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Discussion Starter · #1 ·
Guys,

Hi and great forum! I have a 1991 Mustang that has the following mods:
331 DSS stroker
Trick flow street heat hreads
1.6 roller rockers
trick flow R series intake
70 MM throttle body & C&L 70 MM Mass air
X-303 cam
BBK full length headers
off road x pipe
flowmaster exhaust (single chamber)
underdrive pulleys
alum 4 core radiator
elec fan
24 lb injectors which is correctly matched to the mass air
msd distributor
msd 6AL box

These are all the engine mods that I know of. The car runs terribly rich at idle you can smell fuel at idle, and at higher rpm's it runs very lean. The car feels stronger than a stock one but no where near as strong as it should, it has alot of seemingly fuel issues if you stay at low rpm's in town then it tends to pop and crack as if it were a carb vehicle that were "loading" up on fuel. The computer is stock to my knowledge. My use for the car is mainly to drive on weekends on cruises, and some occasional trips to the track. I am not a fan of the X-cam so I have went and purchased the trick flow stage 2 cam and an adjustible fuel pressure regualtor but I dont think this is a total fix. Any help or suggestions guys??
 

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i wud check fuel pressure first

any chance on a vacuum leak somewhere?
 

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Discussion Starter · #3 ·
re

fuel pressure is about 32 psi at idle and is somewhat sporadic during hard pull, sometimes it actually drops, I am considering a new fuel pump, thats why I bought the new fuel pres reg, but if the pump was going bad whay wuld it be running so rich at idle? I have looked and checked the Vac lines and they all seem to be in great condition.
 

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has it run correctly before with all the listed mods
 

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I would say tune... after my swap i had this issue, assuming everything else is 100% ie: vacuum lines, wiring, fuel, etc... a tune will fix this
 

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have you tried 39 at idle? thats the stock pressure
 

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Discussion Starter · #10 ·
re

pissed pardon the language but boy i am mad We put the new cam in went through the motor and timed it tried to fire it and nothing, I suspected timing issues before the cam change and was told because of the x cam it was related to to computer, well now tells the tell. for the second time you cant time this motor even with the new cam, timing chain and lifters. on ten degrees it will not turn over on 14 barly I think DSS made a big mistake on their crank keyway
 

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you need to make sure you have the following

new 28oz harmonic balancer since thats what the 331 crank will be

new distributor , pickups can give you a fit sometimes

new 255lph intank pump

then retime it at 10 degrees after you triple check your wiring and check for vacuum leaks again

once running set the fuel pressure to 39 with the vacuum off the regulator , and the reconnect it
 

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also, make sure you're not 180* out... I'm not trying to call you dumb but mine would fire and pop and gargle then die and it's because I was off when I dropped the distributer in.
 

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Discussion Starter · #14 ·
Tonight after going back through everything double checking valve adjustment, timing, finding TDC etc etc we finally got the motor to crank but it has a terrible pop and cracking, also seems to be poping back through the intake, I have considered the possibility of the MSD 6AL box giving problems, does anyone else have any ideas? it seems to be getting plenty of fuel, the pressure is around 34 psi, the timing is at 10 degrees with the chip out and with it in the timing is jumping all over, I am not sure what to do.
 

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Discussion Starter · #15 ·
once again

Ok again tonight I went back in, readjusted the valves to make sure adjustment was correct, checked timing, found compression stroke, pulled TDC with a piston stop and the balancer was 1/16 on an inch from the 0 degree mark so close enough. dropped the distributor in pointing right at number one plug wire on the rotor cap, the firing order is correct per cam card (new trick flow stage 2 cam) fire the motor, i have to feather the throttle, we set the timing to ten degrees lots of poping and cracking like its 180 out but its not. I did discover A crack in the plastic bracket on the distributor where the wiring harness plugs into the distributor?
 

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Make sure you are using the correct 302 firing order. It should be the 5.0 HO firing order. I have connected the wrong firing order before and got popping into the intake and backfires out the exhaust. :banghead

289 1-5-4-2-6-3-7-8
302 (Pre-82) 1-5-4-2-6-3-7-8
5.0 1-5-4-2-6-3-7-8
5.0 HO 1-3-7-2-6-5-4-8
5.0 Truck 1-5-4-2-6-3-7-8
351 1-3-7-2-6-5-4-8
 

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yeah, the cam wont change the firing order... also this cracking and popping you describe may be because your 180 out still. I remember when I was dropping my distributor in in would fall right into place and the tab was pointing at #1... but to my surprise it was not firing... so I turn it back to what to me looked like #2 and whalla fired right up, wouldn't idle for ****, but fired up and had no backfires
 

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Discussion Starter · #19 ·
re just a little more progress

After installing the new ignition module that cleared up the cracking and poping. The car is now starting to idle and run somewhat normal, it wants to rev to around 3000 rpm and stay there at times by its self, the headers are also getting quite hot. It seems the intake is pulling air from somewhere (trick flow R series) all bolts are tight, new gaskets, etc but if you use a slight bit of starting fluid around the upper/lower connection the engine rpm's will increase, possibly a vacume line or something as well picking it up as well but now I need to figure this out and stop this leak and see how it runs. Fuel pressure looks good at idle 34-36 psi but at 3000 rpm drops to the mid 20's

thanks
 

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If you have a vacuum leak your FRP wont read correctly... check the two gaskets that sit on the front and back of the block(lifter valley) I know sometimes those move around on me when I sit the manifold down. Also, the obvious replace worn out vacuum line...
 
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