Pulley Help/Advise needed!

[SVT_S5]

Hey!

03 Cobra with 2.8 KB Mammoth (Liquid Cooled), looking for more boost and thought I ask here first since I’m completely new to the whole Terminator scene.

Car has:

LTH
Fore fuel system
60lb injectors
Bassani X and Catback
4.75 MMR stroker kit
3.5” Pulley making 16 PSI

Car made 643whp with a bit of tire spin on dyno. Tuner says there’s more gains with a smaller pulley.

I’m targeting +700whp - Should I go with a 2.5” pulley? What issues do I expect to face when upping the boost that much? It’s not my DD.

Thank you all..

 

[CobraBob]

Moe, if your fuel system will support a jump from 643whp to 700whp I don't see any reason not to. Are you using a tuner local to you? If so, just work with them and you should be fine.

 

[SVT_S5]

Moe, if your fuel system will support a jump from 643whp to 700whp I don't see any reason not to. Are you using a tuner local to you? If so, just work with them and you should be fine.

Bob,

I think it would. Yeah, tuner is local and he did advise me on the smaller pulley.

Problem is I couldn’t find a pulley, YET! lol

In your opinion, how many PSI I’m getting from 3.5” to 2.5”?!

 

[01yellercobra]

For Whipple .1" change in pulley size equals about 1psi. Though I went from a 3.5" to 3.25" and went from 18psi to 21psi. Granted I swapped to a new belt and it was cold the other morning.

What fuel are you running?

 

[DSG2003Mach1]

id look into that combo and make sure belt slip isnt a problem with that small of a blower pulley vs going to a bigger crank pulley (would need a bigger alternator pulley though).

 

[SVT_S5]

For Whipple .1" change in pulley size equals about 1psi. Though I went from a 3.5" to 3.25" and went from 18psi to 21psi. Granted I swapped to a new belt and it was cold the other morning.

What fuel are you running?

Running 98 Ron, think it’s 94 for the US?

I just need to get more 80-100whp, so I randomly thought the smallest pulley would be more than enough, I may be wrong though.

 

[SVT_S5]

id look into that combo and make sure belt slip isnt a problem with that small of a blower pulley vs going to a bigger crank pulley (would need a bigger alternator pulley though).

Yeah read about that. I prefer the smaller upper pulley.

 

[robvas]

Which crank pulley do you have?

MAMMOTH™ Manifold and larger 2.8 decrease hood clearance limiting boost to minimum 18.5 psi (max for street) with the stock 7.5” crank pulley and 3-1/2” supercharger pulley. Note: Use optional 6.55” crank pulley x 3-1/2” supercharger pulley for 15 psi (see Tech & Tuning Tips ‘03 Cobra MAMMOTH™ Kit). Some cars get by with a 3-3/4”x7.5” (17 psi).

 

[SVT_S5]

Which crank pulley do you have?

MAMMOTH™ Manifold and larger 2.8 decrease hood clearance limiting boost to minimum 18.5 psi (max for street) with the stock 7.5” crank pulley and 3-1/2” supercharger pulley. Note: Use optional 6.55” crank pulley x 3-1/2” supercharger pulley for 15 psi (see Tech & Tuning Tips ‘03 Cobra MAMMOTH™ Kit). Some cars get by with a 3-3/4”x7.5” (17 psi).

3-1/2” upper - stock lower, boosting @16 with LTs.

 

[jwcobra03]

You really need to look into a lower pulley. Once you go smaller than a 3.0 upper, belt slip will become an issue.

 

[SVT_S5]

You really need to look into a lower pulley. Once you go smaller than a 3.0 upper, belt slip will become an issue.

Noted, thank you.

Is it a hard task to change the lower pulley?

 

[MG0h3]

Noted, thank you.

Is it a hard task to change the lower pulley?

Oops! We ran into some problems.

newyorkmustangs.com

Instructions for you. I suspect that a 3.0 upper would give you 4-5 psi.

2.5 upper seems like a little much .


Sent from my iPhone using the svtperformance.com mobile app

 

[jwcobra03]

Correct on the KB, when you step down a 1/4" you generally pick up 2lbs of boost. Example 3.5 to a 3.25 will net a 2lb increase. If you go from the 3.5 to a 3" upper will be 4lbs, you'll have substantial gains in hp/tq. Not sure your octane will support it without an octane booster or lower timing. That will defeat your purpose of the added boost.

 

[c6zhombre]

What’s the compression on the motor?

Personally, I’d play it safe on 94 pump gas, it’s not likes it E85 or c16. Sure, you can make it dyno more with additional boost and timing….but it will generate more heat and the tune (if proper) will pull several degrees timing right back out when the IAT2 heats up out in the wild.

 

[03' White Snake]

If you are not on E85, then I would not go over 18 psi, 20 max.

Like stated, each 1/4” is 2 psi.

I run a 3” and 2lb lower pulley for 26 psi on my 2.8h. 3.5” with 2lb lower pulley for 22 psi. All on E85.

 

[SVT_S5]

Yup, tuner confirmed all the above. 19-20 psi max on pump gas.


Sent from my iPhone using Tapatalk

 

[Quick Strike]

Cobra 2003 Up BIG BORE 3.2L, 2.8L, 2.6L & 2.4L, 2.2L Pulley / Boost / Ratio / HP Guide & 1/4 Mile | Kenne Bell

Cobra 2003-Up BIG BORE 3.2L, 2.8L, 2.6L & 2.4L, 2.2L Pulley / Boost / Ratio / HP Guide & 1/4 Mile These are "real" dyno tests performed with calibrated sensors. A Ford NGS Scanner al

kennebell.net

 

[SVT_S5]

Cobra 2003 Up BIG BORE 3.2L, 2.8L, 2.6L & 2.4L, 2.2L Pulley / Boost / Ratio / HP Guide & 1/4 Mile | Kenne Bell

Cobra 2003-Up BIG BORE 3.2L, 2.8L, 2.6L & 2.4L, 2.2L Pulley / Boost / Ratio / HP Guide & 1/4 Mile These are "real" dyno tests performed with calibrated sensors. A Ford NGS Scanner al

kennebell.net

Thanks! Lots of useful info.


Sent from my iPhone using Tapatalk

 

[SVT_S5]

I’m trying to figure out which Billetflow pulley would work with my 2.8 KB (Again to confirm, it’s LC) - But I can’t get past the hub type/size.

I don’t have a caliber, does anyone with a 2.8 knows the size? I looked through Billetflow’s document and it says 0.500/0.665 for the 2.8.

Just want to double check things before placing an order!

Sent from my iPhone using Tapatalk