Which Camshaft

[trderek]

Im sure there has been loads of post about camshaft choice in the past but thing move on

has any competitor in the sprint and hill climb championship got any advise on a good make/profile cam for a 4 cylinder 1900cc TR3

Im building a car to do a few track days and also the odd sprint hill climb.

I Know engine spec plays a big part in my choice however Ive built race engines before for various cars and in many cases the choice of cam has been limited to a couple of cams which fit the bill

And who's cams ? Piper/Kent ?

 

any help would be of great help

[MichaelH]

My advice is to keep the cam as standard as possible, the car will be mainly road use and occasional sprint hill climbs

What you need for this is torque and torque low down

This is what a standard TR4A cam or perhaps piper yellow gives you and it won't spoil you road use

Most of competitive advantage is driving skill rather than engine ability

Hope this helps

Michael

[Motorsport Mickey]

You stand every chance of being disappointed with every facet of your car.
Without a full disclosure of what equipment you will fit a choice of camshaft is likely the very last item to spec. Beware of the "this cam gives you 15 hp" this rocker assembled gives you 4 hp sort of modification suggested by some tuners, The final drivability (which is definitely what you want) is delivered by the combined efforts of the total engine and driveline specification. The power delivery is magnified by part after part, definitely a case of the whole being more than the sum of the parts.
On the other hand driving a tuned car on the road is likely to deliver a noisy uncomfortable beast which has to be driven in third gear to keep the engine from bogging down or fouling plugs.
You can have a fast road specification car but only by careful balancing of the spec with compromises inevitable to deliver a car which will do all the spectrum.
Try explaining your engine spec, exhaust , rocker gear, crankshaft steel or billet, same for the conrods and almost all other equipment on the engine and complementary to it. You say you have built race engines so you will understand the importance of what is discussed and how it affects performance. You say you will retain the 83 mm pistons which although allowing an advantage in being able to run in a smaller capacity class but loses the ability to run 89mm pistons with the consequent large increase in torque which will
Make the car much nicer on the road depending upon why cam is chosen, see what I mean ?

Mick Richards

Edited November 12, 2015 by Motorsport Mickey

[TriumphV8]

In my motorsport days I used a Lotus 4-valve engine with

324 degree cam profile from a Formula 2 BMW engine

together with WEBER 48 DCOE in daily traffic.

To be honest there was a limit, it worked but

really not perfect for street use and car was thirsty.

It took 50% more fuel.....

 

The more you are stepping away from stock the less all the other

parts involved will meet the engine requirements.

Some parts like crank, bearings or rods or the valve train will

simply fail, others like compression ratio or choke size of WEBER DCOE

do a relationship with the cam and if they do not like each other

the result will be disappointing.

 

That is the reason for many people to claim that wild cams in daily traffic

are a pain but what we tried out was a back to back test with my 290 degree

equipped TR6 against similar prepared TR5 with 260 degree Newman PH1.

The result was that both performed same from idle and beyond 3000 rpm

my engine pulled significantly better increasing with every 1000 rpm.

Friend of mine employes a 300 degree Bastuck cam and Weber DCOE in

a TR4 in daily traffic and vacation. It pulls 145HP on the dyno and is idling nice

and puts a smile on owners face whenever accelerated.

 

Right here I would say a cam below the 300 degree tarmac profile

from Newman or the 300 degree Bastuck will make a hill climb

together with some serious competitors an unhappy event.

 

On the other hand also the proper short axle is most important,

we changed axles for every event to have the 4th full reving.

[Motorsport Mickey]

Exactly the point, expecting worthwhile results from purely a cam change is problematical, if you get anything it's just luck.

The whole package of carbs, inlets, exhausts, rockers etc needs to be known and blended with the cam choice to get a car which works on the road and track.

 

Mick Richards

[jellison]

They made a 1900 TR 4 pot!!!!!!!!!!

[hoffman900]

What you really need to start with first is what is your operation rpm?

 

Then to figure out everything else, you need to look at valve size, cylinder head flow, bore, stroke, rod length, and compression. Also how the exhaust is treated can really have an impact on how radical the cam can be and still have tolerable street manners.

 

The TR engine is valve limited - especially with a bore for a 1900cc engine. Ouch! You're going to want as much valve lift as possible. Duration will be dictated on how well (or poorly) the head has been modified as well as operating range.

 

The lobe seperation angle will ultimately dictate how large the overlap period is and the shape of the curve. For something like you're doing, you'd likely want it out as far as 108-110* almost. One thing the TR has is large diameter lifters. This allows one to be a little more aggressive on the lobe ramp, which means you can tighten up the seat to seat duration (and ulimately limit the overlap period), but still keep the shape of the valve opening area pretty "fat".

 

So cam comes down to:

 

Operating range

Bore

Stroke

Rod length (center to center)

Compression ratio

Valve sizes

Cylinder head flow numbers

Individual runners (an engine with individual throttle barrels will be more sensitive to reversion than one with a common wet plenum or a shared carburetor)

Exhaust system (there are plenty of A/R tricks that can be used. Also too large of a system will also cause many reversion (and subsequent tuning) problems).

[Motorsport Mickey]

What you really need to start with first is what is your operation rpm?

 

Then to figure out everything else, you need to look at valve size, cylinder head flow, bore, stroke, rod length, and compression. Also how the exhaust is treated can really have an impact on how radical the cam can be and still have tolerable street manners.

 

The TR engine is valve limited - especially with a bore for a 1900cc engine. Ouch! You're going to want as much valve lift as possible. Duration will be dictated on how well (or poorly) the head has been modified as well as operating range.

 

The lobe seperation angle will ultimately dictate how large the overlap period is and the shape of the curve. For something like you're doing, you'd likely want it out as far as 108-110* almost. One thing the TR has is large diameter lifters. This allows one to be a little more aggressive on the lobe ramp, which means you can tighten up the seat to seat duration (and ulimately limit the overlap period), but still keep the shape of the valve opening area pretty "fat".

 

So cam comes down to:

 

Operating range

Bore

Stroke

Rod length (center to center)

Compression ratio

Valve sizes

Cylinder head flow numbers

Individual runners (an engine with individual throttle barrels will be more sensitive to reversion than one with a common wet plenum or a shared carburetor)

Exhaust system (there are plenty of A/R tricks that can be used. Also too large of a system will also cause many reversion (and subsequent tuning) problems).

 

That's it ! you've done his head in now ! he just thought it was "oh you'll find a Piccolo Yellow cam exactly what you want"

 

Mick Richards

[McMuttley]

".....driving a tuned car on the road is likely to deliver a noisy uncomfortable beast which has to be driven in third gear to keep the engine from bogging down or fouling plugs."

 

I can confirm this fact to be correct

[hoffman900]

Some rough numbers:

 

1991cc

Valve size: 1.56I , 1.30E

A cleaned up head with a really good valve job

10:1 compression ratio

Peak power: ~5800rpm

 

Single pattern camshaft with 282 seat to seat , ~227 @ .050", ~.475" valve lift, and around a 110LCA. Power should be around 120bhp.

 

The "Integral" Stage 2 should fit the bill:

http://www.tildentechnologies.com/Cams/TriumphCams.html

 

Note, The owner of integral retired, Megacycle bought all the masters so you will have to go through him. These are good, modern designed lobes (less jerk and a bit more valve area than you will find with older fashioned designs). Run 1.6 rockers.

Edited November 12, 2015 by hoffman900