how to increase compression of Zenoah 26cc

Lohring,
I do not want this to turn into a war of words and I have respect for all that have posted. I just could not agree more with the last part of Scott's statement. I understand what you are saying perfectly and I don't want this topic to turn into something that it is not, but why would someone want to buy a billet engine that in your words tend to be more fussy and often aren't running at their peak, especially when the performance difference is only really noticeable in SAW boats when 99.9% of the country heat races and small driving and setup errors add up to more difference..
I thought this was a very informative discussion about Zenoahs and hope that it stays that way. I do not believe that anyone mentioned Quickdraw, only billet engines. Do you not have anything to add about angled exhaust ports or flat top pistons in this discussion about Zenoah engines that will help with this discussion?? I have seen you mention on more then one occasion that there is no record with a Zenoah over a 100mph and I will agree, but it is quite common knowledge that a Zenoah powered boat has officially been 102.7mph and broke the sponsons so it could not make a return trip. So even if someone does set the record over 100mph with a Zenoah most people will still remember who did it first. Just for the record the first gasoline engine to do it was a Zenoah.

This is the main reason I stay out of most of these discussions even though most of the time I have quite a bit to say on most of the engine subjects. There is much too much speculation without proof or testing to back up theories and it always turns into a pissing match instead of a good discussion that could possibly teach us all something.

No one has got a Zenoah powered record of over 100 mph yet.

That may be true, but while Carlo may build a mighty fine engine, the only Zenoah boat to go 100 MPH is Jeff Michaud's Insane, but that was only one way. He has yet to back it up with a pass going the other way.

Let's keep this post about what it's supposed to be...not a pissing match!

FTR: That Insane boat WAS in fact powered by a CC Racing Engines motor when it set the record!!!

Question for Carlo of CC racing ....

I understand what your saying about Flat Top pistons further reducing compression and the reason behind your feelings.

But WHAT do you mean or refer too when speaking Sharp Angled Exhaust Ports ???

I know this is off topic, but I should explain some things.

I have owned Quickdraws (26 and 35cc), an M&D cast cylinder engine, and lots of Zenoahs starting with a Hanson G23 in 1997. The only engine other than Zenoahs that I would recommend to average racers is the M&D cast cylinder engine. I don't have enough racing experience with it yet, but it seems very reliable, and is the second most powerful engine we have tested. It has all the modifications usually done to Zenoah cylinders built in with the addition of an inner wall to the transfers. This gives better flow direction. It has .010 squish but similar head volume to the Zenoah. It could be easily modified for higher port timing, but it would probably become more difficult to run. We have tested several other commercially available 26cc gas engines and none equals the quality, reliability, and power of the Zenoah. We do not have experience with the Sikk (Chung Yang) engines.

I hope that a G1 rigger finally sets an over 100 mph record this year. One time, one way, is not an official record. Jeff Michaud was the first gas boat over 100 mph one way, but Mike Bontoft is the only over 100 mph record holder in the world with gas engines. He holds the GX1 and GX2 records of over 100 mph. His Gas Sport Hydro has gone over 100 mph several times, but bad weather ended running before he got an over 100 record with it. We have a friendly rivalry with Jeff. He has helped us with props for several record attempts. It was a big disappointment that he couldn't quite get two back to back runs over 100. We have always run GX engines so we weren't really competing as equals. We have a friendly bet on who can get the G1 record over 100 mph.

Lohring Miller

I'm not trying to start anything. I was there both days when Jeff made his 100 MPH passes. I wish he could have backed it up. It would have really spoken well for both Carlo and Jeff if he had. Maybe next time.

lohring wrote:

To add to what Scott said, I raise the transfers the same amount I took off the bottom of the cylinder to keep the same intake timing. I still take some off the piston skirt on the intake side, but the amount is reduced by the amount I needed to take off the cylinder base. I raise the exhaust port a lot by sharply angling up the last part going into the cylinder. There are a lot of different philosophies on how high to go and whether the port top should be flat or arched. The metal left at the top of the exhaust limits cylinder life and is influenced by how much you take off the base of the cylinder. That's why you don't want to take much off the cylinder base. The only way to seriously raise a Zenoah's compression is with a removable head button cylinder such as those sold at www.davesmotors.com/goped-geo-sport.htm . That makes the engine a GX engine in NAMBA. It still won't have the power of a Quickdraw.

Lohring Miller

Scott,
To answer your question, I was hoping that Lohring would want to discuss the theories behind some of the things he does to his Zenoah. Lohring said 'I raise the exhaust port a lot by sharply angling up the last part going into the cylinder.'. Instead it has turned into a how good the billet engines are discussion since you said that a fully developed Zenoah will run with it's billet counterparts. At this point and time I could care less as these posts always head in the same direction no matter how hard you try to stay on track. I always like to here different theories from other people and there is always something to be learned, but it is almost impossible to just have a discussion without it getting heated. I learned my lesson quite some time ago to stay out of these discussions and I just keep thinking that the end results will be different, but it always heads in the same direction with testosterone getting the best of everyone. I will go back to being a lurker when it comes to engine posts and let you guys do your thing.

I am also curious about the 'angling the port sharply for the last part going into the cylinder' comment. I can see the ex port timing being raise but the overall size of the port isn't changed. I take it this is to try and keep the port physically as strong as possible, but uncertain of what the overall benefits can truly be???

This is not meant in a bad way at all...just trying to learn more on why you do it this wat...

Carlo, I hope you will continue to participate...I know many including myself really want your input!

Is the reason to raise it at the very end towards the cylinder because theres not much metal to take away to keep the cylinder from cracking?I like working on motors as i cant afford the mod zenoahs right now.I never seen one of your motors apart Carlos but being your posting here would be nice to give us people some real tips that works.I really like Scotts mods did one up like he suggests and runs real well.I did a small flat top on the piston and was thinking on trying a stock piston top to see the differances in performance.Please post some more info!

Carlo,

Gotcha, that ANGLED PORT was a statement pertaining to lohrings engine set up.

** If I may :huh: .... Really don't see a pissing match going on here, only a few trying to actually discuss a VERY interesting subject.
Technical subjects NEED TO BE talked about with some attention to the details of the why and what for :S

So please, lets leave our attitudes at he door and lets ALL try and make the sharing of useful information a pleasant experience that actually explores and resolves these types of subjects.