New engine problems

[cpratt1999]

Hello everyone! I 'm new to this forums page, but have been reading from here for a while now.

I recently installed a rebuilt 351W EFI into my 1993 Bronco. The motor came with a mild over stock cam and I used heads with factory spec valves and 1.6 scorpion roller rockers for the rebuild.

I also added a Professional Producst Typhoon Intake Manifold and Plenum which I ported and polished. Then I had to install a Professional products throttle body to complete the build. The new TBI unit was similar to that of a 90's mustang 5.0 (single butterfly) as opposed to the OEM (dual butterfly) TBI unit my truck came with.

The problem is that the truck will barely idle and has a very bad missfire. I have checked the timing, both distributor and wire placement and even had a Ford tech verify I had installed everything correctly.

I'm wondering if it might A) be the throttle position sensor and/or Idle air control unit since they are calibrated for the different TBI and intake, B) the fact that the cam in the short block might have used a roller cam and the lifters are only OEM spec hydraulic not the hydraulic roller.

I also contacted Summit Racing tech support and the guy is suggesting replacing my computer with an OBD2 unit from a 96 Bronco or F150 Lightning and he believes that it might be related to a lack of a Mass Air-Flow sensor. I think that it would still run without the MAF though, but I could be wrong.

Anyway, if anyone has any insight I would LOVE the advice.

Here is the rest of my truck's details:

1993 Police Interceptor Bronco

OBD1

351W EFI

OEM Heads/Valves (rebuilt)

E4OD Trans/4x4

Pace Setter Headders

1.6 Scorpion Roller Rockers

Profesional Products Typhoon Intake and Plenum(Similar to the Edelbrock EFI manifold)

24 lb Accell Injectors

Motorcraft plus

8.8mm wires

 

[Yardape]

Did I read it correctly that you have flat lifters on a rollers cam? You cant do that, the roller cams ramp up and down to sharp for the flat lifters.

 

[Ogeechee 4x4]

You're past the capabilities of speed density. Need to upgrade to a mass air and if it was me, i'd invest in a TwEECer unit so you can tweek all of the computer bits.

www.TwEECer.com

 

[cpratt1999]

Did I read it correctly that you have flat lifters on a rollers cam? You cant do that, the roller cams ramp up and down to sharp for the flat lifters.

What you read was: the fact that the cam in the short block might have used a roller cam and the lifters are only OEM spec hydraulic not the hydraulic roller. I did not install the cam. I bought the shortblock and was informed that it was a mild cam just hotter than OEM specs and not a roller cam.

Under that pretense I did; however, use hydraulic lifters not hydraulic roller lifters.

Redardless, I managed to get some information from the builder of the motor. After quite a bit of searching he went through everything regarding my order and NOW he tells me he did install a roller cam He advised me that the advertised duration of the cam is 284

 

[cpratt1999]

You're past the capabilities of speed density. Need to upgrade to a mass air and if it was me, i'd invest in a TwEECer unit so you can tweek all of the computer bits.
www.TwEECer.com

That's more or less what Summit suggested.

 

[cpratt1999]

You're past the capabilities of speed density. Need to upgrade to a mass air and if it was me, i'd invest in a TwEECer unit so you can tweek all of the computer bits.
www.TwEECer.com

Thank you for the website!

 

[Yardape]

Roller cams are steel so it is unlikely you damaged it by only a few start ups, You might be better off getting roller lifters and just putting those in. If you do definately inspect each cam lobe for any sign of wear, if there is any imperfection then you must remove it. If its good then install the roller lifters. I would say that it your problem, your engine would run like a bag of s**t with the wrong lifters.

 

[Yardape]

Another thing, if you keep the roller cam you need a bronze gear on the distributor, cant use the cast one.

 

[cpratt1999]

Another thing, if you keep the roller cam you need a bronze gear on the distributor, cant use the cast one.

No problem there! I only got the truck to run for about 45 seconds. I will definitely inspect the cam for safe measure as you suggested. Do you think the cam that came with the motor's lift/duration (284/284 .480/.480) might be too much? I also live in Denver (high altitude) which is why I went with the high rise intake to begin with.

Thanks again!

 

[Yardape]

It might be a touch too big but you should be fine, nice lumpy idle. As long as you stick with the stock ratio rockers you should be okay. If you step up to 1.7's you might kiss the pistons.

 

[92bronco_in_progress]

It might be a touch too big but you should be fine, nice lumpy idle. As long as you stick with the stock ratio rockers you should be okay. If you step up to 1.7's you might kiss the pistons.

he most definatly will if he goes with 1.7s

 

[cpratt1999]

I only have the 1.6 roller rockers...no worries there.

 

[Yardape]

Right on, then your good to go. sounds like a pretty nice build.