Fabrizi 50mm Squish

[DirtyE]

Im getting about .9mm. The sheet of paper with specs suggests .6-.7mm. The kit only comes with 1 .45mm base gasket.
What squish clearance are you other fabrizi owners getting?

Thanks

[Wheelman-111]

Greetings:

See Flash 7; mine came out at 0.7 if memory serves. I kept the little segment of solder. It's framed.

[DirtyE]

Huh, I know they updated some things on the kit.... piston, maybe other things. My solder didnt go quite all the way to the edge of the piston, but it was pretty darn close.

[DirtyE]

Ok, so after mounting my cylinder and checking where the piston is at BDC, I've decided that milling the top of the deck is the proper way for me to lower my squish. With about .5-.6mm of base gasket the crown of my piston is at the bottom of the transfer ports. That leaves me with about 1mm squish when fabrizi recommends .6-.7mm.

I'd like to understand more about mean squish velocity

[Wheelman-111]

Greetings:

You did torque everything down to spec, right? Otherwise, aside from some gasket thickness change, it's hard to account for the discrepancy. Maybe Graphie or Eft can inquire of Signori Fabrizi what's a-uppa?

[1man8scoots]

My fabrizi is .6 factory seals and deck height. But I have the 2 ring. Is yours a protruding style head or flush style?

[DirtyE]

O-ring head. It was torqued. Not sure what you mean about the head style, but there is a pic on here comparing it to a mhr head.....somewhere

[bakaracer]

Keep in mind that the recommendation from fabrizi on squish clearance is for racing purposes and intended to be run with race gas. Not pump gas. Yes tighter squish more power but higher friction which means higher heat which causes detonation quicker with lower octane fuel. KABOOM!

[DirtyE]

I agree baka. This cylinder wasnt designed for racing though. I dont recall off hand the exhaust port timing but I think it was low to mid 180's.
I brought that up to near 190. My intention was 186-187 but a novice porting job went a little higher than I wanted. Trab sees are still at 125. I cannot change my base gasket cause it will change my timing, so I habe to go after the deck.

[bakaracer]

Even though the port timing isn't near 190 doesn't mean it's not for racing. Some companies design their cylinders with lower port timings due to the type of race tracks it's used on. Most of the tracks are kart style tracks so midrange power is what's needed. A 10.5-11.5k peak rpm is good enough.

[DirtyE]

Im going to be using this mostly for "street race" profile. It will by no means be a daily driver. Just a fun toy to take out and spit around town for a bit.

[bakaracer]

I recommend running race gas in it then. With a tighter squish and higher rev rpm, less chance of engine knock and running hot without having to run a rich jetting to keep it cool. The closer you get the jetting to optimum air/fuel ratio on these motors, the more crisp throttle response you will get and it makes more power.

[DirtyE]

Ill probably run 93 pump with a synth oil. Ive had mhr 47,6mm race kits with yasuni c20 and 21 pipes on minarelli a.c. build run pump gas fine. Although, I've seen pistons that look like they were hit with a shotgun slug.

Like any other motor I've built, ill take it easy and listen close while ramping up RPMS.

I like to build these motors, but I hate tuning them. They get to be pretty fussy.

Like I said above though, I'd like to learn more about MSV and calculating corrected compression ratio. Maybe ill cruch those numbers before firing it up and see what i get.

[1man8scoots]

Your port timing is for engine speed and power, like baka said it does not dictate race worthiness. Extremely high rpm port timing use is for drag racing and is not good for track riding. If you like light switch power then 190 is what you go for. But you will have a very narrow power band. Blow down duration can make or break your power not just your ceiling.
All of my built engines run a 75% 93/91 octane 25% 110 octane. My fabrizi is built using aggressive porting not necessarily aggressive port timing. Major difference. It's nice to see different views but it comes down to what you plan on doing with the bike and going for it. Sounds like you're going for drag racing. Mine is built for top speed not drag or circuit track. What do you consider street racing?
When I was asking about the head the good older fabrizi kits utilize a protruding head that sits into the cylinder with an o ring. If I still had my pb up I'd be able to show you pictures but I'm sure someone else has to have them.

[1man8scoots]

For my fabrizi build flotek did 187/128/30. No dyno run yet.