which plugs do I use?

[rddiaz]

Well I decided to change out the spark plugs today aswell as wires,cap and rotor, so I went to autozone and asked for all of this stuff for my truck which is a 86 swb 305, well I got home and noticed that on the haynes book they recomend using the r44ts plugs and of course autozone gave me the ac delco r43ts. So my question is do I use ther43 or go back to the store and get the r44? I have not taken the old ones out yet to compare.I should of looked in the book before I went I just don't want to make a trip to the store again.

[VileZambonie]

they should have given you R43CTS

Number: 86-137
 
Section: 6D
 

Date:   AUG., 1986
Subject:     SPARK PLUG USAGE


Model and Year:   1986 LIGHT DUTY VEHICLES WITH GAS ENGINES
TO:   ALL CHEVROLET DEALERS

The following information is being provided to assist dealers in the correct spark plug usage in 1986 Light Duty Trucks. Starting in 1986 many spark plug usages were changed. If it becomes necessary to replace the spark plugs, use the chart below for the correct plug application. It is not recommended that higher heat range plugs (example R43CTS to R44CTS) be substituted to try to correct a driveability complaint as installation of higher heat range plugs can cause engine damage.

MODEL       ENGINE            VIN CODE      SPARK PLUG        GAP           P/N
S/T         2.5L              E             R43CTS6           0.060         5613812
S/T         2.8L              R             R43CTS            0.045         5613810

M Van       2.5L              E             R43CTS6           0.060         5613812
M Van       4.3L              Z             R43CTS            0.035         5613810

C,K,G       4.3L              N             R43CTS            0.035         5613810
C,K,G       4.8L              T             R44T              0.035         5613867
C,K,G       5.0L              H,F           R43CTS            0.045         5613810
C,K,G       5.7L              L,M           R43CTS            0.045         5613810
C,K,G       7.4L              W             R44T              0.045         5613867

NOTE: Spark plugs should be ordered by part numbers. The plug type designation for a given part number may carry either a "C" or a dot to indicate a copper core electrode. AC-Delco is in the process of eliminating the "C" designation, and replacing it with a dot in all copper core plugs.

[rddiaz]

Hey thanks Zambonie, I appreciate that info. Now off to the store I go!!! You're  real knowledgeable about these trucks

[Blazin]

I have always gotton R45TS Delcos for small blocks. I have Autolites in my 55 because a friend of mine runs them in his roundy round pro stock. He says they last longer resit fouling better. So I tried them, have had no problems with them.

[VileZambonie]

Blazin, that's a sure fire way to send your engine to an early grave if you are sustaining any high speeds for a moderate period of time. Short high speed trips you might do ok but if you are running full advance and running down the highway you're engine's asking for it. Runnig a hotter plug is ok in grandmas slow speed 20 year old grocery getter or a tired old puffer but for a daily driver never go hotter.

[Stewart G Griffin]

Blazin, that's a sure fire way to send your engine to an early grave if you are sustaining any high speeds for a moderate period of time. Short high speed trips you might do ok but if you are running full advance and running down the highway you're engine's asking for it. Runnig a hotter plug is ok in grandmas slow speed 20 year old grocery getter or a tired old puffer but for a daily driver never go hotter.

But i thought all pre-86 smallblocks take  R45's?

[VileZambonie]

I was pretty lit up last night so don't miind me if I was rambling! lol What I think I meant to say was the hotter plugs in the later engines especially was a problem because they already ran hotter due to leaner a/f mixtures and high coolant temps. Running a hotter plug lead to cracked heads, burned valves, blown head gaskets and detonation disasters. You should never run a hotter plug in a dd unless it's an oil burner that isn't driven on the highway or specifically for a street rod application. If you run your engine at cooler temps with richer a/f mixtures and don't have a high CR you may benefit from a hotter plug... Basically what I am saying is don't run a hotter plug unless you absolutely need it.

[77c15]

R44TSX  delco plug fine for my 69 vette 355 SBC? The electric fan won't even kick on, so I know the engine isn't getting over 200 degrees, and the dash temp gauge always shows at the quarter mark between cold and half after she warms up and after she gets a beating! I ran them all the time in my 383.

[Blazin]

Newest I run is 86. I also do mostly plowing around town stuff with it 220,000 miles on the motor. When I rebuild it I will be sure to run the cooler plugs.