Don Terrill’s Speed-Talk

How does this plug look? NGK UR4 plugs. 36 degrees of timing. 93 octane with a little Race Gas additive. 355 SBC, 10.3 compression, Sportsman 11 heads, Performer RPM Air Gap, 1/2" open spacer. Comp hydraulic roller .520/.540 .236/.242 @.050 on a 110. 750 DP HP 71 front 80 rear. MSD billet dist 6AL blaster coil. 2004r 3400 Trans Specialties conveter. Monte Carlo SS 3.73 gear. Thanks

I would be inclined to try something colder.

What would one recommend?

Heat range 5 for street and perhaps 6 for the track.

You are using too much manganese additive. Back off about 1/3. How much are you using now, ounces additive per gallon of fuel?

The MMT makes the orange color on the plug and the too-hot plug ceramic fires the metallic to a shiny glaze, same as coloring or glazing pottery, when it goes in the furnace it looks dull and flat and after "firing the glaze" it comes out shiny because the heat melts the metallic and it flows out smooth and shiny.

With MMT it is normal to see a light tan color, but when it starts looking a wet brick orange color it is an indication of too much.

Too much additive... You shouldn't need any additive for that compression.... I would run it without to get a clean look at the plug...then go from there

A little is OK, but too much of even a good thing is too much. He might be lucky he used the additive, the Sportsman II heads have "Fast-Burn combustion chambers" so the 36 deg timing is probably too much advance and another reason the plug looks so shiny.

Should I back off on the timing say 34 degrees? I will leave out additve next go round. I went the additive route to make sure I got tune straight before going without. I also will be putting in a NGK 2771 plug in the 5 range.
Engine runs great pulls hard till 6400.

wilson1970 wrote: ↑Sun Oct 28, 2018 5:21 pm What would one recommend?

Does it stumble after a long WOT run?

wilson1970 wrote: ↑Sun Oct 28, 2018 8:53 pm Should I back off on the timing say 34 degrees? I will leave out additve next go round. I went the additive route to make sure I got tune straight before going without. I also will be putting in a NGK 2771 plug in the 5 range.
Engine runs great pulls hard till 6400.

Fast Burn GM heads are good with 28-30, regular Vortec heads maybe 32. You didn't say how much additive you used in the fuel on that plug. How much in OZ. per gallon? If you answer this you will help others understand how much to use. One OZ per 5 gallons is usually OK with most brands of MMT booster.

I had been using 2oz. Per gallon bringing octane to 95 or so. The thing ran just fine after a hard run. One time last week took it for a drive in the AM air was really cool and crisp and above 5800 it went bump bump like a miss but not a miss it kept pulling. I then shifted and backed out. Lean maybe??

Back to the plugs. I have the NGK UR5 gapped at .035 in it now.
Stepped up the primary jet to 74 from 72 and dropped air bleed from 73 to 69. Secondary from 80 to 82.
Should I go to a NGK UR6 or keep the UR5 in it. No fuel additive 93 octane. Timing is set at 34 degrees.
The engine pulls hard to 6500 never misses a beat. Engine temp is rock steady at 180.

wilson1970 wrote: ↑Sun Apr 14, 2019 6:09 pm Back to the plugs. I have the NGK UR5 gapped at .035 in it now.
Stepped up the primary jet to 74 from 72 and dropped air bleed from 73 to 69. Secondary from 80 to 82.
Should I go to a NGK UR6 or keep the UR5 in it. No fuel additive 93 octane. Timing is set at 34 degrees.
The engine pulls hard to 6500 never misses a beat. Engine temp is rock steady at 180.

there does not seem to be any detonation on your spark plug photo which is a plus
all my own stuff with the later style combustion chamber i only run 32 deg total timing,mine does not run faster at the track with more timing.
as far as octane boost i have used 10% of the recommended dose so i can get half a read on the plug at the track.im really not a fan of the stuff personally,up to 11.0:1 comp try to use the better pump fuel.we have whats called 98 octane but thats the RON in Australia here,but it average at best.my opinion is spark plugs are hard to read with pump gas,if you use a quality 98-100 octane race fuel you will see what i mean.
forget the octane boost you dont need it.
i run NGK -6 on the street and change to a -7 at the track,i have a couple engines 450-520hp pump gas deals with cast iron heads.
Wilson,
you need to see if can get a distinct timing mark on the ground strap of your spark plugs,that will tell you where you are,spark plug heat range will effect the timing mark as well.
just my thoughts.

Thanks for the response. I have noticed the coating on the headers has changed. I am assuming this is a lean condition also.

wilson1970 wrote: ↑Sun Apr 14, 2019 6:55 pm Thanks for the response. I have noticed the coating on the headers has changed. I am assuming this is a lean condition also.

Not....necessarily at all.

Think MSD instructions say to go one colder when you add their ignition box. I've also read a basic guideline was for every 100hp over stock go one colder. So I think the UR6 for track and UR5 for street is great advise.