TW26 vs TW31s : V-Twin Forum: Harley Davidson Forums

nidan · 06-23-2005, 09:56 AM

I've settled in on most of my 95 build plan , and had narrowed down the cam choice to either the TW37 or TW26. As I tend to ride below 4000 rpm and prefer low end the 26 seemed better suited to my style. Then I saw Andrews had a TW31 with the same lobes as the 37 but different timing which appears to put it down towards the 26's rpm range .

I looked around and couldn't find very much information on the TW31.

The rest of the build will be :
Screaming Eagle performance cylinder heads /flat top pistons and the SE clutch kit . I already have the stage I mods i.e rejetted CV / SE cleaner/and SE II slip-ons .

Any opinions between the 26 and 31 ? I will be going with gear drive.

This is on an 02 FXDWG3 and I ride solo , weigh about 225 with gear.

Thanks in advance

Kags · 06-23-2005, 11:27 AM

IMO (I ant the best at this) if you realy want low end TQ the S/E heads may not be the best choice. Folks can port your stock heads to pull much harder at low RPM's then the S/E's. Now the HTTC heads are another story.

SYCLONE · 06-23-2005, 04:31 PM

Forget the 31 . nobody uses it as it was designed as a blower or turbo cam withs lots of help on the exhaust side. You have a lighter bike...go with the 37g as it will out pull the 26 just about everywhere and with flat tops and Se heads which are decked .060 already..your compression should be in the 9.8-10.0 range. perfect for the 37.

GRock · 06-23-2005, 07:28 PM

SYCLONE is dead on. 31 is out and the 37 with heads and 10 to 1 comp is the best choice. 26 is for stock heads and compression.

nidan · 06-24-2005, 06:33 AM

Many Thanks for the input!

electraglider04 · 10-24-2005, 08:40 AM

I have a 2004 flhti with Rinehart true duals, big sucker and dfo. Would a 26g give me lots more low-end, without having to anymore engine work?

Have been debating going too a 2:1 exhaust in pace of the cam, but since the RH's are on already, thought the cam may give me what I'm looking for???

Thanks for any advice!

**HDWRENCH** · 10-24-2005, 01:03 PM

I posted on this in another are. The 31 is a great cam , just becuase some areas have great fuel does not mean that all do. It works best in heavy bikes, and will work with more compression than a 37 and hits sooner. Here in the west with high temps and low octane fuel it works great. Pulls way before the 37 does and will run out for rpm as long. The 26 falls off much earlier. For those that have SE heads with 10.1 plus the 37 is a poor choice as it will ping badly here in the heat, add that to it's late building rpm and a heavy bike you end up with a DOG!!!. I have used the 31 in several builds.

a 98 inch kit at 9.7 and the 31 makes 97 ftlbs of tq at 2500 try that with a 37, it is not going to come on like that. The 37 is a great cam not disagreeing just that I think sometimes we forget that area, elevation and fuel all play a part in choosing a cam as much as riding style.

mainmusic · 10-24-2005, 07:45 PM

I'm running the 31g bought them from HD wrench I have a 03 heritage with HTTC Heads 10.5 HTTC pistons VPC clutch 337 primary V&H bigshot longs robbing power and it did 91HP 97 torque with a custom map on my PC3. Pulls great down low and up past 5 grand I would use it again anytime. I just changed exuast and hope for alittle more with a new map. HDwrench knows his cams and it was great advise Thanks

FXSTCHEWY · 10-28-2005, 05:12 PM

Scroll down to message #15, not bad IMO, Chewy.
http://groups.msn.com/harleytechtalk...44918230319124

FXSTCHEWY · 10-28-2005, 05:23 PM

and also, with the 46 close on the intake you get a easy starter, lose here gain there........... Chewy.

bedemonster · 10-28-2005, 06:50 PM

Quote:

Originally Posted by FXSTCHEWY

Scroll down to message #15, not bad IMO, Chewy.
http://groups.msn.com/harleytechtalk...44918230319124

Not Bad??

...His torque is down almost 10 ftlbs from 2K to 4K with the "new cam or 31G". That is right where you ride 95% of the time and right where you need it to pass without having to downshift.

His HP is down 5 across the same range as well.

I've run my 98" with the 37G's and 9.8 compression at 95 - 105 summer temps without any pinging whatsoever on 91 octane (thats the best we got here)...and thats with a 4* advance key which moved my intake close from 38* to 34*!

bedemonster · 10-28-2005, 07:01 PM

Quote:

Originally Posted by HDWRENCH

a 98 inch kit at 9.7 and the 31 makes 97 ftlbs of tq at 2500 try that with a 37, it is not going to come on like that.

I lost the dyno print out in a move a few months ago, but my 98" w/37G's and a 4* advance key was making 98 ftlbs at 2500.

FXSTCHEWY · 10-28-2005, 08:01 PM

Depends on how you ride and where you want it and also what bike you have and how high you turn it, he might ride at the high end, who knows, he may also downshift and make use of the tranny to multiply the power, no sin in downshifting. the main thing is "THE RIDER LIKES IT" so it must suit "HIS" style. IMHO. Chewy

bedemonster · 10-28-2005, 10:16 PM

Quote:

Originally Posted by FXSTCHEWY

Depends on how you ride and where you want it and also what bike you have and how high you turn it, he might ride at the high end, who knows, he may also downshift and make use of the tranny to multiply the power, no sin in downshifting. the main thing is "THE RIDER LIKES IT" so it must suit "HIS" style. IMHO. Chewy

From the graph, the only performance andvantage in tq & hp with the 31's would be from 5250 to 6200 rpms. You'd really have to be pre-occupied with the red line for the 31 to have any advatage here.

I'm not saying the 31 is a bad cam, but in this apples to apples(build remains the same; the only change is the cam) comparison the 37 performs better throughout most of the rpm range.