Posted By: deaks
indexing plugs - 03/01/10 11:06 PM
I am fitting my 76cc RPM heads to a new short block with 12.5.1 venolia domes, will i need to index the plugs and where can i buy the washers to do it.
Mick
Mick
indexing plugs
Posted By: Cab_Burge
Re: indexing plugs - 03/01/10 11:50 PM
Quote:Mick, every motor is different, I'm sure there is no way to say absolutely yes or absolutely no!
I am fitting my 76cc RPM heads to a new short block with 12.5.1 venolia domes, will i need to index the plugs and where can i buy the washers to do it.
Mick
Take one of the plugs you want to race with and install it(with the head off) so the bend of the ground strap is pointed striaght down so it will hit the piston dome. Install the head with the gasket your going to use ( make sure and install the rod and piston) and then rotate the motor slowly from 20 BTDC to 20 degrees ATDC, you may want to install some clay on the sparkplug end also. check the results and go from there 
I use to thank that there was around .01 to .02 ET increase by indexing all eight plugs in my M.W stocker 
there wasn't 
, it was the weather changing making the ET changes 
All the other racers where seeing the same increases without opening there hoods 
Are you using a projected gap plug or a non projected tip plug? the last thing is are the Venolia pistons tops designed for the Eddy heads only or are they a generic shelf piston for 440 motors with a standard pop up dome?
Posted By: 340king
Re: indexing plugs - 03/01/10 11:55 PM
I usually have extra plugs around and just try fitting several to see where the ground strap ends up. Usually 12 plugs will get you in the ball park. I never use the washers. This comes from doing the same thing on tapered seat plug engines.
Posted By: deaks
Re: indexing plugs - 03/02/10 12:08 AM
The motor had stage VI heads on it, i presume they have straight plugs but i'm not sure.
Without going in the garage to look now, i think the plugs are AR3930.
Mick
Without going in the garage to look now, i think the plugs are AR3930.
Mick
Posted By: Barnstorm
Re: indexing plugs - 03/02/10 01:05 AM
Hi Mick. We don't do it anymore even in the SS/AH motors. Big MSD spark doesn't care. Kinda like cool cans,faded away.
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Posted By: deaks
Re: indexing plugs - 03/02/10 07:36 PM
Sorry, plugs are BK6RE projected tips.
Barnstorm
I dont understand what you mean, i have got msd 6al though.
Mick
Barnstorm
I dont understand what you mean, i have got msd 6al though.
Mick
Posted By: BobR
Re: indexing plugs - 03/02/10 08:45 PM
Quote:
Hi Mick. We don't do it anymore even in the SS/AH motors. Big MSD spark doesn't care. Kinda like cool cans,faded away.
Exactly. Indexing is a waste of time unless it for clearance.
Posted By: Barnstorm
Re: indexing plugs - 03/02/10 09:18 PM
With the stock 60's and 70's standard coil and points system, there may have been some benefit. However with most ignition systems like MSD and the like, they put out so much spark that turning the plug here or there doesn't seem to make a differance in engine performance.
Posted By: deaks
Re: indexing plugs - 03/02/10 09:47 PM
That is the only reason i'm asking, i'm concerned about clearance and would appreciate some solid advice.
Mick
Mick
Posted By: 602heavy
Re: indexing plugs - 03/02/10 10:11 PM
Mick , while the heads off check how far the plug enters into the head , on my 572 heads the plug stop short of the chamber , i'm sure you'll be fine with the non projected type , these are the one's i use for the nitrous , i would imagine you would be running these type plugs on that combo anyway.
Posted By: deaks
Re: indexing plugs - 03/02/10 10:22 PM
Adam
They are the projected type, that's one of the reasons i asked the question, hoping that someone would suggest a plug or a solution to any problem that might arise.
Mick
They are the projected type, that's one of the reasons i asked the question, hoping that someone would suggest a plug or a solution to any problem that might arise.
Mick
Posted By: 602heavy
Re: indexing plugs - 03/02/10 10:29 PM
Mick , you're question was answered by Cab , you need check the plug in the head with the head off , no one can tell you how much those plugs need to be spaced with washers , maybe they don't? , i would.nt take a chance on somebody else telling me how they did it as all motors are different , personally i would'nt use the projected type plugs with that compression ratio , the non projected type plug will gain you more clearance (NGK BCR)
Try Sumit racing for those spacers.
Try Sumit racing for those spacers.
Posted By: Stanton
Re: indexing plugs - 03/02/10 11:26 PM
How many times do you need to hear the same answer before you get it ?!?!?!
Posted By: oldtimer5151
Re: indexing plugs - 03/02/10 11:29 PM
A spark plug is just a ground for coil. I have indexed plugs in different motors from flat heads, to o.h.v. motors. The only benefit from indexing is to turn the spark plug ground`s back toward the intake valve. The reason is it will receive the gas that leaves the air stream and will hit the extended tip, and ground. The small droplets of gas will absorb the heat off the end of the plug and the absorbed heat will help vaporize the gas. Extended plugs move the timing .125 further into the combustion chamber help controlling the flame on top of the piston. You must take a small points file and file ALL sharp corners off the ground. The spark plug will be in the mix of the heat and explosion.
Posted By: deaks
Re: indexing plugs - 03/03/10 09:00 AM
Thanks for the replies, i will try a different plug to see where i am and go from there.
Stanton
Dont take it personal, it's just a question.
Mick
Stanton
Dont take it personal, it's just a question.
Mick