Topic: Header diameter and 836 bore

[scondon]

  I have two exhaust choices. One is a stock header with an aftermarket exhaust(fairly open) and a X-Pipe 4-2 crossover with no baffles(open). X-Pipe has same diameter head pipes as stock. My question is this...

    Will a 836 engine be "held back" by using a stock diameter 4-1 header? Kerker an Mac headers are both larger in diameter than stock and I have heard a few people say that one would want to use either one in order to let the 836 "breathe" better. I've also heard that the 836 is not that big of a jump and that stock header should work fine. I'm not talking about the exhaust can, just the header portion.

    I'd love to hear any opinions/experience on the subject.

[SohcCBs]

Are you taking about an original header that came with the bike, with original muffler?

I've run both the original header on my '76 836 SS (with billet cam) and "air-box", with an early megaphone from the period.  I pulled it off and put on a mac with their can.  Not a lot difference, but I felt the mac header had a little better tuning.  Enough to notice.  With the cam I've got, I notice unusual bottom end torque, then it gets wild at around 5800 rpms.

I don't know what an X pipe is.

The other thing I really like about the MAC with their short muffler, is that it's fairly subtle, but kind'a grouls at mid throttle, but if you openit up, it howls......get loud, sounds great.

[Sam Green Racing]

Sean/ SohcCBs, Re the X pipe, this idea came up quite a while ago.
The manufacturer was selling them off cheap on Ebay with fantastic performance quotes.
It sounded to good to be true but someone in the know said this was true.
Seems he was a crap business man or something (not sure) but a trip to the dyno would confirm or disprove the Idea.
I'm sure you have been thinking about putting your bike on a dyno for some time now Sean

Sam.

[scondon]

Are you taking about an original header that came with the bike, with original muffler?

   I have the original header(78 750F) but not the original exhaust. The stock header appeals to me because it tucks under the engine and has far more ground clearance at the collecter than either Mac or Kerker. I don't actually have an exhaust for it yet but can have one fabbed or adapt one from aftermarket(Supertrapp?).

   

I don't know what an X pipe is.

   Neither do I but I got one anyway    Four pipes go into the collecter under the engine and two short, open pipes come out, one under each rear peg. "Crazy" Monty Campbell sells them on Ebay and makes all kinds of fantastic claims.

  I've got two different Kerkers and a Mac hanging in the garage(all spigot style) and can use them but would really like to try something that will allow more ground clearance when leaning waaaay over in turns. The X-Pipe is neat 'cause there is no exhaust on the side of the bike. Downside is that it will have to be cut and shortened because the collector is too low to the ground.

Sean/ SohcCBs, Re the X pipe, this idea came up quite a while ago.
The manufacturer was selling them off cheap on Ebay with fantastic performance quotes.
It sounded to good to be true but someone in the know said this was true.
Seems he was a crap business man or something (not sure) but a trip to the dyno would confirm or disprove the Idea.
I'm sure you have been thinking about putting your bike on a dyno for some time now Sean

Sam.

    Dyno is scheduled for a week from next Saturday

        I don't expect much from this one though, Sam, since I am still having trouble getting the "burn" sorted out. The next bike, the one that this exhaust question relates to, should put up some pretty good #'s. I'll post what I get

[Sam Green Racing]

And not before f.....in time
Mikes is going on the end of the month
Ours is going on next year

[scondon]

And not before f.....in time

   Had to wait for the shops to open for business. Two shops, Performance Motorcycle and Godspeed, opened there doors within the past two months. Both have dyno's and good mech's with good rep's

Ours is going on next year

 Next YEAR    What's the f.....in holdup, Sam

[Sam Green Racing]

Engine builder very busy, should be starting it next week.

[scondon]

Engine builder very busy, should be starting it next week.

   Weren't we having this discussion about this time LAST year

[Sam Green Racing]

Tell me about it     it was the delays at the back end of last year that lost us our slot in the guys work load.
Now we are first in the que

How long dose it take to put a motor together 

Sam.

[scondon]

How long dose it take to put a motor together

   In my case, about a year      Costs, ya know    And ALL that frickin' cleaning and paint

[Sam Green Racing]

Yes but if every thing was cleaned/new and you was a pro builder with the money in place to do the job.

Sam.

[Terry in Australia]

Sean, that "X Pipe" is no good and will do terrible damage to your engine. Best you send it to me so I can dispose of it thoughtfully.

[Sam Green Racing]

I was gonna say the same but figured you would want the first refusal at disposing of it 

Sam.

[scondon]

Woohoo! Party over at the "header diameter and 836 bore" thread Hopefully anyone with any input on the Q: won't mind wading through all this chatter

Sean, that "X Pipe" is no good and will do terrible damage to your engine. Best you send it to me so I can dispose of it thoughtfully.

   That was my first thought, but shipping$$ was a real biatch    Speaking of, 30lbs. of vintage metal hit your shores on the 20th. Has it made it to your stoop yet?

 

Yes but if every thing was cleaned/new and you was a pro builder with the money in place to do the job.

Sam.

     I'm hurt Sam   Are you implying I am not a Pro builder      Drop it all off and come back in two weeks( I only work on weekends)

[Sam Green Racing]

So ya reckon 4 days.

Sam.

[scondon]

So ya reckon 4 days.

Sam.

   Yeah, I work slow

[Terry in Australia]

It's gonna take me four days just to clean a space in my garage big enough to build an engine! Hell, I might "get back to nature" and build it in the driveway! 

[Jerry Rxman Griffin aka MuthaF'er]

OK guys, lets get the thought process going. What's the inside diameter of the double walled Honda header vs the "effective" diameter of the Kerker or X pipe assuming we're talking inside single walled? I can measure outside diameter but that don't mean #$%*. Now that we have that out of the way for comparative purposes, might I bring up the issue of larger valves?! It seems that when larger valves are installed, only the intakes are increased. 2 parts to this (I'm assuming). 1 - it needs/wants to suck in more air and fuel for more power but it's stated in various articles that the 28mm exhaust valves are sufficient even with the larger 33.5mm intakes?! Now, if the exhausts are sufficient at 28mm stock then why wouldn't stock ID pipes be sufficient also?!
And 2 - Are we keeping the stock 28mm exhausts mainly due to a potential valve overlap issue?! or is 28mm exhaust valves and stock size headers sufficient even with ported heads and 31mm carbs taking in all that extra air and fuel while keeping the air velocity maxed?! Where's Mike the Head Wizard?

Sean, will you be able to use the dyno (jealously exists here !!) to also tune your carbs, etc? or just to get numbers?

I hope you can have comparative numbers with the X pipes versus others. I've seen the hype and "advertising" on EBay which makes me very skeptical. I hope it works for you.

Jerry
  

[Jerry Rxman Griffin aka MuthaF'er]

It's gonna take me four days just to clean a space in my garage big enough to build an engine! Hell, I might "get back to nature" and build it in the driveway! 

As big as that damn engine is I'd think you'd need a 4 car/8 bike garage!

[scondon]

Thanks, Rxman, for bringing us back on topic     You bring up a very interesting point concerning exhaust valve size and I hope some of the "experts" will have some input on this.

   I am putting my Daily Rider(836, Mrieck head, Megacycle cam) on the dyno with the express purpose of tuning the carbs and getting the ignition dialed in. The #'s aren't as important to me as getting the cylinders to burn well through all throttle positions.

   The X-pipe is what I've been planning on using on my second bike Which I'm currently putting together. I am hoping to use the stock header with a non-stock exhaust for the 600 mile break-in at which point I'd like to install the X-pipe. If I can get in good with the dyno operator I'd like to get readings for stock vs. X-pipe. This will be after Christmas, right Terry?

[Terry in Australia]

Well if you need anywhere to store those dangerous ol' X pipes before you get around to fitting them, send 'em to me mate, ha ha!

Hey who said that OEM header pipes are double walled? My K2 4 into 4's are only single walled, and I've got a crap set of F2 headers that also look like they are only single walled, but I'd be happy to disect them for scientific purposes?

Actually the OEM K0 - K6 4 into 4 pipes flowed pretty well, (not the later K7/K8 pipes, they were #$%*e) and a lot of guys here just pulled the baffles out "back in the day", but due to the fact that the OEM's rusted faster than an English sports car, they were quickly replaced by lightweight 4 into 1's or 4 into 2's. Cheers, Terry.

[nteek754]

Hey guys now Im confused on the X pipe I was bidding on one on  ebay but it  or I didnt meet reserve so it didnt get sold  ( it in this case wasnt going for cheap) my is are they any good   the ad sounded really inpresive has any one used, heard, tuned a bike to one. oh by tge way Im running an 836 with KERKER and just the  cone piece in the megaphone and  PLENTY of flow she breathes real good scratching my head in Maine  seven fifty four ever

[MRieck]

OK guys, lets get the thought process going. What's the inside diameter of the double walled Honda header vs the "effective" diameter of the Kerker or X pipe assuming we're talking inside single walled? I can measure outside diameter but that don't mean #$%*. Now that we have that out of the way for comparative purposes, might I bring up the issue of larger valves?! It seems that when larger valves are installed, only the intakes are increased. 2 parts to this (I'm assuming). 1 - it needs/wants to suck in more air and fuel for more power but it's stated in various articles that the 28mm exhaust valves are sufficient even with the larger 33.5mm intakes?! Now, if the exhausts are sufficient at 28mm stock then why wouldn't stock ID pipes be sufficient also?!
And 2 - Are we keeping the stock 28mm exhausts mainly due to a potential valve overlap issue?! or is 28mm exhaust valves and stock size headers sufficient even with ported heads and 31mm carbs taking in all that extra air and fuel while keeping the air velocity maxed?! Where's Mike the Head Wizard?

Sean, will you be able to use the dyno (jealously exists here !!) to also tune your carbs, etc? or just to get numbers?

I hope you can have comparative numbers with the X pipes versus others. I've seen the hype and "advertising" on EBay which makes me very skeptical. I hope it works for you.

Jerry
  

You could fit a 29mm exhaust valve on the stock early seat but you'd probably be down to .030 or .040 valve to valve clearance with a 33.5 or 34mm valve especially with a healthy cam and late exhaust lobe center. You can sink the valves for more clearance but that isn't the best idea either. If you were using Ti valves you could probably get away with .020 valve to valve but at that point you've built a rather "delicate" engine. The 28.5 exhaust valve works OK (unless you use tons of nitrous)....the most important thing is to bore the throat to 90% of the valve diameter. The same with the intake. This really improves flow even with a stock valve. I don't care how much air or how close you are to .5 Mach...it's still got to go through the seat and past the valve. People will say 87% is as far as you should go but I disagree. As for a pipe, tapered pipes basically work better than straight tube designs unless you run a big engine and or use a lot of nitrous. At that point you need real large primary tubes. I remember Vance and Hines ran an X pipe real early in their Pro Stock career.

[scondon]

As for a pipe, tapered pipes basically work better than straight tube designs unless you run a big engine and or use a lot of nitrous. At that point you need real large primary tubes. I remember Vance and Hines ran an X pipe real early in their Pro Stock career.

    Thanks for jumpin' in,Mike. I'm not familiar with the term "tapered pipe". Does this refer to the header? And would a stock header fall into this category? Thanks

[scondon]

Hey guys now Im confused on the X pipe I was bidding on one on ebay but it or I didnt meet reserve so it didnt get sold ( it in this case wasnt going for cheap) my is are they any good the ad sounded really inpresive has any one used, heard, tuned a bike to one. oh by tge way Im running an 836 with KERKER and just the cone piece in the megaphone and PLENTY of flow she breathes real good scratching my head in Maine seven fifty four ever

  Yeah, the X-pipe reserve used to be $250, then $275. By the time I bought one it had hit $300(early last year). Who knows what it's at now. It is not a "bolt on" system since it comes in pieces and once it's mounted you have to weld the collector to the pipes or run a screw through 1&4 into the collector. Mine hangs too  low in the rear and will have to be modified.

  I run a Kerker on my 836 Daily rider. Med. competition baffle, plenty of flow and I like it very much. The X-pipe is more of a curiosity to me so I'd like to try it out on this next bike. I'll be sure to post results when they happen, but that will be some months away.