plug recomandation
Thread Starter
Melting Slicks
Joined: Dec 2000
Posts: 2,130
Likes: 1
From: mesa,az
plug recomandation
got to start somewhere I threw a set of bosch 7584s in the new engine I built to basicly close the plug holes. I'm using 292 head with the TRW 11-1 piston. The bosches give me room but what heat range wouild be a good place to start ?
Drifting
Joined: Nov 2005
Posts: 1,601
Likes: 4
From: Texas
Sorry I cannot give a heat range.... I like the Bosch Platinum 2's or 4's
Smokey Yunick did some testing on spark plugs he had modified by
cutting the electrode back.... what this did was make the nipple arc
to where the electrode was now.... on the side.
The reason he did this was to unshroud the spark from the chamber
in hopes to get a more complete burn... he did have a very very nominal
increase in horsepower.. like 1 to 3hp...measured on his dyno..
The Bosch 2's and 4's do this right out of the box... electrodes on the
side... spark unshrouded... and no need for you to modify.
I read about this in Smokey's book "Power Secrets"..
Im sure someone knows the heat range... good luck.
Smokey Yunick did some testing on spark plugs he had modified by
cutting the electrode back.... what this did was make the nipple arc
to where the electrode was now.... on the side.
The reason he did this was to unshroud the spark from the chamber
in hopes to get a more complete burn... he did have a very very nominal
increase in horsepower.. like 1 to 3hp...measured on his dyno..
The Bosch 2's and 4's do this right out of the box... electrodes on the
side... spark unshrouded... and no need for you to modify.
I read about this in Smokey's book "Power Secrets"..
Im sure someone knows the heat range... good luck.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
Use a 45 series AC plug. There are 2 available and both are a resistor plug which actually means nothing as almost all plugs are resistor types.
With a 11-1 engine I would recommend the AC "R45". The other 45 is the "R45{S}". This is what every catalogue will tell you to use. The "S" means extended tip. Thats it`s problem, the piston may hit the electrode and close it up. Been there, done that! It`s really a bitch to remove and reinstall the spark plug ignition shielding twice when finding out the hard way that the plugs tips are touching the piston and closing the gaps. To be safe use the R45`s.
With a 11-1 engine I would recommend the AC "R45". The other 45 is the "R45{S}". This is what every catalogue will tell you to use. The "S" means extended tip. Thats it`s problem, the piston may hit the electrode and close it up. Been there, done that! It`s really a bitch to remove and reinstall the spark plug ignition shielding twice when finding out the hard way that the plugs tips are touching the piston and closing the gaps. To be safe use the R45`s.
Last edited by Ironcross; Dec 17, 2006 at 11:32 PM.
Le Mans Master
Joined: Sep 2003
Posts: 8,934
Likes: 657
From: Norwalk ohio
2019 Corvette of the Year Winner
St. Jude Donor '15
Use a 45 series AC plug. There are 2 available and both are a resistor plug which actually means nothing as almost all plugs are resistor types.
With a 11-1 engine I would recommend the AC "R45". The other 45 is the "R45{S}". This is what every catalogue will tell you to use. The "S" means extended tip. Thats it`s problem, the piston may hit the electrode and close it up. Been there, done that! It`s really a bitch to remove and reinstall the spark plug ignition shielding twice when finding out the hard way that the plugs tips are touching the piston and closing the gaps. To be safe use the R45`s.
With a 11-1 engine I would recommend the AC "R45". The other 45 is the "R45{S}". This is what every catalogue will tell you to use. The "S" means extended tip. Thats it`s problem, the piston may hit the electrode and close it up. Been there, done that! It`s really a bitch to remove and reinstall the spark plug ignition shielding twice when finding out the hard way that the plugs tips are touching the piston and closing the gaps. To be safe use the R45`s.
regards, Herb
Team Owner
Joined: Oct 2000
Posts: 38,897
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From: Washington Michigan
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
43`s are too cold. The factory correct plug is actually a AC 44. Unfortunately they have been off the market for several years as obsolete available through the E Bay as overpriced not necessary originals. 
Stick to the 45`s unless you just want to become experienced in changing fuel fouled plugs. I even use 45`s in my A990 race hemi
Stick to the 45`s unless you just want to become experienced in changing fuel fouled plugs. I even use 45`s in my A990 race hemi
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Safety Car
Joined: Feb 2003
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From: St. Joseph Mo
Dad said: "Son, put AC plugs in General Motors cars and Champions in everything else."
Le Mans Master
Joined: Apr 2005
Posts: 6,359
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From: Seattle Area WA
Thanks Dan
Thanks Dan,
I plan on using those in my kid's '76 I'm finishing up. It has flat top pistons with '69 vintage 64cc heads and comes in at 10:1 SCR. With the flat tops I don't think I need to worry about the extended tip. This plug is listed as being applicable for a '68 Corvette with 10.5:1 compression so it caught my eye. BTW Dan, we're running the L-79 cam in this motor too
I plan on using those in my kid's '76 I'm finishing up. It has flat top pistons with '69 vintage 64cc heads and comes in at 10:1 SCR. With the flat tops I don't think I need to worry about the extended tip. This plug is listed as being applicable for a '68 Corvette with 10.5:1 compression so it caught my eye. BTW Dan, we're running the L-79 cam in this motor too
