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DRR Sportsman
posted
Throttle response is great free revving, under a load it struggles to rev. Developed out of no where. Car usually runs low 4.80s @ 143. Slowed up to 4.90s at 141 over night.

I’ve changed plugs, wires, cap and rotor, crank trigger pickup, coil, bypassed the grid controller, swapped ignitions, went thru carb, changed converters, verified timing. Verified voltage at the ignition.

Help! Lol
 
Posts: 560 | Location: somewhere between been and never was | Registered: November 03, 2002Reply With QuoteReport This Post
DRR Trophy
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I would recheck the carb,sounds like something plugging a jet.It could be a vacuum leak in the intake gaskets.
 
Posts: 106 | Location: Indy | Registered: April 08, 2008Reply With QuoteReport This Post
DRR Top Comp
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quote:
Originally posted by I Hate Dragsters:
Throttle response is great free revving, under a load it struggles to rev. Developed out of no where. Car usually runs low 4.80s @ 143. Slowed up to 4.90s at 141 over night.

I’ve changed plugs, wires, cap and rotor, crank trigger pickup, coil, bypassed the grid controller, swapped ignitions, went thru carb, changed converters, verified timing. Verified voltage at the ignition.

Help! Lol


Post an image of each racepak graph "4.80's 143"
and "4.90 141"
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Elite
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have you ruled out weather?
 
Posts: 13522 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post
DRR Sportsman
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I don’t have the graphs (Car at the track, I’m not right now) handy but launch rpm fallback are 300ish tighter. My original thought was converter.

I’m going to swap carbs just to rule it out fore sure when I get back.
 
Posts: 560 | Location: somewhere between been and never was | Registered: November 03, 2002Reply With QuoteReport This Post
DRR Sportsman
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I’ve looked at records in the log book and similar conditions it’s about 9 slow from those conditions.
 
Posts: 560 | Location: somewhere between been and never was | Registered: November 03, 2002Reply With QuoteReport This Post
DRR Elite
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similar means nothing. logging exact weather data points and knowing how it effects your car is critical to dialing. Here in the northeast a dragster on gas will swing more than 1 tenth, 2 MPH and .03 in 60 foot. The typical door car on gas will swing 3 tenths, 3 MPH and .05 in 60 foot from the best to the worse air over the course of a full season at the same track in the 1/4 mile.
 
Posts: 13522 | Location: NJ | Registered: August 20, 2000Reply With QuoteReport This Post



DRR Top Comp
posted Hide Post
quote:
Originally posted by I Hate Dragsters:
I don’t have the graphs (Car at the track, I’m not right now) handy but launch rpm fallback are 300 tighter. My original thought was converter.

I’m going to swap carbs just to rule it out fore sure when I get back.


Your original thinking is right, converter, or down on power. But now you have ruled out converter. What about converter pressure? Do you log converter pressure?

Beause you've already swapped converters, you're down to converter pressure which is a function of the transmission in the terms we're speaking, or power. 300 rpms is 50 hp, maybe a little more than 50. I'd leak it compression test for any indication of how it could lose 50hp. Look at converter pressure, if you log it too, could be a stator tube turned. Is it spragless or sprag converter? Mechanical diode (one way clutch converter) is a little more abusive on the tube.

If it's 300 less stall now and you've ruled out a faulty operating converter, it's power or pressure to tighten stall down 300 rpm.

This message has been edited. Last edited by: Mike Rietow,
 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
DRR Trophy
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Make sure cam timing hasn’t changed. Like a broken dowel pin letting cam retard.
 
Posts: 102 | Location: Work | Registered: April 12, 2010Reply With QuoteReport This Post
DRR Sportsman
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Borrowed converter ended up being broke! Swapped in another converter, all good. Ran exactly what it should based on similar conditions.
 
Posts: 560 | Location: somewhere between been and never was | Registered: November 03, 2002Reply With QuoteReport This Post
DRR Top Comp
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Good deal

 
Posts: 9398 | Location: Madeira Beach Fl. | Registered: June 12, 2018Reply With QuoteReport This Post
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