Building a reliable 140-150bhp TC

[garyeanderson]

In my mind the 1700 cc did most of the trick for 'elancoupe' and then he matched everything else to benefit from the added displacement.
Ken

Hi Ken

The displacement is key here, no 1558 is going to produce 133 lb/ft of torque. That is a very good number, even for a 1700cc twin cam.

Gary

[elancoupe]

I would agree about the displacement, porting and cams are fairly mild. The unit was balanced and headers were chosen to match port size.

[handi_andi]

Rohan
Is your avatar an example of what happens if you don't get the head rebuild right and destroy the engine in the process???
Andy

[rgh0]

1700 cc certainly makes getting more power easier but the breathing limit of the standard head and SE / sprint cams / exhaust system is around 135 hp. Without, exhaust mods, cam mods and porting mods you will struggle to get above 135 hp no matter what capacity you put under the head or what revs you run the engine at.

The bigger capacity enables you to get above 140 hp wih milder head work but some will be needed.

Andy
My avatar is to remind me to take care when I build engines. I comprehensivley blew a motor in its second race when a con rod bolt failed. The failure was maybe due to a faulty new rod bolt but probably due to inadequate bolt tension on assembly. I tension my rod bolts now using a stretch guage rather than torque and double check everything and then check it again.

cheers
Rohan

[rt6810]

Hi Jono
I think I recomended the engine guy near Newark. Drop me a PM and I'll fill you in. I'm sure he can get you to where you want to be powerwise. Cheers. Rob

[denicholls2]

Is it worth it?

Are you really going to notice an extra 25bhp on a road car?

This is a genuine question, I'm not trying to start an argument!

I have my engine in pieces at the moment an if its genuinely worth going to the trouble of porting the head and fitting special valves and cams I'd look at doing it.

Cheers
Jon

I believe the throttle bodies are a good idea, because they will make the engine more drivable at about the same horsepower, and more efficient under typical road conditions.

I do question the notion of a "reliable" high-power engine. In many respects, the two are mutually exclusive. Exceptions are porting, improved headers, and balancing, which do not in themselves create additional stressors. Heating up the cam, raising the compression, etc. are power solutions which do things to your engine Chunky did not, probably because he didn't want them twisted within a few millimeters of destruction. These are solutions racers follow because they increase power and/or torque and they are willing to sacrifice longevity (dramatically so) to get them.

Do what you want because it is your car, but don't think that a higher-power engine will be a happier one in your road car. The opposite outcome is much more likely.

[rgh0]

The 25 to 30 extra hp you get is certainly noticeable in a road car if you enjoy using the acceleration of the Elan to its limit. Remember that hp at the rear wheels is around 90 to 95 with a 118 to 125 hp SE or sprint engine and adding 30 hp to this at the engine at similar maximum revs does not change the losses much so you see close to 30% more usable power at the rear wheels. The high lift short duration cam actually gives you a fatter torque curve than the original Lotus cams and a 1700cc engine a fatter torque again so acceleration performance increase more than the 30% power increase.

The increased stresses in the engine if you use a short duration high lift cam and keep the revs to the same 6500 rpm limit are minor and easily within the bottom end capabilties. If you build it right there is no reason why it should not be as reliable as a standard engine. The only area of potential concern is that the high lift cam imposes higher stresses on the cam to bucket interface and careful selection of materials, careful assembly and careful running in is required to avoid problems, a knowlegeable engine builder knows whats required.

Colin Chapman did not do it because the cars did not need the extra power to be competitive and the cost of properly porting the head and the short duration high lift cam profiles were not avaialble when the cars were orginally built. The sprint engine was was small step in the direction but Lotus never really pursued it to its logical limits and their interest shifted to the later cars and 907 engine development anyway.

Today with sticky tyres and modern cars with 4 valve fuel injected engines as the competition then the development to 140 - 150 hp is a sensible internal evolution of the engine that can be done while the car remains standard looking in almost all external respects (apart from the larger exhaust headers).

You only face real cost, tractability and reliability challenges if you want to build a 170 - 180 hp twin cam. 140 -150 hp is relatively low cost and hassle free if you know what your doing - if you dont finding someone who truely does is the real challenge.


just my opinion
cheers
Rohan

[davidholroyd]

145 - 150 hp ... about ? 6,000 plus your engine .. no point in a road car
( this is what the race cars used to have max so it is quite a high state of tune )
But for Track days ... fantastic ...

But ....

Big Bore Race exhaust ...
45 Webbers
QED rally cams
Set new pistons
Port the head
New valve springs and slightly larger valves
Balance standard crank and standard rods - OK for 8000 rpm in top ( not first ! )
New Cosworth Bottom end bolts
Electronic Ignition ..
Baffled Sump
Crack test everything !

Then to cope with extra power...

Solid Drive Shafts
Big Alloy Rad + New Electric Fan
New Rally spec Clutch ... balanaced to fly wheel and crank

[rgh0]

6000 pounds is more than it should take, even in the UK. In Australia I can build an all steel 8000rpm plus full race 180 hp engine from scratch for that amount. Even if you pay someone else for the labor you should be able to build the sort of 140 to 150 hp engine we have been talking about for about half that amount.

The bottom end can stay standard and if in good condition it does not need work if you stick to a 6500 rpm rev limiter. You dont need Weber 45s, the 40's with 34 or 36 mm chokes will be fine. Electronic ignition is nice for a reduction in maintenance and many people do it, but again if you dont have it you dont need it, I run points ignition in 8000 rpm race engines with no problem. A baffled sump is nice if you like doing right hand corners hard but you have that problem with a standard engine anyhow.

The standard clutch will handle the power without problem, you need to replace the donuts if you drive your car hard regardless of engine power and a 3 row core for the standard radiator will handle the extra heat load fine.

Not to say that all the mods listed are not sensible just that developing the engine to 140 - 150 hp does not really need them.

cheers
Rohan

[mopho]

Well, I set out to have my engine built to around 150hp or so but we kind of missed that mark.

I just got the call today (I have not seen the charts yet) that it came off the dyno and it put out 171hp @ 6100 rpm and 150 lb/ft torque @ 5500rpm

I don't know how tractable or reliable it will actually be, but the builder assured me it will be both.

We'll see

Only displacement increase was .030 over pistons that I had done when the engine was first rebuilt.

[msd1107]

Hmmm,

171@6100 is 147 ft-lbs of torque, virtually the peak torque.

Sure it wasn't 6600 or 7100 RPM for peak HP? that would equate to 136 ft-lbs or 127 ft-lbs, 90% and 85% of maximum torque respectively.

150 ft-lbs is 230 psi BMEP, a spectacular figure for a TC 1600. Even in a 1700 long stroke that is 218 psi BMEP, still super strong.

Your engine builder is going to be one popular fella!

[mopho]

Hmmm,

171@6100 is 147 ft-lbs of torque, virtually the peak torque.

Sure it wasn't 6600 or 7100 RPM for peak HP? that would equate to 136 ft-lbs or 127 ft-lbs, 90% and 85% of maximum torque respectively.

150 ft-lbs is 230 psi BMEP, a spectacular figure for a TC 1600. Even in a 1700 long stroke that is 218 psi BMEP, still super strong.

Your engine builder is going to be one popular fella!

That's what he told me over the phone, I have not seen the dyno plots yet.

[steveww]

You will certainly need proper large bore headers / manifold mated to a free flowing system. I recently added these to my tuned twinc and they made a significant difference

The Webers are up to 150bhp no problem, may be just using mapped ignition is more cost effective?

Certainly ?6k will buy you a 150bhp engine ready built from QED. John Wilcox http://www.wilcoxengines.demon.co.uk/twincam.htm can build you a 2.2 twinc for serious power and torque, though I dread to think of the price Then you will have to do some serious work to the transmission.

[cabc26b]

Morgan -

150 ft/lbs ? from 1600cc with a 72mm crank ? I would be interested in hearing about the rest of the setup - cams, carbs, ports and exhaust.

my motors make between 176 and 185hp at the flywheel , but no where near that torque.

Keep us posted - BTW. hope you eliminated everything with a lotus part number south of the crank flange and out through the hubs.

G