verano29

For those of you running Dart Pro1 heads what spark plugs are you using. Dart recommends the following:

1)Autolite 3934
2)NGK FR5
3)NGK BKR6E

The NGK FR5 appears to be an c4 ZR1 spark plug and the autolite 3934 just appears to be a class of spark plug.

So to make sure that I order something that will fit, what spark plug/part number are you using?

LOUDMAN

I went with the NGK BKR6E. even though its only a slight bump in compression i just wanted a colder plug. The FR5 wouldnt be a bad choice either their just a gasketed TR55.
Personally i wouldnt use an autolite in a GM but im shure its a good plug. Dart just gives you a couple of choices because they require a gasketed plug as apposed to the conical sealed plug that the stock head uses.

vettenuts

iTrader: (4)

Here's an old thread where the folks from Dart participated when they still were on this forum. Lots of good information. I would step down one heat range myself (e.g., TR6). I am running a gasket plug, Denso Iridium IK-20, which is one range cooler than stock.

Link

405HP_Z06

iTrader: (11)

I used an NGK BKR6EIX-11, which is one heat range colder than stock. If you use Autolite, here's the numbers/heat ranges:

3924 - Stock heat range
3923 - One heat range colder

For Denso:

IK16 - Stock heat range
IK20 - One heat range colder

All the above part numbers meet the following specs:

Thread – 14mm
Reach – 3/4”
Socket – 5/8 hex
Seat – Gasket
Gap - .059
Installation: 21 lb/ft or 2/3 Turn

Randy WS6

iTrader: (69)

I runned the NGK-TR6's now i use the TR7's

Redlinez

iTrader: (5)

I have the TR55's, ya'll have me thinking I need others.

Redlinez

iTrader: (5)

My cost on the Denso IK20's is $8.46 @.

Sigforty

I run have run NGK Tr55s, and TR6s without any issues in the dart heads.

Redlinez

iTrader: (5)

I'm going with TR6's based on my shop's recommendation as it's one range cooler, the plug also doesn't protrude so far into the chamber as a gasketed one. I also am having some mild detonation in 6th when I roll into it some to maintain speed on inclines.

405HP_Z06

iTrader: (11)

These heads were designed for a gasket seat spark plug, not a taper seat. The head has a taper machined that happens to work with taper seat plugs, but it's not recommended. A taper seat plug is too short, shrouding the spark from the combustion chamber.

Will the taper seat work, yes. Is it optimum, no. It's amazing that one would recommend the incorrect part. Why not use what the manufacturer designed the head for?

DAVESS02

iTrader: (30)

Not so. I called Dart when I purchased my 225's 2 years ago and was told that they are made to accept either gasketed or tapered seat plugs by a Dart tech.

405HP_Z06

iTrader: (11)

Call them again, tapered seat plugs will work but are not correct.

JS

iTrader: (4)

I agree I am running a FR5 in my customers Dart headed 402....

1989GTA

Double check but I believe the Autolite spark plug mentioned may be their racing version. If so it will not have a resistor and could play havoc with the electronics.

Redlinez

iTrader: (5)

That's good to hear......