Epoxy?

[Anonymous]

I have read the stuff about velocity tuning at http://mototuneusa.com/thanx.htm and plan to do this to my head. However I do not think the epoxy he recommends is available in the UK. Has anyone in the UK done this? If so what did you use?

[lhanscom]

Wow, how does one survive without JB Weld?

[mike J]

The really good cylinder head epoxy is made by a company called Kop- Coat (spelling?) It the best available but not cheap. Call Reher-Morrison they carry it, just dig deep in your billfold. Mike J

[duaneage]

In his slideshow on porting he states that a smooth port in a engine behaves like a car windshield, I.E. water droplets walk up glass at 60 mph because of a boundry layer. He also claims smooth ports cause fuel condensation.

Cylinder heads are a lot hotter than windshields in the rain, and gasoline vaporizes pretty fast inside intake ports. I don't subscribe to his theories on port finishes, especially on high rpm engines. but what do I know, I am just another shadetree mechanic. :roll:

[mike J]

I don't buy what this Mototune guy is trying to sell. He claims that when the mfg's come out with a new bike they make the ports too large on purpose so next year's bike can be made smaller so that it will have more power than the previous year. BS, I have talked to a very sucessfull drag racer and looked inside a cylinder head that won a NHRA drag race. None of what this Mototune guy says was in this head I looked at. If you are trying to make max power you will pull out all the stops and there was no epoxy in the floor of these ports, they were ground out bigger!!! This guy's spill, IMO, is to get as many people to sign up so that he can get $$$ from the many advertisers on his site. What he claims on his site will make a head show more flow on a flow bench but there's more to it than just flow numbers. My two cents, Mike J

[pano]

Here is another site bike racing site that mentions the epoxy porting. Scroll down about 8 pics. Bikershaun, if you use the epoxy run a before and after dyno test and keep us posted.

http://www.bertaut.com/gsengine.html

[duaneage]

Having actually ported heads on V-8's I can say for sure that you don't win races grinding out the floor of ports. Definately don't make them smaller. THe engine must draw through the intake, unless there is a blower on the other end you will not get a faster flow, just less flow. This mod he touts will only help the low end and that is not what small motorcycle engines are designed for. The camshafts would have to be completely redesigned around this effort and for what purpose? More torque at 2500 rpm?

Anti-reversion steps are far more effective than JB-Weld. Swirl matters most, valves with swirl heads boost charge density up to 20%. I don't think this guy knows the first thing about volumetric efficiency or breathing, certainly not more than the smart folks that wring 120Hp out of a 1 liter engine that weighs only 250 lbs or so. Flow testing the head is the only real way to test what you have done.

I hope no GSers do this to a classic head, that JB-Weld can be a mother to remove if it doesn't let go on it's own and go for ride in the engine

[duaneage]

Here is another site bike racing site that mentions the epoxy porting. Scroll down about 8 pics. Bikershaun, if you use the epoxy run a before and after dyno test and keep us posted.

http://www.bertaut.com/gsengine.html

Note that on this site he raised the port and made it D shaped and modified the camshaft accordingly. He also did not reduce the port size nearly as much as the other site suggests, not to mention he clearly tested his results scientifically by flowing the head. With a four valve head the dual intakes give excellent swirl and ample valve area, the wider lobe centers allow more time for the cylinders to fill without unnecessary overlap. I suspect that the streetability of this engine suffers somewhat and tuning it would require some skill.

[Nerobro]

He is right. HUGE ports work great through narrow rpm bands. So long as you don't break mach with the port, Smaller ports, and therefore higher port velocitys are better. Manufacturers are learning this. Remember how 600's used to be seriously anemic at low rpms... theyare now picking up midrange horsepower. They are going to smaller ports ;-)

Snag a copy of engine analyzer and try and get over 100% volumetric efficancy. You can get some really nifty numbers by going with huge ports. But by going to tighter ports you can get upwards of 115% percent. And over a much wider rpm range.

It took automobile manufacturers into the thirtys to learn that bigger valves aren't always better. And there are a lot of F1 engines that failed on the same therory!

Waht this guy says seems odd.... But the physics and dyno results back it up.

Higher port velocitys are a GOOD thing. (short of generating shockwaves)

Oh yeah, I am fairly sure the GS's don't have oversized ports. So you wouldn't gain any benifits from this treatment.

[lhanscom]

while shrinking the port size on our GS's isn't a good thing, because they aren't that big to begin with, I think enlarging the ports, but making it have a D shape would have the best gains. At least in theory.

[rosco15]

I have a friend of mine that runs a pro-stock bike. He's been in the 7.20's with it. It has major head work that we wont get into here, but it's safe to say it has epoxy. The raised floor gives you more intake velocity. For proof take a look at one of the new heads on some of those 600 bikes out there. Tiny ports with raised floors. They make over 100Hp. I got a chance to look at one when the local bike shop had the head off. Here is another bike builder talking about the same thing http://www.cycledoctor.com/JohnsonArticles/JET.html
The big problem with epoxy is that it will come out. GUARANTEED. I watched it come out of my friends prostock bike. He was down for quite a while getting the head fixed.
Here read this from ReherMorrison. He doesn't come out and give his secrets away, but....

http://rehermorrison.com/techTalk/16.htm

[crayonjota]

I have meddled with porting and polishing on a number of heads with mixed results. All I can add is bigger is better until it is too big! As to using epoxy? I have always relied on welding new alloy into the head to be the only option, even if it is a SOB to grind it back again.

My money on a GS would be to keep it simple, triple cut the valves, get a wilder cam set and wiseco pistons and rings and a hone on the bores, perhaps skimming the head a little to really add detonation to the equasion. Race fuel @ $6.50 a gallon anyone???

Polishing sure looks nice, but I dont know if the gains are worth the effort, ever, even in a two stroke..

CJ

[BadBillyB]

Intake port 101.........The short side radius and the long side radius should be as close to the same length as possible. The sooner you can "turn" the gases before they reach the back of the valve the better. If the epoxy is placed in the right place it will begin turning the gases earlier and also lengthen the short side radius. I have a shafty or big port head in my dragbike and I used an amount that is about the equivalent of the volume of a marble on the port floor.....It's not actually epoxy but a product that is made by "Manley" ....It's called A&B Compound....It sets up in a matter of minutes where epoxy and JB weld would require baby sitting for at least an hour, it runs........Has been in my intake ports for many years.....My port roofs are cut all the way up into the bucket cavity. As soon as I saw a pin hole show through I knew I had reached the max....I then made some custom aluminum spring bases that were JB welded in to the head to seal the leak......Roof is now raised to the max and the floor is raised also to keep the port to size and to gently turn the gases around the short side.......BadBillyB

[Anonymous]

Oh yeah, I am fairly sure the GS's don't have oversized ports. So you wouldn't gain any benifits from this treatment.

Are you sure? Ryan (Rosco15, www.rccracing.com) posted some dyno charts for his drag bike that showed:

stock displacement - 1073cc, 113hp & 75ft*lb torque.

1166 kit, 128hp & 81.7ft*lb torque

If you do the math to check specific output (divide output by displacement), you will see:

1073cc - Specific HP = 113/1073 = 0.1053 HP/cc
Specific Torque = 75/1073 = 0.0699 ft*lb/cc

1166cc - Specific HP = 128/1166 = 0.1098 HP/cc
Specific Torque = 81.7/1166 = 0.0703 ft*lb/cc

The big bore motor makes 4% more HP (0.1098/0.1053) and 0.5% more torque (0.0703/0.0699) than the displacement increase will explain. If you subscribe to the theory that the ports were correctly sized in the first place, then the big bore motor would make LESS specific power because the ports would be too small for it. Given that the specific power went up, this would inidcate that the ports were too big for the stock displacement. Hmmm...

To those who think the stock ports CAN'T be too big, look at Motoman's flowbench testing. If you can add a bunch of material to the port and not lose any flow, than that port was too big. As he notes, the valve and seat are almost always the choke point for flow. Having a port that will flow more than the valve and seat will is a waste and lowers your intake velocities, which hurts charge mixing and combustion chamber turbulence.

John Britten developed the ports on his motor by mounting a valve and seat on his flowbench, then using modelling clay to build the port back to the intake flange location. Every time he lost flow, he would rework the port to get back to the valve flow number. I bet his ports were pretty small when he was done, and he had the fastest 4 stroke race bike in the world at one point.

For the people that think because you must enlarge a small block Chev port to make power that this applies to bikes as well, consider what you are comparing. The V-8 has a horribly convoluted intake path with a truly ugly intake plenum mounted on top. The bike (almost any bike) has individual throttle bodies or carbs for each cylinder, 4 valves per cylinder and a short, straight shot from the airbox to the combustion chamber. They are completely different creatures and what is applicable to one will not necessarily be to the other.

There, now I feel better.

Mark

[Nerobro]

Keep in mind, even with crappy american heads, and two valves per cylinder.. Pro stock cars bet 120%+ chamber filling :-)