mpg Research

Hey guys. My first project in fuel economy is gong to be with my 2003 Harley Sportster. It already gets 3.5l/100km, but I have the Edelbrock 1200cc conversion kit. So I'll be increasing the displacement from 883cc to 1200cc and also increasing compression from 9:1 to 10.5:1. Now this kit as delivered is pretty detonation resistant... For a Harley anyway. . I already have the pistons coated with a thermal barrier and I will be doing the same to combustion chamber, valve faces and exhaust runner/port. Soon I will be ripping the cylinders off to be rebored for the new pistons, so the heads have to be ready to go. Basically what I need to know is what the optimal quench is for the singh grooves. By removing the base gasket I'm told I should come into a squish band somewhere in between 0.030" and 0.040", which comes out to about 11.2:1 compression ratio. Will the be too small of a gap for them to work? I really don't want to shave down my new heads to increase compression. Any ideas or suggestions would be greatly appreciated.

0.030" - 0.040" is a bit thin for the Groove to work properly. It would help if you could post pics of your pistons and combustion chamber. The Somender Grooves are just a tool. They accomplish something. What they accomplish is determined by how you use them. Let's see what you're working with.

Mike

Here is a pic of the chamber. I should have zoomed out a bit more. If it's not enough, let me know and I'll take another one.
The pistons in this kit are specially made by JE for Edelbrock. The dome (10cc after radius & polish) is designed to fit the head pocket. These are already done with thermal barrier coating, so I won't be touching them again.

I would "edge" that chamber in addition to adding Singh Grooves. There's a lot of improvement to be had. I'll wait for Mike to suggest groove position of the groove(s), though, as he has MUCH more experience.

Oy yes. The chamber needs to have the edges radiused for sure. I have a dremel I was going to use for it, but instead I am going to use an air diegrinder with a rolox pad. That will make a much nicer/smoother job.

I would add 2 grooves per cylinder; one behind the spark plug, aimed at the spark plug, and one opposite the plug, aimed just toward the exhaust side of the spark plug. +1 on the radiusing.

Mike

Thanks for the advice. The more I think about it, the more I am contimplating shaving the head down a bit. Every 0.010" milled off will bring roughly 1.1cc out of the chamber. Basically with the radiusing and the singh grooves, I could shave off 3cc or so and still come out with a touch more compression.

So how did this run after all?

I'm curious as well. And always enjoy looking at combustion chamber porn.

Me too, as I have an 03 sportster in the barn available to me for cheap.....

Combustion chamber porn... LOL. I like engine porn.... I don't just have a chamber fetish....