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Author
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Topic: Sure could use some help on this cleveland
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prostreeter
Gearhead Posts: 157
From: littleton,co
Registered: Mar 2005
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posted 08-22-2005 12:29 PM
   
I've got a stumble or what I would call a "miss" at high rpm's,between 5 and 6k.I do spin the motor to 7000 to 7400.The motor is new and maybe 600 miles on it.Everyting on the motor is new,ie...pro billet dist,msd wires,plugs which are NGK 7.The only items that are old (5 years) is the msd 6al box and blaster coil.Timing set at 40 degress total advance.Running a 1000hp holley with jets of 92/96 with blocked rear power valve.This motor has no vacum plugs.For those of you who are not familiar with the motor it's almost 14:1 comp street/race engine.I've been trying to figure out this problem since march and getting really po'd.Any thoughts/suggestions would be greatly appreciated!
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grego37
Gearhead Posts: 365
From: los angeles,CA,USA
Registered: May 2004
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posted 08-22-2005 12:56 PM
Do you mean a 1000 cfm Holley?Are you sure the carb isnt too big? I was told when you block the power valve up the rear 6 jet sizes to be equal
If thats the case, you have 92/91 jet sizes?
maybe add more jetting to the secondaries? did you do the plug read test?
http://cochise.uia.net/pkelley2/sparkplugreading.html
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steve'66
Gearhead Posts: 9489
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 08-22-2005 08:03 PM
Power valve is worth 6-8 jet sizes.Also, with all the money you have in this engine you may want to spend a few hundred for a dyno tuning session.  SteveW
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jhss2289
Journeyman Posts: 39
From: Pensacola, Fl. USA
Registered: Nov 2003
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posted 08-22-2005 10:44 PM
Had similar proplems. You need to borrow
a good 750 or 850 out of the box carb and try. Also double check for intake gasket leak, don't assume, pull and look good!
I feel the carb is to big and to much jet!
Good Luck! FordDoc, Jessie
PS: you may tune-up to a larger cfm, but you
need a for sure good 750-850 to test.
[email protected][This message has been edited by jhss2289 (edited 08-22-2005).]
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prostreeter
Gearhead Posts: 157
From: littleton,co
Registered: Mar 2005
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posted 08-22-2005 10:45 PM
Grego37...
Yes the carb is a holley 4150hp series 1000cfm carb.I dont think the carb is too big.I beleive this holley came 84 squared from the factory.That's why I changed the jets to 92/96.I have read the plugs with a lighted magnify scope and they look great.And Steve,your right.I do need to dyno test the motor but just have'nt done it yet.Thanks for the advise guys.Your thoughts and opinions are always welcome.
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kid vishus
Gearhead Posts: 6405
From: middle of NC
Registered: Oct 2000
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posted 08-22-2005 11:13 PM
It came with 84's stock and you jetted it up 8 numbers in the front? That sounds like way too much to me. I would probably be inclined to stick the jetting back the way it came and try that first. Or, if you want to leave that much jet in it, plug the front also and leave the jetting alone. My motor picked up decent power on the dyno when I plugged the front powervalve. You'll know as soon as it leaves the line if it's too lean, it will have a lean miss. If it misses, lift right away and you wont hurt anything. I would do either of the above mentioned things first. They are free and easy to do.
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JJonesy99
Journeyman Posts: 97
From: Lakewood, CO USA
Registered: Jan 2005
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posted 08-23-2005 10:50 AM
Carz custom dyno @ 14th and wads (mad caps racing)is a great dyno. Lucas and Tom are great and willing to help you out with your car. Its 3 pulls for $85 but when I went last week they gave me 5 pulls for $85. There web site is www.carzcuststom.comJason ------------------
66' stang, 408W, C4, 4.11 gears, 12.08 1/4 @113mph, DAILY DRIVER
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Hans olsson
Gearhead Posts: 718
From: Sweden
Registered: Apr 2000
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posted 08-23-2005 11:53 AM
quote:
Originally posted by prostreeter:
I've got a stumble or what I would call a "miss" at high rpm's,between 5 and 6k.I do spin the motor to 7000 to 7400.
What happens after 6k? If the power is back then, you could have a problem with valvespring harmonics. Hans ------------------
- VIN 1F05M139343
- 71 Mach 1 Ram-Air
- 351C 4V 285 HP
- F-G/Stock Aut
- Stockers are way cool!
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prostreeter
Gearhead Posts: 157
From: littleton,co
Registered: Mar 2005
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posted 08-23-2005 12:16 PM
Yup,that's right Hans.
After the motor gets thru the stumble and the rpm exceeds 6k,it will rev to the moon without any problems.I really was'nt thinking valve springs as the problem,but it could be.It seems as though when the stumble occures it's as if the motor is running out of fuel.Float levels are fine though.I know that i need a new fuel cell or perhaps mine needs cleaned out.The reason I say this is the filter that is before the fuel pump is getting clogged with very tiny,real tiny debris that look like BB's.
Could this fuel delivery system be causing the problem?
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Hans olsson
Gearhead Posts: 718
From: Sweden
Registered: Apr 2000
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posted 08-23-2005 12:21 PM
Change the spring pressure or change to a different brand of springs.Hans ------------------
- VIN 1F05M139343
- 71 Mach 1 Ram-Air
- 351C 4V 285 HP
- F-G/Stock Aut
- Stockers are way cool!
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prostreeter
Gearhead Posts: 157
From: littleton,co
Registered: Mar 2005
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posted 08-23-2005 04:13 PM
Hans,
the springs that I have were recomended by Crane.They sat me up with the cam,springs,push rods,etc and all were supposed to work together for my combo.If the springs are the cause,could you give me a recomendation as to the springs/pressure I should get?
Thanks.
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Hans olsson
Gearhead Posts: 718
From: Sweden
Registered: Apr 2000
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posted 08-23-2005 04:44 PM
Tell me about your setup.
Springs lifters pushrods rockerarms...Hans ------------------
- VIN 1F05M139343
- 71 Mach 1 Ram-Air
- 351C 4V 285 HP
- F-G/Stock Aut
- Stockers are way cool!
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