Wildcardracing

Have a stock crank that I just trued/welded w/new outer bearings. Trued to .0005" $150 plus the ride. Let me know if you're interested. -Brandon

I can get you the Koyo or HIC center bearings.

Much will depend on what exactly has been done to your cylinders. IMO if you have the PC's you won't appreciate the Toomey's, you'll see very little if any top end gain and will suffer a loss on bottom. The CPI's will offer a slightly higher reving power delivery that will also come on a bit later (with the right porting). The Shearers are going to have a better fit/finish than the CPI's, but they will come on a bit later and will rev quite a bit further (again with the right porting). -Brandon

The 4mil servals are a great pump gas engine. So far in my testing I haven't seen much if any gain from higher compression and timing on them. Typical 2 strokes don't see a peak power gain from increased compression. They see a gain in the frontside curve and can acctually suffer a loss of rpm and peak power potential from too much compression.

Damn Wangers have Hotrods in short supply most everywhere. Pretty sure I could turn it around in less than a month though -B

I wouldn't recommend running it. Heat discoloration on a rod points to extreme heat from friction. That bearing and/or rod will fail, most likely sooner than later. -Brandon

Guess you found the limit lol. I have seen a couple of engines do this as well. It's not good to see piston numbers stamped into the squish band. Wider squish bands (within useable limits) usually improve burn efficiency at lower rpms, divergency angle and combustion chamber shape also play a part here. Too tight of squish clearance can lead to piston-head contact and/or detonation. Squish band width and clearance are directly related to MSV. Ideal MSV numbers are dictated by several factors and influenced by several parameters. Loosened squish clearance can shift the heat range in the pipe/s making them act longer at some rpm's, effectively smoothing the curve on some engines. There are many factors at work here, very briefly touched on. -Brandon

I come up with 6.785cc dome on a 65.5 piston. One thing not taken into account in your calculation is alloy. That Wiseco is not pure aluminum, it is a high silica alloy and will have a slightly different weight per volume. Interesting how you figured that, and gave you much closer figures. Would become quite expensive to cut a piston everytime you built a motor just to establish dome volume.

So my question is: what values are you guys shooting for in compression and squish velocity? Are you setting a standard at static? Do you do a comparison to what you think is happening at different RPM ranges? Seems to me there would be drastic changes in both compression and squish velocity as the rod/crank/piston stretch at different RPMs. The pistons just start to leave marks on the combustion chamber on my RD400 at 10,000 RPM with squish at .02. This by chance Mark? Tried calling you the other day. As for your question, there are some things I won't share. However I establish sqiush velocities based on fuel and application then use a standard rpm to calculate them even if the engine may not achieve that rpm. This give's me a constant to work with. In my opinion, if you're getting piston to head contact within your motors operating range your squish clearance is too tight. You can achieve the same MSV numbers by changing the band design and loosening the squish clearance some. -Brandon

I have found that software, while it may get you close is limited to the experience and theories of the software designer. There is no replacement for trial and error R&D. Area, volume and MSV calculators are the only software I use. I come up with my dome designs and port layouts based on real world trial and error. Just as the theories discussed in Jennings and Bells books are a good starting point, but not going give you the "beat all/end all" build if strictly adhered to. As for piston dome volume, I haven't found an efficient method of cc'ing one without using a dome volume calculator. I use a berret to cc head domes and cylinders though. But, as mentioned the results are only good if done with precision and repeatability. -Brandon

Measure from the crank center axis to the rod pin center should come up with 29mm or 1.142" if it is a +4mm crank

No idle air jets in them. They are a fixed circuit

I can do it longhand just like you, just add the crevis volume to your chamber or dome volume. But, there are some handy calculators that can do it for you. Most are engineered towards 4 strokes, just substitute the intake closing abdc for exhaust closing abdc and it will work great for a 2 stroke. Here is a link to one I like: My link

I come up with 6.68cc dome volume for that piston. Also don't forget to calculate deck height, piston clearance and top ring height into your figures as these will change your ratio's quite a bit. As for your question on max UCCR to run on pump fuel (or any given fuel for that matter): There are too many variables to say "this maximum value will work", this is why recommendations are usually on the conservative side. UCCR, CCR (trapped ratio), MSV, elevation, and port/pipe efficiency are just some of the factors that will dictate what octane of fuel your engine will require. But, as a direct answer to your question: With properly designed domes I have run UCCR approaching 15:1 on pump fuel at our elevation of 5,000" -Brandon

Yes they are the same size Bowl.

Too much compression will limit the engines peak RPM's

I prefer the cobalt tool steel bits for aluminum work vs carbide, you can achieve a much better finish. I use them all the time for my lathe and mill. The two you posted pictures of are tool stock that has been ground by the user. Not sure what the value would be unless I could see all of what you have, trying to sell them? -Brandon

19cc domes are sold Tusk brake blockoff sold Rest is still available!

I'm not going to give numbers or angles, but I'll throw in some advice. 1) Focus on velocity not volume 2) The smooth micropolished finish isn't going to yeild the best possible results 3) Lower blowdown periods will yeild stronger fronstide curves 4) DON'T flatten your transfer roofs 5) Staggered transfer arrangements will work well (develope a good loop charge) 6) Study your dome design, this can make or break a good port layout -Brandon

I seriously doubt you will find an other head to fit better. I suspect you've either got a bent stud or the tollerances on your cub block have the bolt spread slightly off. I've seen this with CP cylinders. Don't take me wrong, they are by far the best aftermarket topend IMO but fitment can be rough with some of them -Brandon

Which way did you install the inner race? The shoulder should be against the web so the bearing can slide off the crank.

I agree with radar. Your UCCR is off the charts lol. You should be looking at domes in the 26-28cc range for that motor on alcohol. I can figure it up for you if you want to contact me, and get you set up with a set of domes that will work. -Brandon

I'm surprised this is still here! this motor should run very well and has all of the "cheetah" bugs worked out of it. -B

Last day to cash in!

TTT