Building A Better Engine

[aaron77]

Hi Guys,

I have a 1977 2500TC engine with twin SU carbs and its all standard.
What can I do to get a bit more torque and ponies out of her.

Thanks

[Greeks]

Short answer: Lots!

Long answer: It depends on your budget, capabilities and priorities.

Lower budget - You could start with better air filter, tubular exhaust manifold, sports exhaust ... although it's still not 'cheap'.

Higher budget - All of the above and then move on to the engine ... ie Head work, fast road cam, bigger pistons, etc.

Have a shufty at Chris Witor's site for http://www.chriswitor.com/ inspiration  ;D

Let us know what you do ... any pic's of the car?

[Gt6s]

Engine management !
Either full or 3D ignition only.

[2.5 Chris]

on my 2.5s, i polished everything inside, crank, inside block, lifter galleries,etc. then fitted ported and flowed head, competion valves, roller rockers, fast road cam, i also had custom made sump, for extra oil, aswell as clearing steering rack in spitfire, aswell as semi race exhaust, and su's, although thinking of webbers. currently changing to custom made stainless exhaust. i am sure theres more, but the first port of call, is brakes, suspension, no good if car does 0-60 in 4secs, if it takes an hour to slow!  triumptune do some bits aswell. cooling might be an issue, depending on how far you go.

[Jason]

I wonder what a spreadsheet of parts, cost and BHP / Torque gain would look like - ie a hit list of the things you can do, what they cost and what you get?

I say Injection :-)

What's the collective view on roller rockers these days?

[Deleted User]

I like them... for reasons stated by Kastner... better action on valve stem at higher lifts and almost no side loading on guides compared to the stock rocker.

If you want to go high ratio (1.65:1) you really need cam bearings.
The standard rocker set up is pretty lame... not even bearing bushes in the rockers ... and the quality of the current replacements shafts  :o

[2.5 Chris]

moss do a quick guide for some mods to engine, i'm sure injection is good, as i know racer who uses that, but i'm sure for the ultimate tuned engine, webbers are more tunable, what say you folks?

[Jason]

[quote by=cjm link=Blah.pl?b=2000,m=1150332781,s=6 date=1154275357]moss do a quick guide for some mods to engine, i'm sure injection is good, as i know racer who uses that, but i'm sure for the ultimate tuned engine, webbers are more tunable, what say you folks?[/quote]

Italian carbs on a British car just ain't right  ::)

[Jason]

[quote by=andythompson link=Blah.pl?b=2000,m=1150332781,s=5 date=1153951781]I like them... for reasons stated by Kastner... better action on valve stem at higher lifts and almost no side loading on guides compared to the stock rocker.

If you want to go high ratio (1.65:1) you really need cam bearings.
The standard rocker set up is pretty lame... not even bearing bushes in the rockers ... and the quality of the current replacements shafts  :o

[/quote]

There seem to be several ratios available, what are the pros and cons of the higher ratios? (Not even sure of my cam or it's lift to be honest!)

[Deleted User]

Higher ratio obviously = more valve lift for the same duration...

This means potentially better cylinder filling if everything is matched... however they mean higher loads on the cam and followers and the potential for coil binding if you don't have the right springs.

I have seen standard 1.46:1, 1.5:1 , 1.55:1, 1.65:1 and 1.75:1 on the market ....  I think 1.75:1 is getting a bit silly

You don't need high ratio with a high lift cam... some might say that it is better to have a moderate lift cam with a higher ratio rocker. If in doubt don't go beyond 1.55:1

[2.5 Chris]

does anyone have any brake horse power figures showing how far 2.5 will go.?

[Deleted User]

All depends on who you believe and for the really big numbers how much money you have...

Most road based 2.5 engines with stock based botom end (rods, crank, pistons etc)  seem to hit an upper bhp limit at about 175- 190 bhp (maybe 155-170 rwbhp)

This is normally at about 5800 - 6200 revs.... to make more bhp you need to spin the engine faster and with the long stroke and relatively small valve area you have to be pretty clever to

1. Make it breath sufficiently well to keep making more power
2. Make it robust enough not to fly apart due to crankshaft torsional vibration at 6300 and 7200rpm

1. Can be solved to a degree... the engines have made around 250bhp in full race trim (that was was done by Kastner 30 odd years ago).. it's all about trick extractors ,the right cam, head work and good induction

2.Costs big bucks... and even steel cranks may still break according to some... the secret is in the crank Super Damper. Jon Wood knows how to do it.... but has gone to ground....  in fact it's so secret that I can't find anyone to sell me one...

anyone?

[JonB67]

ok, its not machined for a triumph, but what about something like this?

http://www.gmpartsdirect.com/performance_parts/store/catalog/Product.jhtmlPRODID=905&CATID=895.html

or the smaller:

http://www.gmpartsdirect.com/performance_parts/store/catalog/Product.jhtmlPRODID=906&CATID=895.html

Jon

[richtriumphnut]

take the head down 60 thou, run a fast cams with as recommended med ratio's tr6 cams ect... fuel injection and polished and gas flowed ect... endless list but budjet is the main question?

speak to dave at canley he'll advise you. you can take the engines to 2.7 but they do crack after a while

[2.5 Chris]

60 thou? around what compression  ratio?has anyone done or heard of comparisions between webbers and injection? i was told that standard engine is 115hp,i was also told webbers could add another 100hp,is this correct?

[Deleted User]

Erm.... yes  standard engine is about 100-130 bhp depending on model...

2500TC = 105
2500Pi  = 120
TR5/6 = 130

All number are approx as so was Triumphs build quality control

Webers may give you 200 bhp if you do EVERYTHING else.....
If all else is equal so will Lucas injection and probably SU carbs if your clever enough

Any way back to point of my reply... I think this is the SUPERDAMPER that I mentioned  thank you JonB67.... you reignited my trail that had gone cold...

Not sure how I will adapt it but here they are...

http://www.fluidampr.com/HOWITWORKS.htm

[john_classic]

Can those types of damper really cure crank resonance issues, anyone tried it?
Not that it would help me, mine won't rev over 5k!

[Deleted User]

Posted on the TR Forum a few year back by Jon Wood

jon wood racecraft
Apr 8 2003, 11:13 PM

Post #4






Group: Members
Posts: 79
Joined: 14-March 02
Member No.: 1,101



The crank winds itself up along its axis, unwinds, then winds up again. It's a bit like the rubber band on your old balsawood model plane. Problem is, at a period of resonance, it increases to the point at which major destruction takes place. First, the flywheel falls off, so 8-bolt it. Next the cam chainwheel falls off, so 4-bolt it. Then the rotor arm keeps shearing. Then the timing chain snaps, having already mashed the tensioner. The crank pulley flies apart wtih varying effects. The fan belt turns upside down or flies off altogether. Then finally the crank snaps at no.6 big-end, and you go back to racing a 4-cylinder or start suing suppliers for deliberately selling you a faulty crank/ flywheel/distributor etc. etc.
Or you buy a proper crank damper kit, suddenly find more power that's not being wasted trying to destroy lumps of steel, and gain the ability to rev the engine to wherever you think fit. Mine is the only kit that works, and it's expensive.
Now, price up all that damage and see what's really expensive...

[Richard B]

I think they meant 10bhp not 100bhp.

A nice inprovement on a 2.5 is a lightened fly-wheel. No more bhp but a vast improvement in th way the engine behaves. The orginal flywheel was set up to make the 2000/2.5 behave when used as a tow car (you need loads of momentum to keep it running).

Personally I go for; Exhaust Manifold, exhauset, carburettors & air filters. If you change to PI you need to replace the 2.5S cam.

Roller rockers are easier to install than a new cam. It's really a case of how much money/time/effort you are willing to put into it, £100, £300, £500, £1000, £2000, £5000.......?

[2.5 Chris]

dave canley? any links or site addresses available,please.not sure if this is help,as regards damper,however buick v6 turbo same crank snout dia' as 2.5 triumph with clearance though might have to skim crank snout , so apparently is small block ford.

[Deleted User]

[quote by=cjm link=Blah.pl?b=2000,m=1150332781,s=20 date=1154688041]regards damper,however buick v6 turbo same crank snout dia' as 2.5 triumph with clearance though might have to skim crank snout , so apparently is small block ford.[/quote]

Thanks mate, I wondered how common the size was... what is the actual measurement?  I am 400 miles from a handy vernier caliper and spare crankshaft

[2.5 Chris]

cannot measure,as crank is at llewellen gears along with all other related pieces,sorry.might be able to find out during week though,if no-one else can post.

[richtriumphnut]

not sure of the compression ask dave at canley classics he'll tell you

rich

as for 100hp from webbers extra sounds a bit far fetched

[richtriumphnut]

try www.canleyclassics.com for contact details, ring them and ask for dave explain what your looking to do, he's really into his 2500 and has done many mods to it, he'll advise you bhp to £ tuning

rich

[2.5 Chris]

nice one ,one and all,bhp sounded abit exagerated to me also,moss figures sound more like those quoted here.