Top End Miss

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Yeah. It's the gears. They're makin it pop. (rolls eyes)
 
if this is an alcohol motor a miss at high rpms will be a lean miss and it doesn't take long to melt pistons with it..can you show a pic of a plug you tune an alky motor by the burning of the thread's on the plug.and champion or NGKs usually work better for this.alky is what we raced on dirt and it cost us allot of money to learn how to tune them.....just trying to help.......Artie
 
godfatherofchry said:
if this is an alcohol motor a miss at high rpms will be a lean miss and it doesn't take long to melt pistons with it..can you show a pic of a plug you tune an alky motor by the burning of the thread's on the plug.and champion or NGKs usually work better for this.alky is what we raced on dirt and it cost us allot of money to learn how to tune them.....just trying to help.......Artie
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its just regular leaded race gas... not alky or fuel
 
O I was skipping thru your thread and seen someone say something about alky my fault for not reading at all..but it still sounds like a lean problem......Artie
 
My cuda was doing the same thing. The distributor bushing and or shaft was worn out. This was a dual point distributor and at high RPM, it would cause the points settings to vary enough to cause problems. I don't know if an electronic pick up (magnetic or infra-red) would do the same.

Switching out a distributor is a heck of a lot easier than alot of the things you have been doing.

Rod
 
I know you've said you pull the air cleaner on occasion... When was the last time you took some aerosol carb clean and blown out the air bleeds? If you dont run the filter, this should be done very often... Just blow directly into and down each air bleed for about 4 seconds.
 
When have you actually took it out and done a bonifide plug read on it? I haven't seen where you posted about that anywhere yet. That will tell the story right quick like.
 
rklein383 said:
My cuda was doing the same thing. The distributor bushing and or shaft was worn out. This was a dual point distributor and at high RPM, it would cause the points settings to vary enough to cause problems. I don't know if an electronic pick up (magnetic or infra-red) would do the same.

Switching out a distributor is a heck of a lot easier than alot of the things you have been doing.

Rod
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i did change dizzy's when i swapped in the MSd box... was just running an ignitor II petronix point conversion in it...

moper said:
I know you've said you pull the air cleaner on occasion... When was the last time you took some aerosol carb clean and blown out the air bleeds? If you dont run the filter, this should be done very often... Just blow directly into and down each air bleed for about 4 seconds.
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i run with the air cleaner off only at the track... but yes i do regularly clean out the air bleeds... also when i do my first jet change at the track i spray thru the ports there to...

StrokerScamp said:
Yeah they made his fuel problem finally show up.
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gonna try a vac 750 carb on it... i think my carb guy has one he will let me test out...
 
I ran the lightest spring I could get in my 750 vacuum, and it ran really well, even though I really needed a higher stall. My car weight was 2,800 and change, 4.86 gears.
 
BBBCUDA said:
I ran the lightest spring I could get in my 750 vacuum, and it ran really well, even though I really needed a higher stall. My car weight was 2,800 and change, 4.86 gears.
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what did it run? and 2800 with or w/o you?
 
Do your self a favor and junk that P.O.S. and buy a CHEVY,,problem solved !!

All kidding aside, I have read and re-read all posts and I gotta say it sounds like a fuel issue. Scamp made a valid point on reading the plugs.Old Harley guys used to jet by the plug readings ONLY.Make a pass(anywere safe) full throttle,when you hit high gear click off the key and drift to a stop pull the plugs and see what they look like.
Gears make it rev faster, sooner,SOOOO how about a fuel pressure reading at high RPM's?
Now this one is just for fun(food for thought)During a B.S. session talking to the guys at Indy Cylinder heads the jetting question came up"how much is enough?"Answer=" if your staging and your eyes ain't waterin' and you still can breath it ain't fat enough !!"
So you said jetting fat made it slow down and still popin,,, it may be fuel delivery as stated before. You runnin' a relay on that pump? Maybe you got a voltage drop.
You tested the ignition and wiring system so I really don't know what to say but anything electrical can die at any time new or not.
I know you can fix this, don't give up or I'll sick MadMax on your a$$.
 
I still think your problem is in the valve train ,but like mentioned read your plugs after a pass to see where everything is at.For the record i have no idea what my timing is set at on my 408 (as i have never put a lite to it) .I set the timing by reading the plugs and did the jetting on the 750 by reading the mph on my time slips...
 
805moparkid said:
what did it run? and 2800 with or w/o you?
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The 2,800 was without me, and there used to be alot less of me... figure 2,975 race weight. I never got that car to the track. From (ahem)
"informal" testing, I'm pretty sure it was in the 14's and mid 90's or so for Mph.
 
BBBCUDA said:
The 2,800 was without me, and there used to be alot less of me... figure 2,975 race weight. I never got that car to the track. From (ahem)
"informal" testing, I'm pretty sure it was in the 14's and mid 90's or so for Mph.
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so your right where i am... good to know....
 
Here's the thing and I am outta this nightmare. If it's shootin ducks at high RPM (and it is) the mutha frigger is RUNNIN lean. PERIOD, end of discussion. Now, as to why is anybody's guess. Ignition not burning the fuel properly at high RPM? Valvetrain not allowing a complete burn? What the hell ever, the sumbitch is leanin out. That's the bottom line.
 
Darter6 said:
Do your self a favor and junk that P.O.S. and buy a CHEVY,,problem solved !!

All kidding aside, I have read and re-read all posts and I gotta say it sounds like a fuel issue. Scamp made a valid point on reading the plugs.Old Harley guys used to jet by the plug readings ONLY.Make a pass(anywere safe) full throttle,when you hit high gear click off the key and drift to a stop pull the plugs and see what they look like.
Gears make it rev faster, sooner,SOOOO how about a fuel pressure reading at high RPM's?
Now this one is just for fun(food for thought)During a B.S. session talking to the guys at Indy Cylinder heads the jetting question came up"how much is enough?"Answer=" if your staging and your eyes ain't waterin' and you still can breath it ain't fat enough !!"
So you said jetting fat made it slow down and still popin,,, it may be fuel delivery as stated before. You runnin' a relay on that pump? Maybe you got a voltage drop.
You tested the ignition and wiring system so I really don't know what to say but anything electrical can die at any time new or not.
I know you can fix this, don't give up or I'll sick MadMax on your a$$.
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what do you mean sick him... he is already all over me LOL...

and when shutting it off wont that screw up the trans? i mean with the pump not running and it still turning?

when i had the pressure gauge on it it read 7-7.5 running and cruising... dropped to 5.5 on launch but steadily came back up thought the run...

as far as jetting they are right when you make ports so big that it runs like crap until you get rpms, kinda the indy way lol...

no reason to keep jettin up if its slowing down...

yes the pump is on a 30amp relay with i think 10ga wiring (pump lead is only like 16 or 14 lol)

The Shocker said:
I still think your problem is in the valve train ,but like mentioned read your plugs after a pass to see where everything is at.For the record i have no idea what my timing is set at on my 408 (as i have never put a lite to it) .I set the timing by reading the plugs and did the jetting on the 750 by reading the mph on my time slips...
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well my rods are good for 400 open pressure, springs are 354 lbs and shimmed as tight as they can be... i can check one of the extra springs to get and exact pressures for my installed height...
 
StrokerScamp said:
Here's the thing and I am outta this nightmare. If it's shootin ducks at high RPM (and it is) the mutha frigger is RUNNIN lean. PERIOD, end of discussion. Now, as to why is anybody's guess. Ignition not burning the fuel properly at high RPM? Valvetrain not allowing a complete burn? What the hell ever, the sumbitch is leanin out. That's the bottom line.
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well i have the wideband gauge and o2 in my hand along with the vacuum gauge... so i'll take a vid with both in view so you guys can see what its doing... also so i can focus on shifting lol...
 
StrokerScamp said:
Here's the thing and I am outta this nightmare. If it's shootin ducks at high RPM (and it is) the mutha frigger is RUNNIN lean. PERIOD, end of discussion. Now, as to why is anybody's guess. Ignition not burning the fuel properly at high RPM? Valvetrain not allowing a complete burn? What the hell ever, the sumbitch is leanin out. That's the bottom line.
Click to expand...

With 600 cfm.
It only needs 390 cfm Max if that.
 
Yea,scamp.couldnt possibly bee gears.Only thing he changed when problem started...I dont know much about anything,,,butt when ya change 1 thing and problems arise,its useally very related to that change.And I dont know much about slants.THINK about change that caused problem.too much gear for his combo.
Guzzi Mark
 
Just throwing out some ideas for you.
Like others have said,You need to read your plugs and while you have them out gap them a little tighter and see what happens.
What model number MSD are you running ? (Some earlier boxes had a problem with 6 cylinders odd fire and even fire,,,If it is a 6200 you are good)
Check the ground connection for the MSD ignition box, If the Heavy Black wire is not connected directly to the battery negative terminal it can cause a breakdown in the ignition at higher RPM.
I know you had the problem before but what if the Valve springs fix the original problem and now you have a high rpm cross fire....
Good luck and curious to see what is wrong ?
 
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