MSD Ignition

[40 Chev Coupe]

I'm currently up grading my ignition system in my 40 Chev. I currently have a points dist. and coil. I'm putting in a MSD Ready To Run dist. with a MSD Master Blaster coil. The motor is probally a stock SBC 350.
My question is do I change the plugs to a hotter or colder plug or leave them alone? Also, do I need to change the gap, and what to?

[wayne petty]

what are you running currently?

msd will fire almost anything..

0.035 to 0.045 is a good gap...

spark plugs have to be examined for their proper heat range to burn off the carbon deposits from  the center electrode..

if you have not already removed the existing distributer..

and its running good.. you might want to take you adjustable timing light and check out where your base timing is currently...

take the engine to 3000 rpms and see the max advance with the vacuum advance hooked up...

then disconnect the vacuum... plug it..   take the engine back to 3000 rpms and see how far the mechanical advances..

if you have a tachometer.. either hand held or dash mounted.. use your timing light to look at the marks with the vacuum advance disconnected.. see if you can figure out what speed the advances starts and stops..

dash mounted.. a friend can help as you slowly rev the engine.. stop increasing as when the advance stops moving ask for the RPMs...

this will give you enough to chart where the advance curve should be..  for your application...

i don't know which curve the MSD comes with out of the box...

lastly...  please.. verify the engine to firewall ground connection is intact.  almost all parts stores have a $5 15" braided ground strap..    you will also want to verify that the power wiring to the MSD unit is larger than with the points... so the MSD does not run at reduced voltage which would cause it to run at higher amps than its designed for..
the MSD uses more current.. and on the external box units run significantly increased voltage to the coil positive to decrease the time needed to saturate the primary windings of the coil..

i am only trying to head off a failure with the proper ground connections...  as the alternator puts out current into the block and it has to get to both the body and the battery negative... lack of a engine to body ground strap.. may result in higher negative voltage on the engine block.. causing issues..

[oj]

Just to reinforce what Wayne has said, the sparkplug heat range deals with heat in the combustion chamber...if your motor runs a little too hot in the summer you can switch to a 'colder' plug and that will remove heat from the engine.  
It has nothing to do with ignition.

[wayne petty]

spark plug color chart

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

this is for FULL THROTTLE shut off and tow back to the pits type of tuning

http://www.enginebasics.com/Engine%20Basics%20Root%20Folder/Reading%20Spark%20Plugs.html

i have not seen these in a while..

http://www.carbtune.co.uk/colortune.html

but using an oxygen sensor and an air fuel ratio display will get you even closer...  allow one to monitor the air fuel ration from idle.. thru idle transition to the mains.. and then back to extended cruise where the engine is operating on part of the idle transition and part of the mains..  1500 to 2200 rpms..


and this.... even though this is from a mopar mag.. its the same theory..

http://www.moparmusclemagazine.com/techarticles/mopp_0612_reading_spark_plugs/viewall.html

[chimp koose]

Just a warning about tuning with an A/F meter. Get your tune up close by plug readings first especially in regard to optimum ignition timing before relying on the A/F meter . Late ignition timing will cause a lean reading . I have seen guys at the drag strip try and get a tune up straight off the A/F meter and get way off.Also when wiring in the MSD do not put power to it through a relay.I have seen a really weird ignition problem that would occur at specific rpms traced back to a firewall mounted relay that would vibrate when the engine reached a certain rpm and cause interrupted power to the msd.When the relay was removed problem was gone.

[1800guy]

" when wiring in the MSD do not put power to it through a relay"

Correct me if I'm wrong, please - but I would suspect a quality or condition problem with the relay in question in the example.  I would think a good relay would be the best way to assure proper voltage.  Or not?

[chimp koose]

This relay was mounted on the firewall. vibration caused it to cycle on and off. 609" BBC on alcohol lost a head gasket as a result.I would not run a relay .

[dirt t 2010]

Thank you for posting your answers. I have learned a lot reading them.
Terry

[Topsterguy]

what are you running currently?

msd will fire almost anything..

0.035 to 0.045 is a good gap...

spark plugs have to be examined for their proper heat range to burn off the carbon deposits from  the center electrode..

if you have not already removed the existing distributer..

and its running good.. you might want to take you adjustable timing light and check out where your base timing is currently...

take the engine to 3000 rpms and see the max advance with the vacuum advance hooked up...

then disconnect the vacuum... plug it..   take the engine back to 3000 rpms and see how far the mechanical advances..

if you have a tachometer.. either hand held or dash mounted.. use your timing light to look at the marks with the vacuum advance disconnected.. see if you can figure out what speed the advances starts and stops..

dash mounted.. a friend can help as you slowly rev the engine.. stop increasing as when the advance stops moving ask for the RPMs...

this will give you enough to chart where the advance curve should be..  for your application...

i don't know which curve the MSD comes with out of the box...

lastly...  please.. verify the engine to firewall ground connection is intact.  almost all parts stores have a $5 15" braided ground strap..    you will also want to verify that the power wiring to the MSD unit is larger than with the points... so the MSD does not run at reduced voltage which would cause it to run at higher amps than its designed for..
the MSD uses more current.. and on the external box units run significantly increased voltage to the coil positive to decrease the time needed to saturate the primary windings of the coil..

i am only trying to head off a failure with the proper ground connections...  as the alternator puts out current into the block and it has to get to both the body and the battery negative... lack of a engine to body ground strap.. may result in higher negative voltage on the engine block.. causing issues..

Excellant points, WP, especially about the ground strap! Thanks!