Bucked Like a Horse!

[madmaxx]

Roush makes three 427. The S, the SR, The R. The SR seams to be the best of both worlds in excess of 500 hp but still drivable. The R likes to live at high rpm. I am confident 99% of the problem is in the carb. As him to pull the air cleaner and look at the front of the carb, there should be a green dot made by a paint marker. I bet he finds a different color. Knock $1k off for a new carb, call Roush and tell them you want this was serviced, I ams sure the cost will be less than $1k but you need to reimburse yourself for the troubleshooting

[mdross1]

It does sound like a carb issue,there are a lot of good carb people out there that can help dail this motor in.Have fun in your search.

[Roush #1]

Ward,

Just to add a bit to this mix .... my repair, from a blue dot to a green dot ....
did not involve a jet change, air bleed change, idle air bleed adjustment, or squirter change.

I checked all of these on the original blue dot and they were the same on the green dot replacement carburetor. What I am saying is the difference in the two carburetors on mine was not visible.

I am aware of one more Roush engine that was built about the same time that had very similar problems. I have heard there are more, but I do not know that for sure. Mine was number 444 and I think Maxx was somewhere about the same time.

Don't give up on the engine. It could be as simple as an air bleed adjustment.

I understand your frustration, but the 427R should not be "bucking like a horse" when it is properly tuned. Mine runs smoothly in any gear at 1,000 RPM and idles well at 800 RPM - and yours can as well.

Gearing has something to do with it and it should be more prone to buck at higher gear ratios (lower numbers), but when I am in 6th gear (.62:1 ratio) with 3.89:1 rear gears, not many Cobras are geared higher which normally causes the bucking.

Good luck!

Jody

[jhv48]

That bucking at cruise speed sounds like a lean condition in the transition between idle and main circuits.

Definitely a carb issue, and a simple one to boot.

[madmaxx]

My guess is any Roush 427 between 400 and 600. The numbers are stamped on the valve cover, and on the dyno sheet, and the roush plaq. Without a doubt my Roush has performed flawlessly from the day I got it, the installer addressed the carb issue before I got it. Oh did I mention Sunny, 65F and 40% humidity in Houston today. How that snow hitting you guys LOL LOL LOL LOL LOL LOL!!!!!

Originally Posted by Roush #1

Ward,

Just to add a bit to this mix .... my repair, from a blue dot to a green dot ....
did not involve a jet change, air bleed change, idle air bleed adjustment, or squirter change.

I checked all of these on the original blue dot and they were the same on the green dot replacement carburetor. What I am saying is the difference in the two carburetors on mine was not visible.

I am aware of one more Roush engine that was built about the same time that had very similar problems. I have heard there are more, but I do not know that for sure. Mine was number 444 and I think Maxx was somewhere about the same time.

Don't give up on the engine. It could be as simple as an air bleed adjustment.

I understand your frustration, but the 427R should not be "bucking like a horse" when it is properly tuned. Mine runs smoothly in any gear at 1,000 RPM and idles well at 800 RPM - and yours can as well.

Gearing has something to do with it and it should be more prone to buck at higher gear ratios (lower numbers), but when I am in 6th gear (.62:1 ratio) with 3.89:1 rear gears, not many Cobras are geared higher which normally causes the bucking.

Good luck!

Jody