I didn't get a chance to mess with it last night. I did pick up a new blaster ss coil this morning, I know it's not as fancy as an HVC or something but I'd feel pretty stupid if the coil wasn't the problem and I spent more on it than I did on the long block.... If the coil change helps out, I can always upgrade later, if I need to. I'm going to try and get it put in today, hopefully be able to go out, change some plugs and make a pull on it. I'll get video and whatnot.

Thanks everyone for the help and suggestions. I really appreciate it.

 

OK! News and not news. Not news first, the coil didn't fix the problem. News is, I've got 2 spark plugs with one hard pass on each, and pictures of both. I've got some really shitty video of one of the 2 passes. And I've got a new theory. My girlfriend came out and met me when I was testing and watched my second pass, she say exhaust backfires "like cannon fire" under load. I think it's got too much fuel. I think the 91's are loading it up and it's back firing everywhere. Looking at the spark plugs (and I'm the first to admit, I don't know shit) they look like timing is fairly happy, if not still a bit retarded. And fuel is fat. Fat, fat. On the first pass it actually stalled out on the top of the run. I might try backing the secondary jet down and see if it clears up. I'm gonna want a second opinion, of course.




Here's the shitty video. My phone was taped to the roll cage. Be warned, I curse in it. That's what I do. It's fairly awful but it is a twin turbo big block truck getting sideways on a sandy road, so it's kinda fun.

I'll get the spark plug pictures up tomorrow.

 

Are you going to cut the plugs, or is it going to be anywhere near that finite yet?
I love the video btw, it looks pretty sporty.

 

Thanks man. It's gonna be a handful when its all sorted. Im gonna cut the plugs monday, when I've got lathe access. Ill get pictures of un-cut plugs up today.

 

Spark plug pictures. I made two passes, the first one I shifted manually, it would rev to about 4500, backfire, keep pulling, back fire, shift. Then it would repeat, it seemed to lessen as I got more speed up and into higher gears. That video is horrible, and it's impossible to tell what's going on. Here is the plug from that run.
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The truck actually stalled at the top of that run, I started it up enough to turn it around in the road and that was all.

I put another plug in and did it again, left it in drive this time, pulls better if it's shifting below 4200 or so. It got pretty sideways a few times. The girlfriend was watching the second run, she says it was shooting big puffs of black smoke out both of the exhaust pipes. I managed to keep it running after I shut it down and pulled the plug. Here's that one.

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You can kinda see the fire ring on this one...
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I'll get the threads cut off tomorrow but I'm really thinking I might try a little less secondary jet and see if that makes any difference at all....
Also, I'm seeing what you mean about nickel plated plugs, I didn't even snap to the fact these were black until I pulled them back out of the engine.

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They look like the timing and heat range are pretty good you are going to haft to cut them or if you can use a magnifying glass and good light you can sometimes see it . Otherwise pull the header and look at the color in the port but you have it shut it down at the point it is to get the reading if your port is black and sooty then you are in fact rich .if it is gray or tan its not. It it's white witch it won't be looking at the plug then you are lean do you have a wideban 02

 

I'm gonna cut them tomorrow. And get some NGK's and try again. I think I'd rather put a campfire out with my face than have to pull one of these headers after making a run, then put the damn thing back on to drive it home. I do have a wideband.

I dropped the secondary jet from a 91 to an 88 and I think it got better. It feels like it backfiring later (4700 rpm-ish) and not as violently, it also seems to pull though it quicker. I'm getting 13's on the gauge when it backfires but other than that I'm seeing 10's under boost. I'm gonna take out a bit more jet and see what happens. It almost looks like we're getting somewhere.

Perhaps the N&S were a huge limiting factor (obviously) and I tried upping the secondary jet a bunch, and adding the BRPV and the vent tube extensions and the fuel tank vent but the N&S just weren't getting enough fuel in. So none of that shit was having any profound effect. I went with the .150's and I was too busy trying to keep it from puking all over itself all the time that I never really drove it under hard throttle. Maybe now, all of a sudden, *everything* is working because it can keep the bowls full. Maybe now it has too much fuel under boost? Those of you who have been kind enough to stick around through all of this might remember that everybody seemed to be kinda surprised that all the carb mods weren't making a huge difference. Maybe they're all working together now? Just speculating, trying to make sense of the whole damn thing...

 

Seems reasonable to me

 

I don't know how practical this thing would be with your headers, but have you looked at a Colortune kit? Just remembered that thing from back in the day. www.carbtune.com

 

Yeah I hear you on n&s lol I get a kick out of people who have all -10 fuel line and just can't wrap their heads around the fact that all that fuel can't get in if you leave the tiny n&s .

 

Nice! I sound reasonable! What do you think of the plugs? I know the black isn't the best for reading but I'd love an opinion.

 

I gotta be honest with ya, I don't have any idea what that would do. I'm confused just looking at the picture of it.

Some of us just learn a little slowly, that's all.

 

Man that had me in tears!! LOL

 

The Colortune will allow you to see inside the cylinder in real time and make adjustments to the mixture. They have a color scale so you can tell whether you're rich, lean or optimal. Been around for ages, could help with the dial in. I'll see if youtube has a video.

 

Ok, there are some videos of the Gunson Colortune, one of them shows an MGB using the device. Just type in Colortune into the search box.

 

The plugs I see all look like you could stand a little more timing, and if it's in the 10s when it's not poppin, you definitely need less fuel. I'd pull some more fuel and leave the timing where it is for now. I'd be lookin for low 12s for AFR at WOT.

 

Yep and then add timing till the heat mark is just past (on the thread sied ) the bend or just below it and bam you have it already figured out. If your timing is really low and is below the bend then go a heat colder on the plug. If you can't get it past the bend go a step hotter.

 

that sounds a good theory bacon ,when i was setting up the 500cc twin , i had a 186 main jet in there , and it would still pop and bang and go lean , then clear then the same ...then i changed my float bowl/fpr feed point to in front if the intercooler , and it went way rich and would run at 4500 and no more ...then i tried a 145 main , and it went from 48 bhp to 112 bhp . ,,ended up with 132 mains and 135 bhp .

really interested to see what a 12:1 afr will do for this !

robert.

 

difinatlet fat, I'm interested to see how they look once cut.

 

definetly fat