plug check on streetcar ??

[69chargerR/T]

    I'm installing a 750 double pumper holley carb on my car. How do I do a plug check so I can check how the jetting is. I know on a race car they install new plugs make run or lap shut it down coast or push it back and then check plugs to see how mixture is. How do I check my jetting and fuel mixture on my street car so I know its not to rich or lean


                                                          Thanks, Alan

[firefighter3931]

Alan, take the car out for a 20 minute cruise and stay out of the secondaries....just normal driving. Pull a few plugs and look for some color....black/charcoal is rich, white/light grey is lean....tan/light brown is good. This will take care of your primary jetting.

Secondary jetting is checked with a wide open throttle pass and immediate shutdown. The plug reading should be the same as above.



Ron

[69chargerR/T]

Alan, take the car out for a 20 minute cruise and stay out of the secondaries....just normal driving. Pull a few plugs and look for some color....black/charcoal is rich, white/light grey is lean....tan/light brown is good. This will take care of your primary jetting.

Secondary jetting is checked with a wide open throttle pass and immediate shutdown. The plug reading should be the same as above.



Ron

  Ron, after doing the primary jetting check should I put in new plugs and then do the secondary jetting check ? Also if the primary setting is to rich can I clean the plugs, change jetting drive and recheck or do I need to use new plugs for every change ?

                                                                           Thanks, Alan

[firefighter3931]

Ron, after doing the primary jetting check should I put in new plugs and then do the secondary jetting check ? Also if the primary setting is to rich can I clean the plugs, change jetting drive and recheck or do I need to use new plugs for every change ?

                                                                           Thanks, Alan

Alan,

If the plugs are rich, then clean them up and rejet until you get the primaries dialed in. Once the front side is good and staying clean then move on to the secondaries.

The 750dp should be very close out of the box unless the engine is heavily built. 


I usually dial in the timing curve before moving on to carburation....so make sure the ignition is where you want it before rejetting the carb. 




Ron

[69chargerR/T]

Ron, after doing the primary jetting check should I put in new plugs and then do the secondary jetting check ? Also if the primary setting is to rich can I clean the plugs, change jetting drive and recheck or do I need to use new plugs for every change ?

                                                                           Thanks, Alan

Alan,

If the plugs are rich, then clean them up and rejet until you get the primaries dialed in. Once the front side is good and staying clean then move on to the secondaries.

The 750dp should be very close out of the box unless the engine is heavily built. 


I usually dial in the timing curve before moving on to carburation....so make sure the ignition is where you want it before rejetting the carb. 




Ron

   Thanks Ron, that what I thought, I have mp dis. orange box I know this isn't a great system but thats what I got for now. I have base timing at 12* and total like 37- 38 I have to check what rpm it is all in, I have heard that mp dis. come in to soon. I would like base timing a little higher but I don't know if there is an adjustment for the mechanical advance on an mp dis. I don't run the vacuum advance so I can get the base at 12*. In the future I will be changing ignition system I was looking at the FBO system it sounds good and having them set up my mp dis. Any thoughts on this.


                                                          Thanks, Alan
                                               

[firefighter3931]

Alan, the newer MP distributors have adjustable stops in the advance plate to allow a reduction in mechanical advance. This allows you to dial in more initial and not overadvance. 

I prefer a multi spark box like MSD over the FBO stuff because it keeps the plugs cleaner, longer and starts easier. The Aftermarket boxes also eliminate the ballist resistor. 


Ron

[john108]

Hi
I am new to this and having trouble with the acronyms:
MP - Is this MoPar?
MSD?
FBO?

Right now, my '68 R/T is totally stock and I am about to start restoring/rebuilding it.
Looking for advice.  I will start a new thread later when I know what to ask.
I am the original owner.
John

[69chargerR/T]

Hi
I am new to this and having trouble with the acronyms:
MP - Is this MoPar?
MSD?
FBO?

Right now, my '68 R/T is totally stock and I am about to start restoring/rebuilding it.
Looking for advice.  I will start a new thread later when I know what to ask.
I am the original owner.
John

  John, mp is mopar performance parts, MSD is a company that makes ignition systems,  FBO is also a company that makes ignition systems and other hi performance parts.

                                                      Alan
                                             

[john108]

Alan

Thank You

John