blkasp2, I have a Roush 402R (with 12,000 miles) that shut down on me the day I install a Pro System carb. I was so sure it was the carb that I call them and raised hell. Only to find that the chromed Holly mechanical fuel pumps we installed, diaphragm was defective. Had to call them and apologies the next day. I also agree with Max DUMP the ford duraspark ignition if you have one, and get a MSD!!!

You can flap your gums all you want. If I PAID for a 550hp engine, it damn well have pretty close to that regardless of whether the correct engine combination was selected. I wouldn't be calling them up on the phone and saying my engine only put out 502 hp and I want a new tag. I'd be saying my engine only put out 502 hp. What the hell are you going to do about it.

If you want the lower hp version, then buy it. This is about what you PAID for, not what you want/need.

I'm not following you here. No one said anything about a Roush engine rated at 550 hp (at the crank) only putting out 502 hp at the crank. :confused:

Had the identical problem with my Roush 402R from the day I took delivery. Problem was the locking gas cap was not venting properly. So, I replaced the cap and the same problem. Therefore, I discarded the gas cap and now running with the racing cap (push down and it locks) only and END OF PROBLEM. THE CAR NOW RUNS LIKE A MONSTER. One downside: don't get in a wreck in which you are upside down as the gas will run out all over the ground.

p.s. My 402R cranked out 554 hp on the dyno.

Isn't the Roush HP rated on an engine dyno and not a chassis dyno? That could account for the loss...

This is what the original poster stated:


"I just got a car with a new Roush 427r 550hp engine and am having a problem."

He then goes on to say in another post a bit later that it only puts out 520hp.

Then another person stated he had the SR version. Madmaxx says Roush rates it at 520hp, but it is putting out 507hp.

"It depends on the Engine I have the 427SR/TW and it dyno'd on the engine stand at 507 hp and 520tq".

All I am saying is if I paid for the 550hp version and it is coming up 30hp short, I would be calling somebody and asking them to explain the difference to me.

Got it. Your post said 502 hp. :)

I'll give you the scientifuc answer to your get what you pay for HP question that applyies to many things. The factory rates the engine at a HP given a set of conditions. It is scientifically impossible to repeat HP checks on an engine HP and get the exact same HP every time it is measured. Measuremnt is usually a bell curve of results. When you retest someting from the factory, it should be within the reproducibility of the test. I don't know what the HP measurement reproducibility is, but it could be something like +/- 25 HP. So on a retest, if you run the exact same test the factory ran, you should get a number +/- 25 of the factory measurement. If you do, then the engine is performing as expected. If you don't, maybe there is a problem or maybe the conditions (temperature, atmospheric pressure, gasoline, etc) are not the same as the factory. Thank goodness everyting is not exact. If it were maybe cops would be giving you speeding tickets for going 0.1 MPH over the speed limit. But Officer, my speedo only said 81 MPH.....

My son and I both have 427R engines in our SPF cars. We both had the same problem, and resloved it. Trust me and the others who have advised you on the fixes. We had the same intermitent stalling or poor performance on 75 degree days here in AZ. We have diagnosed this problem for other enthusiasts on four other carbed cars here in AZ in Cobras and Rods.

1. Check out the gas cap situation. Make sure the tank is vented properly. Mine was not, my sons was.
2. It is most likely vapor lock even with low outside temps. We have discovered that some of the oxygenated fuel in AZ boil at 140 degrees. The fuel in your lines between the mechanical fuel pump and carb (in the fuel log) is boiling when you stop for a few minutes to a half an hour. It is also boiling in the float bowls. The location of the mechanical fuel pump is also a problem when you consider the oil lines to the oil cooler are running right next to the fuel pump. When that oil temp is up about 200 plus degrees, it transfers the heat to the mechanical fuel pump and thereby the fuel, the fuel begins to boil and then the pump cavitates and starts to push air instead of fuel. We installed an inside cab fuel pressure gauge as we diagnosed the problem and could easily watch the fuel pressure drop as the engine heated up and the oil heated up. The pressure would fall below 4lbs and the engine would begin to puke and/or stall. Typical vapor lock. If in doubt, install a fuel pressure gauge in the cab and watch the fuel pressure. If it drops below 5lbs you will have problems. The Holley on your car needs at least 6 lbs to run right. Holley may tell you differently, but that's what we discovered

The Fix: Install an electric fuel pump and regulator. Install a Holley spacer and Holley heat sheild beneath the carb. This will take care of about 98% of the problem. The added height will clear the underside of your hood scoop.

If you want the best fix, do all of the above but add a return fuel line to the tank. We did one of our cars without the return line and one car with. The car with the return line did not experience any problems while the one without the return line would still experience vapor lock, but rarely. We completed the return line install on that car as well. Zero problems on both cars.

But if you really want to get your engine running well, ditch the Holley that Roush provides and go with a Pro-Systems Carb. Outstanding Performance. Runs better, idles smoother no hassle to set it up. The Roush/Holley has been tinkered with at Roush and is difficult to get running perfect all of the time, especially with oxygenated fuels.

PM me if you want the complete specs of what my son and I did. I would be happy to supply them to you.

Just an easy check: Make sure MSD ground wire is properly fastened. I had similar scenario and eliminated problem. Good luck.

I ask the question what version of Roush did you get? The R, if so you should be close to 550HP, if not then you will not. I also advise to read the small print, they are not liable for any reading except the dyno sheet you received with your engine. If you dont like it you dont accept the engine. I asked for mine in advance, they will fax it to you with the engine number. If you relied on your installer or previous owner to ensure it has 550 hp then go whine to them, it aint roush's problem, they supplied the dyno and taged the engine with result prior to leaving their shop so either the previous owner, you or the shop installing could have rejected the engine prior to purchasing if the numbers were not to your liking.

it sounds like a fuel problem. check the float valve on the carb.

Regarding the Roush plate, my motor dynoed at 561.8hp and my motor plate says 561hp as well as the torque # it dynoed at, the installer name and the date. I have never heard of generic plates. There have been some very good suggestions in this thread regarding possible problems. I would start with the easiest and work from there.

motor problem
 

the first thing i'd do would be check the float bowl adjustment.
when the engine has been run, and is hot, shut it off. listen to the carb. if it's guggling, your fuel is boiling-this can normally be fixed with a spacer between the carb and manifold. do not run stock ford ignition, not powerful enough.

check float bowl adjustment.
make sure fuel is not boilin in float bowl

Roush troubleshooting is an oxymoron (if I spelled that right) like fun run. the words just dont go together.

How can you sell engines that are suppose to make 550HP and that is what they are advertised at but they do not make that. If I was paying the extra price for the Roush name I would at least want the engine to make what they advertise it at. They use the same parts as everyone else.
I do not think it is anything with the engine and more than likely an electrical or fuel problem on the car.
Good Luck, Keith

So this has only happened once? Have you been able to recreate the problem since? I'd toss the MSD box. They are complete junk. If it hasn't failed on you yet, it will.

If you look at the Roush Performance site here http://www.roushperformance.com/engines/engines.shtml
You will see the word Maximum, the 427R has a rating of a maximum of 550hp which to me means up to.

The 427SR/TW has a maximum of 515 HP mine dyno'd at 507 I am not irritated about 8hp .:)

Most know you can play with timing and other engine adjustments to get the horspower reading you want, needless to say some affect engine longevity. The SR is 480HP, SRTW is 515 and the torqueless R is 550 hp. mine dynoed at 522 hp so I guess I got the bonus plan with an extra 7 hp. Oh wait maybe the dynoed mine on a cold day or a dry day. Dyno numbers at best are within 10%