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Discussion Starter #1
Has anybody tried the Thunderbike cams in their 865cc Triumphs? They claim to give you

more horsepower while retaining the low end torque and mid-range of the stock cam. My

Thruxton currently has 40 pilots, 130 mains, 3 turns, NH bellmouth, and Predators. The bike

runs a hell of alot better than stock, but I want more without tearing my motor down. I'm

going to get rid of the airbox next and I was thinking these cams would help alot. Maybe if

funds allow a set of Mikuni 42's and head work in the future. Oh yeah , what about

changes to the ignition timing and rev limiter?
 

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Discussion Starter #5
Thanks for the info. I've never seen a stock cam that was ground for optimum performance.

I know there are gains to be made by changing cams but is the horsepower to dollar ratio

worth it in a stock motor?
 

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Has anybody tried the Thunderbike cams in their 865cc Triumphs?
I've looked closely at cams for my thruxton and, until someone in the aftermarket steps up with direct comparison data to state otherwise, the best option out there appears to be the original, 242-degee duration 790 cam from the 2001 model machines.

When I enquired with thunderbike regarding performance improvements their cam provided over the 790-242 cam, they responded with:

"We have not produced a camshaft suitable for use in the 790cc motors I'm afraid, despite several attempts nothing producing significant benefits has been found."

So, in a word, you won't realize any significant difference using their rather pricy thunderbike cam over the 790-242 cam in your 865. I can't speak to the other aftermarket grinds since no one publishes direct cam swap dyno data or cam specs for that matter...

As far as where to go w/ bolt-on mods, you can make about 70 rwhp by losing the airbox, adding the 790-242 cams, and getting the ignitor reprogrammed to match the more aggressive cam. That's where I'm hoping to be by the end of winter too...

Cheers,

--Rich
 

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As far as where to go w/ bolt-on mods, you can make about 70 rwhp by losing the airbox, adding the 790-242 cams, and getting the ignitor reprogrammed to match the more aggressive cam. That's where I'm hoping to be by the end of winter too...

Cheers,

--Rich
the 70hp mark with stock internals and stock carbs is a little out of reach, that is unless your dyno guy is blowing smoke.
 

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The dyno run I saw hitting near 70 rwhp wasn't my bike (unfortunately)...though I'm at a hair over 62 rwhp without the 790-242 cam or enhanced ignitor.

The ignitor tweaking is *supposed* to be good for about 1-2 hp and the cam adds about 4 hp up top...so that'll theoretically put me at about 68 rwhp. Here in Michigan, we round up... :^)

I've selected 70 rwhp as my goal and I'm sticking to it! I'll ditch the CV carbs should I fall short...

Cheers,

--Rich
 

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no air box 790 good ing box and 42mm carbs= 65rwh on a stock motor.I think the guys showing 70hp with stock carbs/motor better look close at there dyno guy and see what there sae c/f is .You might get one now and then as high as 62hp but most are in the high 50s.A bone stock bike should be around 50hp +or- 1 or 2 hp.
 

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I think the guys showing 70hp with stock carbs/motor better look close at there dyno guy and see what there sae c/f is .... bone stock bike should be around 50hp +or- 1 or 2 hp.
I concur...though the runs I've seen approaching 70 hp have all been 865 motors w/ 790 cams. The SAE corrections to the dyno output are suspect in my mind as well.

My most recent dyno run @ 62 RWHP was on the same dyno, using the same operator as my initial baseline run that produced 49 RWHP. Even those runs are not completely comparable due to different temp./pressure on the days they were conducted, but limiting the variables as much as possible provides the most reliable outcome. In that vein, back to back runs are the best way to go to tell if the change made helped or hindered power delivery...though that is tough to do for anything other than carb tuning or ignitor box swaps.
 

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I concur...though the runs I've seen approaching 70 hp have all been 865 motors w/ 790 cams. The SAE corrections to the dyno output are suspect in my mind as well.

My most recent dyno run @ 62 RWHP was on the same dyno, using the same operator as my initial baseline run that produced 49 RWHP. Even those runs are not completely comparable due to different temp./pressure on the days they were conducted, but limiting the variables as much as possible provides the most reliable outcome. In that vein, back to back runs are the best way to go to tell if the change made helped or hindered power delivery...though that is tough to do for anything other than carb tuning or ignitor box swaps.
YEA i agree,what i have been finding lately if the dyno guy will give you the c/f number and you do the math you will atlest know what the bike pulled real world hp the day of the run.From doing that i can see that the raw numbers dont change with wether any where near what the factors tell you they do.I ran mine a few weeks ago on 2 dynos a week apart with out changeing anything on the bike sae c/f hp changed 2 hp but the raw number only 1/2 hp.the temp corection factor is what doesnt work on our bikes.We all know air pressure can change hp alot .but the temp dont work the same on our air cooled motors as it does on the water cooled motors that sae set up the factors for.In cold weather our intakes and carbs are still hot.water cooled motors run near the same eng. temp in any weather.
 

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YEA i agree,what i have been finding lately if the dyno guy will give you the c/f number and you do the math you will atlest know what the bike pulled real world hp the day of the run.From doing that i can see that the raw numbers dont change with wether any where near what the factors tell you they do.I ran mine a few weeks ago on 2 dynos a week apart with out changeing anything on the bike sae c/f hp changed 2 hp but the raw number only 1/2 hp.the temp corection factor is what doesnt work on our bikes.We all know air pressure can change hp alot .but the temp dont work the same on our air cooled motors as it does on the water cooled motors that sae set up the factors for.In cold weather our intakes and carbs are still hot.water cooled motors run near the same eng. temp in any weather.
Good point about using raw number comparisons. I try to keep the temp. variations between my runs as small as possible (~70 degree days/same run time to the dyno, etc.), but short of mounting a frickin' temp. gauge and a barometer on the bike, I'm only guessing. I'll have to start figuring out the uncorrected HP and see how that pans out...maybe do only pressure corrections or something.
 

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Discussion Starter #15
Does anybody have the part# for the "Good" 790 cams? Where would I get the Ignitor box? How much horsepower is flowing the heads worth with these other mods? Thanks.
 

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well the best cams came in 2001 790s but you wont get that grind anymore or so i have read(even if you order that part number) When you price new cams you will be shocked at the price.I think you can get yours re ground alot cheaper.
 

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If the highest performance cams were only supplied on the 2001 Bonneville, what did Triumph do to the cams on the later 790cc engines? Did they re-publish new specs for overlap. lift, duration? Or did they make a change that (a) would have dropped hp, (b) would have most likely increased the max torque, but put it lower in the rpm band, without providing a different set of specs for the cam timing in the later 790cc Bonnie engines (as well as hp and torque specs)?

If Triumph did change the cams on 2002 and later 790cc engines, can someone on the forum provide the specs that show this? The specs for the 2001 cams next to the specs for later 790cc cams?

Or could someone with a 1st edition Service Manual pub those specs, and someone with a much later manual pub their specs.

The reason this is of concern to me is that I spent more time than I needed to re-indexing cams and paying for two demo runs only to come up with near identical hp and torque figures.

Does anyone here recall the crap Mazda stepped in when they published hp numbers that couldn't be quantified? (I think it was Mazda .... they were offering to buy back cars).

Thanks in advance.

Bob

Bob
 

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I dont have the specs but the 01 cam had more duration then the later 790 cams,but the later 790 cams still had more then the 865s.I think the reason was a epa thing.they keep wanting cleaner running bikes.
What you got to look at on stock bikes hp is they dont breath enough to loose much hp because of cams.With air box and stock pipes .top rpm is where you gain hp on these motors but they have to get enough air to feed it up there.
 

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...Does anyone here recall the crap Mazda stepped in when they published hp numbers that couldn't be quantified? (I think it was Mazda .... they were offering to buy back cars)...
I recall a situation with Ford SVT Cobras that had out of spec exhaust pipes that cut power big time & were replaced under warranty...sometime on or about 2003?
 
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