TR2/3/3A Supercharger Advice Requested

I'd like to improve the way my '61 TR3A drives and am considering the Moss Judson-type S/C. I've owned the car only 2 years but from what my mechanics tell me, the engine doesn't show signs of having been rebuilt. Moss offers a low-boost unit for stock engines like mine and a higher-boost model for those with 86mm-diameter cylinders, i.e., rebuilt engines. I don't put on a lot of miles - maybe 500 a year nowadays - and have never actually redlined the car (though I might be tempted with a S/C installed), so the chances of me blowing up the motor are reasonably slim, IMO.

I'd rather not go to the expense of a rebuild, hotter cam, stronger crank, pistons, rods, etc. on top of the cost to buy and install a S/C, if that is avoidable. So, that means the low-boost model for stock engines. I'm also thinking of getting a SS exhaust with headers & a cooling fan to help the radiator. I'd also like the steering converted to rack-&-pinion to make it easier to turn the wheel when parking.

Any comments and advice as to what's the best way to proceed will be much appreciated. Please bear in mind that I am going to be paying for the labor to do all this work as I am not able to do it myself, so keeping an eye toward most bang-for-the-buck is what I'm after.

Thanks.

Let me see if I've got this straight. You have a 50+ year old engine that has never even been freshened up; and you're going to bolt a supercharger on it. And this is because you feel the stock performance is inadequate, and yet you've never even tried getting maximum power from the engine you have.

Be sure to post back here with your results, I'm fascinated!

I don't care what Moss says about the super charger is just a add on. I have a super charger on my Tr 3. I installed it on a good rebuilt engine. Like you I rarely hit. Red line. But the fun of the s/c you just have to use your right foot more. With only about 7000 miles on the motor before I installed the S/C it only took a few thousand more to crack the crank shaft. My point being if you got you will use it. Build a motor that will take a little more abuse than the 50 year old lump under the bonnet. p.s. listen to Randall

Points taken.

OK, so if you have a relatively healthy engine that isn't very lively feeling, what would you do to improve the driving experience? A rebuild would make it strong and smooth but it won't have the oomph I'm missing. I compare it to my '63 Healey 3000 and it of course comes up short performance-wise owing to the fact that it has 2 fewer cylinders. I'd like it to be as lively as that car so I thought of the Moss S/C. Do you instead recommend rebuilding the motor to gain naturally aspirated performance? If so, what is recommended for improved intake? Webers? Mikunis? Will a hotter cam and heavier breathing carburetors be all it takes to give it that missing oomph?

My alternative is to get the higher-boost S/C and rebuild the engine but now were' getting up there in cost. Wouldn't a rebuild plus the S/C plus the headers/exhaust run me $10K or more? I've still got the steering and cooling to invest in on top of the engine. I don't want to make this impractically expensive. That's why I asked for advice.

It's not that difficult to get some nice extra ponies from the TRactor engine. When i did my resto, the engine was rebuilt using 86mm pistons & liners. I also had British Frame & Engine regrind the cam. Nothing too wild. I also shaved the head some to get some more compression. I added a tubular header, but retained the original rebuilt SUs, as they will flow plenty for the modest increases I made. I did have to change needles however based on my O2 sensor readings.

I've never had the car on a dynamometer, but a good estimate of 125 flywheel horsepower is probably not overestimating. I try to keep the revs down to 5k, but the engine is so eager, that revs to 6k happen every now and then, especially in first and second.

Also, I installed an Eaton supercharger on my Miata. I used to swing wrenches for a living, and the job still took me somewhere around 8-10 hours to complete. I would think that the time to do it on a TR3 would be similar. That's a lot of time to pay for a mechanic to add some horsepower to an already suspect engine. At six psi boost, an Eaton SC will add about 40% more power to your engine. I wouldn't trust that on an engine that wasn't built with that in mind.

I feel your money would be better spent on natural aspiration upgrades as you rebuild the engine you have.

I would also recommend a lighter flywheel. Won't add any HP on the dyno, but made a noticeable difference in how responsive the engine felt.

Thanks, Art & Darrell. All very good advice which sounds prudent and reasonable. I will probably go that route.

For your perusal. Lots of interesting info here:

https://www.tr3a.info/Net.htm

Darrell_Walker said:

I would also recommend a lighter flywheel. Won't add any HP on the dyno, but made a noticeable difference in how responsive the engine felt.

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How many hours of work would a mechanic need to replace the flywheel?

Art Did you install the RH needles in the Su's and what O2 sensor did you use? Whereabouts on the header did you install the O2 sensor? Thx Karl

karls59tr said:

Art Did you install the RH needles in the Su's and what O2 sensor did you use? Whereabouts on the header did you install the O2 sensor? Thx Karl

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Nothing has been done to the engine since I first started this thread except replacing the head gasket and a tune up. Never did install the S/C.

61TR3A said:

How many hours of work would a mechanic need to replace the flywheel?

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I think you'd have to ask the mechanic. It isn't a big job (gearbox must come out, clutch/pressure plate must come off) though you may get some other things done while you're there such a new clutch (depending on the condition of the current one) and a new clutch fork pin plus back-up bolt installed (if not already there).

I work slow (but cheap) so am in no position to tell a mechanic how long to take.

Be aware (perhaps you are) a lightened flywheel will indeed change the characteristics of the car, possibly in ways that you would not like. Depends on what sort of driving you have in mind.

Have you abandoned the notion of a supercharger at this time? I'll admit I haven't followed the thread thus far but now that I'm here will add: I concur that doing extreme mods without first doing a basic rebuild seems to be putting things in the wrong order.

61TR3A said:

How many hours of work would a mechanic need to replace the flywheel?

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As Geo says, you'll probably need to as the mechanic.

I would take me a full day, but I've done it before. A lot of that time is taking the interior apart to pull the transmission tunnel.

I've asked the mechanic and was looking for verification from others who have no financial interest, such as yourselves. I haven't gotten an answer yet from him but I should soon as it was in the form of an email, not a face-to-face or phone call.

As for the Moss S/C, they make two models: one with higher boost which is only for installation on a rebuilt motor with bored out cylinders and larger pistons, and a low-boost model for original engines that haven't been rebuilt or bored. I don't think they'd offer 2 models unless there's a viable market for each, hence there are plenty of cars out there sporting their S/C that are bolted onto original engines. It isn't worth it to me to rebuild an otherwise healthy engine and then double that cost by bolting on a supercharger. I'd just as soon bolt on the S/C on my engine as-is since I don't flog my car. If I want fast acceleration I have other cars to take out and WOT so the likelihood of me blowing up my engine is remote.

I don't remember the big Healeys leaving my TR3s in the dust. Perhaps your engine is in more need than you think. I would start there.

The flat rate manual shows 6 hours. 5.5 to R&R the clutch, plus another 0.5 for the flywheel. But I sure don't work that fast!

Thanks!

karls59tr said:

Art Did you install the RH needles in the Su's and what O2 sensor did you use? Whereabouts on the header did you install the O2 sensor? Thx Karl

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Yes, I put RH needles in the the SUs. My O2 sensor is an AEM wideband. See the pics for header location. The O2 sensor in the pics is a narrow band I had in there just to see how it would work out.

Geo Hahn said:

Be aware (perhaps you are) a lightened flywheel will indeed change the characteristics of the car, possibly in ways that you would not like. Depends on what sort of driving you have in mind.

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Seems to also depend on the health of the engine and how well you adapt. I put a Fidanza alloy flywheel (about 10 pounds IIRC) on my former TR3A and, while it did really transform the low speed behavior of the car (much more responsive and nimble), I always had to remember to launch at a higher rpm than I would with a stock engine. And I still killed it from time to time, when driving casually and not thinking about it. That engine was stock otherwise, except for 87mm liners.

My current TR3 seems more forgiving, not sure why. I've still killed it a few times, but overall it seems noticeably easier to launch than the 3A engine and I don't need to think about it every time. Unfortunately, I don't really know what is inside it, forgot to even check bore while I had the head off. But it doesn't make any extra power on the dyno, so it is probably still stock inside and the difference is just the general state of wear (or perhaps 83mm vs 87mm and the matching bump in compression ratio).

There are also certain risks with an alloy flywheel. Lots of racers have reported that they work loose from the crankshaft. But the Fidanza is specifically machined to be a light press fit onto the crankshaft flange, and I saw no signs of damage when I moved it from the wrecked 3A to the current TR3. (Had to use heat to get it off the old crank.) Of course I also don't race, apart from the occasional autocross.