Hello,
About 6 months ago I installed a brand new Holley 350CFM from Jegs onto my stock (except for carb/intake) 225 slant6...the car is a 71 Dodge Dart. This was installed onto a 2bbl intake manifold with the adapter plate, I actually followed the steps on this site, DusterIdiot made an article about it. I am also using a manual choke, and a stock 4bbl air cleaner with a new filter. I also have Mopar electronic ignition.

The car seemed to run well after installing it, but I was having some running lean issues. When driving, I could just barely notice a little surge, mainly in 2nd gear (904 torqueflight) and it felt like the car was running a little lean. I went through the little booklet that came with the carb, and I made sure the float was adjusted correctly, etc. This carb is also hooked-up using the fuel line mod which was provided by SlantSixDan. The carb has the stock #61 jets too.

I checked for vacuum leaks, and I couldn't find any. The vacuum reading from the manifold seemed consistant too. I drove the car for several weeks, trying different octanes of gas, and then I burnt a valve! So now the car idles rougher, but smooths out when driving. I fixed the burnt valve, but now I don't really know what to do. I have the idle screws set propery (in-between where it would die if too rich or too lean). I heard something about a power valve, but I can't find any documentation on it, and I don't even know if that's the problem. Any ideas?

On another note, I will be shortly in-need of new gaskets for a BBD and this 7448. Does anyone know where I can get gaskets? Just the base gasket? All I can find are rebuild kits.

Thanks!

Power valve should not be your problem, it comes into play when you get under load & WOT.


Its kinda hard to do much without a wideband O2 sensor to really know what A/F ratio's you have. But right off one thing you can do is to turn the idle screws out as far as you can and it still idle good. This will richen the cruize and may show you enough about the missing at cruize to say that you are running lean. If richening it up from the idle screws helps the surge then up the main jets. If its that lean that it will surge then I would probably go 4 steps on the main jets (64 or 65 jets).


Its kinda hard for me to believe that it is that lean at cruize that it could burn a valve but still have enough fuel to idle good. There are many ways to tune this on a Holley but without a WBO2 sensor its kinda shoting in the dark. It may be possible that there is some trash or a restriction in the idle/T slot curcuits that are causing this. There could even be a problem with improper air bleeds or idle feed restrictors drilled at the factory.


I can run my engine so lean it will surge and its not burnt any valves, and shouldnt as long as it is at a cruize and light load that it is lean. This makes me think that it burnt the vlve when at heavy load or WOT. If that is the case then it could be a power valve problem. The power valve goes in the back of the metering block that goes between the bowl & the main body of the carb. But if its real lean on a cruize it could still burn when just running at a cruize (it would seem it would be surging pretty bad if thta was the case).


Just wandering, it would happen to be number 6 cylinder that burt a valve would it? Did any other valves on other cylinders show signs of starting to burn? Is there vacuum lines going to the number 6 cylinder from vacuum brakes or any other hookups on the runner port. If so take a pair of pliers and squeeze the line to block it off and see if it effects the idle of the engine.


Jess

I would jet up to 65 as Jess suggests and see how it runs. Can't see how you'd burn a valve at cruise loads either. A standard narrow band O2 sensor would be a great tuning tool here, and about $60-90 total cost.

Lou

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Home of Slant6-powered fun machines since 1988

Lou,

What brand O2 Sensor and part# are you thinking of for that price?
Does it have a digital read out? like leds? or a graphic display?
I would like to buy one, but haven't seen any that affordable........

I have had similar problems with surging but were due to over timing at light loads where the vacuum can kicks in and runs the timing way up there around 52 or more degrees. Never burnt a valve though.

Thanks,

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

I just go to my local parts store and get one for an 80s Chevy Celebrity or something like that. Can't remember exactly, I just wing it when I get there and see what comes in the box - 1 wire is about $30. Got a 3 or 4 wire heated for maybe $50. Sunpro makes an led (about 10) O2 readout that's about $25-35 online or at Advance (?) on the shelf. Has worked well for me.

Everyone pisses on narrowband, but they are a HECK of a lot better than no O2 sensor at all. I considered myself a good "ear and feel" tuner before the NB O2, but man does it save you a lot of guesswork.

Lou

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Home of Slant6-powered fun machines since 1988

Autozone:
$29.99 for an Autometer gauge
$10 for replacement O2 sensor 'bung'
about $32 or so for an O2 sensor for a 1992 Chevy S-10 Blazer 4.3L

I would also drop a few $$$ for a good vacc. gauge to see where things are 'coming on'...

Surging at cruise is caused by lean jetting under load, idle screws will adjust only the area from idle/plates closed to the transistion stage aka. the 'slots'...

Depending on what your vacc. reading says, the power valve may need to change also if it leaves a 'window' between cruise and acceleration (i.e. if you cruise at about 15" on the gauge and you drop down to about 9" when passing that big ol mack truck... then we need to look at a 9 or 10 PV... if you had a 6PV in there it may cause a lean out waiting for some 'enrichment' until the vacc. drops to '6').


It might also be good to map out your timing a bit since you can get fairly lean if it advances too quickly like Ted said... (52 at idle is like Feather Duster timing... not the best for sitting on the street...)

I have just converted to the BBD on Beater Valiant, I have the parts to put the O2 sensor in place here soon, and the last stage of BV project is a Holley 2305 staged 350 cfm carb...

-D.Idiot

Thanks for the info.

Where do you guys general, locate and install the O2 sensor?

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

It should be in the exhaust manifold, but only 1987 manifolds had this option (then end of the end for our /6 in production)...
Your next two choices in aftermarket exhaust is:

1) If headers, it should be put in the collector

2) If 'stockish' exhaust pipe, then place it as close to the manifold as possible (like s close to the mounting flange but not obstructing the access to the flange bolts...)

-D.Idiot

Hi Rob, Hi Lou!

Lou, I sure follow your logic on any beats none and I had been trending towards one...but didn't want to spend $500 on wideband. This thread generates a corollary question do you need a sensor for each exhaust pipe from a dutra dual setup?

rock
'64d100

I run that type of setup on my Hpak/Dutra Duals...and find that suprisingly, there can be a bit of a difference between the front cylinders in the car and the rear cylinders...on a short ram there might not be that much difference, but if tuning the idle circuit and you find that the back half of the intake warms up a bit sooner, you may need to dial it in differently...Also if you toy with a set of 'dual carbs' with dual exhaust or a 'split' manifold (i.e. you weld a wall so half of the 4 barrel carb only feeds one side of the engine like a dual plane manifold on V-8's), then it will help you dial in 'each side' a bit quicker than reading plugs...

The other benefit, when coupled to a vacc. gauge, is being able to monitor engine conditions a bit better on the fly...("I'm doing 55 and the vacc. gauge say 15" at cruise...then floor it to catch mr. '68 Cougar, and I get 3" on the gauge there's a bit of a bog, then 'wham' It goes real rich and vacc. is back up to 6"..." you may at that point want ot check your jetting, secondary action, PV...timing...etc...vs. "Wham", cut ignition put in neutral, pull over, stop, open hood, pull 3 plugs, read color, repeat until the police ask you "What's going on!??!")

-D.Idiot

I have only ever run one sensor in one bank.

Lou

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Home of Slant6-powered fun machines since 1988

What is the Auto Meter gage part number? or at least description name. I can't find any that cheap in Summit or Jegs.

Thanks!

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

With a narrow band O2 sensor you can always use a digital multimeter to get the volts off the O2 sensor............... (good enough for part time usage)

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

DusterIdiot,
Long time no see!
Thanks for the advice, it TOTALLY sounds like the power valve. If i'm speeding up or giving the car more gas, it runs perfect. If i'm cruising I can feel the slite hesistation, especially at higher RPM in 2nd gear. Even if the car is parked, if I slowly rev it it sounds great. Once it's pulling a high vacuum and steady idle, it gets more rough.
The problem is, I have no idea where the power valve is on the Holley 350CFM 7448, as a matter of fact i've never worked with a power valve before! I guess my main questions are:

1. What kind of power valve(s) should I get? And where could I get them?

2. Is there any documentation on how to install/adjust a power valve? Or could you explain it? Pictures?

Thanks!

You'll have to snag another bowl and metering block gasket (new carb versions are nasty, the 'blue' Holley gaskets can be reused a few times before self destructing)...

It's a matter of pulling the fuel bowl screws (start with a lower one and use a cup to catch the excess gas...).
Pulling the bowl
Pulling the metering block.
Using a 1" wrench unscrew the PV, wrench it new PV (snug but not 'overtight')... regasket and reverse the process to put back together (make sure the acc. pump lever is in the correct position, or you'll do this all over again to get it right)

Another thing to 'wonder' about is to make sure you don't have any vacc. leaks before any of this occurs, if you have one, it will have a heavy hand in why things aren't 'calibrated' or working right...

Some auto parts stores (like Baxters, Carquest,etc...) can order PV's and Jets for you... if you don't mind paying a bit more, and 'need' it you can go talk to Steve Tepper over on Portland Road and Pine Street at his performance shop (know his stuff, been there a while, a little pricey, but has jets and PV's in stock behind the counter...

If I didn't have to work the next two weekends, I'd have you over for 'tech and tune' if the weather was in good shape...

maybe next time,

-D.Idiot