Supercharged and DEAD at 3000rpm

5ohjoe87 · Mar 10, 2004

Hey I need some help . i have a 1987 mustang gt converted to mass air with a gt40 iron head long block, e303 and gt40 intake, 24# squirters cl 73 mass air meter with sample tube for 24#.I just added a powerdyne supercharger bd11a with a 11lb pulley. The car also has a msd 6al ignition and jacobs ultra coil with a gss 340 255 lph brand new fuel pump. However when cruising
the car will not run past 3000rpm . The symptoms are its dead at 3000 rpm and 5 pounds of boost showing on the guage no more gain in rpm even if the pedal goes to the floor and she is trying to go but can't and sputters and bucks sounds like alot of misfiring cylinders dit dit dit dit sound from under the hood during this 3000 rpm problem but the car runs smooth as can be below 3000rpm I have no clue whats going on I just had the fuel pump replaced yesterday. The fmu is 10 :1 and is hooked up . PLease help this is frustrating I Should have enough fuel and timing is set at 6 degrees any suggestions on getting rid of the fmu and what size injectors i need will help .

five_o_stang · Mar 10, 2004

i dunno what it is...but search the posts for similar problems w/ superchargers....i've seen this problem before.

IndyBlk5.0 · Mar 10, 2004

alls i know is 24 pound injectors are too small for your setup especially with your blower... I bet thats your problem

gt50stang89 · Mar 10, 2004

I dont know if this has anything to do with it but i think ur supposed to use an 8:1 with 24lb's. You should go up to at least 30's with 11lbs of boost. I would recomend just getting 42's and ditch the fmu.

alanw6 · Mar 10, 2004

Any idea of what your spark plug gap is? If it is still stock, I'd bet you are experiencing spark blowout.

Your symptoms are identical to mine when I first put my s-trim on. The plugs were at the stock (.050ish) gap, and once it was reduced to .035, problem solved.

This was with a 6al/tfi blaster coil/new cap/rotor also. I thought the improved ignition would help, but decreasing the gap was indeed the fix for my problem.

Good luck!

Alan

5ohjoe87 · Mar 11, 2004

The plugs are gaped at 0.40 and are ford motorcraft awsf42c the plugs I was going to drop down to are colder plugs awsf22c or awsf32c motorcraft plugs. I was wandering if the 22c or 32c plug will fit the gt40 iron heads since the1993 cobra uses awsf32c plugs. I am going to change the wires also to see if this helps . Kinda stinks to have a car that can't run past 3000rpm but is smooth below 3000 rpm. I was wondering what would happen if I took the vacum hose off the adjustable bbk regulator would this get me more fuel to the engine? I Know the injectors sound small but the book called 5.0 ford dyno tests built a 400 hp at the flywheel motor using 24 pound squirters and a 10:1 fmu and the gt40 iron head engine the book sells at borders. I AM thinking of ditching the fmu and getting a t rex with 42 lucus injectors kinda expensive though .

gt50stang89 · Mar 11, 2004

Ive seen the 42lb's go on ebay for less then 200. Then ive seen used ones go for 275 also. Just lucking out i guess. I would def. find used ones and just replace the o-rings to keep costs down. What maf are you using to because you will have to match that up to the injectors as well...

SmockDoiley · Mar 11, 2004

42's are way too big for that combo. Youd be running too rich. This may sound stupid but you said you have a 6al ignition box which has a built in rev limiter. Those things come with 3000k rpm pills so double check that. Being just an iron head 302, I would go with 30's because 42's are just way too large.

sleeper89 · Mar 11, 2004

definitely sounds like an ignition issue to me. either you timing is way out of whack (but you said it's been checked), or you're getting blow-out as mentioned. i'd close down your gaps to ~.030-.033 and see if it helps. also, in the future you might want to consider iridium plugs. they're supposed to be great in boosted apps.

-steve

93cobra12 · Mar 11, 2004

sounds like you need to change our ur spark plugs and do some tuning !

5ohjoe87 · Mar 11, 2004

I pulled the plugs and regapped from 0.40 to 0.30 and during this the last spark plug cylinder number 4 on the pasenger side rear well, let's just say were in the hell did the electrode and insulator go the whole lower firing end was gone. The other plugs were fine and the cap and rotor also were ok . I Just remembered that that plug was a bosh platnium 2544 and I HAD not changed it over because it is a pain to get to. Would the plug have caused any of this because the cylinder was dead? MY msd 6al has been connected for two years and before the blower i had no problem hittin 5000 rpm or redline . I will see what happens on friday as long as theres no snow here in pittsburgh. Dose anyone run with the rail mounted fuel preasure regulator disconected from vacume just curious ?

mustangdaren · Mar 12, 2004

gt50stang89 said:
I dont know if this has anything to do with it but i think ur supposed to use an 8:1 with 24lb's. You should go up to at least 30's with 11lbs of boost. I would recomend just getting 42's and ditch the fmu.

8:1 disc to run it on the lean side with 24's and 10:1 disc to run it on the rich side with 24's

mustangdaren · Mar 12, 2004

5ohjoe87 said:
The plugs are gaped at 0.40 and are ford motorcraft awsf42c the plugs I was going to drop down to are colder plugs awsf22c or awsf32c motorcraft plugs. I was wandering if the 22c or 32c plug will fit the gt40 iron heads since the1993 cobra uses awsf32c plugs. I am going to change the wires also to see if this helps . Kinda stinks to have a car that can't run past 3000rpm but is smooth below 3000 rpm. I was wondering what would happen if I took the vacum hose off the adjustable bbk regulator would this get me more fuel to the engine? I Know the injectors sound small but the book called 5.0 ford dyno tests built a 400 hp at the flywheel motor using 24 pound squirters and a 10:1 fmu and the gt40 iron head engine the book sells at borders. I AM thinking of ditching the fmu and getting a t rex with 42 lucus injectors kinda expensive though .

awsf32c will work. That is what I switched to with my gt40 heads after installing the supercharger. They are gapped at .040 right now with no problems. I have heard people go a heat range colder and gap .036 but as long as it is working i'll stick with it. As for the 42lb injectors you can ditch the fmu but seems most people have low rpm rich problems without a custom chip. I have 42's but have not installed them yet due to saving for a custom chip just in case I do run into problems. I would probably be just as happy going with 30's and keeping the fmu. The driveability is so good with the 24's that I almost dread taking the chance with 42's.

sleeper89 · Mar 12, 2004

5ohjoe87 said:
I pulled the plugs and regapped from 0.40 to 0.30 and during this the last spark plug cylinder number 4 on the pasenger side rear well, let's just say were in the hell did the electrode and insulator go the whole lower firing end was gone.

sounds like detonation ate that plug. what heat range was it?

-steve

BarnesGN · Mar 12, 2004

Just tossing in my 2 cents, have you checked your fuel pressure at idle and at 3000rpm or WOT?

Silentst2000 · Mar 12, 2004

Check your Rev limit chip. Make sure you don't have your 3 grand in there and swap it out with a different chip if it isn't to be safe. Your ignition starts to fire every other cylinder if it thinks you are at the targeted limit range.

87AODGT · Mar 12, 2004

I would also check for a pinched return line to the tank seeing as how the pump was just done recently, I pinched mine when I did the pump in my first stang, and it would run pig rich because the fuel was getting backed up. got new lines, ran them where they wouldn't get pinched and it ran fine after that

5ohjoe87 · Mar 12, 2004

The car is running even worse with the plugs gapped at 0.30 I replaced the blown plug in the number 4 cylinder . I pulled the cap and checked it again damn rotor tip and terminals are burned i.e have black track around the distributor cap. I seem to be burning caps and rotors every 2000 miles! the msd6al has the 6000 rpm pill installed also. I am going to change out the plug wires to see if they are the culprit the wires are accel 300 race wires and are of unknown age. Could crappy old wires keep causing the cap and rotor to be burned I just sanded some carbon off before when the car ran like crap missing. It seems that the cap and rotor are burning up warp speed fast. Anyone who ever used the jacobs ultra coil in here have this problem . I always apply dielectric grease to the rotor tip to prevent arching. My fuel preasure is at 45 psi at idle at wideopen throttle the car misses now all the way to 3000rpm but fuel shows 40 psi at 3000 rpm and the cyberdyne rich lean indicates 14.7:1 air fuel at wot seems kinda lean .

Ranchero5.0 · Mar 13, 2004

Will it rev clean without boosting? If not I'd bypass the MSD and put a stock coil back on and finally get a set of Autolite wires $24, then set the timing to 10 degrees and run it up around 5k without boosting it.

Jacob's stuff seems to run well if you use all Jacobs stuff. Accell is just plain junk IMO. Had a guy i work with stop by last week and wanted me to work on his stang as a friend (too damn cheap to pay for good work) Poor idle quality missing, just plain running bad. Told him to toss the Accells. He did a few weeks later after putting about $500 into everything else without success and it fixed it.

Jamie

Ranchero5.0 · Mar 13, 2004

BTW, I run 14 degrees advance with a timing retard set at 1.5 degree's per PSI, all Crane parts except the FMS wires and autolite 2934 plugs.

Fuel is kept at 44psi less vacuum.

Supercharged and DEAD at 3000rpm

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