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Correct spark plugs

Larry's Yellow Rdstr

Well-known member
Joined
Oct 19, 2002
Messages
304
Location
Redlands, Ca.
Corvette
05 black cpe-Porsche GT3
Yesterday I pulled my plugs and found them to be the Bosch (sp) plug once used as replacement plug for the Ac Delcos. Replaced them with the proper ACs and had the fuel rail pressure cleaned and also added a injection cleaner to the gas. Made a big difference. Engine is smoother and now idles at the proper RPM. Just a trivia point I thought I would share.
 
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tigmaned

Guest
could you explain the fuel rail pressure cleaning? is that done by a shop or did at home?
 

Larry's Yellow Rdstr

Well-known member
Joined
Oct 19, 2002
Messages
304
Location
Redlands, Ca.
Corvette
05 black cpe-Porsche GT3
Tig,
I had it done at a friends professional garage. I think it was $50.00. Car runs like new. I didn't watch as I had an appointment and couldn't be there.
 
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tigmaned

Guest
oh, thank for the help.
i was stationed at Norton AFB from 84-88 and then at March from 88-99. spent alot of time in Redlands, lived on Pinewood for be moved to Highland. my wife worked at Beaver Med. man right now i miss the warm temps!!
 

Larry's Yellow Rdstr

Well-known member
Joined
Oct 19, 2002
Messages
304
Location
Redlands, Ca.
Corvette
05 black cpe-Porsche GT3
Tig,
Do you know where Lantern Crest Estates are located (Near Sunset and Edgemont, south of the country club) Weather here is 75 degree today and sunny. You knew Norton closed many years ago.
 

Edmond

Well-known member
Joined
Aug 1, 2001
Messages
5,218
Location
Louisiana
Corvette
2003 Z06
I'll bet you're getting better gas mileage as well because of the work. :D
 

G Winter

Well-known member
Joined
Aug 21, 2004
Messages
2,177
Location
NW Iowa
Corvette
1990 red convert 6 sp
I have been a long time believer in AC plugs in a GM engine.If you compare heat ranges on diff brands of plugs you will find that they stagger. The replacement plugs for an AC in diff brands don't cover the same heat range.
I believe the heat ranges in AC plugs are engineered for the GM engines.
Glenn
:w
 

Edmond

Well-known member
Joined
Aug 1, 2001
Messages
5,218
Location
Louisiana
Corvette
2003 Z06
I agree with Glenn but I even take it a step further with being Delco exclusive when it comes to any electrical components.
 
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Louis Bartay

Guest
My TA/LT1 and my Vette LT4 came from the factory with AC plugs that have small disc's on the electrode that will burn off and widen your plug gap. I have owned the TA for 10 years and the Vette for five and last year I tried the Bosh Platium 4 plug that does not have a ground bent over the end on the threads and it works GREAT. Go to Auto Zone and look at this design as a lot of piston engine air craft use them from the factory. I Really did feel a difference after changing to this design spark plug. I did this with 40,000 orginal miles on my Vette and GM says that the AC plug is good for 100,000 miles, yeah right, five out of eight were missing the plat disc,(way to wide of a plug gap) did they just burn up or did they fall into the engine? I have seen the topic several times on other Vette forums and every one agrees that the GM plug is junk.
 

Toms007

Moderator
Joined
Sep 24, 2004
Messages
6,473
Location
Southwest Kansas
Corvette
2007 Atomic Orange Coupe
I'm not trying to stir things up, but on "another forum" the guys seem to hate Bosch plugs regular platinum the +2's and the +4's. Last year when I decided to change out the ones in my 94 Nobody recommended that I use them. So I put the regular AC's in. Now here's the rub...I have them (+4's) in both of my other vehicles (99 Silverado Z71 and 99 Volvo S80) and love them, but the guys over at the "other place" scared the H out of me so I didn't put them in. I am really glad to hear that you have had good luck. I maybe thinking seriously about changing to the Bosch's.
 

LT4man

Well-known member
Joined
Jun 25, 2003
Messages
2,214
Location
Chicago
Corvette
96 Collectors Edition LT4
All this negative stuff about Bosch +2s and +4s is just that: stuff!

I have been using +4s for as long as they have been made. Put them in my cars and my customers cars. They work great! Cars run smooth, start fast and get great gas mileage. A surface gap is the way to go. Nothing to ever wear out!

I had the same problem with the AC Delco plugs. I had a 92, 94 and now the 96. The little pucks fell off of about 1/2 of them. With four plugs gapped correctly and four plugs gapped wide, you should see how those engine ran. Like ****!

I like the Boschs. Maybe other people don't. That's cool. To each his own!

:beer

Save The Wave! :w
 
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Louis Bartay

Guest
plugs

If you will notice Mid America now sells the Bosh +4. A lot members have different opinions about everything but this product does work and no parts to burn or fall off. Lycom engines for Air Craft uses this design for their piston engines. Back in the late 1960's we use to buy a shim kit to position the ground on a standard spark plug so it was turned parallel with the valves in the head. Think about why Grumpy Jenkins and other engine builders were doing this? Now with the Bosh+4 there is nothing to block the spark in the head.
 
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Black Bart

Guest
How well a design works depends on the engine that it is in and how it is driven.The platinum plugs last longer in a stock engine but in one with a supercharger or Nitrous the thin ground strap will glow and cause engine killing detonation. What plug works good in one application is not necessarily the best for another. I like the AC Delco rapid fire because of their ability to operate in a wide heat range and the heavy ground strap don't glow as quick as most others do. I run a colder plug and it works well unless you drive for several miles without getting on it and then they tend to want to foul but standard heat range will detonate so I just blow it out on a regular bases
 
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96vetteLT4

Guest
There,s a reason that all of the Corvette race teams use Bosch plugs. Does anyone really think that any race team would not use the best plug available?
 

Edmond

Well-known member
Joined
Aug 1, 2001
Messages
5,218
Location
Louisiana
Corvette
2003 Z06
96vetteLT4 said:
Does anyone really think that any race team would not use the best plug available?

Well, if Bosch paid them more, I'm sure they would use Bosch. It's like advertising in a way.
 
9

96vetteLT4

Guest
I,ve raced SCCA, N.H.R.A. and have been a tire changer on a Nascar pit crew. Work is done in tenth of seconds , These guys do research that would blow you mine. And what it always cane down to was the part that made the biggest most reliable difference. And I can tell you that no one I remember ran AC Plugs of any type as it was a known reliability problem. You can't afford to have a disc on on e of your plugs come off at 9000 rpm which the AC plugs were well know to do. As part of the pit crew at the SCCA race in Daytona last year I saw NO ONE using AC plugs. To me that tells the story....
 
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Louis Bartay

Guest
Black Bart said:
How well a design works depends on the engine that it is in and how it is driven.The platinum plugs last longer in a stock engine but in one with a supercharger or Nitrous the thin ground strap will glow and cause engine killing detonation. What plug works good in one application is not necessarily the best for another. I like the AC Delco rapid fire because of their ability to operate in a wide heat range and the heavy ground strap don't glow as quick as most others do. I run a colder plug and it works well unless you drive for several miles without getting on it and then they tend to want to foul but standard heat range will detonate so I just blow it out on a regular bases

The +4 has no ground strap(on top of the electrode) to Glow and if you have not Indexed the plug so that the ground strap is not Blocking the spark facing the intake valve you will lose some HP. . But running a colder plug only helps in keeping the pistion temp down a bit for wide open racing for long period of times. It is your choice but if you have not used a product how can you really know the difference. My point is about the newer C4's with the LT1/LT4 and that AC spark plug does not last(disc's burning off and falling in the cylinder) like GM said. Read my earlier post again. The AC plug you use is a good plug for the L98 but how many miles does it last? The +4 design will produce a hotter spark and last longer as I have 58,000 miles on the set in my wifes 94 TA LT1 that is driven to work every day(stop and go heavy traffic) 58 miles each way and it still gets the same gas milage after two years and it never needs a regular Blast to clean the plug..And look at the +4 again the Four ground straps are not Thin. And the Air Craft engines do use a Turbo Charger.
 
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Black Bart

Guest
Louis Bartay said:
DO you have a super charger or NOS? The +4 has no ground strap(on top of the electrode) to Glow and if you have not Indexed the plug so that the ground strap is not Blocking the spark facing the intake valve you will lose some HP. . But running a colder plug only helps in keeping the pistion temp down a bit for wide open racing for long period of times. It is your choice but if you have not used a product how can you really know the difference. My point is about the newer C4's with the LT1/LT4 and that AC spark plug does not last(disc's burning off and falling in the cylinder) like GM said. Read my earlier post again. The AC plug you use is a good plug for the L98 but how many miles does it last? The +4 design will produce a hotter spark and last longer as I have 58,000 miles on the set in my wifes 94 TA LT1 that is driven to work every day(stop and go heavy traffic) 58 miles each way and it still gets the same gas mileage after two years and it never needs a regular Blast to clean the plug..And look at the +4 again the Four ground straps are not Thin. And the Air Craft engines do use a Turbo Charger.
/ LOUIS you need to reread my post. I'm not trying to argue with you over plug brands. What I said was the plug one should choose depends on the application. You keep talking about aircraft engines but I don't have a slow revving aircraft engine. I have a high revving supercharged nitrous injected 406. Under boost the compression ratio would be 18 to 1.
Your comment about 58000 miles points out what I meant when I said it depends on application. I replaced all the rod and main bearing at 5000 miles they where down to the copper. I would like to get 58000 out of the engine much less that far on plugs. As to the AC plugs with the little disks I have never used them never will. I have tried the Bosch +4 plugs but that was when the engine was only slightly modified. I was not impressed with them.
All that I was trying to point out was don't paint with too wide a brush you seem to think that just because the +4 is idea in your engine it would be the best for everyone. My original post was only trying to point out that some have different requirements. A Corvette with a L98 making 240 hp is not the same as one making over a thousand. While driving on the street at normal speeds then going from that to 20lbs of boost plus a big shot of nitrous sends the combustion temperatures soaring. After spending hundred's of dollars on different plugs I have found that the rapid fires work best in my application.
Your mileage may very.:beer
 
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Louis Bartay

Guest
BlackBart

I read what mod's you have done on the header post. You have a real High Performance engine now. But my post was about a Stock LT1/LT4 AC spark plug. If you have not done so make a Blast and push the clutch in and pull over to the side of the road in a safe place (kill the engine after the Blast A.S.A.P.) pull a spark plug and use a good magnifying glass and look for silver specks on the white porcline that wraps around the electrode if you see little silver/gray specks that is metal from your piston ( you may have known this I was just trying to help) Do at least try a set of the Bosh +4 plugs you may be suprised. As to what heat range that is a different topic as you have done so much and NOS to boot makes reading a plug harder, try what I said without NOS, what have you got to lose but I little time and it seems money is not a problem as you have spent a ton of bucks on a Kick A$$ engine the price of spark plugs is nothing. I am 55 and have built many Small Block Chevy's over the years and I am not a NOS fan for a daily driver, unless you use a controler that does not let All of the NOS inject all at one time. Good Luck and Save the Wave.
 
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Black Bart

Guest
I was using a Jacobs mastermind controller but now control the nitrous with a Accel Gen.7 with wideband. The O2 Sensor controls the fuel and I have it programed so that if it leans out for any reason the computer will shut the nos off With the wideband option the O2 sensor controls the fuel 100 percent of the time instead of only at part throttle like oem ecm's do.
 

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