Valve float problem?

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brytell

New Member

Feb 5, 2009

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Rio Rancho, NM

Mar 10, 2009

#1

• Mar 10, 2009

• #1

Hello, when I'm cruising in the stang I hear a thump in my exhaust randomly. Could this be a valve-floating problem? My springs do have high mileage. Thanks.

 

oz

Founding Member

Jun 29, 2000

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Plymouth, MI

Mar 10, 2009

#2

• Mar 10, 2009

• #2

It's more likely a 'missfire'. One cylinder is not firing and therefore the unburned fuel/air mixture is getting into the exhaust and burning with a 'thump' as it mixes with exhause from other cylinders.

Valve float only occurs at very high RPM anyway...

 

dcurtis

10 Year Member

Jan 19, 2006

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Mar 10, 2009

#3

• Mar 10, 2009

• #3

oz said:

It's more likely a 'missfire'. One cylinder is not firing and therefore the unburned fuel/air mixture is getting into the exhaust and burning with a 'thump' as it mixes with exhause from other cylinders.

Valve float only occurs at very high RPM anyway...

Click to expand...

 

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brytell

New Member

Feb 5, 2009

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Rio Rancho, NM

Mar 10, 2009

#4

• Mar 10, 2009

• #4

so is it my timing then. I was playing around with my distributor making passes to see if the problem would go away and it did. when i checked my timing. it read 26deg adv. Is this really high timing? I'm running low compression, so could this be why i need such high timing? I'm soon planing on running 17 to 20 psi of boost.
Thanks.

 

dcurtis

10 Year Member

Jan 19, 2006

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Mar 10, 2009

#5

• Mar 10, 2009

• #5

What kind of block do you have? I guarantee you that if you try and push 17-20 psi your block will shatter, and when you checked your timing did you pull the advance?

 

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brytell

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Feb 5, 2009

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Rio Rancho, NM

Mar 10, 2009

#6

• Mar 10, 2009

• #6

Ya, Ill probably get a new block or how about a thick main gridle? How much hp will a stock block handle and how much with a main gridle. ya, i pulled the advance.

 

oz

Founding Member

Jun 29, 2000

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Plymouth, MI

Mar 11, 2009

#7

• Mar 11, 2009

• #7

If you pulled the SPOUT connector and you're still running 26 advanced, I'm shocked that the car will even start... or run without detonation.

Are you sure you pulled the SPOUT?

You should set initial timing around 12 degrees.

Oh yea, are you sure you pulled the SPOUT????

 

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brytell

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Feb 5, 2009

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Rio Rancho, NM

Mar 11, 2009

#8

• Mar 11, 2009

• #8

LOL. Your making me double think if i pulled the spout. I'll have to recheck the timing. What is detonation and how can you tell if it is happening? Thanks

 

Wallzy

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Aug 20, 2006

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Orlando, FL

Mar 11, 2009

#9

• Mar 11, 2009

• #9

This has disaster written all over it, abort, ABORT! - just don't "T-5" your motor.

 

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phutch11

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Nov 14, 2005

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Mar 12, 2009

#10

• Mar 12, 2009

• #10

I'm betting you TFI and or Stator are shot. If they go the computer can't advance the timing and thus the car runs reasonably well with 26 degrees initial timing.

Good luck...

Posted via Mobile Device

 

oz

Founding Member

Jun 29, 2000

1,079

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Plymouth, MI

Mar 12, 2009

#11

• Mar 12, 2009

• #11

phutch11 said:

I'm betting you TFI and or Stator are shot. If they go the computer can't advance the timing and thus the car runs reasonably well with 26 degrees initial timing.

Click to expand...

Just goose the engine (W/ SPOUT out) and see if the timing goes up to about 36 degrees total at 2,000 rpm. If not, phutch11 is probably on to something. Change should be about ~26 degrees (~10 at idle to ~36 at 2,000 rpm).

Detonation = pinging = a loud clatter that sounds like a diesel engine... very bad!!!

 

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brytell

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Feb 5, 2009

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Rio Rancho, NM

Mar 12, 2009

#12

• Mar 12, 2009

• #12

Thanks. Couple of questions: what is goose the engine and what is the Stator?

I just checked the timing and these are the numbers: with spout 38deg adv. without spout 28 deg. adv. could it require this much adv. timing, because of my low compression and the altitude im at. I'm around 5000ft. Albuquerque, NM. Holla! I believe its around 4psi lower then at sea level.

 

oz

Founding Member

Jun 29, 2000

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Plymouth, MI

Mar 13, 2009

#13

• Mar 13, 2009

• #13

When I say 'goose' the engine, I mean quickly open the throttle so the RPM's go up. What is the advance when the engine is running at a constant 2000 rpm.

 

90lxcoupe

20+ Year Stangneter

Oct 7, 2003

3,596

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Mar 13, 2009

#14

• Mar 13, 2009

• #14

sounds to me like your gonna need a 2" thick girdle with your plans...


set the timing to 10 degrees BTDC, if it is really reading 26 degrees with the spout out, your gonna break something, unless you have 120 octane in the tank your not telling us about.

 

B

brytell

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Feb 5, 2009

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Rio Rancho, NM

Mar 13, 2009

#15

• Mar 13, 2009

• #15

I dont know what the heck in going on with my car. I reset the timing back to 12deg and it seems to be running fine. I think the air/fuel is not as rich at a lower degree though. I might need an adjustable fuel pressure regulator to up the air/fuel level. What do you think?

So what is the theory behind timing?

 

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89fiveliter

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Nov 5, 2009

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Nov 30, 2009

#16

• Nov 30, 2009

• #16

Not trying to hi jack your thread, but i have the same issue in california at sea level. seems like we have the same problem. i have a stock shortblock. I can put my timing at 11-12 degrees and it detonates and breaks up after 3k rpm and especially in 3rd and 4th gear. I put it at 15 initial and it runs great. no pinging or nothing. But eventually it will run hot and it seems to retard itself to where it will start detonating like it did with 11-12 degrees initial timing...... I pull the computer advance clip before everytime also. Im interested in hearing about the stator or TFI? Or could it be computer? worn timing chain? i have 200k miles on it.