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MG TD TF 1500 - Actual XPAG BHP

Took the TF for a Dyno (rolling road) test today to see what the actual horesy power is. Any guesses as to the real rear wheel horse power on one? I'll post the graph in a couple of days.


OK LaVerne, I'll join in the guessing game:-
26.9bhp @ 3300rpm and 42.3bhp @ 5500rpm.

Will be fun to see how close we get before you spill the beans.

TD/C 7822
G.D. Smith

I would say it's about half its rated power, or abour 27bhp at 5,500.

Denis L Baggi

Horesy? How about Shetland Pony! What upgrades have you done to your engine, if any, 1250, or 1500cc. I hope to post a time to speed, say 40mph to 60 mph, soon.
Len Fanelli

Stock rebuild on a 1250. I'm at 4600 ft elevation if you want to plug that into your guess. How about ft lbs
of torque?

Ft/lbs! My guess would be in inch/pounds! Ok, OEM quotes were 765"/# at the flywheel,@ rear wheel may be 400"/#
Len Fanelli

I thought we might get some more guessing. Anyway as Len has pointed out, these motors have just about the same power as your average margarita blender. The graph was almost identical to one the shop had for a Kawasaki 400. What beasts these are.




Aside from the awe-inspiring [terrifying? hilarious? death-defying?] numbers, it's really good to see both torque and hp rpm peaks. Is that with a standard-grind cam? I'm wondering what my Moss/Crane 260/270 degree cam will look like, whether I'll still have those 3300 and 5500 torque and hp peaks, or whether they'll be moved up the rpm scale a little. what do you think, group - 3300 torque peak to 3600, 5500 hp peak to 5800?

Dave Jorgensen

Now you know why a 3bhp increase is so worthwhile = +10%
Maybe time to start feeding the mousies!

FR Millmore

LED.....I think thats pretty interesting. Will save your image for my files. I would have guess about 50% of advertised HP was correct.
Looks like anything over 4700 rpm is a waste of time and keeps your engine together.
Colin Stafford

Yikes! No wonder the original 0-60 times are so slow. Too bad the engine is finished, as this really makes me want to hop it up. According to my rough calcualtions (and I'm not good at math), this would be about 24.8 HP/L, while a modern 3L Nissan V6 would be about 78HP/L. Big difference. George
George Butz

Don't forget that these readings are at the rear wheels. On small HP engines, its quite normal to have a lot of power soaked up by ancillaries like the water pump, fan, dynamo, gearbox, etc.

I recall Tom Mccahill saying that the Brits were trying to rate their motors like the Americans which was on an engine stand with all ancillaries removed, but I don't think it ever happened.

So 57% is probably not too bad. I can hardly wait 'till the next person asks me about the HP, and I will reply with 31 at 4800 revs.

Gord Clark
Rockburn, Qué.
Gordon A. Clark

As soon as my engine is rebuilt and the Judson is back on, I am going to do a dyno test, Will post results here when that is done. May be till spring since parts are not readily available at this time and winter is comming. Be interesting to see what the diff is with the supercharger on the car.
TRM Maine

I just finished installing a used Moss s/c on my TD. It may only be worth 20 hp at the flywheel and less than that at the rear wheels. But it does change the personality of the car so much. Much smoother and drivable in traffic. Tonight I am trying a freeway pass that used to drag me down to 48 mph at the crest. Hoping to keep above 60. Eventually, I want to try the numerically lower rear gears for better mileage.

The S/C is definitely the way to go, if one can find one.

Tom Balutis

Hi all heres another view to thequestion of
HP Its a 1250 ccm engine. Compare that with a modern 1500ccm car (lots of european and japanese cars have that). Try to start your modern car in 2 gear with the same RPM
the modern engine will stall if you dont
press the pedal to the floor.
As the answer on the qiestion to a ROLLS ROYCE driver How many HP do you have?
ENOUGH Thank you.
I am not racing my TD
Cheers Thoralf. Noway.
t g sorensen


Mr.Downey's HP & Torque numbers look about right.
Do remember that he is almost a mile high in altitude and this will make a big difference in HP numbers.
Years ago when I developed the Moss Supercharger for the T-series we saw the following numbers on our freshly overhauled development TD (Thank you Cody!)
Stock 39 hp, Supercharged 68.5, for a gain of 75% in power! In the course of my everyday work of designing superchargers and systems, we dyno test hundreds of engines and vehicles, typically we figure a 25% loss of HP through the driveline in a 2wd vehicle.
I like to quote HP at the wheels as this is where it really matters, thought the number is always smaller.

"carburation is nice, but I'd rather be blown!"
Terry Peddicord

Tom, I agree that ths SC is the way to go. I also put a 4:11 rear end in mine, going from a 4:55 and that really makes a difference. If you have the stock rear end I would suggest a change to the 4:55 or the4:11 if you can get one. SC is nice but as I can attest there can be some problems with them, IE blown head gaskets and broken crankshafts...Still I am going back with the Judson. I will post photos of the new crank, pistons and rods and the completed engine when all is done.
TRM Maine

The purpose of the dyno test was to obtain a base reading for some future engine modifications. I didn't expect a lot and was certainly not disapointed. With the 5 speed tranny and just about any direction of travel from my home for a long journey requires a climb to over 10000 feet it's clear that some help is in order. I'm not a total gear head but for those of you who want the details... Stock block 1250.. .040 overbore... stock type Moss (Crane) cam... newest Moss tappets.. new lifters... new Moss crankshaft... new timing crank and cam gears... the late Skip Kellsy's allen head pinch bolts on the rods... all new main and rod bolts and nuts( nyloc)...Flywheel surfaced but not lightened and machined for the Moss rear seal water pump..rebuilt oil pump..all pieces statically and dynamically balanced... head is stock thickness... all new valves... bronze guides... original rocker arms and shaft with pedestal shims...slight polish of ports and chambers... same with intake manifold... matching manifold to head and carb bodies... all running through totally rebuilt carbs and out stock powder coated exhaust manifold and Moss ( Falcon) stainless exhaust... MGB air filter bases bolted inside "bumblebee" type air filters to carb faces... power out through Datsun " Steve Neal" 5 speed to a rebuilt stock 4.875 rear end.
Power is ok on the flat with speeds of 80 obtainable if no head wind. Uphill pulls are are a test in patence.



I have heard of the 4.55, easily available, and the 4.3 (from the MGA). But where does one find the 4.11?

BTW, Terry's data is enlightening. I did not realize the SC makes that much of a difference.

Tom Balutis

One of our local guys built it for me. Think it came from an A.. Contact me e mail off line and I can give you the information.
TRM Maine

Tom B. The 4.11 was in the last of the MGA's. Think they were badged MK II and Classic or Custom, something like that. What it was basically was a twin cam without the twin cam engine. It had the knock off type spinners on the wheels and a bunch of other stuff from the twin cam. Not too many of them around.
R. K. (Bob) Jeffers

Thanks, Bob. I do know the model, but I did not know that the differences included the gears. I'm inclined to agree this would be a rare bird.

Tom Balutis

Dave, I would think torque, & H/P, at the lower RPM# (3,300, & 5,500. I sould receive my cams this week with about 3-4 more degrees duration Than the Moss, Crane H/P cam, & should be more in the range of 3,500-3,800 & 5,500- 5,800 range.
Len Fanelli

The 1962 MGA Mk II had a 4.1 (not 4.11) rear end as standard (ie: All the MGA's with the 1622 cc engine).

I have these gears in my TF 1500, it makes expressway driving easy!

When the XPEG engine was rebuilt, it was tuned and broken in on a dyno by Bob Wagner. The engine was Stage 2 tuned as per MG Specs.
It showed 73 HP at 5000 RPM, and estimated an 84 HP at 6000 RPM
(He didn't run over 5K since breaking in)

The HP was measured at the Drive Shaft, not the wheels.

The Factory quoted 57 HP (I think) for the TF 1250, and 64 HP for the XPEG, TF 1500. These were "Advertising" numbers not necessarily actual dyno measured values.

I can outdrive all the MGB's in the mountains.
Don Harmer

Don is correct the correct reading for the rear end in my car is 4:1 not 4:11 and the driving is very nice with that gearing.


I was amused to see you say " .. I can out-drive all the MGB's in the mountains."

Our club had a 2-day event in the New Hampshire mountains last year, and on two occasions, the MGBs couldn't keep up with me.

My engine specs are very similar to LaVerne's. No 5-speed (but would die for a Skyhook conversion), but do run a 4.3 and I have a lovely cyl. head that breathes well.

Gord Clark
Rockburn, Qué.
Gordon A. Clark

This thread was discussed between 01/09/2007 and 10/09/2007

MG TD TF 1500 index

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