[Redrocksdrew]

Hello all,

I have a supercharged 408 that is currently tuned with a Moates Quarterhorse chip, MSD ignition. I have switched out the coil, msd box, msd chip, cap, rotor, distributor and replaced fuel system with 8an lines and Aeromotive A-1000 pump and it still will not rev past 5800. Car makes 670 hp at 5800' in altitude, tuner says there is more power still leftn in it if we can get it to rev to 6800. Checked all the plugs for correct gap and checked all plug wires. My tuner says it is not the tune. Any suggestions would be greatly appreciated.

 

[indy2000]

what is happening at that rpm?

is it misfiring, the tach jumping?

 

[stangjumper]

What are the plugs gapped at?

 

[Jubi351]

I would try putting a stock distributor in it first.

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[408wf1]

your coil is good but the box is not you need a msd 7 box you are having spark blowout with that box

 

[Redrocksdrew]

The tach is jumping like it's hitting the rev limiter

 

[Redrocksdrew]

I replaced the MSD distributor with a stock one, same issue still happens

 

[Redrocksdrew]

Is that a digital box the 7? What else to I have to change if I put in a digital box? thank you

 

[indy2000]

I replaced the MSD distributor with a stock one, same issue still happens

good 'ol part swapping.....

maybe diagnose the issue?

 

[indy2000]

your coil is good but the box is not you need a msd 7 box you are having spark blowout with that box

spark blow out, results in the tach jumping?

 

[Ilusivefox]

your coil is good but the box is not you need a msd 7 box you are having spark blowout with that box

Set up only has 5 lbs of boost and no way is the spark blowing out with only 5 lbs. Honestly the car is a Streetcar practically daily driven with a trick flow R intake and 90 mm throttle body power falls off at 5,500. No need to rev past 5800 rpm. Also making peak torque by 4700 rpm. I already suggested a big stuff get rid of the stock computer. The 5800 RPM that we can't get rid of is a godsend a good thing. Leave it alone and go drive it like you stole it

 

[indy2000]

are you personally helping with this setup, or the same poster?

 

[Patrick Olsen]

your coil is good but the box is not you need a msd 7 box you are having spark blowout with that box

spark blow out, results in the tach jumping?

No. Why would it?

 

[Ilusivefox]

I'm the engine builder and current head mechanic of the car. Been working on it for 5-6 years. Got rid of all the gremlins except the 5800 rpm rev limit and like I said in other post this set up doesn't need anymore rpm than 5800. Other than that the car runs perfect and makes incredible power and torque way before 5800 rpm on 91 octane tune. The tuner thought if it might rev to 6800 it would make more power but that was 2 years ago engine wasn't even broken in then.

 

[Decipha]

if your making 670rwhp at 5800 rpm with only 5 lbs of boost thats naturally aspirated 524rwhp on engine.

In order to get that kind of power it would take serious head work and a serious cam. It should make another 100rwhp with another 1,000 rpm. Thats ALOT to give up.

If its not in the tune and youve upgraded the ignition the only thing it can be is mechanical. I would bet your running in to valve float with how large of a valve and thr amount of spring pressure it would take to make that kind of power.

 

[Mark O'Neal]

Valve springs? Valve float?

 

[Mark O'Neal]

And you can do 700 fwhp on a a set of out of the box AFR-225....or several other heads.

 

[rob]

I'm the engine builder and current head mechanic of the car. Been working on it for 5-6 years. Got rid of all the gremlins except the 5800 rpm rev limit and like I said in other post this set up doesn't need anymore rpm than 5800. Other than that the car runs perfect and makes incredible power and torque way before 5800 rpm on 91 octane tune. The tuner thought if it might rev to 6800 it would make more power but that was 2 years ago engine wasn't even broken in then.

Sounds like he wants more than 5800.

 

[Saleen414]

There may be a reason the engine builder does not want it to spin faster than 5,800 rpm, whereas the owner thinks that it should go to 6,800 with no problems. A 408 should hit 7k with no issues.

 

[stangjumper]

Big question is what cam is in it? Will it make power over 5800rpm with correct supporting parts?