Epoxy?

[Anonymous]

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

True enough, but those heads don't resemble much that comes stock on any car out there. It was the OEM stuff I speak of. Some of the aftermarket stuff is pretty good, considering what they have to work with.

Mark

[duaneage]

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

If all he did to that bike was increase the displacment, I would agree with you. I doubt that was his only modification. Jetting, cam timing, exhaust, etc all play a part. It is the sum of the parts that makes the difference, what works for one does not always work for others. Air temperature differences can mean 10 % variations in HP

Singleplane four barrel intake manifolds on V-8s are anything but convoluted. Straight shot from carb plenum to intake valve. Dual quads are even better.

[rosco15]

No, it was just pistons and I had to go up on the main jet. I think it was from a 125 main to a 130 main.
More disturbing is when I later ported the head and put in 1mm oversized valves. I would have thought a huge gain in power. Take a look.

http://rccracing.com/personalpage/gs1100.htm

I'm putting an 1150 head on this winter. Should have a new dyno sheet in the spring. I'm very interested to see what happens.

[Anonymous]

I have a really good Bellucci stock spigot 1150 head on my 1428. It has a considerable amount of epoxy on the floor of the intake port. It made over 210 at the rear wheel N/A... motor was a previous prostar shootout record holder and #1 plate winner on Godzuki.

Any real serious suzuki 4 valve head will have epoxy. dont do it to a real street motor though.

That NHRA pro stocker most likely had an aftermarket 2 valve vortex head, thats what all the competitive suzukis now run. The ports are designed for that kind of motor.

Anthony

[duaneage]

No, it was just pistons and I had to go up on the main jet. I think it was from a 125 main to a 130 main.
More disturbing is when I later ported the head and put in 1mm oversized valves. I would have thought a huge gain in power. Take a look.

http://rccracing.com/personalpage/gs1100.htm

I'm putting an 1150 head on this winter. Should have a new dyno sheet in the spring. I'm very interested to see what happens.

Your page suggested it was lean. Was that before you bumped the jet? I think that different cams with higher opening rates would work wonders with the ported head, but then we get into the realm of experience versus theory and that is what makes serious engine builders rich and secretive. Try and get a Nascar engine builder to give up his secrets and you'll find everything from tweaking push rod length to bore finish is top secret.

Years ago a friend of mine decided to swap heads on his 400 chevy. We tore it down and were about to install the heads when we found a cracked seat. Not wanting to miss the racing that weekend we reassembled it with the old heads. Ran the 1/4 mile .4 secs faster. Probably had a leaking gasket between two cylinders and never knew it because of the cam. Just goes to show that many variables affect how things run.

[rosco15]

That run was before I upped the main jet. You can see on the graph it goes lean around 7700. If you ignore the lean part and continue the graph up from 7700 it should have hit around 132. So that was my guess. I'd already made a couple passes and the bike was hot and others wanted on the dyno. So I took it home and changed the jet there. I will say this the bike revved faster and would 60' better with the ported head and bigger valves. Stock head and cams in the heat and sucky air I was running in the 10.30-10.40. With the ported head and megacycle cams I was running in the 10.20's. Stock head and pistons would run 10.60's in the heat.

I like those teeny tiny cams set around 110 110. I'm in mortal fear of blowing up. I used to have a high compression 1260 KZ1000. When I built it and did compression checks it pegged my gauge. It had 420 lift cams and I would use a car starter to fire it up. I promptly blew it up and ended up selling the bike as parts. I decided with this bike to go low compression, small cams, and spend my time racing and not working on it.

[Anonymous]

Whats interesting to me is that my fluid mechanics professor was talking about this topic last year. For whatever reason he was down at Indy and talked to a mechanic after looking that the intake. He noticed that they were not polished at all infact were rough and he asked about it. The mechanic told him that a polished intake was the last thing you wanted.

Also we did a lab on flowing a head and during our discussion he talked about whether or not bigger ports were better for intakes.

After looking over mototune, I was pretty impressed with what he was saying. Most people who get porting done also put in piston kits, I would like to see a few other people try something like this to put the theory to the test.He has put a few dyno charts on the website for a R6. How about others who have put larger ports on their bikes?

[Nerobro]

Somethign to keep in mind. Turbulant air flows across rough surfaces better than smooth. Intakes are full of turbulant air.

[Anonymous]

Porting (unless you're racing)

Unless increasing displacement, I recommend blend the heads - that's all. Take out the casting marks where they are abrupt. Don't remove any excessive material.

Then - glass bead the intake tracts. Hazy finish - gas tends to evaporate off of this surface well

Polish the EXHAUST tracts. Here it is OK because the gas has already been burned. I thought Neobros comment on rough surfaces may still apply here but I believe a smooth exhaust track is good. Question: does flow tend to get more or less laminer as flow speed goes up for a given volume and tract irregularity?

Different cam settings affect the turbulence and intake and "blowdown" velocities as well as the sizes of the intake tracts up to the valves. These affect "mach" speeds. Most critical cam is the intake cam and intake design since normal aspiration is only 14.7 lbs / in sq. and exhaust pressures are much higher.

Going up in piston diameter is the same as reducing the intake runner diameters - I would imagine. If your intake diameters are oversize, then of course putting in larger pistons will offset this. Increasing stroke also will increase intake charge speed.

Matching the upper and lower wall lengths in any radius makes much sense and prevents drag and "tumbling". This may be the biggest point for the epoxy method - that of the improved laminar flow...which is in effect enlarging the intake diameters BUT retaining the SPEED of the mixture. His main advantage is laminar in nature without trading off mach speed.

Speaking of laminar flow, anyone remember the Vance & Hines systems that had a baffle at the 4 into 1 collector. The premise of this baffle was to help the flow stay laminar as the "4" ran into the "1". Not sure if they worked, however the principle is recognized and respected.

And the sum of the cams, head design and displacement must come together to assure a high enough "mach" speed is attained to assure good mixing of fuel and air. It is about that mach speed. Speed too low - poor charging and mixing, too high - probably indicates a restrictive tract.

What I found with "Engine Analyzer" is that I couldn't have it all, midrange and peak HP and had to compromise.

I don't know if stock is too large or not to begin with. Anyone know how to measure mach speed on a complete engine? Good posts by all. - Dieter

[Nerobro]

the mach number has to be calculated. I am actually in the process of trying to build my engine in EA. :-) And then we/i can use ea to tell me what is actually going on in the engine.

Anyoen who doubts EA.... My buddy builds his engines in EA first, and in the end comes out with an engine within two or three horsepower of the prediction. And this is on 450hp engines.

[Anonymous]

Unless increasing displacement, I recommend blend the heads - that's all. Take out the casting marks where they are abrupt. Don't remove any excessive material.

Decent advice. Usually the factory had an idea of what it wanted and cleaning up the casting flaws just achieves the ideal of their design.

Then - glass bead the intake tracts. Hazy finish - gas tends to evaporate off of this surface well

I have thought that this would be the optimal surface finish, but never seen anyone try it or heard of a tuner advocating it. It just seems perfect - rough enough to let any fuel droplets wet out the surface and go away and keep the boundary layer tripped, but smooth enough to not cause large amounts of turbulence that will cause the effective area to go down. Anybody ever tried this, or heard of tests done on this surface finish?

Polish the EXHAUST tracts. Here it is OK because the gas has already been burned. I thought Neobros comment on rough surfaces may still apply here but I believe a smooth exhaust track is good.

Shiny exhast ports are OK, because the flow is dry at this point. The surface roughness needed in the intakes is to prevent fuel droplets forming on the intake port walls and to promote good charge mixture. That is not needed here.

Question: does flow tend to get more or less laminer as flow speed goes up for a given volume and tract irregularity?

It gets less laminar. Port velocities are high enough that the flow will be fully turbulent, with very little laminar flow anywhere.

Matching the upper and lower wall lengths in any radius makes much sense and prevents drag and "tumbling". This may be the biggest point for the epoxy method - that of the improved laminar flow...which is in effect enlarging the intake diameters BUT retaining the SPEED of the mixture. His main advantage is laminar in nature without trading off mach speed.

The big hint of what he is achieving is that he flowbench tested the CBR600F2 head and kept filling in the port with clay until he started losing flow. Until the flow started to drop off, all he was doing was improving the flow characteristics in the port by optimizing the shape of the port. This is a great improvement, because it costs no flow, but is increasing the velocity. This improves charge mixing, turbulence in the combustion chamber and gives more resistance to detonation and faster charge burning. All good things that make more power everywhere.

Speaking of laminar flow, anyone remember the Vance & Hines systems that had a baffle at the 4 into 1 collector.

My ZX-9 OEM header has a vertical splitter that runs from the collector to the end of the header, where the tail pipe attaches. It separates the flow from side to side all the way out of the header. Is this similar to what you are describing?

I don't know if stock is too large or not to begin with.

Judging from Rosco15's results and things seen from other tuners, it would seem to be. The only way to know for sure would be to flowbench a head and do the clay test like Motoman did. If you can add a bunch of clay and keep flow the same, the port is too big. Now whether your valves are the right size is another story completely...

Mark

[Anonymous]

Mark M:

I did the glass bead and blending on a GS750 TSCC engine. I didn't do any epoxying.

I used an intake cam off a 1982 for 3 GS1100. So I got a little more lift and duration. Duration was about 232 if I recall..so not a really wild cam.

I piped and rejetted - Kerker header with highly modified FZR600 canister. Worked better than the megaphone - fatter power band and better peak.

Cams set at 107 108 or something..or do I have the numbers reversed for intake and exhaust. Intake opened at about 14 degrees BTDC and exhaust closed at about 46 degrees ABDC...do these numbers sound correct? Duration again was about 232 degrees on the intake cam. Exhaust cam was stock...AND IS THE SAME as the E-cam on the GS1100. So which cam is more important?

Got 60 HP (GS750EZ) at rear wheel at 5500 rpm. 77 RWHP peak at 8500 rpm with stock gearing and wheels. Redline was 9500....so I didn't set the bike up for max HP. Still had 69 RWHP at 11,200 - FYI. Would spin to 11,200 before valve float because I shimmed the valve springs 0.020". Stock springs on GS's are generally set too soft. Look for "cupping" or rounded valve seats when looking in radial direction ---> ( across the valve seat face....this means valves are bouncing which causes cupping. I actually had LESS valve and cam wear when I shimmed the springs.

I thought given the mods, I had much more HP than stock...and the intakes were glass beaded. To date I have not gotten a clear spec on what stock power curve was on the GS750EZ. Anyone know?

Blow a hair dryer across a matt surface finish and a glossy one. Surface tension will cause water to stick and glide across the glossy surface. The matt finish...less surface tension and water evaporates more readily. Didn't do a scientific analysis...but followed sound principles only.

The V & H exhaust had a baffle that was a cross + design and the four "quadrants" tapered to a point downstream. Each quadrant collected the individual pipe and helped straighten and transition the flow before coming together. Wasn't sure if the baffles had a little twist to cause the gas to swirl.

Shoot for maximum intake box and exhaust canister volume. It quiets the backpressure pulses created from the transition at the openings to "atmosphere" at either end. For example, when I put a larger canister volume on the exhaust end than the original megaphone, both midrange and peak jetting leaned out.....2 jet sizes. (Main jets affect needle mixture too). I got a jump of 7 HP peak with this mod. (and both the megaphone and FZR600 modified canister were set up for flow. Kerker HEADER is EXCELLENT though. Large 4 into 1 collector pipe and header pipe lengths are set very well. When I tried a tapered collector pipe reduced to 2 1/2 from 3 " original diameter, bike ran much worse and richer....so large collector pipe diameter and volume are very helpful. AND it's always how it all works together.

Very good post - you confirm my thoughts. - Dieter

[Jethro]

Woha, all this gearhead, greasemonkey, racer tech talk is making my head spin.

[Anonymous]

Got 60 HP (GS750EZ) at rear wheel at 5500 rpm. 77 RWHP peak at 8500 rpm with stock gearing and wheels. Redline was 9500....so I didn't set the bike up for max HP. Still had 69 RWHP at 11,200 - FYI

77rwhp @ 8500 rpm equates to a BMEP (Brake Mean Effective Pressure, a measure of efficiency) of 160psi. That is certainly respectable for an 80's air-cooled bike at the HP peak. 60rwhp @ 5500rpm equates to a BMEP of 192psi. This is a VERY good number for your engine at its torque peak. You must have done a good job with your tuning.

Kerker HEADER is EXCELLENT though. Large 4 into 1 collector pipe and header pipe lengths are set very well.

Good to hear you like the Kerker header. I currently have a Kerker canister system on my 1100. It is obnoxiously loud and I am in the process of fabricating a new megaphone tail pipe for it. I hope to fill in a hole in the torque curve between 3500-4500rpm with the meg and make it a bit quieter at the same time. The existing canister is also very small (3.5"OD x 12" long) and the core pipe is only 1"ID. My new muffler section will be 4"OD with a 2.5" core and should flow much better. We'll see...

Mark

[duaneage]

Tony brought up a great point in that the pulses from the intake tract are a problem to be dealt with. The stock airbox is set back and the carb boots are really velocity stacks that isolate the carbs from each other so that pulses from one carb do not affect another. Somthing to think about if using pods, the lack of a velocity stack can cause problems.

A larger airbox ahead of the carbs offers more compliance and dampening of intake pulses. It is also important to straighten the air flow ahead of the stacks as much as possible to fill them completely and a airbox helps.

I like to think that those contorted shaped boxes and filters may have a purpose, those engineers designed them that way for a reason.