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

I would recheck the carb,sounds like something plugging a jet.It could be a vacuum leak in the intake gaskets.

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"

have you ruled out weather?

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.

I’ve looked at records in the log book and similar conditions it’s about 9 slow from those conditions.

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.

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,

Make sure cam timing hasn’t changed. Like a broken dowel pin letting cam retard.

Borrowed converter ended up being broke! Swapped in another converter, all good. Ran exactly what it should based on similar conditions.

Good deal