Intrigued by Petrol Injection engines.

[2wrench]

Like the way those Brits pack 150 bhp into one of their
little TR6 engines. Upon closer inspection.....dang...
I couldn't handle all those vacum lines, cables,
whatever the dickens they got running all over the
place like something you'd serve with meatballs.

But.....I do like that horsepower.

Anybody got a PI engine?

 

[BryanC]

A few folks here have them but you don't need PI to make the ponies. New cam, more compression and a GOOD header and you're there. Should be an easy thing to do as you rebuild your engine.

Bryan

 

[LastDeadLast]

2wrench,

Bryan's right, quite few of us here have warmed over Tr6 mills. Compression, cam, intake, exhaust.. pretty much in that order. Do that and you can have what the PI guys get and then some. There's also a few other tricks to up the ante and augment the above enhancements; roller rockers, alloy flywheel, electric fan, hipo ignition.. you get the idea (read: how fast do you want to go, how much do you want to spend)

Lots of help on this forum if you want to go that route, but like most modifications, they're not without their own trials and tribulations. It's taken me about a year to really dial in my little TR6 motor, but it runs like stink now!

 

[2wrench]

Thanks, guys, but I'm still a baby, remember?

The operative word is "intrigued."

I have a huge amount of personal mechanical prowess
to garner before worthy of the big ponies.

But I read, look and listen to have some idea of
a path to follow. Right now....just a one small
step up on the cam. Hardly noticeable and very
affordable. Gotta know, though, I love the sound
and the feel of my tractor cranking some revs.
Some day...some day.

 

[LastDeadLast]

Didn't mean to scare you!!! /bcforum/images/%%GRAEMLIN_URL%%/angel.gif

If you are rebuilding your mill, build a good foundation:

<ul>[*]Get the rotating assembly balanced - this is a good idea even if you aren't going for a hot engine [*]Have your head milled for 9.5:1 compression - a really cheap mod that will make a huge difference in performance[*]If your replacing your cam, get nice torque cam, like Goodparts GP2 - this will give you great low end response and good high end power[/list]
The above list won't break the bank and you won't have to tear down the motor again if you decide to take it to the next level.. and if you decide not to, you'll probably be running about 20 hp higher than stock with no side effects.

Is this info more in line with what you wanted?

 

[TR674]

2wrench
a pic of my grubby engine bay. The spaghetti you mention is the fuel hoses from the metering unit, over the rocker cover to the inlet manifold. My engine has been 'tweaked' to 180hp by the previous owner for track use. Those of you familiar with PI motors will notice the modified throttle cable linkage.
Regards
Craig

 

[RobT]

As a reference point - my TR250 with the Goodparts triple ZS setup, street cam, 10:1 compression and dual exhaust header is pobably making north of 140HP (Richard Good's estimate, not mine). So really no need for all the hassel of the PI, just juice up the carbs, compression and cam. BTW the 2500 PI sedans sold in the UK had a de-tuned engine similar to the US TR6s and only made just over a 100HP. All the trouble of a PI system without the HP.

 

[BryanC]

If you are interested, now is the time. Look at Shannon's list and think about it. You are rebuilding anyway. Tell the shop to balance the assembly. That is usually a hundred or so bucks and they do the work - you don't have to know how. Buy a cam and lifters. The cam is coming out for your rebuild so just put a different one in when putting it back together. The shop is going to look over your head to check the valve seats, etc. Have them cut it to raise compression. You can probably get the cam from a specialty shop like TSI and they can help you with shorter pushrods to go with the shaved head. I think Moss also sells shorter pushrods for that purpose. Then you put it all back together. It's a little more money than the standard rebuild but you don't need 20 years experience building engines to get it done.

Bryan

 

[NickMorgan]

I can see the attraction. After all we like old Triumphs because they are different. That is why I have a front-wheel-drive Triumph 1300 saloon.
The poor old PI has a bit of a reputation, but I think it is widely acknowledged that once it is set up properly it is a great system. Certainly the pick-up on my friend's TR6 is fantastic. It's reputation stemmed from good old British mechanics being used to Morris Minors and SUs and they struggled with the modern technology of PI.
I have a friend with a Triumph Vitesse that he converted to 2.5PI spec. He really struggles with fuel vapourisation now on our modern "clean" fuels. But, when it gets going, it really goes!
The weakest part of the system is the fuel pump, but if that is replaced with a Bosch unit the over-heating issues disappear.
Some people here have replaced their warn PI systems with Webber carbs and are able to get a similar output.
The 150hp is said to be an optimistic figure. I think that to change a US engine to PI spec you would have to also replace the cam and increase the compression ratio.
It would certainly cause a lot of interest at shows!

 

[Moseso]

2wrench --
I see you're in Tracy, CA. Is CA doing emission inspection anymore? A longer duration cam ((as has been suggested) will definitely cause an increase in HC emissions to go along with all that extra power. Your car won't pass an emissions test with that kind of mod.

 

[2wrench]

2wrench --
I see you're in Tracy, CA. Is CA doing emission inspection anymore? A longer duration cam ((as has been suggested) will definitely cause an increase in HC emissions to go along with all that extra power. Your car won't pass an emissions test with that kind of mod.

Very good point; but, the beauty of the present state
of affairs in California is that there has been a sunset
on the smog requirements. No need to smog test any
longer. A neat thing in California is this fact and
I think it drives an attraction to refurbish the
old, especially, muscle cars here. After a certain
year of age, no more smog. Coooool.

 

[RonMacPherson]

A greater consideration is timing of the overlap. That has a greater affect on hydrocarbons than just open time.

 

[2wrench]

I have gotten some reluctance from now two machine
shops regarding the 9:5:1 compression by shaving
the head. The second gentleman guarded against
issues like shorter push rods being necessary (I assume,
therefore opening up for greater possibility for error --)
and I intimated, ergo, that other settings would move
off of standard spec as well regarding overall engine
tuning.

Because I'm still a baby at this, I thought I might
just go for the 20 horses from a next level cam
and let it go at that.

Also, I don't think these fellas really like taking
on a shaving/mod to a spec that they would be responsible
for; i.e., the 9.5:1, because they will have to work and
test and work and test, etc. Gets either costly or
they end up giving you their time to do it right.

All in all, I think they'd just rather not do it, and
considering how much I'll rely on them to keep me out of
trouble, I'm inclined to forego the head shave for now.
Think I'll just shave my face and let it go at that.

If I'm making a big mistake because I'm wimping out,
feel free to tell me. I'll listen.

 

[LastDeadLast]

2wrench.. Here's what to do about head shaving. This Goodparts page provides some nice info:

https://www.goodparts.com/tech_docs/TR6_Compression_Ratio.html

BTW, I'm running 10:1 cr with my mill and with the stock length chrome moly push rods (from TRF).

Interesting about California emissions, in NC with my 1972 TR6, I don't even need to have an inspection anymore. But I'd check with Richard Good or Ted at TSI before I'd order any cam. I'm not talking about a wild cam mind you.. just a nice torque cam that'll wake up the engine quite a bit.

 

[TR3driver]

If I'm making a big mistake because I'm wimping out, feel free to tell me. I'll listen.

I wouldn't call it a big mistake, but compression is one of the best engine mods, IMO. It's one of the few that increases torque; and also one of very few that increases power by increasing efficiency rather then burning more fuel (meaning it also improves fuel mileage).

The trick to deal with the machine shop is to tell them how much to take off in .001", rather than asking for a specific compression ratio. I'm sure the folks here can give you some numbers; or you can measure and calculate it for yourself.

Cam and compression go hand-in-hand; so to select the right cam, you really should choose what CR you're going to run as well.

 

[TR3driver]

the beauty of the present state of affairs in California is that there has been a sunset on the smog requirements.

That's true, but don't forget that our lawmakers keep threatening to repeal the sunset provision. There are bills introduced to the legislature every single year trying to rein in us "irresponsible hot rodders"; and there's always a chance that one of them might pass. AB 616, for example, has already passed the assembly once. And although it was sent back to committe this year, it could come up for a vote again next year.
https://www.semasan.com/main/main.aspx?id=62246

 

[piman]

Hello 2wrench,

don't worry about going for the 9.5:1 compression, but you will need shorter pushrods (These were standard Triumph parts and used on the P.I.)
However no one has mentioned that the correct exhaust manifold makes a large difference to this engine. The one to go for is the 6-3-1(or 2) configuration, not 6-2 or 6-1. This releases a lot of power from the TR 2.5 engine.

Rob,
" BTW the 2500 PI sedans sold in the UK had a de-tuned engine similar to the US TR6s and only made just over a 100HP"

No that is not correct, it had a quoted power about 18 less than the 150 of the TR 5\6 due to a slightly softer cam, but well above the U.S. engine.

Alec

 

[heliguy]

Time to though in my 2 cents worth. Sure, the PI had a bad rep in the beginning, and just bolting it on is not going to make the H.P., but then again just bolting on a set of triple webbers is not going to do that either. As has been allready mentioned here its a combination of things. Increase the CR, get the head flowed, use a PI cam, or an aftermarket cam, get an extractor exhaust and balance the rotating parts. With the advent of wide band O2 sensors, the PI system can be "tuned" much more accurately than ever before.
For me, i like the period "mod" of the PI system. Someone else might want a supercharger. Each has its advantages and draw backs. Whatever you do, have fun doing it!

Mitch

 

[vagt6]

As Piman says above, a 6-3-1 ("extractor) header is best for most street applications of the 2.0 & 2.5 engines.

And while you're at it, you'd best install a free-flow exhaust system as well. Installing headers without installing a more efficient exhaust system may defeat the some of the gains provided by the header.

If you don't have it, get a copy of David Vizard's "Tuning Standard Triumphs". Excellent treatise on getting more power from your Triumph lump. If you want a .pdf copy, I'll email it to you (can I post an Adobe .pdf file here??).

Engine mods: it's all interconnected, and it all takes $$$$$$$$ /bcforum/images/%%GRAEMLIN_URL%%/cryin.gif

 

[piman]

Hello Mark,

another, and probably better book, is by Gary Thomas, the original is out of print but I understand that he has just printed a revised version.

So far, I have not been able to get a copy, (no reply to my e-mails) but I will keep trying. If any one is interested, have a look at this link:- https://www.t2000register.org.uk/forum/forum_posts.asp?TID=717&PN=1

Alec