Tuning

1980RS

Veteran Member
Jun 17, 2006
6,004
MN
Best thing I have found for stumbles is the Thomson power plate, it's a little pricey but they work and at the track they work super good.
 

G72Zed

Veteran Member
Sep 8, 2015
3,757
Canada
Newest update: Changed nozzles. Went up and down,28-37.It has 35 in it. Changed cam from green to orange, Changed screw on cam from spot 1 to spot 2. Adjusted the accelerator pump, main and secondary so there in no play. Next I guess I have to check the main jets and the timing.

Good work, but your guessing. If you reversed your working order, you will have better luck, and accurate feedback of what the engine & induction actually needs.

1- timing, initial-centrifugal, then vacuum advanced to get the proper settings/curves.
2- Idle
3- Transition
4- MJ - cruise
5-PV
6- PVCR's - WOT
7- Pump cams - shooters
 

serpent710

Veteran Member
Jul 6, 2007
946
Fort Lauderdale, Florida
Good work, but your guessing. If you reversed your working order, you will have better luck, and accurate feedback of what the engine & induction actually needs.

1- timing, initial-centrifugal, then vacuum advanced to get the proper settings/curves.
2- Idle
3- Transition
4- MJ - cruise
5-PV
6- PVCR's - WOT
7- Pump cams - shooters
Will work on timing this weekend but that is the order in which we got to where e are now. I don't know what #4,5 or 6 are lol
 

G72Zed

Veteran Member
Sep 8, 2015
3,757
Canada
Good to hear, hope all goes well for you. Sorry about that, too many acronyms.

4- It's the main jet, and set's the cruise AFR's if your into them
5- Power Valve opening point based on part throttle cruise signal
6- Power Valve Chanel Restriction's - Use to re-establish WOT AFR
 

G72Zed

Veteran Member
Sep 8, 2015
3,757
Canada
Did not touch the distributor yet. Car starts right up and does not diesel after shutting off. Pulled front bowl and I have 72 jets in it. Do you guys think its to much or not enough?

FWIW those carbs are sold as having an "enhanced fuel curve" and "optimized street-strip" calibration for light weight manual trans or auto's with high stall converters and low gearing.

That being said, those "Ultra" DP come with a 63 main jet and a 73 secondary jet, so yes, you are to much. Most "regular" 650's, straight or down leg, like around a 68-72 front jet pending other details/specs. Those "Ultra" carbs are setup different.
 

serpent710

Veteran Member
Jul 6, 2007
946
Fort Lauderdale, Florida
FWIW those carbs are sold as having an "enhanced fuel curve" and "optimized street-strip" calibration for light weight manual trans or auto's with high stall converters and low gearing.

That being said, those "Ultra" DP come with a 63 main jet and a 73 secondary jet, so yes, you are to much. Most "regular" 650's, straight or down leg, like around a 68-72 front jet pending other details/specs. Those "Ultra" carbs are setup different.
So what do you think, Go down one or more?
 

G72Zed

Veteran Member
Sep 8, 2015
3,757
Canada
Go back to what the carb came with and was calibrated for, so 63 in the primaries and 73 in the secondaries. I always get the right timing dialed in with the right plugs before ever getting at the carb mods/changes.

Need to start from a set baseline. Those Ultra's have a unique Emulsion package and don't have changeable air bleeds, so your limited with that model to a point.
 




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