Anyone want to guess? (sorry, it's a long one)

[89 Cobra LX]

I posted about this a few months back, but here's a refresher. Earlier in the year I purchased a long-block from Excessive Motorsport. It's an Explorer block with GT-40p heads with a stage 2 port and a TFS stage 1 cam. This motor was advertised to make over 325HP with an aftermarket intake.

I added a set of 1.6 roller rockers, 24lb injectors and Cobra intake with 65mm throttle-body thinking I would make an honest 325 HP. Something didn't feel right about the motor after it was all installed, I didn't feel the upper-RPM pull I was expecting. So I went to the dyno for some testing and tuning. After making the appropriate adjustments for parasitic loss, I made 260 peak HP at 4500 RPMs. This was very disturbing, especially the RPM that I made peak power.

So I called Brett at Excessive Motorsport and he questioned everything that I could have done to the combination and insisted the parts they sent were fine. To make a long story short, they didn't replace the valve springs when assembling the motor. They threw in a high-performance cam and didn't bother to match the springs to it. I spoke with Trick Flow and they recommended springs with 120-125lbs pressure. The stock Explorer springs are coming in at about 90 lbs pressure. I ended up ordering a set of spring from Central Coast Mustang (they work with the GT-40p heads so I felt comfortable dealing with them) and made an appointment with HPMotorsport to get them installed.

Well today's the big day. HPMotorsport is installing the springs and I have a dyno appointment for later in the week. I thought it might be fun to have some fellow members guess at how much HP I will gain from swapping the springs. I'm hoping to gain power all the way across the band, but at least above 4500 RPMs. Peak power should be in the neighborhood of 5400 RPMs. I'll post a reply with the results after they are available.

FYI - I will be sending Excessive Motorsport some before and after dyno numbers and a bill for the labor associated with the spring installation. I'm sure those a$$holes won't reimburse me. I can't help but wonder how many people out there have purchased this motor from them. They have all been ripped-off.

In closing, Excessive Motorsport sucks and I will never deal with them again. I recommend the same for others.



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Eric - 89 Mustang LX coupe
302 - Cobra Intake - GT40p heads - TFS stage 1 cam - FRPP 1.6 roller rockers - Naturally Aspirated
3:73 gears - KYB shocks and struts - Eibach springs - HPM Mega-bite Jr lower control arms - HPM upper control arms