Cams...

[Xkvator]

In a 95" motor...

what differences would you feel between the Andrews 26 and Crane 300-2 cams...

would one benefit from porting more than the other?

....................26......................300-2

intake..........11/35....................13/33

exhaust........41/09....................42/14

in. dur..........226.......................226

ex. dur.........230.......................236

overlap.........20........................27

lift...............490.......................505

[genoway]

Longer duration and higher lift Crane benefits more from porting, but they are pretty close.

I think of the Crane 300-2 as halfway between Andrews 26 and 37.

I keep planning a bigger build, then remember it is hard to keep the front wheel of my bagger on the ground now.

[TerryMiller]

Just because ya deserve an answer I'm gonna go on a limb and say the cams are gonna be more exhaust sensitive than intake sensitive.

The intake close determines what rpm's the cam is in its "sweet spot" and both of these cams have fairly early intake closes. That's going to mean lower rpm's where the airflow is less.

The Crane has significantly more overlap meaning the intake and exhaust valves are both open at the same time. Overlap works on the theory that the exiting exhaust gasses help pull in fresh air through the intake. So a more "open" exhaust could help here.

What that means practically from a knowledgeable engine builder has to wait for one, but maximum air flow isn't what you're looking for with either of these cams.

Ensuring the combustion chamber size is the same on both cylinders and correctly matched to the intake close is important no matter which cam you choose. That's part of "porting" even though it has nothing to do with the ports.

[GRock]

Any twin cam will benefit from a good port job, but both of those cams are really fairly mild and the duration and lift doesn't take advantage of the increased velocity and flow of a good port job. The 26 works well with stock or very slightly raised compression as does the Crane. The general rule here is if you are leaving heads stock and going stock or a few tenths of of raised compression go with the 26. If you are doing headwork and getting the compression at or above 9.6 or so, then the Andrews 37 will out do the 26 thruout the powerband. And just to clarify a point that Terry made, flow is not the largest benefit of ported heads, velocity of the intake charge is. A good porter will not only increase flow, (which mostly helps in the upper RPM ranges, but will, most importantly, gain velocity in conjunction with a cam swap. And the 26 simply does not take advantage of that due to the short duration and lift. The overlap doesn't allow the exhaust charge to pull the incoming charge into the cylinder with that much more pressure. As for the more "open" exhaust?.......... that will cost you with a loss of scavenge and will further cost you on the intake velocity of the incoming charge. That 37 is a proven performer if you want to stay on the mild side and will respond much better to compression and porting. You want some real yank on the low to mid range...... try the Wood TW6 that will fit into stock spring height and get you into the 100's for TQ on a 95".

Best of luck

G

[TerryMiller]

Grock,

When I said "knowledgeable engine builder" you were obviously one of the people I was thinking of. Assuming similar lifts the two cams seem almost identical except for the overlap. What practically speaking does the extra 7 degrees of overlap mean to someone considering the two cams in an engine?

[Xkvator]

Originally Posted by TerryMiller

Grock,

When I said "knowledgeable engine builder" you were obviously one of the people I was thinking of. Assuming similar lifts the two cams seem almost identical except for the overlap. What practically speaking does the extra 7 degrees of overlap mean to someone considering the two cams in an engine?

Thanks TM...

That's what I was askin'...but guess i din't make it as clear as you...

[Kfengler]

I went with Wild Things TC-2G Cams for my 95" build.

Intake lift....: .510
Exhaust lift..: .495
In. Dur........: 248
Ex. Dur........: 242

http://www.kuryakyn.com/wtproducts.a...s&sgn=Twin+Cam

TC-2 & TC-2G, TC-2U, TC-2D
Bolt-in performance Cam for 88 to 103 inch motors.
Gain more power over the whole RPM range.
90+ horsepower is possible in an 88 inch with no head work, but really comes alive with more inches and higher compression.

The heads were Ported, Rinehart True Duals, Flat Top Pistons (9.5:1 CR), V&H Fuel Pak...
...I haven't had it on a dyno but she does run pretty strong from the get go, and really pulls after 3K rpm.

[GRock]

Originally Posted by TerryMiller

Grock,

When I said "knowledgeable engine builder" you were obviously one of the people I was thinking of. Assuming similar lifts the two cams seem almost identical except for the overlap. What practically speaking does the extra 7 degrees of overlap mean to someone considering the two cams in an engine?

Terry,

What you have to remember is that when the intake charge is ignited that it is trying to escape because of extreme pressure developed from ignition. When the exhaust valve opens, the gases escape at extremely high velocity and will actually assist in pulling the new intake charge during the overlap. That extra overlap allows this process to go on a bit longer (and develop higher intake pressure) and, if working correctly, will actually help develop so much intake charge pressure that the charge will continue to fill the cylinder even after the exhaust charge is expelled. That is why I stress the importance of an exhaust that will scavenge correctly because it helps this process along. When you go to too large of a flow in the pipes, you develop a pressure drop as the exhaust gases exit the head port and that drop will slow up the exhaust gas process and the intake charge velocity. Too much restriction and the reversion pressure will cause a backup at the exhaust port. It is also a reason why there is a limited powerband because there is a range where the cam, velocity and pipe are really working together even on the best of builds. If you have done the build correctly with well matched parts, the charge will have developed so much intake velocity that the charge will continue to fill the cylinder even after the piston has started to go UP the bore because you have temporarily developed more pressure coming in than the pressure that the piston is causing by shrinking the chamber. That is why the the intake valve stays open a bit even after the compression stroke has started. When all is said and done, the way that an engine makes more power is by getting as much fuel and air in the cylinder during each cycle. We can talk about all the fancy physics and dynamics, quench, cams, pipes, color of the tank, whatever. That simple process as described above is how an engine develops more OOOOMPH. The more fuel and air to ignite, the more power!

Now, where was I and what was the question again???

All the best.

G

[Rock]

Originally Posted by GRock

Terry,

What you have to remember is that when the intake charge is ignited that it is trying to escape because of extreme pressure developed from ignition. When the exhaust valve opens, the gases escape at extremely high velocity and will actually assist in pulling the new intake charge during the overlap. That extra overlap allows this process to go on a bit longer (and develop higher intake pressure) and, if working correctly, will actually help develop so much intake charge pressure that the charge will continue to fill the cylinder even after the exhaust charge is expelled. That is why I stress the importance of an exhaust that will scavenge correctly because it helps this process along. When you go to too large of a flow in the pipes, you develop a pressure drop as the exhaust gases exit the head port and that drop will slow up the exhaust gas process and the intake charge velocity. Too much restriction and the reversion pressure will cause a backup at the exhaust port. It is also a reason why there is a limited powerband because there is a range where the cam, velocity and pipe are really working together even on the best of builds. If you have done the build correctly with well matched parts, the charge will have developed so much intake velocity that the charge will continue to fill the cylinder even after the piston has started to go UP the bore because you have temporarily developed more pressure coming in than the pressure that the piston is causing by shrinking the chamber. That is why the the intake valve stays open a bit even after the compression stroke has started. When all is said and done, the way that an engine makes more power is by getting as much fuel and air in the cylinder during each cycle. We can talk about all the fancy physics and dynamics, quench, cams, pipes, color of the tank, whatever. That simple process as described above is how an engine develops more OOOOMPH. The more fuel and air to ignite, the more power!

Now, where was I and what was the question again???

All the best.

G

You see that bastages! GRock is technical and stuff. And he knows that black paint is faster.

[Xkvator]

Originally Posted by GRock

What you have to remember is that when the intake charge is ignited that it is trying to escape because of extreme pressure developed from ignition. When the exhaust valve opens, the gases escape at extremely high velocity and will actually assist in pulling the new intake charge during the overlap. That extra overlap allows this process to go on a bit longer (and develop higher intake pressure) and, if working correctly, will actually help develop so much intake charge pressure that the charge will continue to fill the cylinder even after the............................................... .... That simple process as described above is how an engine develops more OOOOMPH. The more fuel and air to ignite, the more power!

G

So your sayin'..."Get the Cranes"...

[Jeffytune]

The correct answer is.........



It Depends.

[Xkvator]

Originally Posted by Jeffytune

The correct answer is.........



It Depends.

Don't confuse me anymore, Jeffy...


...unless you want to go on report!...




jus' sayin'

[GRock]

Originally Posted by Rock

You see that bastages! GRock is technical and stuff. And he knows that black paint is faster.

.......and if a black dude has a black bike and wears black clothing...... thats a guarantee that you will be seeing his tail lights!!!

[GRock]

Originally Posted by xkvator

So your sayin'..."Get the Cranes"...

Suggest the 37 with 9.8 compression and headwork. If you are stuck between the two that you mentioned, the power difference is very little.

[Kfengler]

Originally Posted by GRock

.......and if a black dude has a black bike and wears black clothing...... thats a guarantee that you will be seeing his tail lights!!!

...hey, I have a T-Shirt that sez: "Black Bike Boys", and a Black bike... !!!