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Thread: TR8 research before purchase

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    TR8 research before purchase

    I have been looking on line at photos and videos of the TR-8 trying to educate myself about the car in general. There are a couple of things I found that I have questions about. I have ordered a couple of books, which are on the way but have not yet arrived. Not even sure that the books would address the questions so i decided ti ask here.
    1. Speedometer on the TR-8: I have seen photos and videos showing speedometers calibrated to 80mph and 140mph and I may have even seen one calibrated to 130mph. I was wondering if that is determined by vehicle year or maybe factory of manufacture? I read somewhere that all Canadian market cars were calibrated at 140 kph but my question is about U.S. spec cars. I have seen cars listed as a 1980 models showing both 140mph and 80mph speedos. Why the difference?
    2. I saw a video for a TR-8 that looked factory fresh, not highly modified if at all. On the back of the trunk lid it said "Sprint" and the side badges on the front fenders said 3.9 litre instead of 3.5. A special model? or just upgrades to look factory?
    3. I have seen three types of fuel delivery, Twin Zenith SU looking carbs, fuel injection and a 4bbl conversion I believe. I know the Zenith carbs and Bosch, I believe, FI set up to be correct from the factory. What is the main reason owners convert from factory set up to a 4bbl carb? I figure the Bosch FI would be quite reliable. So, I imagine the factory carbs might be the issue.
    Thats all for now. Being new I'm sure I'll have more questions.

    Not completely new to the Brit Car scene. Previously owned a 1960 AH Bugeye.

  2. #2
    Great Pumpkin TR3driver's Avatar
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    Re: TR8 research before purchase

    As I understand it, the Bosch PI was primarily to help meet CA emission requirements (which at the time were tougher than the rest of the US). It's reasonably reliable as such things go; but we're talking about going on 40 years old. When it does have a problem, finding replacement parts can be very difficult and expensive. And it didn't offer much, if any, performance boost. So a 4bbl (Holley or otherwise) is considered an upgrade over either the twin ZS carbs or the Bosch PI.

    As far as I know, the factory never installed the 3.9 engine for production TR8. But Rover used it and it's probably an easy drop-in using factory parts. (ISTR reading an article once that even gave part numbers.) The 'Sprint' tag likely came from a TR7 or Dolomite (both of which were offered in 'Sprint' versions).

    I don't know all the ins and outs of the speedo; but my parts catalogue shows 7 different part numbers; with two only for CA, one for "Federal", and one for later "USA". Apparently the rest of the world (which may or may not include Canada) got a different speedo in either MPH or KPH. Some of those part numbers may have been found on TR7 only (but I'm guessing might be used for replacement on a TR8). IIRC there was actually a rule in the US for a short time that required speedometers to read no higher than 85 mph (and have a big mark at 55 mph, the national speed limit at the time). I would certainly be tempted to install an earlier speedo to get rid of that!

    PS, just to show the kind of problems that can happen; I've got a 2001 Toyota 4Runner sitting in the driveway that needs a fuel injection part. The part (throttle position sensor) is normally under $50 and readily available (bought one on Amazon for $35). But apparently the particular truck I have has an usual combination of options and model year that make it's equivalent part so rare that most parts references don't even list it! So it's solid unobtanium, only way to replace it is to buy the complete throttle body, which the dealer wants over $1000 for (and isn't sure if they can actually get it or not). The truck actually runs quite well and is in good condition for it's age; but very close to not being worth fixing! (It does have some other problems as well.)
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Great Pumpkin DNK's Avatar
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    Re: TR8 research before purchase

    #1 The instrumentation is all wonky cause there is a few different years and some of the early ones were "pre-production" models

    #2 The Sprint was a modified OHC 4 cyl that was used for racing. Very quick and Rare and as Randall points out is a 7
    The 3.9 is a Rover upgrade as the 3.5 and above all share the same block with minor improvements The TR8 only came with the 3.5


    #3 if you ask me there absolutely is no reason to go to a 4 barrel. To me that is backward thinking.
    Then I'm a fI guy

    Caveat. There are a lot of fake TR8s out there (mine being 1) so check the vin and Join TWOA
    Don
    "Stick a Wedge in it!"
    Mount Pleasant,SC

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    Obi Wan M_Pied_Lourd's Avatar
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    Re: TR8 research before purchase

    If you are looking for significant performance improvements though with the stock PI/FI system, I think you might run into issues....Thats why some of the cars (like mine, an81 FI), have switched to an aftermarket intake and carb or a more modern injection system to increase performance.

    Cheers,
    Tush
    81 Alfa Romeo Spider Veloce, 81 Triumph TR8
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    62 Triumph TR4 CT6716LO, 60 Triumph TR3A TS69891LO
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    Great Pumpkin TR3driver's Avatar
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    Re: TR8 research before purchase

    Apparently the TR8 ECU was made by Lucas, not Bosch. That alone seems like reason enough to replace it!

    And if I'd gone to all the trouble to not only install a 3.9 but advertise it on the side; you can bet it would have some performance mods inside, like headers, more compression and more cam. All of which need changes in mixture for best benefit.

    Perhaps Don can enlighten us: I have no idea how to go about modifying that old Lucas ECU for more fuel only under some conditions. I've read that many of the electronic parts are custom-made (no industry part numbers) and Lucas refused to release the schematic for it.
    Randall
    56 TR3 TS13571L once and future daily driver
    71 Stag LE1473L waiting engine rebuild
    71-72-73 Stag LE2013LBW waiting OD gearbox rebuild

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    Re: TR8 research before purchase

    there are a few brains inside the TWOA who have rebuilt those ECU's and the MAF sensor
    They are smart people there
    Randall I think you are have right it's like a Bosch system running Lucas stuff

    Nothing you can do to modify what's there
    You need guts either a GM system like I used to run or there are multiple kits available ...even a 4 barrel FI unit.

    The most common is the Mega Squirt systems
    If it's got a 3.9 and is running FI then it probably has this plenum

    71mm Throttle.jpg
    Don
    "Stick a Wedge in it!"
    Mount Pleasant,SC

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    Jedi Knight Darrell_Walker's Avatar
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    Re: TR8 research before purchase

    On the FI system, all the parts are Bosch (with Lucas part numbers), except the ECU (as Randall stated). The TR7 uses a Bosch ECU, but apparently they didn't have an ECU for a V8, so Lucas rolled their own.

    The stock FI system is pretty well supported via the TWOA, but is very limited in air flow, so you can't make many changes before you run into its limits. It is also tuned for emissions, not performance. When well sorted, it is an improvement over the twin carb system. All CA spec TR8s will are FI, and all 81s were FI.
    Darrell Walker
    66 TR4A IRS-SC CTC67956L
    81 TR8 SATPZ458XBA406206 (daily driver)
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    Re: TR8 research before purchase

    Quote Originally Posted by DNK View Post
    #1 The instrumentation is all wonky cause there is a few different years and some of the early ones were "pre-production" models

    #2 The Sprint was a modified OHC 4 cyl that was used for racing. Very quick and Rare and as Randall points out is a 7
    The 3.9 is a Rover upgrade as the 3.5 and above all share the same block with minor improvements The TR8 only came with the 3.5


    #3 if you ask me there absolutely is no reason to go to a 4 barrel. To me that is backward thinking.
    Then I'm a fI guy

    Caveat. There are a lot of fake TR8s out there (mine being 1) so check the vin and Join TWOA

    I read somewhere that the "pre-production models of the TR-8 were coupes and not convertibles. I have seen models listed as 1980 models with 3 different speedo calibrations. Maybe it is a good possibility that some of the cars I saw were converted TR-7s. No way to know from a pic or video.

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    Great Pumpkin DNK's Avatar
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    Re: TR8 research before purchase

    Also Canada models had funky speedo's
    And true, all PP cars were coupes
    Don
    "Stick a Wedge in it!"
    Mount Pleasant,SC

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    Jedi Knight Darrell_Walker's Avatar
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    Re: TR8 research before purchase

    Quote Originally Posted by DNK View Post
    Also Canada models had funky speedo's
    They also got some built as 82 model year vehicles
    Darrell Walker
    66 TR4A IRS-SC CTC67956L
    81 TR8 SATPZ458XBA406206 (daily driver)
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    Yoda glemon's Avatar
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    Re: TR8 research before purchase

    I heard the pre-production cars were coupes too. They was one advertised as such for sale not too far from me several years back. I got a chance to do a drive by peek on a business trip, but no chance to verify if it was what it was advertised to be. It was white and in Grand Island Nebraska at the time (circa 2000 give or take a couple years) on the very slight chance that will mean something to somebody reading this.

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    Re: TR8 research before purchase

    I saw another 3.9 in a TR-8. My guess that they are conversions since there were no factory 3.9's.

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    Re: TR8 research before purchase

    Also, what is up with the hoods on TR-7s and TR-8s? I watched a video that said that TR-8s have the third smaller bulge on the hood and that TR-7s only have two hood bulges. I have seen plenty of TR-7s that had the smaller third bulge. Is there any rhyme or reason to the hood bulge question?

  14. #14
    Great Pumpkin DNK's Avatar
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    Re: TR8 research before purchase

    IIRC, early hoods had a different bulge
    Smaller I think
    Don
    "Stick a Wedge in it!"
    Mount Pleasant,SC

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    Jedi Knight Darrell_Walker's Avatar
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    Re: TR8 research before purchase

    The double-hump hood came out with the TR8, the space is needed to clear the carbs. But BL switched all models to use that hood, so later TR7s and EFI TR8s will have that hood as well.

    You are correct that a 3.9 would not be an original engine. Likely a conversion, but it could have been an original TR8 that was updated, too.

    Here is a good reference on the Wedge VIN numbers, this will tell you what the car started life as:

    http://www.trdrivers.com/tr7___tr8_vin_numbers.htm
    Darrell Walker
    66 TR4A IRS-SC CTC67956L
    81 TR8 SATPZ458XBA406206 (daily driver)
    Vancouver, WA, USA

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