hey guys I have been messing around a lot on my car with the plugs and I haven't found a set good enough yet. I'm struggling with heat range right now, the porcelain will not stay clean on the set that dart recommended for me (ar133). since then I have gone to ar134,and 135 with the same result then one day I threw in a set of autolite regular copper plugs part number 24 to run it for a 5-10 mile drive (with a handful of WOT runs) and when I pulled them the porcelain was clean, but I could not tell weather or not I was rich because the plating on the plug is black, so it makes the base ring not so easy to read. I want to go with NGK racing plug so my question is with my combo what heat range would you choose( I was thinking -6 or -7)?also should I go projected or non-projected? I plan on taking my car to the track some time next month and I want to have a ok baseline before I get there.
my motor is a 11:1 388
vic jr intake
speed demon 850
dart platinum 230cc heads
solid cam .518in .536exh lift .244in .252exh dur@.050 with 1.5 rockers I have 1.6's 106LSA

 

if you're not spraying nitrous you should be ok with the TR5's, the 6's are the most reccomended plug for nitrous.

 

if i run motor i run my accel shorty plugs on a 175 shot im running ngk 7's its 9.8:1 and you wont keep them clean if you drive it on the street. i probly need to go to an 8 for the bottle because they looked like they porcilin became oblong after racing saturday, probly melting it. i was running yr5s and they were not horrible but arent the best street plug. right now im running ac delco r45ts's lol they stay perfect but dont shoot any nitrous the them.

 

i'm running the accel shortys 276S, one range colder than the hottest 278S and I don't have first complaint....I spray a 150hp shot also.

 

i like my shorties but i dont know that i would shoot juice to them, i can remember which ones they were but i believe they were the 276's

 

Try this link
http://web.camaross.com/forums/showthread.php?t=431689

Jerry

 

NGK -7 race plugs

If they're a tapered seat plug
R5674-7
Stock number 5034

 

NGK -7 race plugs is what I use, my combo is similar to yours.

 

thanks guys ill try -7 and go from there

 

I did it all of last season and it worked like a charm...once you get the tune down(a/f ratio), its all good. Why wouldn't you run them with nitrous xx11seczxx?

 

I would use the 6s for motor or even on a small shot.

 

Rule of thumb for heat range. The tip of the plug needs to be just hot enough to burn off the deposits. Too cold and it fowls up. Too hot and it melts the tip off.

Jetting and timing will affect the plug temperature. Using a -7 for example may be a perfect heat range until you change timing or jetting. Too much timing or jetting and you may need to go up to a -8 for a colder plug.

Like everything else, the temperature range of the plug is a tuning aid. What works well in one engine may not be the best for another.

The race plugs are cheap. Buy a couple of different heat ranges and experiment. If you have any kind of dome on your pistons or the engine has been zero decked, invest in some indexing washers to move the plug ground strap away from the piston.

 

im running flat tops, deck hight is .025. my timing is locked out at 36* ( my car likes the locked out timing for some reason) im running factory size jets in the carb (85P, 93S) the car has had alot of trouble with fouling plugs out at idle. I think it's a combo of the wrong size power valve (I'm running a 6.5 with 8in of vac) and too cold of plugs

 

What the heck kinda motor are you running that size of jet in, what are the DA's, holy crap that is big jetting...call me stupid, but obvious wrong size PV, get a 3.5 or 4.5 in there, are you blocking PV's on the rear i take it? give me engine specs, your waay over jetted, how do i know..been there done that trying to read plugs, throw all that out the window now, lean out jetting/PV's until you get to the track for now, and then and only then WATCH the mph, make 2 baseline, then go down 4 sizes and see what happens to mph.

but yeah, your approaching alcohole jet size there.

 

it's the factory size jets for a speed demon 850, right from their web site. rear pv is blocked. any Idea how much I should lean it out??

 

The only thing i want to know about BG carbs is that they belong in the trash based off what i've seen in person, talked to guys that have tried to dyno/tune them, and guys that tried to use them for racing....but anyways LOL!! I know they use a different metering block set up than a standard holley, so i have no idea how swapping jets will affect A/F ratio...i cant believe that BG has things so screwed up internally they need alcohol sized jets box stock in a 850cfm carb...that's just fricken crazy.

Me personally, if the rear PV is blocked, I would go 4.5 PV based on your 8" of vacuum then install 78's in the front and 84's in the back for now, then once you get to the track and can see what your mph is doing, get two solid baseline runs and then start going up in jet size from there, I always went up 4 initally, if it slowed down i'd drop down 2, if it was still slow, then I'd drop 4 below inital baseline jetting and see what happens.

That just blows my mind though, if nothing else this is precisely why BG has such a terrible reputation, **** poor quality control, and from what i've heard the worst customer service in the industry.

Let us know how you come out when you get time to rejet initally, but i think this will help tons with your plug fouling LOL!!! might as well pull the carb off, and stick a gas can upside down in the plenum and drive around.

 

I was fouling plugs even with a 650dp holley with 67P, 78S the only thing my BG850 and my holley 650 has in common is the they both have the same size PV, which is whats making me think it's the PV. I will buy a set -6 and -7. I have thought about blocking the front PV as well but the car needs to be street friendly so im not to sure about that

 

I have a BG850 speed demon DP in a cupboard in my garage. They're jetted fat but that doesn't mean much. I had it on a 383 and a 454 but yanked it off when I switched to alcohol.

You can have 3 Holley 750's with 3 different list numbers sitting beside each other right out of the box. All three will be jetted differently and all three will perform differently in power and mileage even though all three are calibrated the same to give the best air/fuel ratio.

The factory jetting is a starting point and is jetted for sea level conditions. Typically for every 2000 feet in altitude or density altitude, you can drop down one jet size. When removing a power valve and installing a plug, you need to go up 8 jet sizes to compensate for the lost fuel from the power valve.

Drag racers don't normally use power valves because of the inconsistency of when they'll open or close. For street use, keep the power valves in.

As I've said before, jetting is only a part of reading plugs. Jetted too fat can be also corrected by adjusting the timing however every engine setup likes a specific timing. The only real way to know what timing your engine likes best is on a dyno. You find the best timing before doing any other tuning. Any tuning you do to the engine will not affect where it likes it's best timing. If the timing is already at it's best place, then you can play with other things like jetting, plug temperatures and gaps, valve lash, etc.

 

wee both of these carbs you tried brand new or brand used? that will explain alot, if even the old holley was brand new and you were still fouling this bad, i dunno what to tell you other than plug temp range for n/a driving wont make that big of a difference to cure what your talking about, it'll help a tiny bit, but is not the cure all.

the PV is there to help make the jump from idle to wot, racing only, sure you can get rid of it since the gas pedal is to the floor before the lights come down anyhow, but trying to drive around the pits, or trying to do any driving other than wot...your going to have serious, serious plug fouling problems since your going to have to up jet soo much to help give carb more gas that PV normally does when installed.

 

both carbs were used but rebuilt by me before I used them, Its got to be the power valve thats causing my fouling problem. If the power valve is open at idle cause my vacuum is to low wouldn't that dump fuel in it at idle??

 

With every engine we've ever had in our street/strip arsenal, we've always just cut the vacuum reading in half, and installed whatever that was for the PV's, never had a problem. Then since i started blocking the rears, I tend to go 6 over whatever the front jet is and it's usually pretty happy there too, but i typically tune to a lean setting for racing so car does'nt move around as much # wise, my race ET's are typically .2-.3 slower than what it can do with just up jetting.

I'll say this now since you brought the voodoo....you said USED CARB and REBUILT....rarely...i take that back, I've NEVER seen a used rebuilt carb do anything but cause nightmares such as this, if sent out to a carb company, that's another story, but there must be some bad mojo with homebrewed rebuilds...nothing, absloutely nothing but troubles.

Is there anyway you can beg, borrow, steal a known working carb...and when i mean known/working carb, i mean pull it off a running car, not one that's been on a shelf that worked good last season/year ago...I'm being absolutely serious here, it may just be the black cloud over my city, but never have i seen a used/rebuilt carb, or good working carb that's been sitting on a shelf ever bolt on and be right, put down your tools now, and start a serious search for a carb to borrow and try, and see what happen...my guess, your going to put these carbs your fighting back on the shelf, put a new carb on, and wonder why you did'nt do this earlier...if i'da known this posts and posts ago, it'd a saved everybody ALOT of time diagnosing-seriously. I thought i could revive my neighbors 650DP, thought i could be smarter/better than all the buddies that tried a rebuild in the past, I spent hours, being stupidly methotical since i was going to prove a point a home rebuilt carb could be accomplished and work.

Sadly, it did'nt work. Granted once we put it in the car the car finally started, ran, idled, and he was able to drive it, but i was sick/embarrased at the amount of time i put into it, and felt bad i had the guy buy all the new stuff i listed, and we just could not, no matter what we tried, no matter what guru we called over, we just could not get it to run right, neighbor started thinking maybe ignition was the problem, I went over and pulled the 950hp off my car, bolted it on...car fired right up, and ran like a top. no more loading up, chugging, black smoke, off idle hesitation, etc...i did warn him prior to ordering parts, theres no guaruntee i could get it to run right based on never seeing anybody having luck doing it, but he wanted to give it a shot, so i did the best i could give him and it did'ntpan out

 

you never asked if it was rebuilt until your last post IMO I didn't think it made much difference to mention. I have personally rebuilt a couple dozen carbs for people and no one ever complained. the only thing you do is replace gaskets, pump diaphragms, and needle and seats. I'm not sure what the difference is internally between one that has been rebuilt and a new one that would make it run that much worse. I'm not a well off (financially) person I can't afford to drop the coin on a new carb, right now I am still paying off the loans from my bottom and top end. anyways I have friend with a quick fuel 950 carb I see if I can borrow it for and hour.

 

well I got the new 4.5 power valve in, and the ngk -6 (4449). I also jetted the carb down to the jets IHI suggested. I sat let it idle for 5min the putted around the neighborhood for 10 min pulled the plugs and there CLEAN!!! (yes I was surprised) before the changes if I let it idle for 2 min it would have fouled all the plugs out, it actually looks like I need to fatten up the IMS a little. also the idle quality improved 10 fold I noticed a big difference as soon as it fired up (didn't seem to load up like it did before). I have been fighting this problem for awhile. anyways if the weather holds out I might do a little WOT testing tomorrow.
thanks every one for your help, ill post some pics of the plug tomorrow

 

Glad to see your on your way to figuring this out, but reading about being able to do some WOT testing....that sucks!!! as i sit here getting ready to go out and start ANOTHER round of snow plowing, and once again single digit temps and below zero windchills

 

yeah I know what your talking about (I lived in western PA for a year), well I thought I was running lean so I jetted up 4 sizes to 82P 88S and heres a pic of a WOT run after the jet change it still looks lean to me.
[IMG][/IMG]

I guess I can return it to the stock sizes of 85p 93s??? and see what happens i'm just glade I got the idle circuit taken care of.

 

what type of ignition are you running?

When are you going to be able to goto the track for true testing to see where you need to be at? Reason being, ever since i switched to msd stuff i gave up trying to read plugs, i was in your same situation yrs ago, i kept trying to jet until i got some color...the color never came until i got into the alcohol sized jets you just took out. I asked some other guys at the track WTF, and everybody told me, stop trying to read plugs, start looking and tuning for mph since aftermarket ignitions will play tricks on ya as far as tuning goes.

So i'm offering the same advise to you, drop the looking for color issue for now, it's running clean, and so long as your not getting pre ignition or lean pops, your fine. take it to the track and start jetting up or down for best mph and you'll be fine.

 

I have a Mallory unilite dizzy (locked out) MSD 6AL, MSD multi-stage retard(for nitrous when I use it) with start retard control(to help starting with lock out timing),and Accell super coil. not sure when I'll take it to the track next. anyways thanks for you help IHI

 

halo plugs
http://www.haloplug.com/