shift points for stock cam???

Foxfan88

My Grandpa has great wood.

Sep 13, 2004

2,487

4

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Miami, Ok

Jan 4, 2006

#1

• Jan 4, 2006

• #1

whats the best rpm to shift on the stock cam???
do i shift at this same rpm in every gear or do i shift at other points in other gears??

 

TomCat

New Member

Apr 19, 2005

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Utah

Jan 4, 2006

#2

• Jan 4, 2006

• #2

5200 is what I've heard on the stock setup... I try to shift a little higher because of my cam.

 

TrunkFunk

Banned

Dec 28, 2005

83

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0

A1A - Beach Front Avenue ...

Jan 4, 2006

#3

• Jan 4, 2006

• #3

A lot of it is feeling derived from just driving the car. If you are numb to the world around you it may be a bit more involved. Knowing the mannerisms of your car is more helpful than internet racers throwing figures out.

If you want a figure, how about 5200-5500 depending on which gear. The drop between each gear is not the same either.
Get to know your car.

Where were you shifting when you beat that Cobra?

 

onefstsnake

New Member

Nov 25, 2005

792

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Northern VA

Jan 4, 2006

#4

• Jan 4, 2006

• #4

Well if you can find a stock 5.0 Dyno sheet then shift when the power drops off.

The shop I take my car to says that a stock 5.0's power drops off before 5K.

I usually shift at 4800. After 5K the valves start to float...

 

I

IntenseBlue

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Jul 10, 2005

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Jan 4, 2006

#5

• Jan 4, 2006

• #5

How do you know the valves float?

 

timewarped1972

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Jun 17, 2004

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mesa, az

Jan 4, 2006

#6

• Jan 4, 2006

• #6

the power falls totally flat when they start to float........and the rpms decrease somewhat...

 

Michael Yount

Mustang Master

Apr 10, 2002

9,039

6

79

Charlotte, NC

Jan 4, 2006

#7

• Jan 4, 2006

• #7

Try these as a starting point -- let your et's guide your adjustments.

1-2 shift - 5000 rpm
2-3 shift - 4800 rpm
3-4 shift - 4600 rpm

Those should let the car drop back to right around the torque peak with each successive shift. Your quickest acceleration times should come if you can keep the car in the meat of the torque/HP curves.

 

onefstsnake

New Member

Nov 25, 2005

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Northern VA

Jan 4, 2006

#8

• Jan 4, 2006

• #8

IntenseBlue said:

How do you know the valves float?

Click to expand...

It happens alot on older engines. The springs are old and cant close the valves quick enough at higher RPM.

 

Foxfan88

My Grandpa has great wood.

Sep 13, 2004

2,487

4

0

Miami, Ok

Jan 5, 2006

#9

• Jan 5, 2006

• #9

so after each shift i want the rpms to land right around 3k? (torque peak)
and when i raced the cobra, i just shifted around 5k each time, only got to 3rd gear though....

 

25thmustang

Mustang Master

Sep 5, 2003

2,021

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99

Montgomery, NY

Jan 5, 2006

#10

• Jan 5, 2006

• #10

My stock motor I would shift at 5200 on an aftermarket tach (stock tachs are usually off some) and it got me decent times...

But like stated before, you have to know your car and where it likes to be shifted! Some cars its higher some lower (also with all the tachs being off different amounts, who knows where your actually pulling the gear)!

 

Michael Yount

Mustang Master

Apr 10, 2002

9,039

6

79

Charlotte, NC

Jan 5, 2006

#11

• Jan 5, 2006

• #11

Foxfan - a set of dyno curves are really helpful -- you'll clearly see at what rpm the torque/HP to the wheels peak at. Armed with that, and your tranny gear ratios you can calculate what rpm you'll fall back to with each shift. You don't want to hold to far PAST the power peak in a gear, and you don't want to fall to far below the torque peak with each upshift. I suspect your torque peak occurs a bit higher than 3000. However, if it does actually occur at 3000, then your power peak is probably in the low 4000 range somewhere, and shifting even lower than I suggested may result in quicker times.

The old C4 Corvettes (mid 80's LT1) were shifted around 4400 rpm to achieve quickest lap times in road racing. Other than making noise, there was simply no reason to rev them any higher even though you could spin them up past 5000 in the lower gears -- it just resulted in going slower because you were well past the engine's power peak.

If you're serious about optimizing shift points, spend $50-70 for a dyno day and see what your actual torque/power peaks occur at rpm-wise. As mentioned above, a tach that matches up with the dyno tach helps too....

 

Michael Yount

Mustang Master

Apr 10, 2002

9,039

6

79

Charlotte, NC

Jan 5, 2006

#12

• Jan 5, 2006

• #12

Keep in mind too the shape of the curves has an impact on all this. If the curves are real 'peaky' then shifting too high or too low has a bigger impact on acceleration rate compared to what happens with relatively flat curves.

 

25thmustang

Mustang Master

Sep 5, 2003

2,021

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99

Montgomery, NY

Jan 5, 2006

#13

• Jan 5, 2006

• #13

Your best bet. Go to the track with a notebook...

Change only the shift RPM, and see what was affected (where in the pass did it improve or was it hurt). This is the only real way to see what your car likes.

 

ninety1gt

New Member

Aug 27, 2005

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san antonio

Jan 5, 2006

#14

• Jan 5, 2006

• #14

onefstsnake said:

It happens alot on older engines. The springs are old and cant close the valves quick enough at higher RPM.

Click to expand...

ur 1.7 rr's have alot to do with it, should have, gotten new springs

 

onefstsnake

New Member

Nov 25, 2005

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Northern VA

Jan 5, 2006

#15

• Jan 5, 2006

• #15

ninety1gt said:

ur 1.7 rr's have alot to do with it, should have, gotten new springs

Click to expand...

Yeah springs are pretty cheap.

Although the keepers are a PITA...

 

Bad92GT

The 5 Minute Plan Man

Jun 10, 2004

492

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SC

Jan 5, 2006

#16

• Jan 5, 2006

• #16

4500.. thats as high as i run it.. ive run it to 5500 and it made no difference in ET's except for .1 of a difference

 

25thmustang

Mustang Master

Sep 5, 2003

2,021

85

99

Montgomery, NY

Jan 5, 2006

#17

• Jan 5, 2006

• #17

TheChevyEater said:

4500.. thats as high as i run it.. ive run it to 5500 and it made no difference in ET's except for .1 of a difference

Click to expand...

Care to share the ETs you speak of???

My dads car with a stock cam (4 degrees retarded) went from 12.4s to 12.1s merely by going from 5500 shift points, to 6000 RPM! Granted his isnt like the cars mentioned here, but the right shift point for a car can be a huge improvement!