Help! HUGE disappointment at dyno 324 Hp and 372 FT LBS. torque

Today I resprocketed my bike and installed my flush mount signals..So I had only a little time to check a few things on the mustang..Vacuum leaks, plug wires, distributor, etc.

Just going back to basics here - when I built up my 5.0 and ran it for awhile it started bucking, pausing before accelerating etc... I had two burned plug wires that would fire at idle but would arc to the headers under load. Equal length headers are hard on wires. Just make sure you don't have the same problem I did.

I don't know what kind of mufflers the car has but I had fiberglass filled mufflers back in high school that failed and pluged the exit of the muffler... car would run but not very well. If you're running rich you could melt enough fiberglass to allow it to enter the outlet...

Since you've already ruled out a compression issue, it's either fuel or ignition related. The fact that your plugs are black right away tells me you have a fuel issue - way too much of it. Get the wideband O2 sensors working and start tuning... You'll score the cylinders if you run rich for too long so be careful.

I sprayed the wires down with water and found no arching...The look relatively new and have no corrossion on either end..
I've seen plenty of plugged cats and exhausts.... The car doesn't bog down like a plugged exhuast system under load...I have 3" equal lenght headers with a hooker x-pipe and single chamber 3" mufflers...Very loud and unrestrictive..the mufflers are tiny..I'm actually debatting switching to flowmasters dual chamber, just to quiet it up a little...
 
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Sounds like way too much fuel...also, the plug gaps are questionable. I had a very similar issue in my Lightning...turns out the plugs were gapped to large. I think both are contributing to your problem.

Try NGK TR7's...IIRC.

I put those in the L and with the correct gap, they worked awesome.

TR7's are the part #?? How do I know they are the correct heat range, etc for my motor??? I'd be very interested in a chart or information to help me pick the correct plug and gap for my application.



Yo Fella's. Lets look at the basics here. A NON MODDED, Factory 302 H.O. Engine could easily hit 324 RWHP with a D-1 Procharger, let alone a decked and tricked out 351 Windsor. Your Tuning is Extremely Off, If it is a reputable shop they would know this and would atleast help you solve your problem. I feel the problem lies with the Injectors and the ECU, maybe even the Spark Plug gap like someone noted earlier. I'm no engine builder but I really feel, the best thing to do right now, would be checking your code's and do a standard rundown from there.

I'm starting to wonder if this is where I should start digging deeper before throwing a bunch of IGN parts on it.

First thing I would do is pull the distributor itself and put in a stock replacment one that will work with with the 351 swap ........those MSD distributors are well known for causing untraceable problems

The contacts all look good... What makes you think it might be a distributor problem seeing as how the problem happens under any RPM/Load condition while WOT...If it's not WOT it doesn't happen....I'm just curious if this is really worth messing with?


It's about 200rwhp off, something is seriously wrong.
I'd suspect it's the standalone system. Which in most situations it's better for the professionals to handle.

If all you are expecting to run is in the vicinity of 500rwhp, at least drop down to 60's.
The sale of the 80's would fund the purchase of smaller injectors.

+200 would be nice...Personally, if I could hit 450 with this set-up I'd be very happy.. I 'd be satisified with anything over 420....The dyno is brand new and just calibrated, so it doesn't read as high as some of the other dyno shops....Some other shops probably would have shown +30-40 horse on my set-up..The difference I don't know..But I know they are different..
Why would dropping down to 60 lb injectors be any different than dropping the pulse width on the 80's?? Do they have a finer mist?? Once I get the right adaptor's I'll be able to tap into the ecm.


I would be looking at ignition for a few reasons. Ignition module problems could account for not only the running issues, but the starting ones, as well. In fact, I had very similar problems (though on NA engines) in both my 351 Bronco (turned out to be coil), and my 85 Twister II (ignition module X 2). Symptoms were similar to yours both during start and WOT. So, if you have a spare module and / or coil lying around, you may want to try ruling them out before you dump a ton of cash into other theories. I'll warn you that it's very difficult to bench test modern CDI boxes unless you have some pretty decent knowledge of the systems. Accel took back my box for testing twice and gave me the thumbs-up both times (which led me down a very expensive troubleshooting path). Finally, I threw on a stock Duraspark since nothing else was helping, and all my problems were cured. I sent the box back to Accel again, and they finally admitted that the box was bad.
......

A test box would be very expensive for just a test part.....enyawix mentioned something about advance or autozone testing parts...If they can test the box for me, like I said above it's worth a shot....


I guess this is the approach I am going to take...If it sounds ass backwards let me know...

1.) I need to figure out what plug/gap I need....There has to be a method to do this? :shrug: ...
2.) Once I get the right plugs and serial/usb connector I'll datalog my sensors and see if there is anything else the ecm changes with throttle position @ WOT....I'll check my timing to make sure it is where I need to be.
3.)If I don't figure anything out from step 1 and 2 try a new msd box and distributor...(these are expensive test parts, so I'll try this last.) Am I on the right track here? any other recommendations? If anything I should be able to see what's going on with my A/F ratio when I'm getting this problem.
 
Bullitt347, Thanks for the response.

I'm not sure what the timing is at. I'll deifently check it before going any further...
As for the exhaust side, I see where there could be a restrictive issue, but with the exhaust on this thing it's almost like a stright pipe...very unrestrictive...plus this problem hasn't always been their on this build... I was thinking of switching to 3" dual chamber flow masters, but if you think that's to restrictive, I'll stick with what I got..
 
The injectors seem alittle big (any a/f #'s) and same as bullitt347 says you need to find out the total timing. Filter on valve cover cant help ( hot air compressed isnt any good).
My combo aint as wild and I wasn't happy with the dyno #'s I got last week. Not as bad as yours though. Sorry. Your combo should have at least 550 to 600.
 
A good tuner would not have thrown that car on the dyno, got that number and shipped it. It should make well over 500 to the ground. There's something seriously wrong, and he should have noticed and told you. What does the dyno sheet look like? Where's your a/f? He should be able to tell you how much timing is in it too. I wouldn't even begin trying to figure it out without at least knowing what the a/f is. You don't have any kind of gauge or data recording? I'm not gonna say the problem is definitely tune related, but having the car on the dyno should have at least given you a really good idea of what's going on. I would suggest finding another tuner. Where are you located??
 
im assuming since your using a 3 bar gm map sensor sense your using fast setup and i dont see a maf in the picture.

What kind of dyno did the tuner try to check the tune on? If it was done on a non-loading dynojet then it wont be the same as on the road obviously since you saw the change when you drove it. Stand-alone speed density setup's rely on load on the car to determine fuel requirements.

What kind of plugs are you running? Just making sure you are using copper plugs.

Where are you located? Depending on where your located maybe someone can recommend a good local tuner to you.
 
Don't feel too bad, my first pull was 277 rwhp,lol! Blown 302 with out of the box tfs heads,afm B-31HR,holley intake,2.95 pulley, yada yada. Blew the tires off as soon as he hit it,lol. Next pull it still sucked...367. Added some timing via the PMS and again, another **** pull. Some more minor tuning and...417. Found out my timing light is a pos and the base timing was off 6 degrees(suppose to be 10, it was 4). Set it to 10, with no other changes it picked up 73 rwhp! Look at the simple things first!

Another thing, don't get to caught up dyno #'s. Sure, i could have left with over 500 rwhp easily if i pushed it...or just added some methanol to the Mr. Freeze. I'd rather it be extremely safe on the street. Should still run the #'s i'm looking for at the track. :nice: Besides, its still a stock shortblock...i want to get SOME street miles out of it this summer! :lol:

Oh yeah, it will be tuned for the Mr Freeze hopefully this week...and an ABACO DBX meter. :D
 
Bullitt347, Thanks for the response.

I'm not sure what the timing is at. I'll deifently check it before going any further...
As for the exhaust side, I see where there could be a restrictive issue, but with the exhaust on this thing it's almost like a stright pipe...very unrestrictive...plus this problem hasn't always been their on this build... I was thinking of switching to 3" dual chamber flow masters, but if you think that's to restrictive, I'll stick with what I got..

I do not think that the Edelbrock Performer RPM heads would be a restriction until some point after the 500 rwhp level, especially with the exhaust system on your car. My point was more to the use of a more stock size cylinder head. Even with a stock cylinder head, your engine should have made more power.
 
I am going to money on the fact its a tune issue. Clearly there is a problem if its making way more torque then hp with a centrifical supercharger. Figure out your a/f and total timing guessing the problem will have something to do with that. I gained 200 rwhp from tuning. Had to get pushing the timing, total was 32 degrees when it was said and done with a nice and rich a/f very safe tune.
 
On the dyno my A/F is @ about 10.8 to one coming out the exhuast pipe...Problem I'm having is exhaust leaks from the headers, where the headers slip into the 3" pipe and the flanges that bolt to the rest of the exhaust system....I don't really know what my A/F ratio is...I'm sure it's not 10.8:1...

Thanks everyone for all the help I've received.....You've given me a pretty good path to follow.... I'm going to wait for the serial/usb adaptor and buy some better gaskets for the headers/exhaust system and check/adjust the timing.....Hopefully by this time next week I'll have a good idea of my actual A/F ratio and have this problem cured....

Last question is how do I know I'm running the correct plugs?? My current plugs are NGK Racing v-powers... part # 7173...Yes they are copper..
Personally, I've never been a big fan of dual tip plugs......The "v-powers" have only one ground electrode..They are not like bosch platinum +4's....The "v-powers" look like a regulaur plug, except the center of the center electrode doesn't protude evenly with the rest of the electrode. It's shaped like a "V"...
I was thinking of maybe running a hotter plug, but I don't want to burn up the engine either..
Should I stick with the plugs that are in it now and just tune it with these plugs or get a hotter plug then tune it?? If I run a hotter plug I won't be able to lean it out as much...The less fuel in the chamber the better...let me know what you think.
 
obviously something is wrong or you have over looked something

there is another guys who has that same s/c setup and he has a stock bottom end with edlebrock performers, gt-40 intake and he made 515hp and 11 seconds on street tires (obviously more mods, just listed the basics)
 
I think you should definatly try tightening up your plug gap. Besides that check your timing and look in to the datalogs once you get that USB/serial adapter.

See if you can find a tuner who is familiar with FAST as well, because you current tuner has no idea what he is doing with it and has terrible workmanship for letting your car go out the door like that without any useful insight with what needs to be fixed.
 
I missed that it ran great for first 400 miles of ownership. I would check for vacuum leaks, look at cap and rotor, check the pick coil, check the ignition control module at advance or auto zone, and check fuel pressure. A small exhaust leak would not create all of your issues.

I had a very "invisible crack" in my rotor that caused my car to carbon up the plugs very quickly and run poorly. Ended up having to tow the car home before finding the actual problem which I (and 10 other motorheads) misdiagnosed at the race track.
 
im having the pretty much the same problem
do you loose fuel pressure when you turn the engine off
try makeing a pass with the vacume line off the fuel reg plug it off and tell me how it runs
i just tried it today and walah car ran like a bat out of hell
i think i have a leak at one of my couplers
i'v been plauged with this problem for a couple of years so i hear your pain
e-mail me @ [email protected] if you want to excange phone #'s
i think we could help each other out
lata
chris