View Full Version : TR5/TR250 tr4 to 250....

11-16-2004, 11:14 AM
ive a couple of projects for friends here and one guys is very interested in changing his tr-4 motor over to a 2.5 6cyc.

anyone out there done one? I assume there isnt much to do in the way of changes

Just fyi, Ive done a 2.5 6 in a spitfire which is much more complicated, though easy if you know what bits to use. the only cutting is to clear a gt-6 startermotor , everything else is bolt in. You just better have a big pile of gt-6 trannys laying around

Simon TR4a
11-16-2004, 11:57 AM
Kerry this can certainly be done, and other than motor mounts should be fairly easy, BUT the result is not a TR250, it is a bit of a mongrel, worth less than a proper TR4a.
If the guy is not trying to pass it off as a genuine car but building it only for his own enjoyment then o.k., the 6 is smoother and sounds very nice, but is less rugged than the 4 and slightly heavier.

Geo Hahn
11-16-2004, 04:01 PM
I have not and would not do this... but if I would and could I think I would favor copying a TR5 (PI) rather than a 250.

Just $.02 worth from someone with no stake in the work or outcome.

11-16-2004, 04:11 PM
Hello Geo,
I would agree that the injection engine is worthwhile but what availability is there in America as I understand that they were never imported there. (Ironically as Triumph went the PI route because of your emmission regulations but found that the Strombergs could meet them and the injection couldn't)


11-16-2004, 07:11 PM
I'm with Geo in suggesting that it's only worth a swap for the PI system, for which parts are available from a handfull of importers/vendors etc... I've seen a few TR5 clones here in the northwest.

It's actually urban myth that the PI system didn't meet emissions in the US. For instance, the Mercedes 300SL with its Bosch system had been coming into the US for many years and needed no changes to meet '67-'69 emmissions criteria.
Furthermore, tests to retrofitted American cars showed the PI system had lower actual emmissions than the dual Strombergs (certainly after those "service free" sealed carbs began to wear!)

There were other issues that have been documented, but seldom discussed regarding the decision to utilize the Lucas PI system, but the most likely reasons were 1)inability for Lucas to produce the 8400+ units required to meet production. 2) Replacement parts necessary 3)Lack of trained PI servicepeople in America 4)Additional cost for a PI system on a TR-250PI would have priced it with delivery (especially on the West Coast of the US) into competition with much better cars. 5) The quality/longevity of the Lucas system was unproven, and Triumph didn't have the money to support numerous warranty claims (even though warranty time periods in 67-68 wasn't like the 3-year 30,000 mile minimums we have today!)

PI systems can be purchased complete for about $1500 in the States the last time I checked. Also, the owner of the Roadster Factory in Pennsylvania, Charles Runyan, owns a real TR5.

11-17-2004, 02:34 AM
please note this tr-4 is a rat, truly fit only to be thrashed. in almost anywhere else this would be someones parts car. I however have of course logged thousands of miles in it with rusty bits flying up into my eyes from the floorboards and other such gaping holes.

its not the car i would start with. He is not really interested in playing the car off as anything beyond what it is, this is just about fun. knowing the way he drives it will most likely be his casket anyway!

basicly we drive anything that will start. at one point my tr-6 engined Spit had no starter, no reverse (bad combo!) and little or no brakes. but with webers and cam (and of course huge hole in the bonnet) it went like **** blowing flames on overrevs. I think i drove it that way daily for 6 months when i was broke.

Now i'm all for saving and restoring, but i do feel there is a place for the ratty cars that are still being driven. For me Triumphs will always be the fun thrashers as we would fear for our wallets if the jags were driven with such abandon.

11-17-2004, 05:37 AM
Hello Sam,
that is very interresting and different to what I had read elsewhere.
There certainly were issues between Lucas and Triumph, with cost being a factor as the P.I. components needed very high quality manufacture due to the tight tolerances.
One thing that I have not seen explained is why the U.S. spec head has a different port spacing on the inlets and so a P.I. manifold will not line up with a U.S. head. Do you know anything about that?

Kerry, I agree up to a point, cars should be driven, be they Triumphs or Jags, but I would draw the line at poor braking.

Alec /ubbthreads/images/graemlins/thirsty.gif

11-17-2004, 10:41 AM
i do agree on the brakes, and it certainly got me into trouble. thankfully that level of insanity is years behind me and was mostly driven by the early years of self employment (read here , being broke). Times have been good and it took a bit of damage to the front of my E to really rub it in.

12-09-2004, 02:50 PM
In placing that six into the existing cavity you may find the inner fender wells will not provide clearance in some spots. I do have a new set of inner 250 front wings , left and right that came on a 4A I took apart. If you friend is interested you can email me or just hammer away at the existing panels on the car. /ubbthreads/images/graemlins/hammer.gif /ubbthreads/images/graemlins/canpatriot.GIF

12-10-2004, 06:39 AM
The TR4 is truly a sexy car. But before we wedge a 2.0/2.5 lump in there, we might remember that the six weighs in at about 660 pounds!

I've seen a small, but emerging trend among folks who are considering the 6 cylinder swap ("Spit-6) for Spitfires to forget the huge six and simply modify the existing four cylinder engine.

The stock 2.0 GT6 engine has about 100 HP, and approx. 140 or so is the limit for street driving (without fuel additives, etc.). And, It's relatively easy to get 100 HP out of the Spit engine, and the weight difference is significant.

One of the major deficits of the Triumph 2000/2500 engine is the weight. That makes 4 cylinder performance upgrades very attractive, especially with the abundance of performance parts on today's marketplace.

Maybe this will help in your decision, and save time and money. Good luck, please let us know what you decide.

12-10-2004, 05:39 PM
Hi, I agree with much of what's been said, why bother putting a 6 cylinder in a TR4. The 4 cylinder is lighter and can be tuned to give you 150 HP pretty easily, if that's the goal. That would even be roughly comparable to the PI 6-cyl.

If I were considering an engiine swap, I'd look at dropping in a V-6 or even a small V-8. In fact, one of the previous owners of my car had another TR4 that was seriously altered with a V-8, a narrowed rear end from some American car, body mods to accommodate very wide tires, etc. etc. It was quite a machine! But, not one I'd personally care to own and drive.

On the other hand, from your description of your friend's driving style, maybe keeping the 4-cylinder would lengthen his life expectancy.

A little food for thought....

I witnessed an incident near my home a couple years ago. A new, black Corvette was attempting a left turn from a side street onto a fairly busy divided parkway. Without a light to stop the steady flow of cross traffic, and lacking much patience, he just floored it when there was a small break. The car made it across the street before he totally lost it, spun 180 degrees, came back across the median, somehow managed to miss 4 lanes of traffic, jumped a curb, wiped out a fence and bushes in someone's backyard and ended up on their patio. This maneuver was performed on clean, dry pavement. Fortunately there were no injuries, except to the car, fence, oleanders and pride. It was just a case of too much car and not enough driver.

12-10-2004, 06:24 PM
Dumb question, but has anyone ever dropped a TR4 engine into a TR6? A well tuned stock TR4 will outrun a well tuned stock TR6 most any day of the week. Or would it be too embarrassing at the car shows. Triumph didn't accomplish a whole lot by adding another half of a tractor motor into the same basic car, unless you are lucky enough to have a PI. Just a thought.


Geo Hahn
12-10-2004, 06:50 PM
Not a dumb question at all but rather counter-intuitive. Your points are well-taken, especially the one about embarrassment at car shows.

IMO, TR4s are fine cars... TR6s are fine cars... but mixing the two is not necessarily an improvement.

12-11-2004, 07:58 AM
Go for the 3.5 rover,I saw one in a 4a at the nationals this summer.Wow was it ever cool. used a gm 5 spd ,but needed several joints in the steering to clear the exhaust.Other than that he said it was too simple and improved the cars handling.
MD(mad dog)

12-11-2004, 02:46 PM
Geo, I don't know about dropping a 4 pot into a TR6, but I do know a couple of folks who are putting a GT6 bonnet and other GT6 goodies on a Spit, modding the Spit's 4 Cylinder for about 100 HP or so, instead of going the Spit-Six route.

Makes sense to me, lots lighter, 100++ HP, etc.

12-11-2004, 03:54 PM
I did the spit-6 2.5 thing a few years ago. Lightly modified the engine,susp, etc. Came out great and is quite fast.Embarrased my friends Lotus, 3 out of 3. I wanted to keep things all TR. Yes it is a little nose heavy. Some day I will figure out this photo thing and submit a photo.