70442rag

HI Guys,
Quick question....I'm not sure which spark plugs to get for my 455 Olds and wanted to ask others what they might recommend pls?
Here are some bullet points on the 455....
9.7 compression ratio final
iron heads light port & polish
SP L2323 forged pistons HC
big valve iron heads
headers
AED 850
Dick Miller cam 520 lift int & ex
Tremec TKO 600 5 sp
Edelbrock Air Gap RPM
Car is 70' 442 vert

I have been using NGK- 3332 V power but I see others are using....
Accell 0786-4

Any recommendations pls?
Thanks in advance for your assistance!

Olds64

I use AC Delco R45S and gap them to .040 in.

70442rag

Thanks Olds64!
Not sure if it makes a difference but the distributor is a "Ready to Run" MSD unit w a high output shock resistant coil?
Also, the cam spec above is incorrect....I should have said 552 lift- int & exh
Thanks again

Olds442redberet

I used the R45S and found it was running cold. I am now using R46S plugs. They're a little hotter.

I had to order them off Ebay. But a few members here have sets for sale.

Olds64

That's a good point. The plugs are hotter as the number goes up (R46S) and colder as the number goes down (R44S). You may have to go up or down a size or two to find the plugs your car likes.

ReallyWildStuff

What say you about today's ACDELCO 7 "Professional, Rapidfire" plugs?

This is the type that I pulled out of my motor from 14 years ago, I recall them running "excellent"...but one of them has a cracked porcelain insulator, so now I will have to get 8 new ones...

Olds442redberet

The new plugs are excellent. They've come a long way. But when it comes to my old Cutlass I'm just stuck in the seventies. LOL

cutlassefi

0786 is a long reach (3/4") plug. Can't use that on your iron heads.

ReallyWildStuff

My O'Reilly doesn't carry the AC DELCO 7 - there are apparently no O'Reillys in Houston with these plugs, which is usually what happens to all the good parts.

O'Reilly recommended NGK 7082 - what do you think about those as a replacement for AC DELCO 7s?

I can't find the 7082s on RockAuto's site at all - nor, for that matter, O'Reillys...

EDIT: I called back, the 7082s are apparently "extended reach" as well. What are these good for - the Edelbrock aluminum heads only?

ReallyWildStuff

I am going to pick up some R45S plugs, as that's what is locally available and I'm impatient to get my stuff running on the test stand this weekend. I guess I will gap them .045 for use with HEI on premium gas.

Again, I was running ACDELCO 7s previously that worked great - but those are not readily available in Houston, TX today/this weekend. I'd be interested in hearing about comparables that are not made out of unobtanium.

O'Reilly doesn't list R46S.

O'Reilly's computer calls for R43S in the "1970 Olds 442 w/ 455" - but I'm guessing those will be too cold.

O'Reilly says they have Q:20 ACDELCO 7s in California, but I have to pay UPS = I'll get these online myself.

olds 307 and 403

The R46S are now R46SZ, I believe. I bet the 45S is a better heat range for you.