[DBLDREW]

First off the stock headers are junk you need to change them. I would contact Factory Five and find out if they make a full header option and go with this if it is in your budget. If you cant afford it (or they don’t offer it) there are a bunch of companies that offer a shortly header that will fit the oem mustang exhaust, BBK, JBA to name a few. This will much improve the exhaust flow over the stock header.


Another possibility that could be hurting you is your heads. I have a 89 mustang that I pulled out the 302 and put a 351 that was pretty built up. But I was running a little low on funds so rather then buying a new set of heads I just had my stock 5.0 heads ported and polished and new valves put in. Well the car didn’t run the way I thought it would, I never had it on a dyno but the best time at the track was 13.60 @104 mph I had the same problem that you are describing it would pull strong but start to drop off around 4500 rpm. Well after a ton of diagnostics I figured that it must be the heads and I opted to bite the bullet and buy a new set of heads. I bought the Performer RPM heads (this was about 8 or 9 yrs ago so I didn’t have the AFR option) Well after I bolted them up it was unbelievable how much more powerful the car was. With no other changes other then the heads I went from a 13.60 to a 12.40@ 113mph! So the guy that did my port job obviously didn’t know what he was doing.

I’m not saying that you should go out and buy new heads yet (that’s a very expensive experiment) but maybe try the headers first and see if it improves things. It’s possible that the guy that did your port job knew what he was doing and they will work fine.

Also some one else made a comment about an E-303 vs. a B-303 cam. I would be very careful with switching cams. If the heads you have do actually have 2.02 valves there is a potential valve to piston clearance issue. I believe that if you go with a cam that is much over .500-inch lift you will need to fly cut your pistons. I don’t know off the top of my head what the lift is of the E-303 I do know that the B-303 is .480 and is in the save zone.

Anyway good luck.