Quick Question; I'd like to find out what the best spark plug would be for this set-up.

Engine = 1987 LB9
Heads = 1986 '416'

Right now the car has Bosh Platinum's and they do not require a gap. When using a standard type of spark plug,.... what should be used ??

Thanx in advance !

 

ACDelco = R43TS
NGK = UR5

Edit: These plugs are stock replacements.

 

AC delco R45TS gapped at .045"

 

Ya',.... It's been a toss up between those 2. Here's why I'm not sure;


86 used the same 416 heads on all V8's
Carb = 45TS with .45 gap 6 degrees BTDC
TPI = 43TS with .45 gap 8 degrees BTDC

87 TPI changed to perimeter 081 heads ( Did 87 Carb cars get 081's too ?? )
87 TPI = 43TS with .35 gap and 6 degrees BTDC


I believe the 86 heads I used were from an 86 Carb car. As you can see the plug is different, & the gap is different on the heads and the engine I mated together. To add to my confusion,.. while the plug was the same, the gap & timing was changed on the TPI from 86-to-87 cars.

I'm thinking that I'll need to stick with the factory 87 engines' 6 degrees BTDC on the engine since the cam is original. But that still leaves me guessing about the plug; should I use the 43TS called for by the TPI's ?? If so; what Gap is best ( .35 or .45 ). Or,.... Should I use the plug that was original to the 86 head ( 45TS ) and if so; should I use the .45 gap or should I go with the .35 that ALL 87 engines called for ??

I'm sure the car with run with both,..... but I'm also sure that one plug must be 'better' than the other for this head/engine comb.

 

Think you are over thinking this. Its not really gonna make a difference. I use ngk stuff, UR4-UR5 is what i'd use.

.040 gap is fine. My 305 ran .030 ur5's with 9 psi boost and now i left them in when i took turbo off. Still runs fine

 

I'm sure your right !

Figured since I wasn't sure about it I'd ask here to get a few opinions before throwing caution to the wind and buying a set of new plugs.

 

old thread but here goes I have a R43TS from China and another r43ts from mexico but the Chinese is longer so im confused...its longer from the hex up.