Tuning help:496 BBC w/177 blower

[olds48]

I got a 496 BBC
11.2:1 comp.
Canfield 310 heads,lightly ported
1050 Dominator on a fully ported no-name intake
Solid roller 652 lift 308 adv. dur. [email protected](Comp street roller)
2 1/8" fender well headers

Car (3375lbs w/me) has run a best of [email protected] mph.Sucky 60' of 1.56.
I run 84 jets,squared,with no powervalves forever.All of a sudden it started running lean,and now it has settled out at 93 jets.Don't know what changed.ET and mph stayed the same?????

Anyway,wanted a little more power,so I borrowed a Weiand 177 mini-blower from a buddy.It has a 4150 mounting pad cast into it,so I used his 950HP carb on it.Put my 93 jets in for a starting point and it poured fuel out the boosters.Started pulling over at about 2000 rpms.Dropped back to 74 jets,squared,no powervalves to stop the pullover.The car feels like an animal up to about 4000 rpm then just noses over.Figured it was lean,but when you pull the plugs(NGK #8s) they are a little fat. :? Is there a cubic inch/rpm limitation for those little blowers?Am I wasting my time in general?Plus,it idles at like 20" of vacuum,compared to 5" normally aspirated :shock: When you rev it in nuetral it'll drop to around 15".Wide open in 3rd(in the neighborhood,so I'm only kicking it at about 50-60 mph the boost gauge reads "0".No boost and no vacuum.I'm wide open to suggestions any which way.Thinking about trying a tunnel ram with 2 750s.Probably just go back to the 1050.It was slow,but at least it was consistent and easy to tune.Suggestions please! :D

[jmarksdragster]

I don't know how you ran a 1050 with 84 jets and no PV's, 92 to 93 is about right. The 950 would want somewhere around 86 without PV's. If the jet requirements stray to far from those #'s, you have issues with the carb. Plugged air bleeds or passages, leakage between passages, stuck needles, incorrect float level or fuel pressure...

[Tod74]

My 1050 had 86 new I think with no pv

[jmarksdragster]

My 1050 had 86 new I think with no pv

That would be a 9375-1, the only one of the 8896 and up 1050 carbs jetted that low without PV's. Uses different metering blocks.

[Tod74]

My 1050 had 86 new I think with no pv

That would be a 9375-1, the only one of the 8896 and up 1050 carbs jetted that low without PV's. Uses different metering blocks.

Mine is an 8896

and I was mistaken...it had 88 jets not 86

http://www.holley.com/data/TechService/Technical/Carb%20Numerical%20Listing.pdf

[olds48]

Like I said,it ran fine for about 20-30 passes and then one day it started lean popping and ended up at 93s.Whatever the case it runs fine now.Fuel pressure and all seems to be fine.Got a gauge on the main line of the pump,before the regulator,that I can watch thru the windshield.Just idling it runs13-14 psi and going thru the lights it usually sits at 12-13 psi.I try to keep all my stuff good and clean.I clean out my filters regularly and have just recently blew out the bleeds on the Dominator.My real question was about the 177 blower,but I talked to a "tech" at Weiand today and he said "no way,that blower will never do anything for 500 cubic inches"Oh,well.

[kwillymac]

http://www.chevyhiperformance.com/techarticles/0610ch_big_block_chevy_engine/index.html

I think the biggest problem is the compression and cam. You just can't throw on one of the smaller blowers and use it without lowering compression and using a more blower specific cam. In this article they used a 489 and made great power. But you need less cam and compression. I have a 174 B&M Blower. They will make power on the bigger motor if the motor is set up for it. Years ago B&M told me I wouldn't make anymore then 550 HP with a smaller blower. It made 670 HP AND 646 ftlbs. torque on a mild 454. I DISAGREE!!

[olds48]

Thanks kwillymac.See,I'm already making pretty much those same power numbers with my naturally aspirated 496.That's kinda why I'm thinking it might be undersized for me.Don't really know that,just guessing.

[kwillymac]

Thanks kwillymac.See,I'm already making pretty much those same power numbers with my naturally aspirated 496.That's kinda why I'm thinking it might be undersized for me.Don't really know that,just guessing.The biggest thing with these little blowers is the torque. If you look at the rpm/torque curve it is really awesome. They will sacrifice horsepower on a bigger motor though.

You could check and make sure the blower pulley is small enough to make boost.