mw66nova

iTrader: (13)

Well I went out last night for a Friday night tnt. The whole night I fought with the car. Actually been fighting with it all season. Looks like I'm going to do a hard reset and put the car back to the way it was last October.

Went from a 4.11 to a 4.30 gear. Best 60' was a 1.49 with the 4.11's. Best 60' with the 4.30's has been a 1.52.

Also changed from a cobbled together 750 with an older proform center section that was pretty well dialed in, to a holley ultra HP 850 that I have been chasing my tail on the tune for the last 8 months.

Not really looking for advice, just venting.

Oh, and I nearly smacked the wall at 1000'.

t-top havoc

iTrader: (3)

Did you see Elvis..??..

Good luck with the tune,
Best of luck for the season!!

brandoz28

iTrader: (1)

Carb tuning issues can be frustrating. What part of the track are you fighting?

mw66nova

iTrader: (13)

All of it. The jetting to get it "right" ends up in the mid and upper 90's. I've tried all sorts of airbleed combinations to try to get the jetting closer to box stock (84's squared with two powervalves). Last night I tried some stuff again but still ended up way lean.(82's and 90's, one powervalve) The track went away and we called it a night shortly after I nearly kissed the wall.

Best time to date with the new carb is a 10.91@125 with a 1.52 60' in about 1800' DA.

In similar air the old carb goes bottom 10.80's@126ish with 1.49-1.51 60'.

And it appears the 4.30's are hurting more than helping as the best 60' with them with either carb has been a 1.54 and best mph is 123-124.

zz17iroc

iTrader: (4)

Sorry I didn't make it Bro.

xpndbl3

iTrader: (5)

so you had to jet to the moon again to get it to mph best? Return the carb man. Something isn't correct with that thing.

cp87GTA

Have you ever thought about trying to tune the carb without the power valves? i don't run power valves, but I don't run a carb onthe street either. You can always put the power valve back in the front after you get your tune down. I'm only running mid 90 jets on a 406 sbc 950 carb on E85, no power valves. Don't have a clue what a lsx likes for jetting, but it sounds rich.

mw66nova

iTrader: (13)

Yup, that's the problem. Holley says the carb is too big...maybe it is...but quickfuel suggested a 950 for this engine, and pro systems suggested an 830. I'm at a loss. I'm at the point of looking into other fueling options all together. With the future goals of this car, fuel injection is making more and more sense. I'm looking into some of the new self learning systems.

1gary

Yepper-a EFI as long as you can dial in the fuel curve right certainly is more exact.For now maybe some old school plug reading might help get you in the ballpark.I know it doesn't cover the full range of your RPM,but at least it gives you a idea if you heading in the right direction.

mw66nova

iTrader: (13)

I am reading the plugs. Put fresh plug in, make pass, pull out on return road. This has been an ongoing ordeal since November.

Plugs show its lean unless I have like 96/98 jets in, with a number 28 high speed air bleed, and a front powervalve. It's got an aeromotive tsunami pump, sumped tank, #8 feed line, and a solid 6.5#'s all the way down the track as confirmed with a cowl mounted fuel pressure gauge.

Plug looks perfect with the old 750 and 86/93 jets with a front powervalve.

1BADRZ28

iTrader: (2)

you lost torque with the new carb. I would have kept a 750 cfm for your application. Patrick always over carbs most engines usuaslly. fyi i run a 1000 cfm with my 555. the 1150 is only worth 15 extra hp. You can get that 850 to work but it will take some work for sure. I Dynoed a few weeks ago with a new 950 Ultra and the fuel curve was all over the place throughout the pulls. It needs a lot of metering block work to make it right.

Truthfully that 750 Proform is 700 cfm wet (around 750 cfm dry)and the new Ultras flow a true 850 wet. So you added roughly 150 cfm to that engine through the carb. IMO that's a lot. I don't expect that carb to work well in a race application until you adjust the metering blocks.

I'd expect to see an increase in 60ft if you put old carb back on with the 4.30 gear.

mw66nova

iTrader: (13)

Well, I'm going to do a hard reset, putting everything back to the way it was last season. 4.11's will go back in, go back to the 750, the whole nine yards. Get it to where it will run the number again like it did last season and go from there.

RWB____s

why not do just a carb swap at the track? See what happens. lots of LS powered
F-body cars run well in the 9 secs range with just a 750 with a good tune on it. I realize that your not set up to run that quick "yet" but you are well on your way!

1gary

Truly I wish you well with this change and look forward to your follow-up posts.

DIGGLER

iTrader: (1)

did you look at your mph as you were changing jetting or just the plugs?
loss of torque could deffinately have merit when you are running a streetable torque converter. if you had a 5k converter in there it might not be as much of an issue.

i think first thing i would do is swap carbs and see how it runs. don't mess with the gear yet.

mw66nova

iTrader: (13)

i took both carbs with me to the track. here's the best passes from friday night:

best pass with the 850:
1.55
7.10
97mph
11.17
122mph

best pass with the 750 with a known good tune up:
1.54
7.02
98mph
11.02
124mph

last season in similar conditions and the 4.11's with the 750 the car ran 10.80's at 126 on a 1.50 60'

the absolute best passes to date:
10.76@126 on a 1.51 60' with the 750 and 4.11's in -273ft DA

10.91@ 125 on a 1.52 60' with the 850 and 4.11's in 980ft DA

TB2

iTrader: (1)

Those are large jet sizes when using powervalves. Are you running the same jets, powervalves, squirters, etc setup in each carb? Reading your posts I'm wondering if one carb just has a tune closer to what the motor wants and is not necessarily the carb cfm itself. Normally from my experience I will first jet for mph, and then worry about reading plugs. When I went to E85 I was having a lot of issue getting a proper tune on the carb that the motor liked. Reading plugs with the E85 was very difficult. I picked up an inovate afr gauge. They will work with all fuels, and they datalog. Best $200 I've spent on that car in a while.

http://www.summitracing.com/parts/INN-3844/

Shagwell

I fixed my carb woes.......put block-off plates on in place of the blocks & bowls, screwed the nozzles back in the manifold and hung the 110 pump back off the front......CURED!

ZONES89RS

iTrader: (2)

Hate to see that happen, it seems the if it isnt broke dont fix it statement is there, i would have bet the larger carb would have helped, but evidently it is in tune with the engine from TQ to HP.

You really have me wondering what a SV1 will do on my car, how much it will help or hurt, we will see if the clutch acts right when the time comes, this Texralia 700 doesnt act like the old CF.

84firebird383

I feel your pain. I went to a slightly larger cam and a slightly better converter only to run about the same. I went 10.9@ 124 in average air. where my best before was a 10.8@125. I think I hit the limits of my 870 street avenger and turbo mufflers.