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Author Topic:   Help Me Out Steve Hendren.....Please...
outlawstock17
Member
posted April 18, 2004 01:25 PM
would fuel fouled spark plugs cause a high rpm miss? the floats stuck on my carb when i first started it at the track. after i got them freed up and got on the track i had a high rpm miss. the engine would get wound up just so far and would start popping and crackling like it was on the rev limiter only rougher. i could "flat foot" it in the middle of the corners without a stumble, but when i got onto the straights and started gaining rpms it seemed like the engine came up to a brick wall and stop pulling rpms....cracking, popping and missing even if i eased out of the throttle when it started missing.

could fouled plugs be the culprit? they're not black, but they are dirty brown and the sides of the tip facing the electrode have "eroded" somewhat. autolite 135's on racing gasoline.

i forgot to add......the day after the races i warmed up the engine and brought it up to the rev limiter in neutral without the misfire, so it only happens under load....

[This message has been edited by outlawstock17 (edited April 18, 2004).]

joetaylor
Member
posted April 18, 2004 02:25 PM
when any spark plug gets fouled it has is limiations as for your problem I would have to say that you spark plugs have seen better days if it were a mooule it would do when you reved the engine without a load on it now the plugs will have a miss with a load if they have been fouled now I'm not steve but have been a mechanic for 14 years and seen alot of this in dayley drivers

change your spark plugsand you willbe fine

outlawstock17
Member
posted April 18, 2004 05:21 PM
thanks joe.....6 race old MSD 6AL and 2 race old blaster2 coil. i was thinking the same thing and just needed a second opinion that concurred. i'll change the plugs for next week. you know how it is diagnosing an "out of the blue" problem. i was about to pull out what little hair i have left!

[This message has been edited by outlawstock17 (edited April 18, 2004).]

Ego Racing
Member
posted April 18, 2004 08:13 PM
Disconnect your tach and see connect a different one and see if the problem goes away. I had a Tach do this once.


joetaylor
Member
posted April 18, 2004 08:51 PM
ego has a point as well but still leanning on the plugs Idon't think that a tach will do that undera load but any thing is posible let me know what you find


outlawstock17
Member
posted April 18, 2004 08:55 PM
i didn't have the tach in the car at the time of the problem. i'll let you guys know if the new plugs clear it up...


sdhnc29
Member
posted April 18, 2004 09:55 PM
Well I would definitely change your spark plug's if they are looking as rough as you describe. But I doubt that the plug's alone are your high RPM miss. Generally a fuel fouled plug will cause a miss throughout the rpm range, and would eventually clear up, somewhat.

I'm really wondering about your "stuck" float situation. It is common, if you have brass float's in the carb, to crush them if the car pop's back through the carb when your trying to start it. This will bend the float, and it will not function properly. This is most common with alky engines, but can happen with gas engines as well. Generally the float will stick open or closed. Either flooding the engine or running it out of fuel. You should investigate the cause of you stuck float problem further.

The popping through the exhaust leads me to believe you have an ignition problem of some sort however. There are of course a number of potential ignition problems that can cause this problem. But the number 1 problem that I run across is this...... If your mag pick-up wire's from the MSD, and the black and orange wire's from the MSD to the coil are running in the same loom, or parallel to each other, this will cause the problem your encountering. This will create induction firing from the coil wire's to the mag pick-up wire's, false triggering the MSD. All this equal high RPM miss. Another thing that causes this would be reverse polarity on the mag pick-up wire's. If you have anything other than the factory MSD wire loom for the mag pick-up wire's (you've rewired them yourself), call or write to me and I'll tell you how to determine the correct polarity. Every other electrical cause is pretty obvious, bad ground somewhere, bad switch, bad plug wire's, black marker pen used on spark plugs for indexing, etc.

You've got the week to check thing's out, so I'd change your plug's as advised in the above post's, and look into your float issue. If you don't find anything wrong there, be sure to check out a few of the thing's that I mentioned. You don't want to go back to the track with the same problem.

Steve

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Hendren Racing Engines
Rutherfordton , NC
(828)286-0780
Check out my other business at www.solemnvow.com A special thanks to jammin for the awesome job he has done for me on this site!!


avila
Member
posted April 18, 2004 10:14 PM
i had an iginition related problem. to sum it up,
a had a battery that was under charged. under load, above 4500 rpm, it would decrease
the voltage at the distributor from 13.5 volts down to 9-10 volts. this caused the miss like you described.


outlawstock17
Member
posted April 19, 2004 05:55 AM
thanks for the replies everyone.

steve, i'm using all the original wiring for the MSD including the ford duraspark distributor adapter and the problem started this last weekend. the whole ignition system is new this season. i'm going to replace the cap and rotor along with the plugs. the tip of the rotor looks a little rusty so i'm getting a new cap and rotor with brass terminals. i should've already had one...

the floats have stuck once before. i believe it was caused from the car sitting too long. it sat outside under a tarp for 2 weeks after a rainout. a couple of taps with the handle of a screwdriver and the floats stopped leaking. the carb is an 830 holley annular discharge. i'm making all the changes i just mentioned plus i'll have a new 750 demon with me to change the carb if necessary. i really like the 830 though.

i'll let you guys know how things shake out.....thanks again.

Raz_900
Member
posted April 19, 2004 02:12 PM
What comp. ratio is your engine? 135s are a little hot for a high comp. engine. I run 134's in a 9.8 355 and 133's (or Accel 263s) in a 10.2-10.3 355. Both use blended 115 race gas with 93 pump gas for a 102-104 mixture.

The eroding of the tip might be hints of detonation or the plug starting to melt if you're running high CR.

joetaylor
Member
posted April 19, 2004 03:22 PM
hey out law one outher question do you have a remote coil? My chevy will breake uo witha stock ign coil on top the the dist the magnetic field would mess with pick up coil just anouther thought

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U LIFT U LOOSE


akadirtracer7
Member
posted April 19, 2004 05:12 PM
Hey Outlaw I've been running the 135's in my 347.i went to practice with last years plugs in it and it run pretty bad it tryed to clean up but didn't completely do so.i put a new set of new plugs in and it runs flawless fron bottom to top.I'd toss a set of new plugs in it and see what it does.Check and make sure you don't have any bad connections or switches in your wiring or water infiltration.


outlawstock17
Member
posted April 19, 2004 07:42 PM
it's a ford, so yes it has a remote coil. AR135's are what towers and harwood recommends for N351 heads on gasoline. compression is about 11:1.

thanks dirtracer7, that's the plan....new plugs, new cap and rotor and a new carb ready to go on it if necessary. your yoke is on the way. i shipped it this morning. i got yours this afternoon and it looks good, thanks.

outlawstock17
Member
posted May 08, 2004 07:38 AM
thanks everyone.....the new plugs cleared it up.


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