The Old Camshaft Argument

[rob83ke70]

Can I start the whole camshaft discussion up again? what camshaft are you running in your 4k and why? what does it idle like, how does it drive, do you race it, what carburettors/exhaust/cr are you running?

 

I have noticed in the faq that the tighe 104 apparently does not have an agressive or lumpy idle. I'm assuming that this is because the inlet opens at the same time the exhaust closes rather than having them overlap? anyone running this cam who can shed some light on the subject?

 

Kylie's cam is quite lumpy sounding, it runs 228/234 inlet/exhaust duration at .050" with the inlet opening at 6 degrees, closing at 42 degrees, exhaust opening at 47 degrees and closing at 7 degrees, 1 degree advance ground on cam. not quite sure why this idles lumpy when the inlet opens a degree after the exhaust closes? lift at valves is .4007" and lash is set at 0.014/0.016", if I go any less, the compression at idle drops really badly.

 

I'm planning on building a 4k with twin aisan 3kb carburettors, and its going to be a daily driver and race car, and I'm trying to work out what cam profile to use. Thinking about the tighe 104 but I just want some input into the matter. I want something with really really good midrange. Its going in a ke11 and going to be as light as I can make it as well :D

 

Robert.

[OniBerserker]

look on youtube for some ideas

medicineman has thrown up a few video's of his ke70, and he has twin dellorto's with a tighe 104

 

 

nick's car sounds crazy with the cam he has but his is pretty extreme

[coln72]

Had good results running a Wade 169 grind in a sinilar set up to the one you plan. Only I was running a 5k. Reasonable idle, good mid range, and it would rev to 7500-8000rpm with no probs.

 

Problem I can't remember the specs :D

 

[bLinded_]

I use a 104 in my 5K. Reason being, I knew other people who used the same grind with good results (Medicine_Man etc) so I went with something tried and proven. I have twin 40mm Dellortos and a basic 4-1 extractor to 2" exhaust on the engine, and it pulls really well. Makes 7000rpm easily, and would keep going if you choose to.

 

[rob83ke70]

specifications are confuzzling.... the tighe 104 theoretically has more overlap than kylie's does, maybe kylie's idles funny because the timing is advanced a degree (in the grind)??

 

the 104 doesn't sound very lumpy at all compared to kylie's cam. kylies is at least as lumpy as nick's, but in the specs i mentioned above it doesn't seem to have that much overlap?

 

I have my suspicions that kylie's car may perform a lot better with a different cam. Crow cams seem to make things that sound lumpy but don't perform quite as well as other company's grinds. Anyone else have thoughts on this?

 

I'm thinking i'm going to go with the 104 for my 4k. A 5k still seems to be a bit much hassle (engine capacity, engineering cert, and the whole hyd lash adjusters and dished pistons) whereas a 4k is a nice simple thing (to me anyway).

 

Robert.

[Felix]

I've used a tighe 113 which is the same as a 104 but with 0.5mm less lift at the valve. Great cam, have used it in a 4k for 3 years or so before putting it in a 5k with solid lifter conversion.

 

It made best power between 3500-8000 in the 4k. In the 5k best power is between 2500-7000.

 

Just keep in mind that a cam recommended by someone with a 5k will move the powerange up by approx an extra 1000 rpms in a 4k.

Also things like extractor design will move the powerband around. 4-2-1's will have a wider powerband starting lower in the rev range, and not so much up top (effectively like running a smaller cam). 4 into 1's will have less low end and make more power in the mid to top end than 4-2-1s. Carbs are the same... an oversized carb will need more revs to get into its powerange, whereas a carb on the small side will get into its' power band sooner but also run out of puff sooner.

 

Robert the Tighe 104 cam has 50 degrees overlap.

 

Check out the camshaft animation

Edited May 23, 2009 by Felix

[rob83ke70]

i'm slightly confuzzled still, kylie's cam has 13 degrees overlap but has a mad lumpy idle to it, but the tighe 104 seems to have a smooth idle (a bit more interesting than stock, but definitely not lumpy) and it runs 50 degrees of overlap?

 

kylie's cam starts to work properly at 2500rpm with max torque probably around 4000rpm and max power around 6500-7000rpm. with the twin carbies on it (and 4-2-1 extractors) it is quite streetable and smooth to drive. with the downdraught weber it was lumpy under 2500.

 

I'm not after a really lopey idle, and I want something with really really REALLY punchy midrange.

 

Robert.

[Felix]

Your timing specs for your cam you quoted are messed up. What cam is in your missus car, ie grind number?

 

A Tighe 104 has 215 degs duration at 50thou lift. It has 50 degrees overlap.

 

A stock 4k cam has 32 degrees overlap. :D

Edited May 23, 2009 by Felix

[coln72]

Found the Wade 169 specs.

 

Lift (at lobe) - 0.269"

Ex opens - 75deg closes 36deg

Inlet opens - 41deg closes 70deg

[Felix]

^^^^^

 

coln72's cam has 77 degrees overlap

 

Inlet opening + Exhaust closing = Overlap where both the inlet and exhaust valves are open at the same time.

 

41+36=77 degrees overlap.

 

Edited May 23, 2009 by Felix

[rob83ke70]

.050" valve timing

inlet opens: 6 BTDC closes: 42 ABDC .050" duration: 228

exhaust opens: 47 BBDC Closes: 7 ATDC .050" duration 234

 

advertised valve timing

inlet opens: 32 BTDC closes: 68 ABDC advertised duration: 280

exhaust opens: 73 BBDC closes: 33 ATDC advertised duration: 286

inlet lobe lift at TDC on overlap .070

 

crow cams 740 is what it was called. quite a few years ago now :D

 

at 0.050" lift i have a whopping 13 degrees overlap, if i look at the advertised specs then i have 65 degrees overlap.

 

visualising it all in your head is a bit confuzzling but possible. try visualising the valve/crank timing events of a four stroke inline three cylinder engine in your head and working out when the exhaust pulses happen!!

 

Robert.

[Felix]

Your cam data makes more sense now. Don't worry about the 50thou figures too much.

 

With overlap base the calcs on the advertised figures.

[rob83ke70]

that explains why kylie's cam has a lopey lumpy idle, and the 104 has a relatively smooth idle. 104 has more lift though.

 

shouldn't be too hard to tune a 4k with a 104 and twin aisans i hope :dance:

 

Robert.

[Felix]

Yea the 104 should go well with a slight lope at idle.

 

I found one of my David Vizard books today. I'll put up a few interesting quotes:

 

"Camshafts: The camshaft, more so than any other engine component, critically influences the selection and function of virtually every other engine system. Consider: The camshaft directly affects the carburetion, compression ratio, and to a lesser degree, even the chassis and driveline must be "built around" the camshaft. Put simply, cam design dominates part and full-throttle horsepower output, and selecting this component is one of the most important decisions that an engine builder can make."

 

"If you are not building a race engine, don't take the apparent "short cut" to high horsepower by using a race-engine camshaft; you'll instead take the short cut to poor performance and reliability, lousy throttle response, and downright embarrassing low-speed acceleration."

 

"As a rough guideline I have found that cams with up to 270 degrees of seat-to-seat intake timing are quite suitable as replacements for stock camshafts. For high performance street-strip applications where power is more important, I draw the line at about 285 degrees of intake duration. Cams with 285 to 295 degrees are mild race cams, and a any cam with greater than 295 degrees of intake timing is almost certainly a serious race cam."

[rob83ke70]

hear hear!! The first thing I did in terms of modifications was change the cam, and if I hadn't have done that, I probably would have been sorely dissappointed with both the exhaust and carburettor(s) upgrades. Probably still would have been happy with elec dizzy but not as dramatic an improvement.

 

the 104 has 270 degrees of inlet duration, and not as much overlap as kylie's, hence the smoother idle. I like how it is described in the tighe cams catalog, "strong midrange". Pretty sure that would be what i'm after. Most of your driving in a daily is midrange, and even racing, especially motorkhanas and khanacrosses the midrange i'm pretty sure would be better than the outright power.

 

I had a fella who raced speedway tell me that rather than pick the full race cam when he built an engine, he put a milder cam in it, and not only was it easier to tune and more reliable, but he was heaps quicker than other guys with the same size engine. They were all quite stumped and wanted to know what he did to his engine!

 

Robert.