TR2/3/3A TR3A cam which should I buy

[bluemiata90]

I'm going to rebuild my TR3A engine this winter and was wondering if I should change out the cam to a little more performance cam. I'm not looking for anything radical, a very mild improvement. Anyways, can anyone suggest what brand/make/model cam I should get for street performance. Also could I purchase a street cam for this model car. Last, but not least, do you think it's worth changing at all. As I stated earlier, I'm not going to be racing this, but I would like a little more performance on the street.
Any ideas would be appreciated. /ubbthreads/images/graemlins/confused.gif

 

[Alan_Myers]

Hi,

Yes, a mildly improved cam would be nice. The stock one has 245 degrees of duration, approx. If you increased that to around 260-270, with a little more lift than original, it would be a nice street cam. 280 is getting more aggressive, but still can be workable on the street. 290-300+ degrees is what I'd call "race only". You are right to be conservative for the most fun on the street. A lot of people over-specify the cam and then aren't happy with lopey idle and power curves that don't start kicking in until 3500 rpm.

Whatever you do, be sure to have the cam hardened and get new cam followers. The best available currently are "GT40" followers with sleeves to fit TR.

Are you putting in a new piston/liner set? If so, you might want to bump up to 87 or even 89mm. More displacement will increase both horsepower and torque.

While having the head skimmed, assuming that's planned, you could up compression a little by taking off .060-.090", too, if you wished. Still very much "street" modified. With some TR3, you need to watch the head doesn't bump into the water pump housing, after skimming. But, I doubt it would with this small amount off the head. You might also use the shim steel head gasket by itself to increase compression a little (Triumph originally sold it to reduce compression slightly, to be used in combination with the stock original head gasket, for cars sold in countries where gasoline quality was poor.)

Will you be putting in unleaded quality valves, valve guides and exhaust seat inserts?

While it's apart, you might consider a moderately lightened flywheel, too. You'll see improved engine response. It does require a little more care in balancing the rest of the engine, though.

A set of headers and some port matching and gas flow work on the head/manifolds would help all the above work well.

For more ideas, you might want to check out TeriAnn Wakeman's TR3A at https://www.tjwakeman.net/TR/index.html She has a blast driving it around in the Bay Area and had a lot of the engine work done by Greg Sulow in Santa Cruz. He's a Morgan guru, specializing in the TRactor motor we all know and love. TeriAnn's is a nicely balanced car that's not unpleasant to drive, but might be a little "hotter" than you seem to want.
/ubbthreads/images/graemlins/cheers.gif

 

[Bob Claffie]

Why bother! Most cam changes only move horsepower around rather than making more. Increasing horsepower at 5000 RPM and reducing torque at 2000 RPM is self defeating for most street applications which is what happens in the majority of "performance" cam changes. As noted above a cam is just the tip of the iceberg as far as modifying an engine ($$$$$$$), and doesn't usually make much positive difference if that's the only change. Bob

 

[bluemiata90]

I appreciate both Alans and Bobs responses. After reading your replies and doing some more research on the web. I decided that for my application, I'm going to stay with a stock cam. The engine already has 89mm piston liners in it with new pistons and the head has been reconditioned. I really don't want to get into reseting everything in the engine. Considering I'm rebuilding it myself and I've never done a TR3 engine before, I'll keep it simple. If interested, you can see where I'm at with this restoration by going to www.cardomain.com/ride/816145 Thanks again /ubbthreads/images/graemlins/smile.gif

 

[trfourtune]

while i hear bob's comment, i think his info is a little too generalized. if you've gone to 89mm bore, you can go to more cam and gain more bottom, mid, and top without moving the rpm band. even with 87's you can gain more overall without power band changes. modern designed cams are just plain better! 50 yrs of cam developement is worthwhile. elgin cams can custom grind for your engine and others like racetorations, that do "best suited" cams for YOUR engine that have "way" more development than a 50 yr old cam. good luck. remember all good things come from: knowledge, experience, and hard work.
rob

 

[Dave Russell]

[ QUOTE ]
while i hear bob's comment, i think his info is a little too generalized. -- Modern designed cams are just plain better! 50 yrs of cam developement is worthwhile. Elgin cams can custom grind for your engine and others like racetorations, that do "best suited" cams for YOUR engine that have "way" more development than a 50 yr old cam.

[/ QUOTE ]
The principles of cam design have not changed "that" much in 50 years. Metallurgy has changed a little. Obviously, the cam grinders have to claim some advantages to "their way" to sell anything. Many claim to match the cam characteristics to your specific engine design & intended use. It has always been so & obviously requires some common sense when selecting a cam.

I think you will find that the "way more development" & accompanying claims pretty much go in circles. Don't believe all of the sales hype.
D

 

[trfourtune]

ok, in basics, true, cams have lift, duration, lobe separation, ramp angles etc. our lovely tr 3,4 has a symetrical cam. built for mass production and simplicity. same profile on each side of the lobe (more or less). we can regrind this cam to have an assymetric lobe profile with different ramp angle (opening and closing) rates, more duration at peak lift, optimized by computer to match your port velocities, spring rates, for intake and exhaust lobes and still have the exact same "numbers" for the cam as the "old" one but work better. also we can regrind our old cam (symetric opening and closing numbers) with non symetric opening and closing numbers. (ie 30/70-70/30 and 37/63-73/27)
not all cams are created equal, thats all i'm saying.

 

[trfourtune]

ps, take a look at revington tr cam specs on their web site which can be downloaded, then look at the triumph cam.
we don't get huge differences, but for me every tenth adds to the other tenths that add up to fun.

 

[Dave Russell]

[ QUOTE ]
ok, in basics, true, cams have lift, duration, lobe separation, ramp angles etc. our lovely tr 3,4 has a symetrical cam. built for mass production and simplicity. same profile on each side of the lobe (more or less). we can regrind this cam to have an assymetric lobe profile with different ramp angle (opening and closing) rates, more duration at peak lift, optimized by computer to match your port velocities, spring rates, for intake and exhaust lobes and still have the exact same "numbers" for the cam as the "old" one but work better. also we can regrind our old cam (symetric opening and closing numbers) with non symetric opening and closing numbers. (ie 30/70-70/30 and 37/63-73/27)
not all cams are created equal, thats all i'm saying.

[/ QUOTE ]
Many factory cams in the 50's had nonsymetric timing, as well as dual patterns, it is not new. Opening & closing rates for a given cam timing have limitations based on the permissible valve spring tension & lifter geometry. Cam designs all have to work within the same limitations. Obviously the cam characteristics have to be matched to the rest of the engine components & intended engine use. My contention is that not much has changed regarding cam design & application in the last 50 years, including the sales hype.
D

 

[trfourtune]

observe nascar. same small block basically. still push rod v8 same displacement. notice how 30 yrs ago they could only make 500 hp (or less) out of a small block and now its 800. all the little things add up. no-one uses a cam designed 50 yrs ago. go figure.

 

[trfourtune]

also, these things may not be new but its new compared to that old tr camshaft.

 

[TRTEL]

I think I would still vote for trying a mild cam change. The fellow who built my race car back in the sixties used to have a 'rolling road' dyno in his garage. (What a thrill that was to use.) We would make these small incremental changes of a few degrees and presto another 3 or 4 bhp would magically appear at 6500. And I would highly recommend using one of the new adjustable cam gears on the market to further simplify your life. Have fun.
Tom Lains

 

[Alan_Myers]

Hi,

I looked at your project. Looks like fun!

Hmmmm, sounds like you have made a decision. But especially with 89mm pistons (and any other engine improvements you might have already done, or have planned) I'd want a modestly upgraded cam to help the engine breathe better. The extra capacity is going to need it. Running a stock cam would be an opportunity missed, IMHO. And, if you need to regrind the cam anyway, there is little or no additional cost to improve over the very mild, stock cam which is:
240 degree duration, .238" lift at lobe (early, I'd guess TR2 with 1-1/2" SUs) or .248" (late).

For comparison, "factory" upgrade cams include:
"D" 282 degrees, .273" lift (estimated)
"F" 300 degrees, .300" lift (est.)RACE ONLY
"G3" 309 degrees, .346" lift (est.) RACE ONLY
The above is from Ted Schumacher's www.tsimportedautomotive.com, lift is estimated because his site states total lift at the valve, not at the lobe. These estimates are calculated assuming standard 1.44:1 rocker ratio. I think there was a milder "C" cam, too, but don't know the specs. There were other race cams tested, too, but the ones shown are the grinds that proved best.

You might also want to look at www.elgincams.com for lots of general info on choosing cams and how they can be improved. For TR 4-cylinder, Elgin offers a pretty mildly improved cam:
TR3/4 - 264 degree, .262" lift

I am fairly certain www.britishframeandengine.com could grind a similar cam for you. Ken Gillanders offers a variety, but I don't have all the specs. Ken has been building TR engines since the mid-Fifties and is a great source of info. Give him a call on his 800 number if you want lots and lots of TR engine building info, just be sure you have plenty of cell phone minutes ;-) My TR4 is getting BF&E's:
#149 282 degrees, .287" lift

British Parts Northwest (www.bpnorthwest.com) offers a relatively mild cam:
BOP270 - 270 duration, .285" intake/.278" exhaust lift.

I believe all the above are symetrical cams, meaning that if the intake valve begins opening at 30 degrees center and closes fully at 60 degrees, the exhaust valve will begin opening at 60 degrees and close at 30 degrees. Revington TR are pretty expert at setting up TR engines, too, and offer four asymetrical TR cams, as mentioned above:
Fast Road - 270 degrees, .270" lift
Sprint - 280 degrees, .293" lift
Rally - 290 degrees, .309" lift
Race - 300 degrees, .324" lift
Asymetrical cam timing can make for more precise events inside the combustion chamber, improving filling and scavanging. I haven't any experience with these, but would like to give one a try sometime.

Higher lift cams require greater valve lash to allow for expansion when the engine warms up. On the #149 cam I'm using, for example, valvelash needs to be .016" intake/.018" exhaust. This makes for more noise at startup (but an alloy valve cover will offset some of that). The milder Elgin cam, by comparison, is very close to stock at .010" intake, .012" exhaust.

Another other thing to consider is an adjustable (vernier) sprocket, to be able to most precisely dial in cam timing. The stock TR sprocket offers pretty good adjustability, can get you at least within 1 or 2 degrees of ideal and maybe closer. The adjustable sprocket is just the icing on the cake to get cam timing dead on.

Note: to calculate total valve lift, multiply by 1.44 if using stock rocker arms, 1.5x roller rockers... higher ratio rockers are not generally recommended (although you'll find some selling 1.55:1, 1.6:1 and even 1.7:1).

Whatever you choose, stock or upgraded, a reground cam needs to be hardened and new cam followers are important.

Cheers!

 

[bluemiata90]

Alan, Thanks for the information. I think I understand about 3/4s of what you stated. I truly appreciate your help, but as I mentioned before, I'm very new to this engine rebuilding stuff and I don't want to get in over my head. When the time comes, I going to be building this engine on my own and want to make it as understandable to me as possible. I am going to contact Ken and ask about a mild street cam and if it sounds like it will meet my needs, I'll get one. You mentioned your TR4 is getting a
282 degree 287 lift cam, do you consider this a mild or race cam. Will it idle smooth or will it have a lobing idle?

 

[trfourtune]

alan,
your comments are spot on. i am told that with the larger capacity 89mm, you go to a cam with more duration about 10 degrees and it acts the same as the cam with 87mm. ie 270 deg.with 87mm = 280 deg with 89mm basically.
rob

 

[Simon TR4a]

It is my opinion that torque is mainly the product of displacement and compression ratio, so with what you have already done you should have plenty. I think horsepower comes from the cylinder head flow, including cam design, and engine revs.
However, other, more subtle factors are involved, in complex relationships with each other.I do feel modern cams will outperform older designs, and can give benefits in both areas, but I doubt that regrinding an original single pattern camshaft will do the same.
When I purchased my TR4a it already had a fast road cam installed when the engine was rebuilt in 1973. I do not have the exact specs in the notes that came from the previous owner, but it had a close-to-stock idle and "came on" at about 2000 rpm. I rebuilt the cylinder head to 9.75 compression with Triumphtune gas flowed valves and a 3 angle valve job. The car dynoed 91bhp and 110 lb. ft of torque at the back wheels.

Two years later I cracked the head and built a new one with oversize valves and chromemoly pushrods, and slightly larger ports, again 9.75 compression. As I was using the car for both road use and track events I decided on a stronger cam, from Kent cams, an asymetrical design with .310 lift and 290 degrees duration, a very strong cam, but one described in the Triumphtune catalogue as still having a wide spread of power.

Conventional wisdom told me to expect a peaky curve because a bigger cam, bigger ports and bigger valves all point in that direction. However, on the same dyno, with the same 86mm pistons, the same 13/4 SUs, and the same set of wheels and tires (different size or weight wheel/tire combinations affect the readings) I had 4 ft.lbs more torque at every rpm from 2000 up, and 4 ft.lbs more at the peak. Rear wheel bhp was up by 2 at low revs rising to 9 higher at peak.(Both cams were installed "straight up".)

This seems to support the argument that you can gain all round with modern cam designs; my theory is that using the same carbs and exhaust header helped the torque curve while limiting the gain in bhp.

This cam is likely too big for most people, it has a loping idle at 1200rpm, and Kent claims it makes power to over 7,000rpm(!) which I am not able to verify for you!
But I do think you can get gains in both power and torque, not just borrow from one to feed the other.

Good luck with your decision. Simon.

 

[trfourtune]

just a quick note. i've heard that 89mm size does quite a bit for the tr4 engine with some head work to unshroud the valves. your engine should respond rather well to to a cam around 270-280 deg. you WILL have to modify your carb (needles and jets) to see the benefits (as always). also its the exhaust side of the tr4 engine (header & ports)that first needs help to wake up that motor. you want long primary tubes (low rpm torque) (i'm making my own headers-39" lg X 1.5" dia. 2" dia collector 14" lg with 2.25" dia exhaust) with smallish dia. tubes. the only ones i've seen like this are from cambridge. i used an online header design program to test different header designs. it's called "headerdesign.com". seems to agree with my own math and wave theory.
ps- revington (who does not do his own cam design) and racetorations (darryl uprichard) ,who developes his own cams and motors on an ongoing basis with 40 yrs triumph race building experience, bothe use non symetrical cams.
rob

 

[Bob Claffie]

On the COMP CAMS web site is a statement to the effect that: " We get more complaints from people about over-cammed engines than any other problem". Bob

 

[Alan_Myers]

[ QUOTE ]
...as I mentioned before, I'm very new to this engine rebuilding stuff and I don't want to get in over my head.

[/ QUOTE ]

Hi,

Yes, good reasons to pick a "guidance counselor" and ask lot's of questions. That's why I suggested Ken Gillanders at British Frame & Engine. He works closely with all the tuners in England, imports a lot of the special items from them and has been building these engines for over 50 years himself.

[ QUOTE ]
When the time comes, I going to be building this engine on my own and want to make it as understandable to me as possible.

[/ QUOTE ]

The TRactor motor is a good one to learn on! It's relatively easy to rebuild and modify. Ken will let you know if something is out of whack on your build sheet. Discuss with him, write up a list of items that you plan and email it and/or post here for discussion.

[ QUOTE ]
You mentioned your TR4 is getting a
282 degree 287 lift cam, do you consider this a mild or race cam. Will it idle smooth or will it have a lobing idle?

[/ QUOTE ]

It sort of depends. I'm thinking about ordering a set of 89mm pistons and liners from Ken. With those, it would be a hot "street" cam. On the other hand, I've got a brand new set of 87mm AE pistons & liners in the garage already. With those, I would consider it more of a modest "race" cam that is still tame enough to drive on the street. I expect some increase in idle, probably a little bit of lope around 900-1000 rpm, but nothing objectionable. I am sticking with stock size valves and standard ratio rockers, too. My car is fitted with Weber DCOE, which offer a wide range of tuning possibilities. Plus, it's got a set of 4-2-1 headers and "sport" exhaust (slightly larger diameter than stock).

I think there have been some other good points made here about different considerations. But, the upshot of it all is that when you make a modification to the engine, it invariably leads to others. In other words, just increasing displacement will have limited value, without doing some other matching modifications.

Maybe we should be asking what carburetion you will be using, what's been done to the head already, any changes to the ignition, and what exhaust setup you plan.

Larger displacement will give more horsepower and torque. So will increased compression from a milled head (which is to some degree offset by larger displacement and a higher lift/longer duration cam). But, other things need to be matched to the changes you are making.

On a street car there is some compromise. Too large carburetors, too aggressive a cam, too large valves and too free-flowing exhaust can all lead to a car that's not much fun in daily traffic. The same is true of too light a flywheel, too strong a clutch, too close gear ratios or too stiff suspension. They all might be lots of fun going through the corners or running wide open on a straight at Laguna Seca, but how often do we get to do that?

/ubbthreads/images/graemlins/cheers.gif

 

[bluemiata90]

I tried calling Ken, but I got no answer. I also emailed his website and as of today, have gotten no reply. I'm not in a hurry with this rebuild, so I'll just keep trying. I appreciate everyones replies. Thanks