figuring out cam specs

[wagoon 2,429]

Have been chatting to a bloke that is interested in doing a crossflow conversion into his landcruiser 60 series and it got me thinking about camshaft configuration and specification.

Just using Camtech cams as an example:

Camtech cam with part number ending 110 : duration 264 degrees, 208@50thou, total valve lift .477, 110 LSA, RPM range 1400-5000

Camtech cam with part number ending 517: duration 274 degrees, 218@50thou, total valve lift .510, 110 LSA, RPM range 1800-5500

 

To make the most torque out of a crossflow while still having usable torque very low in the rpm range(off idle so to speak) would it be possible to:

use the 517 cam as shown above but install it 2 or 4 degrees retarded so that it has a closer rpm range to the first cam but with increased lift benefit of the 517

                                                                                                 OR

get the 110 cam made on a smaller LSA (like 108 for example) and install correctly and use the shorter LSA to boost mid range torque(does the shorter LSA sacrifice power elsewhere??)

                                                                                                 OR

just use one of the Camtech cams as supplied or even Tighe cam part number 725 : duration 268 degrees, 210@50thou, total valve lift .517, doesn't list LSA or RPM but remarks are "mid range"

 

Purpose of the landcruiser is towing/ general mild off roading (bumpy undulating tracks/sandy tracks hence low torque requirement-NO rock crawling type stuff) and daily driver. My experience with 3F carby petrol cruiser engine is it has stupid amounts of torque from idle(take off in 2nd on all but steep uphill) but started falling over at 3800rpm and was just making noise over 4200rpm. Guys wants to retain as much torque down low as possible to help move the heavy car(is approx 2150kgs) but wants it to make usable power to 5000ish rpm max. Is it possible with a crossflow?

 

 

[gerg 10,871]

The further you move away from standard timing the further up the rpm band you will move. If you look at the specs of a towing cam, they're not much more than stock.

 

I have a 204/214, 0.510" in my 302 and low-mid torque is very good for a supposedly revvy engine, and mine is installed dot-to-dot. You start feeling the peak come in at around 2000, gently tapers off at 4000 but hits 5500 no dramas. I would guess on a 250 that the rpm band on this grind would start and finish about 500 rpm earlier.

 

So for off-idle torque, go with the smaller one. Save the money you'd spend getting a custom grind and clean up the ports and get a valve back cut and 3-angle seat for even more torque.

[wagoon 2,429]

My carby powered landcruiser did the exact same thing where it noticably picked up after 2000 rpm, it was bog stock other than exhaust and electric dizzy even my wagon does the same thing. But the landcruiser you could feel run out of puff at 4200rpm.

 

So when comparing the Camtech 110 to the Tighe 725 they both have very similar spec and similar "size" except for the total lift where the Tighe has even more lift than the bigger Camtech 517. So is the Tighe cam better for torque because of its smaller size (less duration) but increased lift?

[Grimmy 312]

The way I understand it , lift and tighter lsa = torque . But the less lobe separation means the power comes on quicker but falls over quicker aswell .

[FORD_MAN 1,026]

the Tighe 725 is a 110LSA on a 106ICL,

yeah I think your thinking right less ADV duration will make more torque

Tighter LSA will make more torque & move power band down,

[wagoon 2,429]

Thanks guys for that. I doubt the falling off quick will be an issue as the power will last longer than his current setup anyway. But that is good to know. And moving the power band down is exactly what he wants so I think we have a winner.

[matt_lamb_160 252]

The 517 cam is too big and retarding it will make it worse.

 

Tightening the lobe sep on the other cam will make an already narrow banded engine even narrower. The cam is fine as is or go the 206 deg cam.

 

The Tighe cam has good specs, but may be a bit big. All the specs needed to work out LSA are listed.