A question for you guys who know engine mechanics better than I

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dazco

dazco

Well-Known Member
Supporting Member
for a while now i have been contemplating having the cams from triumph's big bore kit for the Tbird installed. They ARE indeed available seperately and my mechanic said he'd install them when he does the 12k valve adjustment so basically the labor will be in effect free since i would have to pay it for valve adjustment anyways. (cams have to come out for that) The cost of the BB kit complete with labor is $1900. The cams are $600 for the pair and as i said labor is in effect free.

So heres the question to those who know thier way around a engine....what do you think about doing this as far as whether the power gained will be close to the BB kit and whether there will be any issues? To answer that you will need to know that the BB kit retains the same compression ratio as the stock bike, so i have to think the majority of the 13 HP 10 Lbs of torque gained is from the cams. After all, how much can 100CC contribute to a 1600? Also, the BB tune should be fine with the cams because there are guys running it with the stock 1600. Which actually seems odd because i would thing the changes would be more timing then fuel with that due to the cam difference. But they are doing this so i assume it should work well with a cams only mod. also, my mehanic didn't mention any problems doing this so i just assumed there would be no valve interference issues, but i will ask him to be sure he has thought about that. He's the press fleet manager for triumph, so he's done more BB kits than probably any 10 dealers if not more.

anyways, what are your thoughts.....with only a 100cc difference and no difference in CR, do you think the cams will offer say 80% as much power as the whole kit/ Do you see any issues that could cause it to actually not run as well or show very little improvement? Any thoughts are welcome, as i need all the help i can get to make a decision as to whether this is a good idea or not. I'd as the mech, but he's biased being the guy who take my $, so i don't trust his answer.
 
No, but as i was saying there are several guys running the BB tune with bikes that don't have the BB and they say it runs better. So with the cams it should be fine. Remember, triumph's tunes are very lean, and the timing in the BB tune should fit a 1600 with the cams better than a stock 1600. So if anything it may actually be closer to a perfect tune for a cams only bike than a BB'd bike because the BB tune would require a bit richer tune, but will be lean because triumph tunes them lean for emissions regs. So the cams only bike should require less fuel in the mix and therefore mat be closer to an optimal tune with the BB tune than the BB bike would. Maybe i'm off....i'm no mech. But the short of it is that it should be fine with the BB tune from all i've seen.
 
In the days of carbs and vacuum advance timing, changing the cams resulted in a different power band changing the torque curve. It also increased the power somewhat. You had to jet and set the timing accordingly. Guys commonly did this in street rods. How it affects EFI, I have no idea. Maybe GP or AJ can answer this.
 
One or the other will give you a nominal gain.

Re-mapping will need to be done regardless of the change. You might be suprised how much difference an inexpensive re-mapping makes ALL BY ITSELF!

Do BOTH hardware mods AND the re-map, and it will be like having a different bike.

Iff there is a higher compression BB kit, you may consider it for additional gains, but your fuel quality may then be the deciding factor as to whether you have a significant gain that can be appreciated.
 
Yeah, i've been impatiently waiting to remap it optimally because i know the stock maps are lean and not at all nominal. But we Tbird owners have been waiting a year now and so far no tuning solution besides Tuneboy is available, and tuneboy isn't giving any support at all. He hasn't uploaded a single Tbird map even tho he's mapped several tbirds for guys in his area, and those Tbird owners who bought a TB and try to email him have gotten no response. So thats out. The power commander, which isn't a very desirable solution anyways said they're a year away from being ready a few months ago. The 3rd and best possibility seems to be tuneECU which you probably heard of. He said he's looking at the Tbird now and hopefully it will be supported. The fact it's free is of course a huge bonus, but it's a crap shoot as to whether he can make it work with the Tbird due to it's can bus system i guess. so it's possibly we won't have a working tuning solution for a long time or maybe never, and we've already been waiting a year. This is one reason i considered cams only. I thin the BB tube should be pretty optimal for the cams only since it would be lean with the BB kit. So it's possible it would work even better with cams only. It's a way to get some better power and possibly a more optimal tune for the bike w/o paying the $2k for the BB kit+labor and to also avoid having my engine removed. (yes, they remove the engine !) So thats why im posted this....i just want to try and get some opinions as to whether it would be worthwhile or not.

[quote author=grandpaul link=topic=9919.msg49220#msg49220 date=1282654459]
One or the other will give you a nominal gain.

Re-mapping will need to be done regardless of the change. You might be suprised how much difference an inexpensive re-mapping makes ALL BY ITSELF!

Do BOTH hardware mods AND the re-map, and it will be like having a different bike.

Iff there is a higher compression BB kit, you may consider it for additional gains, but your fuel quality may then be the deciding factor as to whether you have a significant gain that can be appreciated.
[/quote]
 
Dale, you have bubbled your CC's from your old bike... So why mess with it? Save the coin and take a long bike trip..
 
DANGER WILL ROBINSON!

Going big bore and/or cams WITHOUT increasing the available fuel delivery is installing a grenade and pulling the pin.

The bike is ALREADY running lean. Increasing the relative leanness with the upgrades is introducing the potential to hole pistons and stick the lump.

Re-mapping will need to be done regardless of the change
Click to expand...

You've got to get more fuel into the mix, period.
 
[quote author=grandpaul link=topic=9919.msg49277#msg49277 date=1282743785]
DANGER WILL ROBINSON!

Going big bore and/or cams WITHOUT increasing the available fuel delivery is installing a grenade and pulling the pin.

The bike is ALREADY running lean. Increasing the relative leanness with the upgrades is introducing the potential to hole pistons and stick the lump.

You've got to get more fuel into the mix, period.
[/quote]

Spot on advice. That is why I mentioned rejetting with carbed engines when changing the cams. Increasing the fuel flow is an integral part of the modifications.
 
[quote author=grandpaul link=topic=9919.msg49277#msg49277 date=1282743785]
DANGER WILL ROBINSON!

Going big bore and/or cams WITHOUT increasing the available fuel delivery is installing a grenade and pulling the pin.

The bike is ALREADY running lean. Increasing the relative leanness with the upgrades is introducing the potential to hole pistons and stick the lump.

You've got to get more fuel into the mix, period.
[/quote]

yes, i'm fully aware of that. But he would be using the BB tune if i did this, and if anything that should be a bit richer than the bike would be now or with that same tune and the full BB kit. So no problem there. Just to be sure you all realize this, i'm talking about the genuine triumph BB kit, not an after market one. And they have tunes for the kit with and w/o TORs.

Heres another possible issue tho, and maybe GP will have a thought on this. Someone who says he's an old engine rebuilder mentioned that if you replace the cams on an engine with more than just a few miles on it that you need to replace the cam chain too for the same reason you should replace the sprockets too when you replace a final drive drive chain. he said the chain may well snap eventually due to the mismatch in the wear pattern of the chain not matching the new cam sprockets. But my thought there is that if that is true, then why is it triumph doesn't give you a chain with the BB kit? Any thoughts on this?

By the way guys, i'm not after a lot of extra speed here....i just want the bike to have the most linear power curve possible w/o flat spots and more importantly improve the higher RPM area. Because while this bike's low end torque is great, once you get past about 4000-4500 RPM's the bike just stops breathing. I'm not trying to make it into a speed triple, i just want the other half of the RPM range to be usable. As it is now i may as well move the redline on the tach to 4500.
 
Now I understood why you are looking at engine mods. And your situation is why I prefer carbs to EFI. Have you considered the BB tune without TOR's? I don't know if that would be too rich. I have to think that since it is a Triumph produced tune, it would be designed to keep the bike on the lean side with the BB kit. If you went that route, perhaps you could open the breathing a little? I'm just kind of thinking in writing here. What I am trying to say is that if you could get the bike a little more on the rich side, it might do what you are wanting it to do without an engine mod.
 
Well, i'm now looking at one of these Dobeck injection controllers that are made by the originators of the dynotune guys who sold that company and went off to build these new units. Someone mentioned this unit for thier triple in a thread elsewhere on this forum months ago and i just saw it yesterday which is what prompted me to call them. They are made for people who like tuning carbs but have a injected bike. They work in the same way as carb tuning, but instead of replacing various sized jets you use up/down buttons to adjust each range. there are buttons to adjust what would be the main jet range on a carb, ones for needle and one for pilot. But it also has the ability to adjust things automatically on the fly to compensate for load. They say it's better than the power commander in that and other ways, but of course this is coming from the maker so....

Anyways, they are having me take pics of the connectors at the injectors and the sensors and once i send them they will make one up for the bike and send it to me sans $ ! they will help me thru the install and use which is supposedly simple, then assuming it all works great they will market it for the Tbird. the unit is not dangerous as far as running lean because it cannot change the fueling to make it leaner, it can only add to make it richer. So at the moment i am hoping to get this unit, do the airbox mods i been wanting to do, and seeing how that helps the high RPMs. If it gets me where i want to be i will then consider just a regular 12k service w/o adding cams. i don't want a huge power boost, just want that range to be equally as good as the lower range.
 
This is actually a very cool unit and you sure are lucky getting them to make it for you like this. Really looking forward to your review on this. tell them we will punt it here if they give us one as a free give away as well :y114: We need more TB members :y18:
 
Wouldn't do ya much good with carbs. :D But to anyone with a EFI speedy/america or bonnie i think you could get a free one too sonce those bikes also aren't supported by them. You can try by calling them and asking if they will do the same thing....have you take pics of the parts they need to see and ask if so will they send u a free one. Anyone with any bike thats not supported i believe could get this deal because it gives them another model they can sell for. I imagine if it's a bike with tiny production numbers they may pass but otherwise it's a good bet i think. they go for around $250 if you pay for it. Still a great deal compared to PC and TB.
 

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