no power

pvicari · #1 (**permalink**) 09-23-2003, 05:34 PM

someone please help!!!!
I have a 351W in my cobra and am having trouble with power above 3000RPM. I replaced the ignition system with an MSD 6AL, MSD distributor, cap and wires. Ever since I changed this, I can not get any high end power. I regapped the plugs as MSD said and this has not helped. I checked the timing and it is dead on. I checked the plugs and three of them show carbon buildup, the remaining 5 look perfect. The three with carbon are 3, 4, and 7. I checked the compression in all the cylinders and they are all consistant. If I accellerate slow it seems fine but if I jump on it, it bogs down and really bogs down at hiway speeds.
Any help in diagnosing would be extreeeemmely appreciated.

JFBucy · #2 (**permalink**) 09-23-2003, 05:45 PM

Just a thought.

Did you recurve the dist. ?
New they come with two heavy centrifugal advance springs.Total advance won't be all in until around 4,500 rpm.
Try one light and one medium spring.It should be all in around the 2,500 range. Then set the ignition for total timing and then use the initial advance as just a reference.

HighPlainsDrifter · #3 (**permalink**) 09-23-2003, 05:51 PM

Hi,
You probably have the timing retarded about 6 degrees.
Recheck it with the vacuum disconected and try it at 14* btdc.
Perry.

pvicari · #4 (**permalink**) 09-23-2003, 06:36 PM

I did recurve the distributor, i am pretty sure I have a large and small spring. I just checked the timing and I am at the heavy check mark on the damper. Reading timing is hard in the cramped space. I have tried moving the timing by a vacuum guage but I was never really sure where it was set.

Tinker51 · #5 (**permalink**) 09-23-2003, 11:33 PM

I have seen something similar with a friends jet boat once. Same symptom. No power above about 2800 RPM if you tried to get there quickly. If you eased into it the motor ran ok, not great but ok. After a TON of ignition diagnostics we found that there were no jets installed in the secondaries so when they opened up it was dumping way too much fuel. This was an old carb he had around so we never really looked that hard at it before installing it. We laughed like hell because we had exhausted all ignition possibilities (two days work) and out of sheer desparation we cracked the bowl on the carb and found the jets missing. If you have gone clear through the spark then you might have a fuel problem.

trularin · #6 (**permalink**) 09-24-2003, 05:40 AM

Sounds like ignition timing. However, a restricted exhaust can do this as well.

Just another thought

Wade Chamberlain · #7 (**permalink**) 09-24-2003, 06:58 AM

Check to make sure you used the correct firing order for your cam. Your 351W could have a 351 or 302 cam in it. If you chose the wrong firing order when you reinstalled the plug wires, cylinders 3,4,5 & 7 would be out of order. This jives with the fact that you're showing excess carbon on 3,4 & 7.

351W & 302HO === 13726548
302 (non HO) === 15426378

pvicari · #8 (**permalink**) 09-24-2003, 06:16 PM

I've had the carb open because I replaced the bowl seals. I still think it is a timing issue but I have adjusted it many times and just can't seem to make it go away. I tried the other firing order just to see if it possibly had a 302 cam in it. I couldn't even get it to run using 13726548. I thought about an exhaust restriction but I have headers and I tapped on the two tubes with a rubber mallet and it sounds pretty hollow. From everything I read, I thought changing the firing order would fix it but it didn't. I will keep trying anything.
One question on the Ford engines, if I am off by a few degrees on the timing, does this make sense that these three cylinders would look like they are mis firing.

zipzip · #9 (**permalink**) 09-24-2003, 06:39 PM

Have you checked which rev limiter chip is in it? Little white plastic piece on the side with a number on it - that indicates the rev limit. There is a 3000 rpm chip....

pvicari · #10 (**permalink**) 09-24-2003, 06:52 PM

yep, I have the 7000 in it right now. I tried a couple of the pills to see if one was bad. I even took the MSD back and had it tested and it was fine.

KobraKarl · #11 (**permalink**) 09-24-2003, 07:44 PM

PV,

any chance your floats are set too low?

KK

Wade Chamberlain · #12 (**permalink**) 09-25-2003, 06:38 AM

Another possibility...still looking at the firing order thing. Make sure you're numbering the cylinders correctly. Easy to goof up if you're not a die-hard FORD guy. 1 thru 4 are on the passenger side, starting at the front. 5 thru 8 are on the driver side, starting from the front.