Webco Head Question

[MWL]

I plan to use this Webco head on my Super Rat project. The picture shows the Webco head and an Ace head for comparison. I do not have a Super Rat head to compare. I'm assuming the Webco head was designed for a Super Rat based on the reduced volume in the combustion chamber but I really don't know. I decided to get a Super rat piston but I'm not to a point where I can check compression to be sure. Does anybody know if this head is for a Super Rat or an Ace 100?
thanks
Mike

[taber hodaka]

I am going to say Ace 90 racing , Ace 100 racing or super rat. ----------Clarence

[hodakamax]

I posted this question a while back under "Day One Project. I have the same Webco head (no extra plug boss) I would like to use on a 93 cylinder. There was a dome change in there at some point. Which piston do I need?

Max

OK, I just found the answer under FAQ on the SH site. 92s are higher dome than 93s. The Webco head was made for high dome 90 and 92 pistons which means that compression will be lower on a 93 piston. It looks like I need the high dome piston for the Webco head.

[Zyx]

It looks like I need the high dome piston for the Webco head.

Not necessarily. Assuming, as I do, that neither of the piston choices will cause a contact issue, the question becomes how much compression will each of the piston choices generate with the Webco head. Broad assumptions would suggest that if the combustion chamber volume is greater due to the Webco head having a greater volume, compression will be lower. However, running compression is not the same as measured by kicking over the machine. Compression at high rpm is frequently higher than you think. The super rat piston is made to run faster than the multi ring piston from the Ace series. So slightly lower static compression might actually be a good thing.

I would start with the super rat piston, and if I liked the way it runs, I would stay with it.

[MWL]

I cc'd the heads and this is what I found. Ace head is 13.5 cc and the webco head is 11.8 cc. I took these values and plugged them in to a two stroke compression ratio program. Results are in "trapped compression". Ace head is 5.22 and webco head is 5.83. While I have no idea how accurate this is, I think this is good for comparison. My initial impression by appearance was that the webco head would produce much higher compression but I don't think that's the case. Unfortunately I don't have a super rat head to compare. I guess I will be trading in my super rat piston for an Ace piston.

[hodakahunter]

Just following up to see where this ended up. Did the Ace piston work out?

[Joe Ormonde]

Here is the whole problem with the High Dome Verses Low Dome Piston: In a 2 Stroke Engine, Compression starts building when the TOP Ring on the Piston seals off the exhaust port. Because the Super Rat Ring is at the very top, it starts building cylinder pressure sooner than the Model 92 Piston does. Why? The top Ring on the Model 92 Piston is located 3 Millimeters lower on the piston than on the Model 93 Piston. The Dome on the 92 Piston is around 1.5mm Higher than the Model 93 Piston but that`s in a arch. In a 4 Stroke Engine, cylinder pressure starts building when the Intake Valve is fully closed so Ring location is not critical. Dome and chamber volume is.The Super Rat Piston and Factory Head has in my case out performed any other combination of pistons and heads that I could ever come up with. Webco heads look trick but they made my Rat run Hotter and SLOWER. Hodaka Factory parts for the Super Rat are Superior to anything made by Webco or Wiseco in my opinion. BUT that`s MINE ! No matter what I have tried since I bought my Super Rat off of the Showroom Floor at Rural Cycle in Norco, CA, I keep going back to the Factory parts. Hodaka hit that combination spot on PERFECT! Any one that wants to come on by my place and test your Webco head on my Super Rat will find out how it performs compared to the Factory Head. You will probably sell that Webco Head on EBAY once you do! Joe Ormonde.

[thrownchain]

Webco head would make a pretty cool paper weight......

[Joe Ormonde]

Pretty and Powerful are 2 different things! I`m not putting down Webco parts. I`m only pointing out that Hodaka parts are better. Joe.

[Joe Ormonde]

One more thing: before you start sticking Needles into your Voodoo Doll that you just named Joe because of my Webco Head comments,I`m ONLY referring to the Model 93 Super Rat head. Webco made some Ultra Trick parts. Just look at Hodakamax and his project! Ultra Trick!!! Joe.

[Al Harpster]

I found Joe's description of the rat ring location vs the standard Ace two ring location very interesting.

I'd never thought of that, and all the things I've been able to find about the Dykes ring never mentioned it

Great input Joe. I certainly never woulda thought of it.

I appreciate the perspective you've provided. Gives a guy something to think about.

[[email protected]]

I am looking for a WEBCO Hi Compression Head, Compression Release, cable, and lever for my Model 92, Ace 100.
In Years gone by, I had one on my Hodaka and LOVED it!

Rick in Grants, NM