I NEED SPARK PLUG RECOMMENDATIONS

Hey, Guys: My build is a 545 cu in, A429 heads, .719 lift mech roller, Victor intake, 13.3 c.r. with a Pro Systems SV-1 carburetor. I run 110 octane, and the car see's mostly street duty (cruises, and shows). I have Autolite AR 3934 plugs in it presently, but they seem to be breaking down. The car runs just great, until I get into it - then it bucks, stumbles, and back fires, and just won't accelerate. I've been through the ignition system, and haven't found anything wrong, fuel pressure is steady at about 8 PSI. Any suggestions??

Wayne (SAWDOFF) Pearce

3922 plugs?

Have you tuned the carb? The 3934's should be right for that combo. Are the Plugs old?

The street it may want a warmer plug.........AR3935 or the carb may need some tuning.
May use a extented tip plug if you are doing a lot of part throttle/idling....AR3923.

Thanks to all that reponded! No, the carb has had no tuning done to it yet as I want to get Pro Systems involved in that - besides, I wouldn't know how, or where to start. The plugs have less than thirty miles on them, but they ain't looking pretty - black and sooty, but until I jump on it - it runs beautifully. My header coating is turning hazy for about six inches from the heads, I was told that this is caused by a lean condition. How can I have both a lean condition and sooty plugs at the same time? I've tried a new cap, rotor, coil, and different wires, because I had all this stuff on hand (I even put my old 1150 Dominator back on just to satisfy my suspicions about the SV-1). I thought I saw the fuel pressure dip for a second, so dropped and cleaned the fuel filter - and it still runs like crap when I jump on it! Ugh - embarrassing!

Wayne (SAWDOFF) Pearce

Sounds like you have fouled the plugs.........rich carb or too cold of a plug for low rpm driving.

Hey, Lem: You recommended AR 3923 extended tip plugs, is there a risk that the electrode will come in contact with the pistons? If you think they'll be okay, I will start looking for a set of them tomorrow, thanks!

Wayne (SAWDOFF) Pearce

Wayne Pearce wrote:Hey, Lem: You recommended AR 3923 extended tip plugs, is there a risk that the electrode will come in contact with the pistons? If you think they'll be okay, I will start looking for a set of them tomorrow, thanks!

Wayne (SAWDOFF) Pearce

You gotta dome?

Hi, Lem: No, the pistons are Diamond Flat tops 13.3 cr about .010 in the hole.

Wayne

You are good to go.....nothing in there for the ground wire to hit

Thanks, Lem! I couldn't find them locally, so I ordered them from NAPA - promised for Saturday! I will let you know how they work out for me, thanks again!

Wayne (SAWDOFF) Pearce

Lem Evans wrote:Sounds like you have fouled the plugs.........rich carb or too cold of a plug for low rpm driving.

I've had good luck with Autolite 51's. I've run them on the dyno and in the boat for years, they stand -up to 250-300 Nos shots very very well.

One year we ran a set of Champion:C5PCX


The dyno guy have them in on the dyno ran just fine. Put the engine in the boat and went to the river the next weekend. Boat ran about 3-4 miles up river and started dropping cylinders( felt like the timing was retarding) it finally about stopped running. After trying to figure out what the hell was going on I changed 4 plugs ( always keep at least a spare set in the boat) to Autolite 51's, fired up and went a couple hundred yards and the other 4 champions fouled. Pulled those out and all was good. Those things didn't like part throttle crusing at 3,800.

I was surprised the MSD and MSD coil couldn't keep them happy.

G-

Hey, Lem: I just wanted to let you know that the AR-3923 spark plugs did the trick, the 545 pulls VERY hard through 1st, 2nd, and 3rd gear. By the time I got into 4th it stumbled a little around 6,000 RPM, but I noticed that I might have a fuel pump problem starting to rear it's ugly head! When I get the high RPM stumble, the fuel pressure starts to fall off. I also noticed that the fuel pump has been running quieter than usual (Holley Dominator) it normally roars and growls like a hungry bear. It didn't lose pressure, but it fluctuated from 8 PSI down to about 4 1/2 to 5 PSI. Think maybe it's time to say good bye to the Holley pump?? Thanks for the plug recommendation!

Wayne (SAWDOFF) Pearce

Bolt an Aeromotive A1000 and be done with that.

Hey, Guy's: Installed a new Mallory pump, all is well now!

Wayne

I just changed a few things on my car this week and installed a new set of AR3934's. Fired it up and I noticed fire jumping all around the fat part of the porceline just before the socet flats on 1 of my plugs. Pulled the plug to inspect and can't find even a hairline crack In stalled a new one and it's A/ok. I wonder if Autolite is made overseas now too

Hey, Rick: I had the same problem with a set of AC plugs with my first big block. I was in too big a hurry to get it running, instead of waiting for the correct Autolite plugs. They too were giving me the spark jumping all around the porcelain, and giving only a low grade "fizzle" of a spark at the electrode after only a couple hours running time!

Wayne (SAWDOFF) Pearce

Wayne I have never seen an Engine that needed 8 psi fuel pressure, I think you can drop that to 6.5 to 7 psi and it might help with your richness....


Randy

Hey, Randy: Thanks for the suggestion - tomorrow I will drop the pressure back to 6 PSI and give her a try. I thought I read an entry here just recently (can't find it now) that said to raise the fuel pressure up to about 8 PSI to make the SV-1 happier at higher RPM's.

Wayne (SAWDOFF) Pearce

Wanye,
I got a SV-1 also and I had the same issue, threw alot of things at it it would only do it at top of 1st gear 6400 slight miss and at top of sec very slight there, I called Patrick of PRO SYSTEMS and discussed it. I had one of his regulators but was not using it and have a mallory 250 pump . I had steady 7psi on both bowls, both had gauges. He insisted I install his system which has a vacuum line going to it to adjust psi as vac decreases. Well I installed and went to the track, set at 6 psi at idle with fuel level just at the bottom of the window. At WOT it would go to 12psi. It never missed again and ran .16 faster than it ever has, I was surpised to say the least. On your SV-I you may have to adjust air bleeds to clean up the idle, I have experimented with it alot the past summer made close to 300 passes on it. The carb setup is just about excactly what it came from pro systems now and is deadly consistent.