#60498 - 09/14/10 07:54 PM
Re: GM 4 cylinders 151 153 181
[Re: Beater of the Pack]
|
will6er
Active BB Member
Registered: 03/05/05
Posts: 88
Loc: Lakewood, CO
|
I second Jalopy's recommendation of http://quad4rods.com/. They have some neat stuff and John Ehrlich is a great guy.
will6er
_________________________
President: Inliners International
|
|
Top
|
|
|
|
#60759 - 09/28/10 07:24 PM
Re: GM 4 cylinders 151 153 181
[Re: Beater of the Pack]
|
Nexxussian
Active BB Member
   
Registered: 06/12/07
Posts: 1337
Loc: Anchorage
|
|
|
Top
|
|
|
|
#60856 - 10/04/10 08:13 PM
Re: GM 4 cylinders 151 153 181
[Re: panic]
|
Bob s Performance
Active BB Member
Registered: 05/03/00
Posts: 8
Loc: Moca,Puerto Rico
|
The mains are the same,only the rods are 2.00" on the 153 and 2.100 on the 181 crank.
|
|
Top
|
|
|
|
#60925 - 10/07/10 08:32 PM
Re: GM 4 cylinders 151 153 181
[Re: jalopy45 #4899]
|
panic
Active BB Member

Registered: 01/11/05
Posts: 1341
Loc: Hempstead, Long Island, NY
|
The highest piston speed is never at mid-stroke, it's where the rod beam is at 90° to the crankpin, at roughly 70-80° B/ATDC depending on the rod ratio (unless the ratio is infinite). The exact point is easy to calculate using sine of rod thrust angle = .5 ÷ R/S ratio (1.8, etc.) 1 Double-click your “Calculator” icon to open it 2 Click “View”, then “Scientific” 3 Input the result from the formula above 4 In the left margin of Calculator, look for the check-box that says “Inv” - check it 5 Make sure the box marked “Degrees” (not Radians) is checked 6 Click on “sin” 7 The rod thrust angle in degrees will show in the window 8 subtract 90 (you'll get a negative number, ignore it) 9 The result is the crank position for maximum piston speed Example: 1.8:1 rod ratio .5 ÷ 1.8 = .27778 arcsin .27778 = 16.13° 90 - 16.13 = 73.87° ATDC
Piston speeds around TDC and BDC are always different, except for exactly TDC & BDC, when they're stopped (assuming centered piston pin, and nothing else odd). 90° crank rotation has already done more than 50% of the stroke in all engines (57% in a 1.8:1 rod motor), so the motion around TDC is faster.
|
|
Top
|
|
|
|
Moderator: Webmaster
|
1 registered
(Shore)
and 53 anonymous users online.
|
|
|