COMET CENTRAL

I don't really have ideas but I am looking for opinions to see if there is a consensus. The questions I have relate to building whatever 6 cylinder I end up with, but I think they are valid for any engine build so I thought here was as good as any to post this.

I am heavily leaning toward building a 250cid 6 right now so those are the numbers I am going to use here and was looking at piston options etc. remember that I don't get a ton of options, so anyway here goes, and I will probably say some ignorant stuff so just correct me and move on

When increasing compression ratio, what does everybody think a good number to shoot for, for a street car running regular pump gas (possibly premium because I can get it ethanol free)?

To increase compression is it better to mill the head or deck the block or use a different piston? In my situation I have a choice of about 3 or 4 different pistons I can use; stock cast with either a 6.5cc or a 13cc dish, a flat top cast piston out of a Ford Tempo, or a Ford 255cid V8 piston with a compression height of 1.585" as opposed to the stock height of 1.50" for the 6 (the stock piston has between .120" and .150" of deck height).

Cam Timing (this is where everything goes fuzzy) the most I know is reading "Ford Falcon 6 Cylinder Performance Handbook" it tells me to use a '69 chain and gear set because Ford kept advancing timing for fuel economy, not sure what I am looking for here so I will include the stock timing on the cam - Duration 256°, Int. Open 10° BTC, Int. Close 66° ABC, Ex. Open 58° BBC, Ex. Close 18° ATC, Overlap 28°, Lift .368. There are several different cam grinds available but not sure what would work best.

Hopefully that is enough to get the discussion started so I can get more confused.

I have a few questions about V8 drivetrain stuff but will post over in that section.

See Ya,
Mike

i dont know much about six cyl engines but the basics should be the same.9-10 to 1 is safe on pump gas, headers, cam,good spark,etc.my dad used to race sixes back in the day on dirt,but i remember them running pretty good.

Mike if I remember correctly it doesn't take much to push the compression raito up on the little sixes. I know some heads have a smaller chamber and after being milled with the stock piston your in the high range. You might want to get the block and head your going to build before you start thinking about what your going to need to build it for the compression your after. I would shoot for 10:1 on pump gas and no higher. Remember the new head gaskets are a little thicker than the stock ones so you will need to add that to the equation.

Matt

Loner wrote:You might want to get the block and head your going to build before you start thinking about what your going to need to build it for the compression your after.

Yes I was just trying to get a few ideas of "Best Practices"

fryedaddy wrote:i dont know much about six cyl engines but the basics should be the same.

Yep an engine is an engine, mostly, what works on and V8, a 6 or a 4 banger is pretty universal I would think, there might be different methods to reach the desired results but compression ratios etc. should hold true no matter what it is.

Thanks for any input.

See Ya,
Mike

my 64 f100 has a 240 with 300 fuel injection heads. A strong motor, dont know anything about it, it came with the truck. It pulls a car on a trailer well.

Compression ratio near 10 to 1 should work good. I'm running pump gas in mt street/strip comet, which is 94 octane. Just over 10 to 1. The timing chain- make sure you index the crank and cam when building the motor. Make sure 0 degrees is top dead on #1. I got burned as a teenager by installing a new gear set on my 69 351W. Timing was way off. lessons never trust a chevy guy behind the parts counter.
Roger