Planning on doing a 107 with heads this winter. I'm wanting to go with Wood 999-6 or 999-6a. What is the better choice? Will either one work? Which one comes on earlier, has higher peak numbers, more area under the curves, and goes out further to redline? There seems to be some confusion when discussing these cams as to what specific one is being discussed, be it the 999-6 or 999-6a. Both seem to be referred to as 999.

 

The A's are designed to be a bolt in and will peak a tad lower in the rpms than the 999-6's Don't expect 135 hp with either one though. There isn't a huge difference between the 2, I'd bet you wouldn't be able to feel the difference if everything else in your motor was the same.

 

It all depends on the specific combination, most specifically the compression and exhaust you are running. The 999-6A has more advance and overlap which will push the curve more to the left with earlier torque, where the extra lift on the 999-6 will run out slightly further to the right if you have the right cylinder head and exhaust combo. We use both cams frequently with our combinations, we like to run the 999-6A in the 10.5 compression range and like to see the 999-6 close to 11.0. Both cams have the protential for excellent Hp/Tq in a 107 application it comes down to what you are looking for and the rest of the combination, one important aspect to note is that tdc lift is extremely high on the 999-6A so valve to valve clearance needs to be considered and the head needs to be set up accordingly, assuming you are using larger than stock valve sizes.

 

Agreed.
Scott

 

What type bike and what type riding?

Ask you head porter what he/she recommends IMO. They know what works with their heads.

 

What is the better choice?
Depends on where you want your power...

Will either one work?
Yes...

Which one comes on earlier?
The numbers on the 6a would indicate that...

Which one has higher peak numbers?
The numbers on the 6 would indicate that...

Which one has more area under the curves?
The numbers on the 6 would indicate that...

Which one carries out further to the red line?
The numbers on the 6 would indicate that...

This is all potentially based on the static compression and the amount of flow in cfm of the cylinder heads. If everything was identical, Heads and static comp, throttle body, pipes etc.etc. it would still be hard to tell without a dyno and even that would be very similar.

One thing I find hard to swallow is that The 6a is a bolt in. with the lift at tdc the valve to valve clearance has got to be so freakin close I don't think I would chance it....

 

For reference the dyno chart below is a direct comparison of the Wood TW-999-6 and the TW-999-6A in the same motor on our 2015 Road Glide test bike. This motor is a 107" @ 10.75 compression with FM Level B CNC heads & FM E-Series 2/1 exhaust, tuned with Dynojet Power Vision. Note these runs were done a day apart.

 

Thanks for posting this. Great info!

 

Below 3500 the 6A has a pretty decent advantage, all else being pretty close. I'd have to favor that option for the street.

 

Great info! Thanks!