Hello. I just finished putting a cam and a set of gt40p heads on my truck the grind number on the cam is FW X4 250H-11. It's supposed to be a bottom end cam. Will I need bigger injectors? And can it run on regular gas? I was hoping to keep the 19lbs cause part of the reason I did this build is for better fuel mileage. I haven't driven the trick much yet only a couple feet here and there. I need to get the exhaust hooked up to the headers first

 

I should mention that it's a 351

 

Yes that should work with the stock injectors, the intake will sufficiently bottleneck the motor to prevent over running fuel supply capacity. And that cam isn't technically EFI friendly but given the rather short lobe durations I think it will work reasonably well.

 

I eventually plan on putting the 3881 edelbrock intake on. Will they still be fine then? Why isn't the cam efi friendly? It seems to idle nice. I haven't tested it out on the road yet. I'm afraid I'll catch something on fire or burn valves with no exhaust.

 

It should be fine with all of those mods, but after modding any gasser (and particularly of this vintage) it's a good idea to have a wideband to confirm it runs right and stays running right. Even a weak fuel pump can cause a lean condition, so it's best to monitor the system.

Also, larger injectors does not automatically equate to worse mileage...it just means the larger injector will operate at a lesser duty cycle at cruise acceleration, and be able to supply adequate fuel under hard acceleration.

 

What's a wide ban? I used to have a cummins for a long time and I remember fuel mileage wasn't affected till 75hp injectors where put in cause it was easier to get the truck rolling with the extra power. But I have no idea with these gas trucks. They are horrible on fuel compared to a cummins.

 

Ha! That they are....there are a lot of differences between adding larger injectors (75hp injectors are modest) on a turbo diesel and adding them on a naturally aspirated gasser with homogeneous injection. But rather than write a book on it, I'll leave it at that.

A wideband is a monitoring system for air fuel ratio (also irrelevant on the diesel you are accustomed to). It comes with an o2 sensor that you plumb into the exhaust with a gauge in the cab to tell you the air fuel ratio. It's the only way to know what is happening, as lean conditions can be catastrophic in a gasser.

 

Can it be done with the stock o2 sensor? Or another one has to be put in?

 

no, the stock sensor does not supply the same information to be interpreted for a dynamic air/fuel reading. The wideband kit comes with the o2 sensor, processor, and gauge.

 

Ok I'll look into it. Where can you get them from?

 

Can I change the a/f ratio with a wide band ? Or does it just tell you what you are getting

 

The listed Lobe Separation Angle (LSA) is listed as 111 degrees. General rule for Ford Speed Density is a LSA of 114 or greater.

According to the manufacturer's own literature

Computer-Controlled Compatible: No

As Paul stated the rest of the specifications are relatively mild so that will help "smooth over" the shorter LSA.

 

I wish I knew that before. I just saw that it was compatible for 95 and older trucks and it helps the bottom end. It was advertised as a "4x4 and towing" cam. I didn't mind tearing down the motor but it was stressful. I hope I don't have to do it again

 

Should of joined this forum earlier ...

 

It tells you the AFR. Stoichiometric is 14.7:1. Higher ratios are lean and lower are rich. If it is lean, you'll need to address that with more fuel. It is an instrument, not a fuel system modification.