Looking for the 351w gurus. Ive got an 87 bronco, 351w with the C6. 4bbl holley 650cfm. After market intake and headers. All the emissions stuff is long gone. Power is pathetic. Like cant hold 45 in second on a 5-7% grade pathetic. Starts and idles fine. Timed and retimed (but to show my ignorance, this was lining up the marks with a timing light at 2k rpms) I followed the instructions i was given basically. I've adjusted the mix on the holley and tried multiple carbs. The one that is on it works perfect on my old vette so it isnt likely to be the issue. The mech pump is fairly new and the fuel looks clean through the filter. The tank seems to like building pressure but i havent noticed any effect on performance.

As a potential symptom, if floored, the c6 shifts at 2500ish. She will eventually get to 55 and hold it but only on flat level ground. Sub 10mpg is standard and she gets warm (180 thermostat and the temp gets to 220ish or higher) climbing any hills. I'm pondering swapping in the 7.3 diesel radiator and twin electric fans to fix that in the long run.

Sorry about the possible info overload but I'm trying to be thorough about what's been tested.

Thanks in advance!

 

A bit more info: New plugs and wires just a couple hundred miles ago. This truck is a junk yard rescue. When I had the water pump off, the interior looked way better then it should for a motor with 130k that was junked so I wonder if it's a crate motor or a rebuild. She burns very little oil for the mileage but I'm beginning to wonder if an old cam or crank was used.

Other modifications: It's got the serpentine setup off a 93 with a mustang water pump. Had to convert it because the parts for the 87 AC were nearly impossible to find. Not running the AC at all currently. The starter is the compact one from a 93 as well with a bypass and push button start. (I've had nothing but problems with the separate ford solenoids but I'm beginning to suspect it's just a connectivity issue with the ignition wires.)

At this point, I'm open to any and all suggestions as I'm out of ideas short of pulling the motor apart.

 

now our trucks that run the serp setup use a reverse rotation water pump. a mustang pump would turn the wrong way. this could cause your over heating issue. you can and probably should run a 180* Tstat as well.

I am unsure what the timing should be on that motor with that said you might look it up in a Haynes or chiltons manual if you are unable to find it searching the forum. you would want the idle to be in the 650 range when setting the timing.