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MG TD TF 1500 - To supercharge or not, that is the question
|I know this issue has been covered over and over again, almost like "what is the correct hue of MG red". So first of all my apologies for bringing it back up again, but I am still a bit confused. |
I will do some engine hop-up jobs this winter, and at this point I see two alternative routes:
1: Port the head and have it skimmed to ca. 9:1 c.r. and install extractor manifold. Plus 10 hp?
2: Buy and install an Eaton supercharger. About twice the cost, plus 20 hp?
Put into the equation more engine stress.
Car/engine: TF with stock XPEG engine. 12.000 miles since professional rebuild 25 years ago. Everything seems to be fine, compresson about 150 psi on all four cylinders, noe blue smoke, burns very little oil and oil is always crystal clear and the colour of Newcastle Brown Ale at the end of the season - when I change both oil and (spin on) filter. Probably on its first crank and standard cam.
Is there anyone out there with a standard crank and a supercharger that really, I mean REALLY use the car?
Engine has been moved forward and lowered due to the installation of a Ford Sierra 5 speed box. Will that mean added issues when fitting an Eaton SC to the TF? Space is already cramped under that TF bonnet.
Although there is the possibility of having the car run on a dyno around here, no dyno shops seem to know the SU carbs, so I might be on my own without a dyno if I go the SC route.
Thank you for your advice gentlemen,
|Jan Emil Kristoffersen|
|All I can offer is that my TC's 1250 is running 9.1:1 at 40 over with a mild cam, and all of the supercharged TCs I drive with pull away from me in the hills. You aren't just adding horsepower with a supercharger, you're adding torque across the entire range. My MGB (larger engine obviously) has a supercharger and the torque makes it feel like a V8 at times. If I could afford a kit for the TC, I would probably go for it. But, it's a huge cost versus performance gain so if money is an issue then I'd stay with a normally aspirated engine, bump the compression and run a hot cam.|
|I have run my TF 1250 since 1980 with a Marshall 75. I hill climb and race the car every year since then and still do so.|
I have had the supercharger seals replaced twice as I ware them out, broke a crankshaft in a hill climb, replaced it with a later 4/44 one and do fit new crankshaft and big end bearings every 10 years.
I have a similar spec to your proposal but a 1250cc, I have fitted a competition cam.
It's a fast road car with an anti roll bar, that's essential.
All those years of enjoyment would never change my opinion, I just wish I was younger and could enjoy it for another 30 years. I hope I can! Oh that compressor wine!!!
A TC is lighter than a TF but a TF is still enjoyable.
Cost plus enjoyment factor is a decision one has to make, I am pleased I made that decision all those years ago.
|A street performance roller camshaft in a normally aspirated engine will outperform some supercharged XPAG cars, @ 1/3 the price, you can also use a roller cam designed for supercharged applications, I have both.|
In what way can a normally aspirated engine with a roller cam outperform a supercharged engine? Or are you talking about a fully built "race" engine?
|My use will be fast road use, and feeling the joy of some more get-up-and-go! I would rather not tear down a fully working engine to change cams etc.|
|Jan Emil Kristoffersen|
|Then supercharge...best bang for your buck!|
|Clearance is already tight in the TF without moving the engine forward Jan. How far forward did you go with the gearbox change? |
I've ridden in a highly "tuned" 1500 TF and I'd say it's comparable to my blown 1250 to a point. There is no question in my mind that I would leave him in the dust at some point down the road and if altitude becomes a factor then there is even more of an advantage to the blower.
Getting the engine to a comparable state of tune will be just about as expensive as the blower. In addition I wouldn't be comfortable pushing the engine in either configuration with a stock crankshaft.
I have no reason to doubt Len's claim on the cam, but it would be nice to see some dyno data comparisons to back that up.
|I have been playing with a '53 TD with a Marshall J75 (alleged factory installation) for 20+ years, ten years of fast road use followed by ten plus years of vintage racing.|
If your goal is fast road use, I recommend the supercharger due to its torque advantage; that is really what you need for drive-ability. The "horsepower" rating is really peak hp and it is only measured as the engine is revved up to the rpm that will give you peak power. For road use, you are seldom there.
When racing my TD I am usually in the middle of the T-series pack. I have trouble keeping up with those high compression "built" engines pulling almost 7k rpm. If you are not planning on racing, this is no concern to you.
I also recommend that you re-think the five speed, especially if it requires moving the engine forward. With a belt-driven blower you will need an additional pulley up front and you will need access in order to replace it. (Have you ever seen a supercharged TF with a five speed installed? I don't think I have.)
Instead of the five speed, just change your differential gears to the 4.3. It will be an excellent match for your supercharged torque curve (and you will not offend the originality police).
As your question suggests, you can expect to break that stock crankshaft, typically on the first journal. When I cracked mine (during fast road use) I replaced it with a forged crank from Moss Motors. (There are also other alternatives.)
Your engine sounds like it is in good shape so I would leave it as it is and add the blower with the 4.3 rear end. When the crankshaft goes you can consider building up the engine internals.
shrmnmrk at gmail dot com
|Mark A. Sherman|
|I have a stage 3 tuned TF 1500, 9.5 compression ratio. etc |
It was run in and tested on the dyno and showed 75 HP at 5000 RPM
and projected 84 at 6000 ( as a precaution we limited it to 5K)
It outruns MGB's in the hills
Scott & I are restoring a TF 1250 with the Moss blower, it also testrd
at 74 HP at 5000 RPM (8.3 Comp Ratio)
So I found the same HP but many problems found putting the blower on a TF There just ain't no room under the hood
|LaVerne and Mark; |
The five speed box installation made it necessary to move the engine 10 millimeters forward, and the new rubber cushioned front mount is also 10 millimeters lower. And yes I am concerned about the space between the frame transverse member and the engine. Seems that the TF front fender brace will have to go , or be heavily modified.
On the other hand I will have more space for the SC air filter!
I will have to do some measurements in the front of the engine bay it seems
|Jan Emil Kristoffersen|
|From everything I've read... if you've got the $$$, get the supercharger. Nothing else comes close. As far as wear on the engine; I think all the other work you're thinking of, which will raise your stock hp, will provide their own kind of stresses.|
If you want to run with more hp, day in and day out, it's going to cost you in wear and tear any way you look at it.
So if you have the deep pockets, go for it.
Me? Still waiting to win the lottery before that project number comes up :)
|Geoffrey M Baker|
|Virtually all blowers have been designed for the 1250 engine. We cruise with 3-4 psi boost regularly, up to 5 psi sometimes and 6 rarely. I'm expecting our new roller lifter cam will trap more boost with less overlap and our pressure would nudge a touch higher.|
However, the XPAG I'm rebuilding is punched out to 1466cc. Given that the 1466 cc is 17% larger displacement than the 1250 XPAG, the typical pulley ratios will not add significant boost. Check into pulley ratio before procuring a supercharger package.
|There is a new cross member setup for the five speed that allows the stock engine location. The rear cross member is now cut off leaving the original tube stubs from the frame in place. The new mounting then clamps solidly to the stubs. I don't own a TF so I certainly have no experience in that regard but I here about the space limitations all the time. Why can there not be a blister fabricated and hole put in the side panel to gain the necessary clearance, ie the blister similar to the one found on for the dynamo on a TD or a TD MKII for the H4 carbs?? Just asking|
Bill Chasser Jr
|W. A. Chasser Jr|
|Hello again, |
I have been assessing the space in my TFs engine bay for an Eaton blower along the lines of LaVernes setup. There is a lof of room in front of the cranckshaft fan belt pulley, so doubling up with a SC pulley is not a problem. As the five speeed box meant the fan had to be moved closer to the engine I installed a slimmer distance piece behind the fan. The fan can be moved forward towards the rad, but that will make it imposssible to remove or install the fan without removing the radiator. So maybe a front mounted Kenlowe pusher fan should be the only fan.
the front fender cross brace will have to go or be modified into a semirectangular shape pointing forwards and almost touching the rad.
If I judge LaVernes engine bay with SC picture correctly I may have to shave off a tiny piece of sheet metal from the sidewall of the engine compartment, just in front of where the TF1500 emblems are mounted.
My conclusion then, is that a modern Eaton SC seems feasible but fiddly in a TF with a Sierra gear box. I would love to get in touch with a TF owner who has already been through the process with the five-speed/Eaton SC combination. Should make a hell of car.
|Jan Emil Kristoffersen|
|Gene, an XPAG brought up to MK 2 specifications, larger valves, 9:1 CR 1 1/2" carbs with a roller cam will outrun a stock supercharged XPAG.|
Customer reports of a supercharged XPAG, "I can now go up a hill in 5th gear, instead of 3rd gear, with your roller cam"
LaVerne 99HP on a dyno, supercharged XPAG STREET roller cam, 2,200-5,200 RPM.
|What I'd like to see Len is something along this line in order to get a real feel for the improvement. Comparing my numbers to your's is really mixing apples and oranges. Different dynos... rear wheel verses flywheel I'm guessing...4500 FT vs close to sea level?|
I think before and afters on the same equipment at the same location really show the story. While many may not find these numbers impressive I imagine the engine would be on par to what you have if measured on the same equipment. I can feel a big difference in performance between driving at 5000 ft and crusing around sea level elevations.
Personally the real beauty of your roller setup is the expected longevity verses the tappet eating design of the stock set up.
Jan I have the Datsun 5 speed and a 4.3 rear as well. I'd really like to have a 4.55 rear to test as I really would like a little closer spacing between gears when pulling 11000 ft passes with 6 percent grades. There is no way to keep the cross brace with the super charger..after 25000 miles on my TF I don't see any issue with leaving it out.
|Do you floor your car often? That is, pedal to the metal, and hold it there a while while the engine screams? And do you enjoy frequent shifting? If you do, then you will be happy with cam/porting/header-type mods. If you are one of those people who feel guilty pushing it down more than 3/4 of the way then by all means get the supercharger.|
As others have pointed out, the SC increases power throughout the range.
But the flip side is that "breathing" type mods increase it mostly only at higher RPMs, which many T-series drivers don't seem to use anyhow.
Oh if you are one of those drives you can get a significant performance boost just by putting on a noisier muffler and pretending you have just had the engine tuneded, and using a heavier foot on the throttle and a quicker hand on the shift.
|Not by choice...the packing is gone and I'm not afraid of 5500 rpm anytime.|
|LaVerne, a friend is moving to your state, if you have a chance to get near Denver. I am sure he would let you drive his TF. He removed a Judson supercharger, & installed a roller cam, he is very happy with the results.|
(The cam removed was an OEM cam with a slightly worn lobe).
|"Gene, an XPAG brought up to MK 2 specifications, larger valves, 9:1 CR 1 1/2" carbs with a roller cam will outrun a stock supercharged XPAG."|
Perhaps, and if true then I'd love to see the data supporting it. However, having an engine built up in this manner will cost far more than a supercharger.
You can compare any manner of builds to each other, but it's always going to be apples and oranges. I've never seen any data suggesting that changing from a flat cam to a roller cam of relatively equal spec, with no other changes, will produce the performance of a supercharger. But I would love to see hard evidence to the contrary.
One of my MGs has a purpose-built engine with a supercharger and power was increased by 50%, and torque by even more. But a stock engine of the same model with a supercharger bolted on gives only 20%, maybe 30% at best. I just don't see that happening with any normally aspirated engine, roller cam or not, without sacrificing the ability to drive the car around town.
|Oops, hit reply too soon. Meant to add that of course the modern supercharger kit will offer better performance than an older design so I could see the TF mentioned above having similar performance to a Judson and a stock cam, especially since it was worn. But a dyno before and after would be more convincing of the roller cam kit's potential. Personally I would love to see the results.|
|Steve the increase I got on a stock engine.|
was in the order of 40%.
And yes before and after was what I was getting at ...like I posted.
Just looking at Len's roller set up I believe it allows for a much quicker open and close and should breath a whole lot better even if nothing else is done.
|It will certainly breathe better and last longer.|
40% is a great power gain, especially the torque gained from the blower. What cam are you running? Any head work done? Boost level?
|Stock rebuild..Crane stock grind cam...Just cleaned up the head a bit..no grinding ... 6 lbs boost|
I have another pulley I played with a bit 10 lbs boost also had Jeff recurve the dizzy. Lots of fun but in the interest of longevity I put the larger pulley back on the blower.
|6PSI is still plenty, and more than many of the old tech units. Judsons I believe only put out 2-3PSI off the shelf, and still weren't very durable.|
This thread was discussed between 22/10/2014 and 25/10/2014
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