[doger5]

Should you do a cam swap or regrind at your old cam tpusa, also what do you do about the cam bearings clearance or will the old cam work better using the old bearing

 

[beemerrich]

The only vendor selling cams not requiring a core is (or was) thunderbike in NZ...so you're pretty much looking at a regrind unless you buy cams from Triumph or the Thunderbike ones. That would be foolish IMHO since the best grinds are from either Web Cams/TPUSA or Megacycle. I've had the same cam bearings for 2 different cams & 3 installs (original 865 grind, a early 790 grind, and the TPUSA 813 cams) without issue.

The beauty of having the second cam set was that there was essentially no riding down time waiting for my cams from TPUSA. I seriously doubt that the cams I sent TPUSA for cores were the same ones that came back...

YMMV,

--Rich

 

[propforward]

I swapped my cams with TPUSA. I know very well I did not get my original cams back (the turnaround was very fast). I had no issuse at all with the cam bearings. There's no reason there should be an issue really.

 

[Andrewluz]

I have the 790 cams. How do the 865 cams compare to these?

 

[beemerrich]

I have the 790 cams. How do the 865 cams compare to these?

They don't. My jump from 865 cams to 790 cams yielded 4 ft-lbs peak torque and 5 RWHP:

http://www.triumphrat.net/twins-technical-talk/97729-twins-dyno-results-thread-3.html#post1263465

The thunderbike cams are similar to the 790 cams in terms of power generation, so - depending on your tuning goals - the only possible RWHP increases for you resides in buying a longer duration cam grind, like the TPUSA 813 grind (slightly more lift/longer duration). Gains are mostly realized from 7,000 to 9,000 rpms and require a reprogrammed ignitor to get the full benefit. Also, if you don't rev over 7,000 rpms or so, you won't see any significant increase in HP and you should spend your money on something else.

Cheers,

--Rich

 

[mikeinva]

if you have later 790 cams the 813s will give you alot more gain.Stock cams got worst as time whent by the early 01 cams where the best of the stock cams ,then the later 790 cams then the 865 cams .The 813s are better then any of them.In most cases they pick you up all the way through the rpm range.

 

[propforward]

I can't comment on the difference between TPUSA cams and 790 cams, having never run the 790's, so frankly I'll defer to beemerrich and mikeinva on that.

However, if you are running an 865, I can tell you that you pick up performance through the whole range switching to these. Very nice they are. And I haven't even had the igniter remapped yet. I really need to get on that.

 

[Andrewluz]

Thanks for the advice. I will definitely look into the 813's.

 

[Aussie_T100]

At the risk of upsetting the "powers that be" I'll dare risk a comment on a cam thread. There are some potential benefits from having your original cams reground as opposed to doing a core exchange particularly if your engine has a few miles on the clock. An often overlooked factor in swapping cams is the straight cut gears that drive the cams, these gears "mate" over time just like any other break-in process and any mismatch between these gears is a potential source of valve train noise which usually presents as a high pitched whirr or whistle. Mismatched gears will eventually "mate" over time and the noise will reduce but if you use your original cams you know for sure that you are not going to experience this problem.

The above is a particular problem with Thunderbike cams as the billet material used to machine the cams from is very hard and the bedding in process between the cam gears and the OEM central driving gear is very slow. I've had Thunderbike cams fitted for over 30,000Klm's and the noise has just started to abate recently but when the cams were first fitted there was a definite high pitched "whistling" noise emanating from those gears that was very disconcerting.

I've measured Thunderbike cams against early 790 cams and yes there is not a lot of difference but the Thunderbike cams do have slightly more lift, slightly more duration and slightly wider lobe centres. Having seen the specs for 813 cams I would suggest that the Thunderbike cams are approximately halfway between the early 790 cams and 813's. I would also suggest that the only way you would tell any difference between these cams as far as performance delivery goes is on a dyno. The primary advantages of Thunderbike cams are that no core exchange is required (a privilege you pay for) and that they are machined from billet so they are much stronger than the OEM cast cams.

Regardless of what anyone tells you any gains in low to mid range performance from Thunderbike or 813 cams alone is minimal to say the least. Noticeable performance gains start at about 4,500rpm and rocket skyward from there. There is little point in adding any of these cams unless you raise the rev limit to take advantage of the increased top end breathing. Having said that a set of FCR carbs should be mandatory once you have fitted either of these cams.

If you are looking for increased performance in the mid range (3,000 to 5,000rpm) I would advise you look at a grind designed to increase mid range torque specifically rather than top end power. Neither the Thunderbike cams or 813's meet that criteria.

All of the above is my personal opinion based on my personal experience however YMMV. I'm very happy with the results:-

 

[GDCobra]

I guess that this is half on topic, if not I apologise in advance.

Presumably a 'performance' cam has more material in most if not all places, higher peek & fuller profile to give more lift earlier. How is this achieved using a stock cam? I can only imagine either material is added or the base circle is reduced

 

[Calliway]

I have to say I road my Bonneville to the max this year all the time, I am ready for more power so cams, carbs and ignitor are on the list for this year

 

[mikeinva]

I guess that this is half on topic, if not I apologise in advance.

Presumably a 'performance' cam has more material in most if not all places, higher peek & fuller profile to give more lift earlier. How is this achieved using a stock cam? I can only imagine either material is added or the base circle is reduced

the lobs are built up then the whole thing is reground and reharden.They seam to last as long as stock.

 

[mikeinva]

At the risk of upsetting the "powers that be" I'll dare risk a comment on a cam thread. There are some potential benefits from having your original cams reground as opposed to doing a core exchange particularly if your engine has a few miles on the clock. An often overlooked factor in swapping cams is the straight cut gears that drive the cams, these gears "mate" over time just like any other break-in process and any mismatch between these gears is a potential source of valve train noise which usually presents as a high pitched whirr or whistle. Mismatched gears will eventually "mate" over time and the noise will reduce but if you use your original cams you know for sure that you are not going to experience this problem.

The above is a particular problem with Thunderbike cams as the billet material used to machine the cams from is very hard and the bedding in process between the cam gears and the OEM central driving gear is very slow. I've had Thunderbike cams fitted for over 30,000Klm's and the noise has just started to abate recently but when the cams were first fitted there was a definite high pitched "whistling" noise emanating from those gears that was very disconcerting.

I've measured Thunderbike cams against early 790 cams and yes there is not a lot of difference but the Thunderbike cams do have slightly more lift, slightly more duration and slightly wider lobe centres. Having seen the specs for 813 cams I would suggest that the Thunderbike cams are approximately halfway between the early 790 cams and 813's. I would also suggest that the only way you would tell any difference between these cams as far as performance delivery goes is on a dyno. The primary advantages of Thunderbike cams are that no core exchange is required (a privilege you pay for) and that they are machined from billet so they are much stronger than the OEM cast cams.

Regardless of what anyone tells you any gains in low to mid range performance from Thunderbike or 813 cams alone is minimal to say the least. Noticeable performance gains start at about 4,500rpm and rocket skyward from there. There is little point in adding any of these cams unless you raise the rev limit to take advantage of the increased top end breathing. Having said that a set of FCR carbs should be mandatory once you have fitted either of these cams.

If you are looking for increased performance in the mid range (3,000 to 5,000rpm) I would advise you look at a grind designed to increase mid range torque specifically rather than top end power. Neither the Thunderbike cams or 813's meet that criteria.

All of the above is my personal opinion based on my personal experience however YMMV. I'm very happy with the results:-

http://www.youtube.com/watch?v=r6vc0IEg5so

you do gain below 5000rpms with the right setup with 813 cams maybe all 813 cams arent like the ones you saw the spec for who knows.BUT to get any big gains in torque you got to go with more cc.

 

[ShaneDuc]

Aussie_T100; I'm telling you, I had excellent gains across the board from the 813 cams. The original Thunderbike cam specs came from TPUSA. Then were slightly changed, so they wouldn't get sued.

I run TPUSA; 813 cams, Plus-Pro Street Head, 903 Big Bore Kit w/Hyde Lightened Flywheel and 39CR Smoothbores. The single addition of the 813 cams, gave an honest 20% increase in hp/tq nearly across the board.

 

[Aussiematt]

The gains from the 813 cams are most noticeable around 4500-5000 rpm

 

[Aussie_T100]

I run TPUSA; 813 cams, Plus-Pro Street Head, 903 Big Bore Kit w/Hyde Lightened Flywheel and 39CR Smoothbores. The single addition of the 813 cams, gave an honest 20% increase in hp/tq nearly across the board.

I'm not disagreeing with you but I'd like to see the before and after dyno charts.

The original Thunderbike cam specs came from TPUSA. Then were slightly changed, so they wouldn't get sued.

Where did you get this information from? Can it be verified?

The gains from the 813 cams are most noticeable around 4500-5000 rpm

That's about where the Thunderbike cams come "on cam" so I can imagine the 813's would behave in a similar manner however I'm sure that a dyno chart would reveal that the greatest improvement occurs higher in the rpm range. My experience is that that is the case with Thunderbike cams anyway.

you do gain below 5000rpms with the right setup with 813 cams

I don't want to argue with you Mike but I've been fooling with engines long enough to know that when it comes to cams alone you cannot increase HP at the top end without sacrificing the loss of some low end power. There's no magic in this, you simply rob Peter to pay Paul. Yes you can make other modifications that will increase volumetric efficiency at lower rpms and thus regain the power lost in that rpm range by altering the cam profiles but that increase is down to those mods not the cam.

maybe all 813 cams arent like the ones you saw the spec for who knows.

Specs can be changed at a moments notice. I do know that the 813 specs I saw are no different to cam profiles that have been in use in the industry for years, even before Hinckley Bonnevilles were even thought of. No magic here the grind has been around for years.

BUT to get any big gains in torque you got to go with more cc.

Agree 100%.

I guess that this is half on topic, if not I apologise in advance.

Presumably a 'performance' cam has more material in most if not all places, higher peek & fuller profile to give more lift earlier. How is this achieved using a stock cam? I can only imagine either material is added or the base circle is reduced

In this particular case you can't reduce the base circle by anything significant as this would require thicker shims to maintain correct valve clearances. Most reground cams are welded to build up the lobes then ground to a specific profile and then hardened. Done properly this process has proven to be very durable.

 

[Siskiyou]

So, if a person wanted a cam ground with mid range power in mind rather than top end,
what cam would that be, and what other mods would help achieve that? I know more
cc's will do it in terms of total torque: I'm thinking in terms of how to achieve the
maximum mid range power for a given displacement.

 

[beemerrich]

The original Thunderbike cam specs came from TPUSA. Then were slightly changed, so they wouldn't get sued.

Oh...okay. It's your story.

There aren't any magic bullets here. The cams in question do what hot rodders have been doing for decades....opening up separation angles, increasing lift, and adding duration. The 813 cams go well beyond the Thunderbike specs in terms of lift and separation angle...they're not even close to be honest. So I know for a fact that your statement is utter horse hockey.

Also, I think the "20% across the board" statement would also need before and after dynos to be believable. I went from a best dyno of 73.5 RWHP with 790 cams to 76.5 RWHP with the 813 cams. All of that gain came in over 7,000 rpms. While there is more to gain & lose on a higher tuned machine, I doubt anything over maybe 5-10% is credible to only changes in cam profile.

I don't want to argue with you Mike but I've been fooling with engines long enough to know that when it comes to cams alone you cannot increase HP at the top end without sacrificing the loss of some low end power. [/B].

Lawrie,

In most cases, I agree 100% with this. However, the 865 cams that came in the '04 & later 865 motors are so stifling to the motor's performance that when I switched to early 790 cams in my '04 thruxton, I gained both low end torque (~4 ft. lbs) and upper end HP (~5 RWHP). It was completely contrary to my prior experiences with tuning motors in other machines and I was completely baffled to how this could be since the only change I made with the cams...but the numbers don't lie. Basically, I take it as a testimony to how bad the 865 cams profiles are...

Regards,

--Rich

 

[beemerrich]

So, if a person wanted a cam ground with mid range power in mind rather than top end,
what cam would that be, and what other mods would help achieve that? I know more
cc's will do it in terms of total torque: I'm thinking in terms of how to achieve the
maximum mid range power for a given displacement.

Torque cams have less duration and tighter lobe separation angles than those for making peak RWHP. For our machines, my guess is that the 790 cams are the best torque cam grind for an off-the-shelf cam...though I didn't really give up anything down low when I went to the 813 cams. If I did lose torque, it wasn't noticable on either the dyno or in street use.

Tuning for torque results in longer intake tract lengths and longer primary header pipe lengths for a given pipe diameter....there is software that helps with determining the initial lengths for these variables. Here's on example for exhaust design:

http://www.mez.co.uk/mezporting/exhaust_length.html

and here's another couple for determining intake runner lengths:

http://www.velocity-of-sound.com/velocity_of_sound/calculator3.htm

http://www.exx.se/techinfo/runners/runners.html

These merely give you a starting point for your tuning efforts...there is no substitute for properly executed testing of several phases of design to provide perspective/focus and allow optimization of the tune.

Evaluation of my stock thruxton headers with the stock cams and D&D cans indicated that they are tuned for a power peak of around 4,700 rpms. I frankly have no clue on how to determine the design power peak for the stepped D&D system I now have...not that it matters....

Hope this helps.

--Rich

 

[GDCobra]

the lobs are built up then the whole thing is reground and reharden.They seam to last as long as stock.

Thanks Mike, so they are metal sprayed (or something similar) then re ground and the base circle remains as per spec'.