Best plug for LT-1
 

Recently Purchased stocker (350 LT1 fuel inj.) has AC Delco Rapidfire #3 plugs.
What are you guys using in this combo?
Typically I've used autolites in my previous BBC engines....but this is new territory for me.
Thanks.

Re: Best plug for LT-1
 

104 Autolite.

Re: Best plug for LT-1
 

Ed
There are two Autolite 104 plugs. There is the standard which is .032 gap and a alternate desgin which is .044. I used the .032. Should I have used the other? That seemed like alot of gap to me even with MSD ignition. Did I guess right?

Re: Best plug for LT-1
 

I use NGK with larger gap can't remember the number but can get it for you.

Re: Best plug for LT-1
 

I set mine to .045". I run my MSD stuff off two 16 volts batteries.

As for NGK, I have had to pull so many new NGK plugs out of customer's cars brought in for dyno tuning, I would not put them in my lawn mower. Kids would say "I never heard it miss like that before." "You never stood at the back of the car, running at WOT, in a tin building before." A new set of Autolites always fixed them. Had a box full of those things on one of those work benches in the middle of the shop area. I know they aren't all bad, but too many for me to ever use them.

Re: Best plug for LT-1
 

We used the crap out of NGK's for a long time with no problems.
Mike Taylor 3601

Re: Best plug for LT-1
 

Ed, Are you using the 104 or the AR 104(racing plug)?

Re: Best plug for LT-1
 

Plain old 104.

Re: Best plug for LT-1
 

Ed, Thanks for the info. I'll pick some up today. Do you index them?

Re: Best plug for LT-1
 

Sometimes. Have never found anything there. Can't hurt.
Used to index them in my old C/SM Camaro back in the '70s, straight plug heads and big domes. To prevent knocking them shut. LOL

Re: Best plug for LT-1
 

Thanks.

Re: Best plug for LT-1
 

Bosche Platinum 4 Prong Plugs...

Re: Best plug for LT-1
 

Dan, Advantages??

Re: Best plug for LT-1
 

Another plug I have seen too many problems with. Ditto mis-fires, sorry I meant split fires. E3 are also problem prone. I have found no "trick" spark plug that makes more power than an AC, Champion or Autolite. Motorcraft plugs are good too.

I owned & operated an extremely busy & successful performance tuning shop for over forty years. Probably sold & installed more spark plugs than most here. Autolite & Champion have, in my experience, been more reliable that any others. I have had ACs with open resistors right out of the box. Look like a bad plug wire on the engine analyzer's 'scope. Zero issues with Champion, Motorcraft & Autolite.

You may have a good set of those plugs, but I have seen enough bad ones I would never recommend them.

Re: Best plug for LT-1
 

These are my observations using Bosche 4 Prong plugs.
My engine is an Iron Head LT-1 and many of our Impala and Vette Bloggers have had zero problems.
Some go back to copper plugs and work fine until the tip wears out.
Blower or Turbo guys use just about all of them with good success and have their preferred set ups.

My experience is that Bosche Platinum last forever...though 4 prong more expensive.
Use them on all my cars and look perfect every time they are checked.
Our Impala guys retrofit the GM 8 Coil LCCC from the LSx Series to get rid of the Opti and add Accel or MSD Coils.
I have just the one MDS Coil replacing the Stock one and carry extra Opti Harness.

The 4 Prongs are spaced perfectly apart which attract a clean Spark.
Prongs are vertical and should reduce flow restriction over a L shaped Prong.
Never had to index them for better performance.
OR
Drill a Hole in the Tip like on a L-shaped Prong to prevent blow out..

Bosche makes a 2 Prong..
Figure 4 prong reduces a touch of combustion chamber volume.


D

Re: Best plug for LT-1
 

Dan, you may be over your head here. Most everybody knows you do not use platinum plugs with a blower or turbo.

Re: Best plug for LT-1
 

Dan,
What gap do you run, and what is the procedure for setting it?

Bill

Re: Best plug for LT-1
 

DID not say that.. !!
Stated our community of our B-Body Clubs and ECIRS and ISSCA Racers were using just about everything with success.
They have their preferred set ups.

Got years of ImpalaSSforum details to back me up..

D

Re: Best plug for LT-1
 

I do not gap the Bosche 4 Prong.. Just visually check them for defects.
Have measured them before and consistently have the same gap from the box.
Only time they had to adjust one is when it got dropped and bent a prong.

It has always been a quality product no maintenance plug.
They are built to German Standards.

In fact replaced them when I rebuilt the engine but kept them as they were in perfect condition.
Put them in my 1994 Caprice SSuperWagon at 145,000 miles and now have 205,000miles and purrs like a kitten.

Dan

Re: Best plug for LT-1
 

We use the Rapid Fire #3. Never an issue.

Re: Best plug for LT-1
 

Yeah, that's where I would go for technical information. Lmao!