Thank you. :thumbsup:

Your car is awesome! Appears our builds have somewhat similar objectives and I'm a big fan of 2nd Gen's and Yellow.

My carb came with 6.5 power valves and 70 air bleeds.......seat of the pants tuning and experimenting along with baselines from the previous Demon carb have lead me to 5.0 power valve and richening the idle circuit. Somewhat opposite of your situation..........how many inches of vacuum does your motor have at idle? What A/F monitor are you running?

The carb circuit that I don't have a good feel for yet is the idle bypass valve........as is the idle circuit wants that valve completely shut (no additional air) which leads me to believe the idle air bleeds were too big. On the scale of available jets 70's are close to the largest. So I'm assuming smaller idle air bleeds will make the idle bypass valve functional. I don't like having any circuit set at the extreme range of adjustment high or low. If altitude, temp, and air desity change I want to insure there's room to adjust the circuit........balance is good. :)

Here's the tuning guide for the Ultra HP.
http://www.holley.com/data/Products/...R10565rev1.pdf

Getting a carb right in the garages is one thing, on the street is another, and under hard braking yet another.........there are times it could be considered a masochistic process. :D

Sieg... I bought an AEM wideband AFR system. Here is a link to their website http://www.aemelectronics.com/

This setup worked out well, the gauge is easy to read. It's a great tool to get real time feedback on the AFR for tuning like protour73 said.

:thumbsup:

Thanks for the kind words on the car!

Even with the GM H.O.T. cam (fairly mild, but better than the stock ZZ4 cam), I'm at 16-17" inches of vacuum at idle. I've gone to bigger idle air bleeds to try to lean out that rich idle which has improved it, but still needs work. I still have a slight stumble at take off.

The wideband O2 sensor I went with was the Innovate Motorsports MTX-L http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

http://www.innovatemotorsports.com/p...XL_All_Web.jpg

Thanks for the info gentlemen. :thumbsup:

The Innovative unit and Amazon Prime :unibrow:

Were did you boys mount your O2 sensor and guage?
The ideal world would be both engine compartment and cockpit. :grin:

Scott - That stumble may be a simple as lengthening your primary accel pump link by turning 1 or 2 flats (or more) of the adjuster nut. The timing of that squirt of fuel is pretty sensitive and critical in the final stages of clutch engagement IMO. Once that stumble is gone you can then tune for power with squirter volume and cam profiles which effect the fuel delivery curve.

The off-idle power and roll-on performance of my old Demon improved dramtically with a little larger squirter (.028 drilled to .033) and the dark green pump cam in the #1 position.

Roads are actually dry for a change - time to test!

The O2 sensor goes (If running headers) in the header collector (welded bung) just after where the 4 tubes dump into the collector and put the gauage anywhere you can see it

Gauge location:

http://i145.photobucket.com/albums/r...l/IMG_4408.jpg

Sensor location:

http://i145.photobucket.com/albums/r...l/IMG_4399.jpg

I put the bung for the sensor on the inside of the header on the drivers side a few inches back from where the pipes merge.

Here is a shot of the gauge location I used.

http://i1048.photobucket.com/albums/...psd63f0721.jpg

Thanks again guys :thumbsup:

Is it a major foul to mount it in the pipe behind the flange like Scott did?

I already beat the crap out of the #5 head pipe yesterday, torturing it again vs. installing the bung when the new pipes are installed would be easier. :sieg:

Mounting the bung behind the header flange is fine. On the new LS engine I put the O2 sensor for the ECM on the header side of the flange and the O2 sensor for the wideband on the exhaust side of the flange. Works fine.

:thumbsup:

Sieg, it was way easier when I picked up these new Hooker reducers with the welded flange which seal way better than the slip flange type. I brought the driver side into a locally owned muffler shop and they welded the bung on for $20!!

http://shop.advanceautoparts.com/wcs...r_pri_larg.jpg

Scott! Sieg is a master with the TIG torch!



:thumbsup: :D

Greg, having never laid down a single bead in my life (yet) I have to depend on local talent!!

SO Sieg is a master TIG artist? or is there an inside joke I'm unaware of? :headscratch:

http://www.acurazine.com/forums/imag...ies/finger.gif

I was out diligently practicing last night with my NEW Hot Rod NO Excuse $$ helmet and the reality is my eyes SUCK for TIG. I'm going to try higher powered readers or the 250+ magnifying lens offered for the helmet. :bang:

Thanks for reminding me and................ :cheers: to shat on your carpet! :D

Nobody ever said gettin' old was going to be easy...



I find that light is a big issue with lower power settings on the TIG -- which is why I have a helmet that's range starts at 5.... A lot of the time I'm welding at 7

No -- I'm just poking him...



If it positively absolutely must look perfect.... I take mine to a couple buddies that can lay it down. Me - not so much.

Nobody said it was going to be this hard either........being known as the Lat-g TIGtard is one thing :sieg: ........... Ol' Tucker's got his horn on tonight, ever have a Dane lick you on the ears then try to put the hump on ya standing up? :confused59:

NOooooo! Just put the money you'd spend on the equipment in savings account earning .001% interest, pay Billy Bob when you need something done and you'll be money ahead over a five year term! :lol:

That would be Abstract Artist son...................:lmao: :lmao: :lmao: :lmao:

Poor Tucker.... trying to find love in all the wrong places.

Close Jer but that guy looks like he could tune a carb. The glassed look like the right power though!

New boot in place.

http://photos.smugmug.com/photos/i-z...-zSbNsqf-M.jpg

Carb off and disassembled once again to triple check everything.

http://photos.smugmug.com/photos/i-P...PB4bbHL-XL.jpg

Pulled idle mixture screws, blew out passages, changed out the 6.5 power valves to 5.0, blueprinted the throttle shaft idle screws relationship to transfer slots so I don't have to pull the carb to know where they're at. 3/4 turn in on primary side puts the bottom side of the butterfly at the bottom of the transfer slot, 1/2 turn exposes .023", secondary uses a different thread pitch, 5/8 turn to bottom and 3/8 turn for .023.

You have to look close to see the transfer slot exposure.

http://photos.smugmug.com/photos/i-T...-TXbhdW9-L.jpg

If verified baseline carb settings don't get rid of the off idle stumble it's time to bump initial ignition advance from 14* to 15-16* and see what we get.

OK Sieg, "blueprint" the idle screws!! What a great frickin idea!! Excellent attention to detail. I have the carb off for the winter, as is tradition, so that I don't leave the corrosive 10% ethanol fuel in the bowls all winter. I will do the same to my carb. THANKS for the great idea. :idea:

I had some AFR heads with straight plugs on my gen 1 engine and had the same problem with header clearance on number 5 cylinder. I also had to dimple the header to make clearance to get the plug out. I used one of those cloth type insulating boots over the plug wire and it helped to keep the plug boot from melting.

Keep at that tune... one change at a time and you'll get there. Sounds like your making progress :thumbsup:

Are you thinking of getting a wideband AFR system for your car while your at it?

Had a chance to fire it with an absolutely positively proper and documented baseline this afternoon. When the temp was nearing 160* the idle was climbing toward 2K rpm with the pri/sec transfer slots exposed .023 and idle bypass valve at 1.5 turns out. :headscratch:

I said F it and started experimenting to see what it would take to get good off-idle throttle response. First move was reduce secondary butterfly opening 1/4 turn to lower the idle (Set at 5/8 out from closed) which dropped the idle to 1,600, another 1/4 turn dropped it to 1,250, this time I knew the butterflies were an 1/8 turn from closed. :headscratch:

I was checking response in between adjustments and it was still hollow with a stumble but improving. I reduced the primary butterflies a 1/8 turn and the idle went to 1,150, then another 1/8 to 1,050 and finally the hollowness and stumble was minimize. Next was 1/4 turn in on the idle bypass valve which had little effect on idle speed, another 1/4 turn moved the idle to 950 which is about optimum for this cam.

Next was idle mixture screws, keep in mind the transfer slot exposure indicated the butterflies were not equal dimensions from passenger to driver side on primary or secondary bores. The sweet spots ended up being 1.2 to 1.4 turns out and 10.75-11" of vacuum. Throttle response was finally close!

The test drive confirmed the carb was now in the ballpark, still has a very slight stumble but I can roll a 90* residential turn in 2nd gear and not have the motor fall on it's face which tells me the idle signal strength is finally close! I'm guessing it's within a 1/16 of a turn on the butterflies and idle mixture screws. :happy23:

I also switched power valves from 6.5 hi-flow 2-port to 5.0 hi-flow 4 port and that appears to have created a slight hesitation transitioning into the secondaries that wasn't there before. I'll throw some 5.5's in and see what happens.

So much for the Holley tech telling me that the transfer slot spec on this carb was supposed to be .025". Only thing I can think of is he must have been giving specs for a 4150 without the idle bypass valve. I ended up with the the primary butterflies about one turn open which is about .010" transfer slot exposure and the secondaries are open a 1/16 of a turn so no slot exposure.

I'm guessing closing the primaries a little further and raising the idle with the idle bypass valve will strengthen the signal and get it in the sweet spot.

I know.........it would be way too easy to plug the car into a laptop and push buttons. :sieg:

But I have a 60's muscle car not a Y2K tuner car. :rules: :D

I have Moroso sleeves sitting on the workbench and a spare boot.

Yes, I'm thinking about an AFR system, but I need a job before luxury items. :D

When I owned those heads -- I whacked the 3 and 5 tubes and extended them out to the driver side about an 1" or more (can't remember the exact number)... all it cost me was a cermachrome job on the one side header.

This mod entailed a LOT of work -- and lucky for me Stans Headers is not far from me and I'm one of the two people that Stan actually likes (that's a relative term) so they were very helpful making bends etc for me.

I had to cut the tubes to free the flange - mill out the remainder of 3 and 5 from the flange without enlarging the hole... mock stuff up -- get new 3 and 5 tubes... weld it all back up and.... Well -- it was more work than it was worth but it was a challenge and I like a challenge.

There are headers made for STRAIGHT PLUG heads.... but nobody will sell you just the one side.

The steering box is one limiting factor...........
http://photos.smugmug.com/photos/i-w...-wS8LC2Z-L.jpg

The limiting factor regarding header choices was the D-port exhaust. Doug's notes for my model 368 are 32, 56, 92, 93. http://www.pertronix.com/search/dougs/notes.asp

If needed the tube can be massaged a little more. :warning:

If you look closely at the header (driver side) now mounted to the wall by the leaking BeCool radiator.... you'll see the welded #1 tube (you can make out several mods on various tubes) - which also was "moved" in order to make room for the extended 3/5 tubes... which -- since I had to cut everything out - to mill the flange for re-use... new tubes were bent and a new collector.... and well -- you get the point.




http://i919.photobucket.com/albums/a...Pix/file-5.jpg

It appears the MSD high-temp "Race" boots won't handle as much temp as their standard grey boots. This Race boot had more clearance and less than an hour run time vs. the standard boot had 200 miles.

http://photos.smugmug.com/photos/i-x...-xFksms7-L.jpg

Massaged the tube a couple mm, cut down a Moroso sleeve and edge sealed with Permatex Ultra to control fraying, with the tight clearance slipping the sleeve over the plug first made it easy fit the boot.

http://photos.smugmug.com/photos/i-7...-7krfcrn-L.jpg

http://photos.smugmug.com/photos/i-2...-29cxLRn-M.jpg

I know this stuff isn't rocket science but hopefully a few may benefit from it.

Try an aluminum shield like you would see on a factory vehicle. Many used a full circumfrance shield the boot would slide into with a semi interference fit.
http://www.taylorvertex.com/Products...ting?id=220066

Thanks Todd, haven't seen those on the "open" market. :thumbsup:

you should be good now that you clearanced the primary. You could put all the tricks in there but it take air flow to keep it from burning up.

Nice job on the carb. Sometime you have to thow the book out the window and go by gut feel and fact. Are you getting any idle circuit from the secondaries?

:idea: Awesome! I can be the only guy at Lat-g with a mini-brake duct routed to the #5 primary! I'm on it! :D

Thanks - I should have tossed the rules on the carb sooner, but fell victim to trusting the tech's specification. :bang: I did email him my experience and results so hopefully it benefits others.

I do have a reasonable signal from the secondaries, now that I've found the zone I'll be able to fine tune balance front to rear and optimize signal and vacuum. Then I can get into tuning and testing the fun stuff - pump cams and squirters.

Wouldn't that be called a "plug duct?? :rules:

Glad you're making progress :thumbsup:

Gotcha.

Plug Duct acquired, installation should be relatively simple.

http://photos.smugmug.com/photos/i-K...-KLvG9Lz-L.jpg

:whistling:

Back to business..........

I fiddled with the fuel screws and throttle positions and obtained near 12" vacuum at 1K rpm which is as good as it gets with this cam IMO.

Throttle response right off idle felt good actuating it by hand. The initial timing was 13-14* with 21* mechanical. I decided to experiment with initial timing and see how the motor would respond. I bumped it to 15-16* and immediately had a big flat spot right off idle. WTF? Dropped it to 12-13* and still had the flat spot. Put it back to 13-14* and the flat spot was still there......I managed to create a flat spot without touching the carb settings, just changing the initial advance. :headscratch:

I list timing as 12-13*, 13-14*, 15-16* because that's what it is when locked down.

I've had subtle doubts since this motor went back together...........something hasn't seemed quite right and this latest issue is supporting my suspicions.

Gear drive or distributor possibly creating issues?

Dammit Sieg, hate to hear this!!! I am living vicariously through your ability to be able to be out working on your car. We are getting our butts kicked by winter this week here in Chicago. :bang:

I'm taking a little break from it........5 hours yesterday, 6 hours today, and probably 4 hours tomorrow...........pressure-washing concrete in the rain. :woot: :woot:

Probably best, or else you get wrenches stuck in the garage walls from the ole "Frustration Toss"!! LOL :warning:

Man carbs can be a bi?€h. Makes me want to mow lawns for a month to get efi...