What plugs for a 68 440 motor.....

[bandit67]

Guys, hopefully getting closer to firing up my first home rebuilt bb. I have put an HEI system for this motor and want to open the plug gaps to .45. Some had suggested some NKG plugs but they were almost 3/4 inch long. That would have put almost a 1/4 inch of threads INSIDE the combustion chamber on my old 68 915 heads. Don t see that working out so well So, any suggestions or just open up the stock number plugs to a wider gap...thanks....

 

[turbine68rt]

Guys, hopefully getting closer to firing up my first home rebuilt bb. I have put an HEI system for this motor and want to open the plug gaps to .45. Some had suggested some NKG plugs but they were almost 3/4 inch long. That would have put almost a 1/4 inch of threads INSIDE the combustion chamber on my old 68 915 heads. Don t see that working out so well So, any suggestions or just open up the stock number plugs to a wider gap...thanks....

I went with ngk iridiums XR4IX 7189. Runs great so far.

 

[MW 413]

Do not put those 3/4"plugs in a big block. They are for a small block appl. In Champion numbers you want a shorter "J" number plug for big blocks. The 3/4"plugs are an "N" number. I run J14Y Champion plugs in my 68 440. What heat range you run can vary depending on the engine build. If stock spec engine just look up on the net. I think stock plugs would be J11Y if I remember correctly but don't quote me.

 

[moparedtn]

Do not put those 3/4"plugs in a big block. They are for a small block appl. In Champion numbers you want a shorter "J" number plug for big blocks. The 3/4"plugs are an "N" number. I run J14Y Champion plugs in my 68 440. What heat range you run can vary depending on the engine build. If stock spec engine just look up on the net. I think stock plugs would be J11Y if I remember correctly but don't quote me.

J11 is correct, sir. I buy the Mopar originals (Champion) just for the heck of it. They're plentiful on eBay.
I like using the little reminder decals that come with them:

Yeah, they probably aren't the optimum plug for the engine, but.....

 

[threewood]

I am a fan of NGK plugs. The NGK 3332 will work for stock heads.

 

[66Satellite47]

Back in day I ran mostly Champions J10Y to J12Y depending on the CR, with my 12.2 CR motors liked the NGK, the Autolite also worked very well in the high CR. Not sure who's parts are the same now. I currently run NGK's in my 12.4 CR 512 motor (aftermarket heads 3/4" style though, not for stock style).

 

[bandit67]

Thanks Guys, just the info I was looking for. I assume the stock gap for a 73 was .35 and all of these will be fine opening them up to .45 provided I got the juice to fire them. Was informed opening up plugs more than stock gap with a stock electronic system will lead to misfires.

 

[Frank Mopar]

Guys, hopefully getting closer to firing up my first home rebuilt bb. I have put an HEI system for this motor and want to open the plug gaps to .45. Some had suggested some NKG plugs but they were almost 3/4 inch long. That would have put almost a 1/4 inch of threads INSIDE the combustion chamber on my old 68 915 heads. Don t see that working out so well So, any suggestions or just open up the stock number plugs to a wider gap...thanks....

That’s what I have done. Works fine.

 

[RJRENTON]

The type of plug (heat range and reach) are determined by the head. Aluminum heads usually use a 3/4" reach design. The typical Mopar iron heads use s 3/8" reach plug. The heat range is determined by many factors, starting with spark advance, total compression ratio, cam shaft configuration, intended use, carb jetting, etc.
Mopar used J-11y as std equipment for a stock engine. For my application, my RS23V0A******, modified engine, I use Champion UJ-11G or HO-8A NON projected nose plugs. Many people prefer NGK, or Autolite or AC. Perhaps, innitially, pick a middle of the road heat range in your brand preference and after a 100 miles or so run, read the plugs for engine operating conditions....white, gray or black color insulators, and make the determination to go up or down in heat range. There is no exact resolution....its a trial and error process.
Just my opinion of course.
BOB RENTON

 

[BSB67]

Funny stuff. There are all kinds of suggestion, but we have no information from the OP to even speculate as to what might be a good plug.

I'll assume a big block based on his "bb" statement. Is it a 440? There was no 915 head in 68. So is it a 68 head, or a 915 head? What is the compression ratio?

 

[bandit67]

Ok, BSB, your questions prompted me to relook and you indeed are correct. My 440 block, 2538430, was cast 11-4-66 and the 915 heads I pulled from this engine, 2780915, were cast in 67. HP BB Mopar book states they were a 67 year only, had closed chambers and another source said they were 74 cc chambers. I now believe it is a 1967 motor and not a 68. The block was stated to have been cast from 66 -72. The pistons I used are forged flat tops with small valve cuts.
KB piston book states that their simular flat top piston, with stock rod and stroke , and 72 cc head produces 11.5 compression with zero piston deck height. Mine was minus 4 k deck height and I used a .39 head gasket. I am GUESSING , as I did not calculate, that I am in the 10.6 to 10.8 comp range. I do not know what comp. ratio was when stock but have learned thru this thread that a colder plug is sometimes better as comp.ratio s go up...and that test driving and inspection of the plugs is best way to determine what needed. thanks guys, love the info from you all

 

[BSB67]

Okay. Good info.
I'm not sure what a 4k deck height is. Do you mean 0.004" below the deck? Four shallow valve notches?

If so, you are approaching 11:1 compression ratio with iron heads. Will you be running pump gas? The typical J11Y - J14Y will be too hot. Probably NGKR5670-7. This is two or three steps cooler than the J11Y.

 

[bandit67]

Yes on 0.004 below deck and yes on seeing how pump gas will work. Just two notches on the pistons, not four. Will start with the NGKs...thanks much..

 

[petieg383]

I too have 915 heads on my 440. I do not know the internals but previous owner claims to have had it rebuilt. It does have a forged crank, a mild cam, Weiand intake and 750 Holley with basic electronic ignition and iron manifolds. I've been running the Champion RJ12YC plugs for a while. No matter what I do with timing:

• No Vacuum advance which helped
• Dialed it back as far as 10 initial and 32 total, tried all initial settings from 10 to 18, all in by 3000rpm
• Tried octane boost - don't bother
• Got frustrated and set it to 18 initial and 34 total where it probably should be anyway
• I've tried other plugs but nothing seems to help (XR5's, Autolite 85s too). I probably should go 1 or 2 ranges colder for the hell of it.

I cannot get stop it from pinging under heavy load or full throttle acceleration. It has to be pushing 11:1 compression. I'm about to drop $70 on a 5 gallon bucket of Sunoco 110 leaded to see if that gets it to not ping.

Just be forewarned with these closed chamber heads. I'm sure they can make good power with the right application. I'm just not excited about paying $12 a gallon for gas. Welcome everyone's opinions and thoughts as well.

 

[Frank Mopar]

I too have 915 heads on my 440. I do not know the internals but previous owner claims to have had it rebuilt. It does have a forged crank, a mild cam, Weiand intake and 750 Holley with basic electronic ignition and iron manifolds. I've been running the Champion RJ12YC plugs for a while. No matter what I do with timing:

• No Vacuum advance which helped
• Dialed it back as far as 10 initial and 32 total, tried all initial settings from 10 to 18, all in by 3000rpm
• Tried octane boost - don't bother
• Got frustrated and set it to 18 initial and 34 total where it probably should be anyway
• I've tried other plugs but nothing seems to help (XR5's, Autolite 85s too). I probably should go 1 or 2 ranges colder for the hell of it.

I cannot get stop it from pinging under heavy load or full throttle acceleration. It has to be pushing 11:1 compression. I'm about to drop $70 on a 5 gallon bucket of Sunoco 110 leaded to see if that gets it to not ping.

Just be forewarned with these closed chamber heads. I'm sure they can make good power with the right application. I'm just not excited about paying $12 a gallon for gas. Welcome everyone's opinions and thoughts as well.

You said it. Colder plugs.

 

[Dennis H]

NGK. XR?

 

[Don Frelier]

I too have 915 heads on my 440. I do not know the internals but previous owner claims to have had it rebuilt. It does have a forged crank, a mild cam, Weiand intake and 750 Holley with basic electronic ignition and iron manifolds. I've been running the Champion RJ12YC plugs for a while. No matter what I do with timing:

• No Vacuum advance which helped
• Dialed it back as far as 10 initial and 32 total, tried all initial settings from 10 to 18, all in by 3000rpm
• Tried octane boost - don't bother
• Got frustrated and set it to 18 initial and 34 total where it probably should be anyway
• I've tried other plugs but nothing seems to help (XR5's, Autolite 85s too). I probably should go 1 or 2 ranges colder for the hell of it.

I cannot get stop it from pinging under heavy load or full throttle acceleration. It has to be pushing 11:1 compression. I'm about to drop $70 on a 5 gallon bucket of Sunoco 110 leaded to see if that gets it to not ping.

Just be forewarned with these closed chamber heads. I'm sure they can make good power with the right application. I'm just not excited about paying $12 a gallon for gas. Welcome everyone's opinions and thoughts as well.

My brother's 440 had the same issues. He ended up going to aluminum heads and a cam with more overlap. Cylinder pressures are still quite high. He was over 220 psi. Bandit67 is likely to experience the same problem. 10.5 : 1 with 915 heads is a problem.

 

[gooser]

you could try some champion J63 and good gas the stock 915 head was about 84cc back in the day they told you to mill the head. 060 and the chamber would be about 73.5cc

 

[BSB67]

As mentioned above. The details of tune-up, temp, cooling, timing, plugs can help. But if have cast iron cylinder heads and you're at a compression ratio of > 10:1, and a cylinder cranking pressure of > 165 psi., there is probably not simple fix