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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
So I'm getting close on my new 383. RHS specifies a Champion plug, and I know people either love em or hate em, but I've always used AC delco. From what I can tell, basically I'm looking at a plug about 2 heat ranges lower, and this would make sense from what I've read. Basically I'm one full point of compression higher, so go 1 step colder...and on a new engine with all new variables, go one more step colder to be safe and test, tune, and read the plugs.
...but I can't seem to shop for AC Delco plugs. I can find all the websites to buy em, but I can't find any list or chart to pick one plug I need?
Thoughts? Looking for an R45TS, but a step or two colder.
They are RHS 180cc Pro Action heads. ...they call for Champion S57YC or C57YC. Tapered or flat. ...but the heads themselves seam to have a tapered seat.
...the reach IS .750" on the Champions. ....are Delco's shorter? Maybe I should just use the plug the call for and quit trying to out think the professionals. ...those champions also have a TINY gap. ....like .028. .....sure they can be re-gapped, but it just seems really tight.
That's odd. I haven't come across a cylinder head that takes either flat or tapered seat plugs yet that's what the spark plug chart at RHS indicates.
My RHS Pro Torker iron heads take a 14mm, .708" reach, 5/8" hex, taper seat style. Same as GM Vortecs.
The difference with the .750" vs .708" seems to be the seat profile with the flat seat being longer. My understanding is that you can't get a .750" reach plug in a tapered seat. That makes sense seeing as the washer on the flat plug takes up about .040" which would put the end of the threads in the same spot relative to the combustion chamber.
As for gap, what the spark plug comes makes no difference to me. Using the MSD 6AL ignition allows me to open the gap to .045". This is an NA application. No power adders or NO2.
Well I think the .750" reach was a brain fart on my part. ...everywhere I looks seems those Champions are .708", like pretty much every other plug on the cross reference chart.
...and I think the taper/flat is probably due to different head/part numbers. Maybe some are one way, some are another. Just an uneducated guess.
...as for gap, I know my Delco R45TS were always darn close to perfect, but apparently in the aftermarket world, you're expected to gap them for your needs. Never had to chose a plug before so I didn't know.
AC Delco R44LTS. The L in the suffix is what makes it a .708". Without the "L", you get the .430". Which, interestingly, I had mistaken installed in my Vortecs at one time.
Have you seen this chart? It completely confuses me. There are so many variables to determine the reach that if I didn't have the plug right in front of me, I wouldn't know how to select one.
EDIT: The chart says the LT plug is .715" reach (tapered seat) but the difference between .715 and .708 is almost unmeasurable with my calipers. .007"
I have NOT seen that.....and I looked real quick, and decided to stop and close it! I found that with many of the brands I looked at, it was very confusing.
The way I see it, AC Delco has always served me well, and I'm not building some crazy race motor, so as long as I choose the right part number, I should be ok sticking with AC Delco.
The TS means it has an extended tip. Unless you are using flat top or dished pistons, I wouldn't recommend a TS plug.
Correct plug heat range should but a slightly blue divider line about half way down the ground strap on the plug. If you have a hard time reading plugs, just look for deposits. Run the coldest plug possible that doesn't foul up. Timing, jetting, engine rpm operating range etc can all change what heat range you need.
I run NGK plugs in my race car. The NGK heat range goes colder as the number goes up. I run a -9 plug in my race engine. Plugs are cheap. Buy a few sets in different heat ranges to see what works best. Stay away from gimmicky plugs. They're not worth the extra money. If you want a plug that will last and doesn't need to be changed every few years, install some basic platinum plugs.
In the older style of AC delco # you will need an 'XL' plug, not an 'LT'
The 'LT' is .715" reach, where the XL is a .750"
Isn't also the case that the LT is tapered seat and the XL is gasketed?
That's how I interpret the preceding chart. In a case where a cylinder head is cut for both seats, the length difference would perfect sense as the additional .035" is about the thickness of the gasket.
T for tapered seat. S for extended tip. Put the L in there as in LTS and you have a long reach (.715") tapered seat extended tip plug. Sound about right?
Originally Posted by Night rider327
In the older style of AC delco # you will need an 'XL' plug, not an 'LT'
The 'LT' is .715" reach, where the XL is a .750"
Isn't it also the case that the LT is tapered seat and the XL is gasketed?
That's how I interpret the preceding chart. In a case where a cylinder head is cut for both seats, the length difference would perfect sense as the additional .035" is about the thickness of the gasket.
I'm pretty sure the plugs in my heads are gasketed. Plugs with gaskets are easier to index with indexing washers. When I was still using iron heads with tapered seat plugs, the indexing washers were a pain. Almost a use once design. If it didn't index properly, the index washers were hard to remove because of how they get crushed.
I use a non extended tip plug and index each plug so that the ground strap is up and away from the piston. With the huge dome pistons I use, I have to.
Not saying they're not out there but I've never seen a head that will properly accept gasket or tapered seat plugs. It's usually one or the other even though the thread size is the same.
Champion C57YC is a 14mm thread, .750" reach, 5/8" hex plug with flat gasket seat.
I agree. This is ONE of the part numbers listed by RHS. The other is S57YC, with is a tapered plug. .708"reach. .....as mentioned earlier, I can only assume they list both, because your heads could be either tapered or flat. Mine are tapered.
Not saying they're not out there but I've never seen a head that will properly accept gasket or tapered seat plugs. It's usually one or the other even though the thread size is the same.
I'm guessing that RHS lists two part numbers because you could have one or the other. ....if you look on RHS site, it does look like they recommend one or the other, but I'm with you, I can't see them being for "both"
Not saying they're not out there but I've never seen a head that will properly accept gasket or tapered seat plugs. It's usually one or the other even though the thread size is the same.
Originally Posted by Abubaca
I can only assume they list both, because your heads could be either tapered or flat. Mine are tapered.
Originally Posted by Abubaca
I'm guessing that RHS lists two part numbers because you could have one or the other. ....if you look on RHS site, it does look like they recommend one or the other, but I'm with you, I can't see them being for "both"
I only mention the "both" factor based I'm some internet postings (BS?) inferring that some AFR heads were/are built this way. Looking at it from an application point of view, it doesn't seem feasible seeing the tapered portion of the seat would occupy the same space as where the gasket would have to seal. But given the machining operation between the two styles, the reach of the thread in the head could be made the same (.715") and the seat portion of the operation a choice by the manufacturer. The plug makes up the difference in the seat style. .715" vs .750". Makes sense.
Looking at the literature that came along with my RHS heads, it's listed as a gasketed plug in version one, and a tapered plug for version two. I have version two which is why I had the plugs on hand to measure up.
At any rate, I think Abubaca has it figured out and can find the correct plugs.
And I have a fresh set of AC Delco R44LTS ready to go for my newly repaired (and ported!) RHS heads.
As an aside: Alky...are you getting to Castrol Raceway this season?
As an aside: Alky...are you getting to Castrol Raceway this season?
As much as I would love to, I highly doubt it. Car needs a chassis cert and I never got one this spring. Still need to change the back brace cross tube to pass a cert. Wall thickness just barely passes the sonic testing so it's better to just replace it. I managed 2 certs with the tube. I doubt he would allow a third.
Minor other stuff needs to be done. Still need to fabricate new throttle linkage and need to fabricate a new transmission tunnel. I do want that 8 second timeslip.
05-01-2016, 09:49 PM
Plugs are cheap. Buy a few sets in different heat ranges to see what works best. Stay away from gimmicky plugs. They're not worth the extra money. If you want a plug that will last and doesn't need to be changed every few years, install some basic platinum plugs. 
