Topic: *Dumbing it down? vote!

[B.O.X.N.I.F.E.]

I'm considering dropping my 550 down to 500 so I don't have to race in the 650 class out at Bonneville.

Are there tables anywhere online that calculate displacement & compression after decking & .25/.5/.75/1mm bores? I've tried a search but haven't found anything straightforward to use.

[cavebear]

Displacement is pi r squared x bore x 4

[B.O.X.N.I.F.E.]

Does that take stroke into account??

This handy calculator: http://www.ajdesigner.com/fl_engine_displacement/engine_displacement.php

gives me 502 with a .25 overbore, the smallest I can readily find pistons in. I guess my question should have been more focused on results of milling the head; can I lose those 2 cc's without raising the compression ratio too high and maintaining piston/valve clearance? Are there formula's for this?

[dave500]

pi r squared x stroke,,then times four,when you rebore oversize your static compression goes up.

[cavebear]

I made a mistake. It is stroke instead of bore

[B.O.X.N.I.F.E.]

Anyone know what the formula is for calculating displaement after decking?

[KJ790]

Anyone know what the formula is for calculating displaement after decking?

The displacement of the engine doesn't change from decking the head. Displacement is strictly a function of stroke and bore. Decking the head will increase your compression ratio by decreasing your combustion chamber volume, but the amount that it decreases depends completely on the shape of your combustion chamber to begin with, so there is no universal formula for that.

[B.O.X.N.I.F.E.]

I didn't realize that.

Well crapo. I can get a set of std. pistons, but what are the chances someone out there is still making std. bore sleeves....

[bwaller]

You're in luck, go to LASLEEVE.com

[B.O.X.N.I.F.E.]

You're in luck, go to LASLEEVE.com

90$ per sleeve... wow

[MCRider]

To expand on what KJ said, displacement is just that. The amount displaced by the stroke of the piston. All else is a constant, and doesn't figure in.

My favorite calculator:
http://www.nightrider.com/biketech/calc_displacement.htm

[B.O.X.N.I.F.E.]

To expand on what KJ said, displacement is just that. The amount displaced by the stroke of the piston. All else is a constant, and doesn't figure in.

My favorite calculator:
http://www.nightrider.com/biketech/calc_displacement.htm

Saving that, thank you!

[B.O.X.N.I.F.E.]

Hmmm... so if I do a .25 over on a 500 block that puts me at 502. That won't cut cheese on the salt in the 500 class.

Would you:

A: Find a low mile 500 block, hone up, run NOS std. 500 pistons

B: Bore up the 550 to 590ish and run with the 650's

?

[heffay]

Just because you're in the 650 class doesn't mean everyone is runnin' 650s.  They're all runnin hopped up 550s like you.

[scottly]

Look for a 500 block and pistons; they don't have to be low mileage, as long as they are within wear limits. (Race motors are built "loose", anyway. )

[B.O.X.N.I.F.E.]

Look for a 500 block and pistons; they don't have to be low mileage, as long as they are within wear limits. (Race motors are built "loose", anyway. )

I gotta say I'm leaning towards the 500. Cost is a contributing factor; maybe $200 all in for the 500. A big 550 after machining would be $500 - 800. Thats money I could put into the head, which is probably where the most bang for my buck is anyways.

[scottly]

Even at 590cc, the 650s have a 60cc (5-6 HP) advantage....

[geminimotors]

If I were in you shoes, I'd run the biggest 500 pistons, cylinders, etc that the class allows and use the 550 bottom end, and work all of the magic I could beg, borrow, or steal on the head, intake, and carbs. It's been said by NHRA B-stock engine builders- "If you aren't winning, you aren't cheating"

[754]

 Get good used 500 bores like Scottly said, get new rings..
 Dont go streamlined there is a guy running 205 +.. Canadian team.

 I would not worry so much about how fast you will go as getting there, and figuring out how the game plays. You can run in RWYB for cheap, and get trhe feel of  the salt.. then you will be hooked !!
 RWYB=run what you brung... are you thinking Speedweek or Bub Bike week?..Bub is earlier this year..

[B.O.X.N.I.F.E.]

Get good used 500 bores like Scottly said, get new rings..
 Dont go streamlined there is a guy running 205 +.. Canadian team.

 I would not worry so much about how fast you will go as getting there, and figuring out how the game plays. You can run in RWYB for cheap, and get trhe feel of  the salt.. then you will be hooked !!
 RWYB=run what you brung... are you thinking Speedweek or Bub Bike week?..Bub is earlier this year..

I doubt I'd go out for Speedweek. BUB is already a week earlier, and Speedweek is earlier than that. I have a little list, and if I stick to it, I should have her put together with about 3 weeks leftover for tuning. We'll see...

It'll be RWYB for me this year. Running official seems like a differect ball game. And if it were Speedweek I doubt I'd ever pass SCTA tech anyways.

[754]

 Good choice, Speedweek is very busy.. and Bub is very bike friendly.. no matter how fast you go you will have fun there.. hope I make it to BUB this year..