cosmicvette

Hi all,

I wanted to start tuning my 70 350/300 auto (stock compression from what I am told) it as well as I can. I currently have the recommended AC R43S's in, but after checking the plugs I think I may want to go to a slightly hotter plug, they look ok (light brown/tan mostly) but there is a very small amount of black dry sooty residue.

First question I have been running the the R43S's (the S stands for extended tip I believe) there were a few people saying this extended tip may be a problem on higher compression cars, but I am guessing only LT1's would run any risk of hitting the plug right? and since I have had the 'S' tips in for 4-5years now I guess I am ok for sure lol.

Second thing is what heat range do you think I should try, a few people I have seen in previous threads recommended R45's or even R46's, what does everyone think? I do sometimes get stuck in stop and go traffic and don't want it fouling up on me.

midyearvette

if you have been running 43's, they are a shade cold, i would not go to a 46 for sure but you should try 44's, the s tip will not be a problem......

Jay-Dog

The 43 is one step cooler than factory, I believe. Probably should not change by more than one heat range at a time. Are you having fouling or hard restart problems with your 43's?

cosmicvette

Ok from what has been said I think I will order a set of R44S's and R45S's and try them both.

Now the problem is I can't seem to find the R44S's on the Summit website (found the R45S's fine http://www.summitracing.com/parts/ACF-R45S/), have tried searching and all that comes up is the R44TS whatever that is????? Any help appreciated.


cosmic

Peterbuilt

I think the TS in r44ts stands for 'Tapered Seat' and that is what you want, and you can buy them at your local parts store.

cosmicvette

Hi,

Thanks for the reply, pardon my ignorance but what is a tapered seat design sparkplug? how does it differ from the regular type? So it is ok to use an R44TS (should I be ordering the R45TS as well instead of the R45S?)?

Also Summit IS my 'local parts store', auto stores here in Australia suck big time and charge through the roof, it is sad but true I can get most things quicker and cheaper (even including the shipping) ordering from the USA than from the auto store 5 min drive away, plus they never have anything in stock and definitely no AC Delco stuff!!!! What a strange world.

Peterbuilt

If you look at where the plug screws into the head the plugs for our 350 motors are convex and the hole is concave so they seal 100%.

Some plugs are flat where they go into the head and the head is also flat, heads made like that have a seal between the bottom of the plug and the head.

If you look at the link you provided you can see the plug you picked is flat at the threaded end. Click on the link where it says 'ACDelco Conventional Resistor Spark Plugs' and scroll down to AC45TS and you'll see the difference.

Correction on the 'TS' I think only the 'T' means tapered. The 'S' means something else.

A longer insulator = a hotter plug and is best in a low performance engine to burn off combustion deposits.
A shorter insulator = a cooler plug and is best in a high performance, high compression engine.

Either stock or 1 heat range higher will be OK for your Vette.

midyearvette

"S"...extended tip.....

Ironcross

correct,

And the 'T' means tapered,

and 70 engines are not tapered

use the #45 or #45S

44`s were correct but no longer available unless E Bay has them

Some early V8`s also use #46

cosmicvette

Thanks exactly the info I was after, funny they don't make the R44S anymore.

Peterbuilt

Sorry about the misinformation regarding tapered or not, based my information on my 74.
Great forum, learn something new every day.