Hello yall, I've put about 3k miles on my freshly rebuilt engine, and I wanted to get some opinions. I ported and polished the heads, installed the Comp Cams 35-255-5, along with the springs, and threw a set of long tubes but augured out a spot for the EGR tube, a custom Y pipe and a high flow cat with a glass pack behind it, it sounds pretty good, but its not preforming that well, let me explain.

So I have been getting around 7mpg, that's my first complaint, I know the truck weighs 5400 lbs but 7 seems way to low. Secondly I feel like I have no power, like I step on the gas and I don't go anywhere, it gets louder just not faster. I almost feel like its a flow problem, or a spark related problem, I just replaced all the plug wires, and it seemed to help, but I kid you not I am getting gapped by chevys of similar year. (just jokes)

I can upload some pictures of the exhaust system, I will try and pull codes, I chased a lean condition for a while, but a new 02 sensor fixed that.

Also worth mentioning, I keep it below 3k RPM 95% of the time, I am not flooring it except when I try and merge on the interstate.

It pulls HARD in the 2500-3000RPM range, and then just falls on its face, rpm may increase but it takes forever, and you have to FLOOR it, like pedal DOWN to even get up to interstate speeds.

I appreciate any insight, or experiences, let me know if I need to upload pictures or better describe something. Thank you in advance.

 

Yea check codes and fuel pressure.

Did you remove the spout when you set the timing? Could be as simple as that.

 

I'd also like to add...does it have a cat? If so is it the original? Just a thought. Had a 92 Camaro awhile back and similar issues. It had a loose distributor so it ran horrible but cat was plugged too and the thing was gutless.

 

A couple things I'd check -
Timing, verifying initial timing AND total timing at RPM.
Fuel pressure, both at idle and at RPM. If your fuel pressure reduces significantly at RPM, your pumps cannot keep up with demand.
What do the plugs look like? Rich/lean?
If you do not have a real wideband O2 sensor installed, it might be a good idea to purchase one and see what the air fuel ratio is at the RPMs where power drops off significantly. It would not surprise me if the stock 19# injectors just cannot keep up with the new demand.

 

Install a wideband to confirm what the fuel mixture is. No restrictions in the intake and exhaust systems. Set the ignition timing to specs. Maybe advance it a little to see if there is more power.

 

Sounds like a fuel pressure problem but as others have suggested check codes and that base timing is set correctly.

 

What truck F150/250?, 2wd, 4wd, big tires, that cam isnt that big, dont expect much, stock is 0.444 lift and its at 0.475, your not roasting tires with it.

 

0.444" cams were HO, truck cams way less.

 

Yes, I set it to 10* BTDC, I will double check it, as I have a timing gun.

 

I bought an aftermarket high flow 3 inch cat, its pretty clean, I am going to take off my muffler and see if that improves it.

 

I will verify the initial timing and total timing tonight. I will also check the pumps also, I know they are a bit low, but I will check to see if its spec.
Plugs look lean almost or really hot. I have aftermarket injectors, but I don't know the flow rate as PO installed them.

 

F-250 4wd with 33s but I got the 4.10s in the diffs, so it shouldn't be struggling so much.

 

Alright just got the results.
Code was 412, it seems it couldn't control the rpm during the high idle test, which it did actually, so I have no idea whats thats about.
Initial timing was 12* (spout disconnected) and total timing was around 32* the balancer only goes up to 30 but I am confident its dang near 32.
Fuel pressure time, so key on engine off it was less than 10 PSI, probably doesn't mean much, when it fired up running both tanks for about 28 PSI, although when I revved it it went up to 30 ish. Still really low, its out of range from the manual, I found some new pumps on rock auto, but I recently changed the fuel filter, it was really bad, but my front tank is full of rust, I haven't had a chance to look at my rear tank yet.

From what I understand I want my timing around 36* in total?
The fuel pressure is low, but I wonder if there is a ground or something that's bad, or corroded, or its probably that my pumps are shot bc the fuel tanks are full of crap. How do yall think I should go about removing the rust? I was looking at rust remover, or like evapo rust. If I am going to replace the pumps I will probably take my bed off, I hate working on the ground especially since its barely getting above freezing.

Also quick side note, I decided to reuse the glasspack the PO put on the truck, but I made the whole system out of 3 in, and the glass pack is 2.5" and I used some adapters for the muffler, its the only part thats 2.5", I imagine that could be killing flow, I will take it off and just replace it with some 3" pipe to see if if that helps.

I appreciate everyone's willingness to help, its been stumping me.

 

No the muffler isn't the problem the fuel pressre is, you're at least 10psi low and likely falling behind in volume as RPMs increase under load.

 

I’d check the regulator since both tanks are low and at the same pressure if it were mine. Could be an easy fix. Maybe pinch the return line for a second and see if it’s sending too much fuel back to the tank