I have a 96 F250 that had a motor with terrible blow by. I found a 89 non roller motor to replace it with. I took off both plenums and swapped my wiring harness to the new motor along with my fuel rail and injectors. I used my flywheel and headers on it and put it in the truck.

First shot at firing the new motor it wouldnt catch. Took #1 piston to TDC and re seated my distributor with rotor pointed at #1 wire. This time when i turned it over it back fired and caught the truck on fire. First the rear of the motor then the top of the trans. Proceded to get water hose and put it out Come to find out the #8 injector wasnt seated and fuel would spray out when the pump primed. I then took off the plenum to see the damage. All it did was melt the tape off the harness and chared the firewall, nothing else was damaged. After i reseated ALL of the injectors i put everything back together and tried starting it agian. It wouldnt fire right away with it at 0* but would start up at with the throttle open slightly. It sounds as if it is missing terribly, but i changed all plugs, wires, cap, and rotor. It has the correct firing order also. even when you rev it up higher it sounds as if its missing and doesnt sound like it should. Let off of the throttle and it will idle for a few and then die. I changed the thing on the side of the throttle body (IAC?) and it had little to no effect.

What could i be missing here? I am going to do a compression test on the motor soon, but have not done so yet.

 

when you set the timing, did you unhook the connector at the distributor to put timing in retard mode? and how long was this engine sitting before you swapped it in?

 

Is this a 351 ? the 302 had two different FO for these years , when you put the distributor in at TDC it needs to be on the compression stroke or you will be 180 deg off....

 

Its a 351w. It sat only for a few weeks before i put it in the truck. I have it set where the piston is at TDC and the harmonic balancer reads 0*. It would fire like this with some throttle and idle like crap, even at 10-14* didnt seem to change (SPOUT was out). Tried taking it 180 arter this and it wouldnt even fire...

Lew52- Was just thinking yesterday that i havent seen you around much anymore, how ya been?

 

Everythings fine , been on here and there , let us know how the comp checks out ...

 

Well the compression test showed that wach cylindar was between 166-183. I do not see why this thing is giving me so much trouble starting and idling... Can anyone think of anything that could be wrong that i am missing?

 

I did the compression test myself this time and found that each cylinder is as follows:
1-122
2-125
3-120
4-120
5-114
6-122
7-124
8-90.

Oil pressure- between 55-60
Fuel pressure- between 37-43 (vacuum removed) holds when key shut off

Now that number eight cylinder is what bothers me. Do those look like OK numbers? They all held at that PSI. All of the plugs were black so i checked the fuel pressure and it is 37 psi, 43 with vacuum removed. I have all of my vacuum lines ran correctly and the correct firing order.

The truck will idle roughly now that i have a few plug wires on correctly, but when given throttle it will pop real loud out of the tail pipe. Can anyone think of what i may be overlooking here?

 

Well # 8 is low and with the poping out the tail pipe , i sounds like a bad exhaust valve or a valve hanging up , i would do a leak down test on # 8...and the truck will idle rough with just a few wires on correctly ??

 

All of them on now. I had two that were on but nit pushed down all the way. It will idle, but real rough and will stall within a few minutes. How do you do a leak down test?

 

Is the distributor rotor pointing at the #1 on the cap when it is installed, with the piston at TDC? Because they rotate a bit with the cam teeth when installed. Just asking

 

Just hook an airline up to your compression tester and put air into the # 8 clylinder with the valves closed , on the compression stroke for the # 8 cly , see if you have air coming out the exhaust...

 

With #1 at TDC and the harmonic balancer pointer pointed at 0 i set the rotor and distributor at #1 spark plug. Start it there and set the timing at 8-10* BTDC.

It only has 10psi of vacuum at idle. I am going to change the upper and lower intake gaskets and see what happens. If not i think i am going to pull out my rebuilt E4OD, take my JBA SS headers off of it, pull off the plow frame and scrap it.

Help me save it! I need thoughts here people before i crush it

 

I will do that Lew. What will this tell me exactly? If the valve seals are bad in/on that cylindar?

 

What was the original engine?

You took your 1996 computer and all sensors and EFI stuff and attached it to a 1989 351W, is this correct?

 

The origional motor was a roller 351w. It died at 203K. I replaced that one with a motor i had from a previous truck. Rings went bad in that motor and blew oil out the dipstick and oil breather tube. About a quart a day is what i had to use to use the truck. That motor got so bad it wouldnt even pull my 8x10 landscape trailer.

I now have another motor that is from another 89. I changed the distributor gear to a cast one for the flat tappet cam, the origional wiring harness from the truck and simply plugged it into the complete FI motor. Computer never changed.