maybe half of what you said. I can certainly appreciate your point, though, that the 1275 is a better motor all around.

I'm now starting the planning process for the Tunebug. It's time to figure out what way I want to go with it, and budget time and cash accordingly. I can feel that old "shipwright's disease" coming on... pull the motor, might as well redo the other brake lines, while at that, probably should take care of the few rust spots, might mean paint, maybe interior... /ubbthreads/images/graemlins/grin.gif
 
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