What spark plug to use in my Hemi Stroker?

[Beekeeper]

I started my Hemi a few times over this past week and am wondering if
I made the right choice on the plugs. I have autolite AR 53 plugs in it now but they
seem a bit on the cold side but im not a plug reader. After a few runs i pulled them and they are black and it’s running or at least smells rich. I’m running the edelbrock AVS2 carbs 650 cfm and have not done any jetting as of yet maybe i need to. Could the plugs be to cold? this is a 496 stroker with stage V
intake. Oh and am running it on 93 non ethanol pump gas.

 

[toolmanmike]

I started my Hemi a few times over this past week and am wondering if
I made the right choice on the plugs. I have autolite AR 53 plugs in it now but they
seem a bit on the cold side but im not a plug reader. After a few runs i pulled them and they are black and it’s running or at least smells rich. I’m running the edelbrock AVS2 carbs 650 cfm and have not done any jetting as of yet maybe i need to. Could the plugs be to cold? this is a 496 stroker with stage V
intake. Oh and am running it on 93 non ethanol pump gas.

If you have a 496 Hemi stroker with a 650 AVS2 and you are running Autolite plugs you need to go back and start over. Sorry to be so brash but speaking the truth.

 

[Beekeeper]

If you have a 496 Hemi stroker with a 650 AVS2 and you are running Autolite plugs you need to go back to about second grade and start over. Sorry to be so brash but speaking the truth.

Dang Mike just shoot straight with me! this is the first hemi i’ve ever built or owned so yes im really in first grade. So how about a helpful response now? and thats Two 650 avs carbs

 

[Hemirunner]

If you have a 496 Hemi stroker with a 650 AVS2 and you are running Autolite plugs you need to go back to about second grade and start over. Sorry to be so brash but speaking the truth.

That’s not helpful at all. He’s running two of them on a 496 stroker. Out of the box, they’re not configured for a dual quad application so you’ll need to take a ton of main jet out. Get a jet, rod and spring kit and get to tuning them. Get an NGK BPR6ES plug, as they’re much easier to read. Nothing wrong with the autolite plug other than they are difficult to read. That plug crosses to an NGK 6 which isn’t bad for that combo. It might want a 5 but I’d start with 6s until you get the fuel in the ballpark.

 

[Beekeeper]

That’s not helpful at all. He’s running two of them on a 496 stroker. Out of the box, they’re not configured for a dual quad application so you’ll need to take a ton of main jet out. Get a jet, rod and spring kit and get to tuning them. Get an NGK BPR6ES plug, as they’re much easier to read. Nothing wrong with the autolite plug other than they are difficult to read. That plug crosses to an NGK 6 which isn’t bad for that combo. It might want a 5 but I’d start with 6s until you get the fuel in the ballpark.

Now that helps thanks!

 

[toolmanmike]

Dang Mike just shoot straight with me! this is the first hemi i’ve ever built or owned so yes im really in first grade. So how about a helpful response now?

A 496 would probably like a 1000 cfm or so. Sorry I didn't see the (s) behind the word carbs in your description. I wouldn't run AVS2's on that combo. They are hard enough to tune on a 318 let alone 600 cubes. I personally don't like Autolite plugs. Designed for Fords and the converted numbers are often too cold which will make it run like crap unless you are at the drag strip always or buzzing around a Nascar track at 200 mph. You really need a hands on tuner that deals with Hemi's.

 

[Hemirunner]

A 496 would probably like a 1000 cfm or so. Sorry I didn't see the (s) behind the word carbs in your description. I wouldn't run AVS2's on that combo. They are hard enough to tune on a 318 let alone 600 cubes. I personally don't like Autolite plugs. Designed for Fords and the converted numbers are often too cold which will make it run like crap unless you are at the drag strip always or buzzing around a Nascar track at 200 mph. You really need a hands on tuner that deals with Hemi's.

They’ll be fine on that combo. They don’t flow as much as advertised and the AVS2 has a much better throttle response than the original. They’re simple carbs to tune and don’t require the headache of disconnecting fuel feeds and dropping the bowls to change jets. I ran twin 800s on my last two big cube hemis. I’m tuning the current one with a laptop.

 

[diesel_lv]

I run 496 at 610 crank hp w a 800hp fuel injection setup. The cfm is about 800. On a carb, I ran an Olds 455 w tunnel ram w 2 x 425cfm carbs n was right at 525 hp no problem with great response down low n never ran out of fuel up to 6500. I'd say 650 is a bit small for 496 but 850 would definitely be in the ballpark.

 

[Beekeeper]

I’ve been trying to find a jet kit that’s in stock for a while now. I had one on back order with summit for a while and they canceled it after I waited for a few weeks.

 

[Hemirunner]

I’ve been trying to find a jet kit that’s in stock for a while now. I had one on back order with summit for a while and they canceled it after I waited for a few weeks.

Looks like next year before those will be available.

 

[Beekeeper]

Yea that’s what I see as well. Guess it will be a good time to address the main seal leak.

 

[RJRENTON]

IMO.....
Are the Carter/Edelbrock AVS2 carbs configured to open in progression, like the origional AFB's were? Front half of the rear carb for approximately 1/2 of the time with the front half of the front carb opening and the rear half of both the rear carb and the rear half of the front carb opening together (governed by in this case, the AVS's air valve blade spring tension). I concur with the others, the carbs appear to be too large or jetted too rich. I'm not sure that the primaries of both carbs can be leaned sufficiently to prevent the over rich condition noted, without some modifications
Remember that the Carter/Edelbrock carb design utilizes the primary booster venturii as the source for ALL the idle and off idle fuel transition circuits. The metering jets and rods DO NOT control the fuel during low speed operation but the fuel flow origionstes in the jet with the metering rod at its largest diameter when the step up piston is fully down. The primary boosters and venturii design are very efficient and are likely feeding too much fuel at lower RPM operation. The black plugs are not likely to blame but are the results of the excess fuel but are collateral result. You don't say what cam, engine vacuum, compression ratio or ignition system settings, all of which will effect spark plug coloration and overall performance. Running two AVS carbs in tandem, was IMO, ill advised, but since they're bought and paid for, we'll have to figure out how to "fix" the issues. Do you have any info on the carbs innitial jetting....INCLUDING primary booster fuel feed restrictions, air bleed orifice sizes and any primary throttle plate closing angle dimensions (opposite the idle fuel transition slot), as this affects when the transaction starts to feed fuel. These primary booster venturii fuel feed circuits are thru drilled orifices and are not readily change-able except by drilling, but making them smaller is extremely difficult. Just talking out loud about possibilities......
BOB RENTON

 

[Hemirunner]

The primary jet/metering rod combo take over fuel duty once it’s off the idle circuit. The primary jet can be reduced and the metering rod enlarged enough to tune the carbs. The secondary jets will also need downsizing for this application. Standard setup is a .101 jet and a 7037 rod. The tuning kits are not in stock but it does look as though individual jets and rods are.

https://www.summitracing.com/search...etering-jets-for-performer-series-carburetors

 

[RJRENTON]

The primary jet/metering rod combo take over fuel duty once it’s off the idle circuit. The primary jet can be reduced and the metering rod enlarged enough to tune the carbs. The secondary jets will also need downsizing for this application. Standard setup is a .101 jet and a 7037 rod. The tuning kits are not in stock but it does look as though individual jets and rods are.

https://www.summitracing.com/search...etering-jets-for-performer-series-carburetors

Very true.....but its important to remember the jet ID and the metering rod OD relationship.....its not strictly dimensional considerations but area relationship. And we all know, area varies as the square of the diameter differences and to accurately measure fuel flow area, simple calcs must be done. To your point, the solution may be a combination of idle fuel thru the primary booster venturii metering orifices AND the primary jets and rods and the secondary metering jets, depending on the percentage of the time the engine is operated in each of the aforementioned fuel delivery circuits. I'm sure it will take a little time and effort to sort out the issues. OP should be concerned about oil dilution due to excessive fuel consumption, especially bearing scuffing and crank journal wear.....at least the possibility.....
BOB RENTON

 

[Beekeeper]

Thanks RJ I have checked the oil a couple times for fuel so far none I’ve only run this thing for a few minutes total as of now. I will post all the engine specifics here tomorrow evening when I’m back in the shop.

 

[Fran Blacker]

Thanks RJ I have checked the oil a couple times for fuel so far none I’ve only run this thing for a few minutes total as of now. I will post all the engine specifics here tomorrow evening when I’m back in the shop.

Are you running a vacuum advance? If not it might improve plug readings. Agree it needs jet/rod changes. If you individual jets rods I'd buy say 2 sizes smaller and 4 sizes smaller. Where ever you start I'd jump 2 sizes at a time to not piss away money.
Hooked up vacuum advance on my crossram by removing plug in manifold and tapping vacuum there. Short run time on it but plugs weren't black.

 

[Beekeeper]

Thanks Fran I will pickup some jets 2 sizes and 4 sizes smaller along with the correct rods. I have not connected the vacuum advance yet @HALIFAXHOPS (Ray) told me to connect it to timed vac port. I will fire it up again in the next few days and check timing and post where it’s at currently and get some jets ordered up from the summit link @Hemirunner posted above along with the plugs he recommended .
I appreciate all the help I know I could call some carb tuning guru to dial the carbs in but I want to learn to tune dual carbs.

 

[Hemirunner]

Very true.....but its important to remember the jet ID and the metering rod OD relationship.....its not strictly dimensional considerations but area relationship. And we all know, area varies as the square of the diameter differences and to accurately measure fuel flow area, simple calcs must be done. To your point, the solution may be a combination of idle fuel thru the primary booster venturii metering orifices AND the primary jets and rods and the secondary metering jets, depending on the percentage of the time the engine is operated in each of the aforementioned fuel delivery circuits. I'm sure it will take a little time and effort to sort out the issues. OP should be concerned about oil dilution due to excessive fuel consumption, especially bearing scuffing and crank journal wear.....at least the possibility.....
BOB RENTON

Calcs done for us...

 

[Beekeeper]

Calcs done for us...

View attachment 1183882

where did you find that chart? I found it for other models but not the 1905/06

 

[Bee1971]

I won’t even bolt on a new out of the box Edelbrock carb without pulling the top and checking float levels first , plus drop

Mine included , AVS-2 800 , honestly I don’t think it would of even ran out of the box , was so far off on one float

Plus one of the baffles was just laying in the bottom of the float bowl

Two other AVS-2 650s on friends cars , way off out of the box


How is quality control at Edelbrock over the course of the last few years ?