Engine and Transmission Tech

tips, technology, tools and techniques related to vehicle driveline components

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mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 16, 2017 06:32PM

Rob, Here are examples for the cams I mentioned above. The HO cam with 1.7 rockers only makes sense if you already had that cam. The E303 beats it in lower RPM TQ and is about a tie at upper RPM. EDIT: 272 TQ on HO cam.
HO 1.7 rockers 001.jpg
E303 001.jpg



Edited 1 time(s). Last edit at 11/17/2017 06:30PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 16, 2017 06:54PM

B303(your cam) Advanced 4 degrees moves TQ curve from 5000 RPM to 4500 RPM. Surprisingly the mildest HO cam still is at 5000 RPM when 4 degrees advanced.
B303 001.jpg



Edited 1 time(s). Last edit at 11/17/2017 11:20AM by mgb260.


IaTR6
Dennis Costello
Central Iowa
(116 posts)

Registered:
12/29/2007 02:53PM

Main British Car:
'73 TR 6

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: IaTR6
Date: November 16, 2017 07:47PM

Jim, I am curious, since Larry Shimp changed from the B cam to Comp's XE264HR. If I recall correctly,
it has 212/218 duration @ .050 and would have .512 lift with 1.6 rockers. Would you plug that in to see?
(truth in advertising, or whatever-it's what I have)
Thanks,
Dennis


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 16, 2017 08:02PM

Dennis, Here you go! This is fun but rather addictive! It looks very similar to the "B" cam advanced 4 degrees. The same cam Kelly has. I don't know why the bottom of the chart is cut off but, max TQ is at 4500 RPM, HP is at 6500 RPM.
Compcams XE 264 HR-14 001.jpg



Edited 1 time(s). Last edit at 11/16/2017 08:09PM by mgb260.


MGBV8
Carl Floyd
Kingsport, TN
(3235 posts)

Registered:
10/23/2007 11:32PM

Main British Car:
79 MGB, Buick 215

authors avatar
Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: MGBV8
Date: November 16, 2017 09:58PM

Kelly's cam is ideal for fast street. I have never had so much fun passing cars in places mere mortals wouldn't even consider! :-0


ex-tyke
Graham Creswick
Chatham, Ontario, Canada
(974 posts)

Registered:
10/25/2007 11:17AM

Main British Car:
1976 MGB Ford 302

authors avatar
Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: ex-tyke
Date: November 17, 2017 08:43AM

All hail the mighty 'B' cam!


kstevusa
kelly stevenson
Southern Middle Tennessee
(818 posts)

Registered:
10/25/2007 09:37AM

Main British Car:
2003 Jaguar XK8 Coupe 4.2L DOHC/ VVT / 6sp. AT

authors avatar
Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: kstevusa
Date: November 17, 2017 09:47AM

Here's copy from earlier pages of this forum. These pulls were for different timing settings. the most advanced was the great fuel mileage. the other pull was for max power. These points were determined over time from different dyno sessions. The A9L (std Trans.) (A3M ?? A/T) ECM was near top of chart for OBD1 technology. Time dims my memory, but was into Ford Tech at that time. Total package for my car, weight 2440# wet, no driver,T5Z (Ford racing), 3.55 Ford 8.8 Trac Loc,Ford Focus wheels w/205-50R16 tires 24.1" Dia, Similar engine configured to Factory Crate with Hyperutetic pistons, X-303 heads, XE-264-HR Cam, Roller Rockers 1.6 ratio, 65 mm T/B, Pro-M MAF on GT40 Tubular Intake ported Lower by T. Moss, March serpentine pulley system,& Explorer T/C & Crank Damper. Donor car odometer read 118K miles when I got the package to begin my conversion. Carl did initial run at Townsend 2006 after the Terre Haute unveiling in 2005. Usually returned 27-28 MPG at interstate speed with adequate performance. ;-)
Tx 2012 Dyno results.jpg



mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 10:36AM

Kelly's pic is not showing. Here is the thread.

[forum.britishv8.org]

Good HP at the wheels and max TQ 700 RPM lower than the simulation. I used Rob's engine specs's for the cam comparisons. I picked the Performance Trends program because it doesn't show inflated numbers like some. Those simulations would be at the flywheel with open headers, electric water pump and no accessories. Typically chassis dyno's show peak HP and TQ 500 RPM's lower than engine dyno's. Deduct 20% from the engine simulations above to get approximate @ the wheels.



Edited 3 time(s). Last edit at 11/17/2017 11:40AM by mgb260.


rficalora
Rob Ficalora
Cypress, TX
(2389 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: rficalora
Date: November 17, 2017 11:36AM

Here's the chart for Kelley's car...
Tx 2012 Dyno results.jpg


rficalora
Rob Ficalora
Cypress, TX
(2389 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: rficalora
Date: November 17, 2017 11:42AM

Jim - do the simulations change if you assume my motor but with the Edelbrock Pro-Flo EFI system? It has a different intake & of course throttle body vs. carb.


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 11:50AM

Rob, It may, but generally equal carb or fuel injection show very little difference. What you will notice is better throttle response, easier cold starting with no warm up and better mileage. I would need the specs for injectors and cfm of throttle body, TBI or port injection and I'll run it to see.


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 12:05PM

Rob, My program had the Edelbrock Pro-Flow system in its library. Max TQ is 500 RPM's lower and HP 1000 RPM lower than with carb. This is with your cam advanced 4 degrees.
Edelbrock Pro-Flo Injection 001.jpg



Edited 2 time(s). Last edit at 11/17/2017 12:28PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 12:44PM

Fuel injection is very tuneable. I think if you change timing and A/F mixture you would increase HP and lower TQ a bit. I'm going to show that last chart again in a different scale and by itself so it is not cut off.


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 12:48PM

Pic:


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 12:49PM

Here Goes!
Edelbrock Pro-Flo 3 001.jpg



Edited 2 time(s). Last edit at 11/17/2017 12:53PM by mgb260.



rficalora
Rob Ficalora
Cypress, TX
(2389 posts)

Registered:
10/24/2007 02:46PM

Main British Car:
'76 MGB w/CB front, Sebring rear, early metal dash Ford 302

authors avatar
Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: rficalora
Date: November 17, 2017 04:44PM

Great info Jim!

I just talked to Comp Cams & they recommended their XE266HR -- pretty close to what Kelley had. Thoughts on 266 vs 264? Looks like I'm down to one of those or the E303 (which is about $100 cheaper).


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 05:21PM

Rob, Or advance your cam 4 degrees for free. I can run the XE266HR to see I there is any difference. I can do back to back carb and Edelbrock Pro-Flow fuel injected.


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 05:40PM

Rob, Here you go!
XE266HR FI 001.jpg
XE266HR Carb 001.jpg


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 05:51PM

The fuel injection moves the power curve down for more TQ and less HP vs carb for more HP less TQ. I think A/F and ignition tuning will fix the HP to TQ ratio. The XE266HR doesn't seem much different to the XE264HR or the B303. It's higher lift probably isn't utilized by your heads and it would be a good idea to check piston to valve clearance. Most street engines don't need more than .500 lift. It has .544 IN and .555 EX lift. XE264HR has .512 @ both. B303 has .480 @ both and E303 has .498 @ both.



Edited 2 time(s). Last edit at 11/17/2017 06:01PM by mgb260.


mgb260
Jim Nichols
Sequim,WA
(1811 posts)

Registered:
02/29/2008 08:29PM

Main British Car:
1973 MGB roadster 260 Ford V8

Re: Gear ratio calculator, rear gears, and transmission ratios
Posted by: mgb260
Date: November 17, 2017 06:10PM

If you wonder why I advance these cams 4 degrees it is not only to move the TQ curve down but also to get the Dynamic compression around 7. Straight up is only around 6.5.
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