RPM drop while on Stop
 

Running an APD Max Speed carb with built in stop and ive noticed on my logger that the car will drop roughly 100 to 120 RPMs while on the stop. Is this normal or has anyone else had this issue.

Re: RPM drop while on Stop
 

Max speed a great piece but very finicky imo..

Are you running a 02?

Re: RPM drop while on Stop
 

Not running an 02 just yet, have a set up coming.

Re: RPM drop while on Stop
 

Does the RPM drop coincide with the shift?

Re: RPM drop while on Stop
 

It doesn't appear to coincide with the shift.

Re: RPM drop while on Stop
 

02 is a absolute must for this carb!!! Make sure you place them 12ish” off the head.

More than likely its your front jets.

Re: RPM drop while on Stop
 

Whats your recommendation of what I should try with the front jets?

Re: RPM drop while on Stop
 

I don’t have my log book handy and I only made a few hits last year so I Just can’t remember what way you gonna go for the loss of RPM. Really need to see what the A/F is doing on the stop.

Until you get the O2s I’d play it safe and start by giving it more fuel and see what it does. If it gets worse go down a few sizes from what’s in there now.

For the most part the front jets control what its doing on the stop then you tune the restrictors behind the power valve and rear jets for down track.

Re: RPM drop while on Stop
 

Sent you a PM

Re: RPM drop while on Stop
 

need to go smaller on front jet

what is your current setup? main jets front and rear and restrictor sizing in front?

Re: RPM drop while on Stop
 

What kind of car are we talking about??.. my 27 Roadster has a torsion bar front end, and when it touches down when the stop comes on, it unsettles the floats, and causes an RPM drop similar to yours.. we have tried just about everything to improve it, even putting jet extensions on the front jets.. helped, but not a real fix.. the only thing seems to work for me, is increasing the cruise RPM.. but then you have to add numbers to the timer.. not always a good thing, and can affect MPH if to many numbers are added..

You can also head to left field, and fiddle with the timers and shift points, but don't get lost out there..

The up side is that I can over-lay my graphs, and they are almost identical run to run.. SOOOOO, I dial it, and let go of the button..

Re: RPM drop while on Stop
 

I ran a Max Speed carb on 3 cars for years.....so I do have some experience with them. Before you go changing the whole tune-up on the carb, I think a few simple questions need to be answered first.

1. What rpm are you sitting on the stop at?
2. What is timer 1 set at?
3. What is shift timer at?
4. How quickly is the stop shutting down?
5. Do you have pics of your graphs?