347 vs 427 engine mounts

[ggunter]

I think I know the answer to this question and I believe the frame mounts for the 347 and 427 Windsor engine are the same, but please correct me if I'm wrong. This is for a MKIV Roadster.I thought the exhaust headers were the same as well but found out they are different as the 351 windsor is wider then the 302. I am changing out my 347 for a 427 Wndsor and want to avoid any chassis fitment issues. Thanks Gary.

[Jeff Kleiner]

You are correct; mounts are the same and headers are different. Watch how high you go with the intake and air cleaner combination to avoid hood contact.

Jeff

[ggunter]

Do you know if the dual plane that comes with the Blueprint engine would have any clearance issue? I would think not, but stranger things have happened. I am running the long oval Cobra air cleaner. I know some of the taller single plane manifolds would be too tall. I'm a Chevy guy all my life, this Cobra is my first foray into the Ford world so I'm learning as I go.

[Jeff Kleiner]

It’s the tall “Air Gap” intakes that cause the clearance issues (and also negatively impact low speed drivability.) You should be fine.

Jeff

[CaptB]

I think I know the answer to this question and I believe the frame mounts for the 347 and 427 Windsor engine are the same, but please correct me if I'm wrong. This is for a MKIV Roadster.I thought the exhaust headers were the same as well but found out they are different as the 351 windsor is wider then the 302. I am changing out my 347 for a 427 Wndsor and want to avoid any chassis fitment issues. Thanks Gary.

You're going through the same question that I had before (went from 347 back to a 427). The 351 stroked to 427 will use the same motor mounts as the 302. The headers are different though, but I confirmed through FFR and GasNGo that everything else is the same.

Where are you getting your 427?

[FF33rod]

It’s the tall “Air Gap” intakes that .... negatively impact low speed drivability...

Jeff

Interesting, first time I've heard that Jeff, care to elaborate? I have one on my 347 and have no complaints but maybe it's certain situations or combinations?

Steve

[Jim1855]

Performer RPM v. AirGap What I was told years ago was that the AirGap had smaller ports but potentially offered a cooler charger and that the Performer RPM would make more power. I think the AirGap is taller which might cause hood clearance issues, air cleaner dependent. A friend has a 351/427w, Vic Jr and drop base air cleaner, it fits.

I ran a Performer RPM on my 427w. With a 670 CFM vac carb it ran really well at low rpms <2,500 up to the 6,000 range. Very drivable, almost civilized.

I gained upper rpm power (>6,000) with a Vic Jr and 780 carb and was still making sufficient torque at 2,500 to spin tires with just gas. This configuration might not be for everyone and is less civilized, but more fun.

Jim

[FF33rod]

Performer RPM v. AirGap What I was told years ago was that the AirGap had smaller ports but potentially offered a cooler charger and that the Performer RPM would make more power.
Jim

Edelbrock description says the opposite actually, well for runner size at least: "The 7521 RPM Air-Gap features larger runners (7% at the plenum entries) than the standard 7121 Performer RPM design that is beneficial to larger CID stroker engines."

[Jeff Kleiner]

Right, the Air Gap has larger runners so at low RPM the velocity isn’t there to maintain atomization and in general most engines won’t be happy or responsive below 1,500…but twist it’s tail to 5,000+ and it will scream like a banshee!

Jeff

[Jim1855]

Well boys, my old info seems to be incorrect. My apologies. Sorry
For my engine, in 2004, the builder recommended the Performer RPM.
Jim