howdy-

my new 2300 series 350cfm holley 2barrel came with 61 jets and 85 power valve. It initially ran good until the vac. dipped low enough to open the power valve (8.5") then it would stutter and choke on all the gas. It idles at 12" of vac, so as per the holley instructions, I put a 65 power valve in. Now it pulls up to 6.5" of vac, then stumbles.

My question is- I have read that the power valve's job is to supply fuel when vaccuum isn't high enough to pull enough gas- extended high load or wide open throttle. The power valve allows the car to jetted lean for economy, while still having power at low vac. So then if my car is choking on the power valve, even at 6.5" of vac, could that mean that I am running rich main jets, and would be helped more by dropping the main jet size instead of delaying the power valve (I have a 55 I can put in, and I wonder if it would still choke at 5.5" or if it would need the extra gas)

the reason I am confused is that my plugs are looking nice, not black, but clean with a little brownish grey. Do I need to let the car stutter at low vac and turn off the ign and coast to a stop and check the plugs? I am planning on hooking up a narrow band a/f meter to help me get a clue.

thanks

kevin

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madam im adam

Can you post or send me some pics of your throttle linkage? I am installing the carb right now. I dont know if what I have will work or not. My email is stelki@yahoo.com Thanks

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Excuse me, does this smell like chloroform to you?

Are you talking about mainifold vacum . 12 lbs would be low for that. Something is not right here with 12 lbs of manifold vacum. That is about what my race engine has . But it is radical race engine . Thanks Ron Parker









Bagels Juiced Im Bamboozled

i assume you have a relatively stock engine? you should be pulling more than 12" of vacuum at idle. how does the engine run otherwise?

the power valve supplies extra fuel that is needed at full throttle/high load so that the engine won't be too rich when running at part throttle/low load. it's more of a compromise.

give some info on the rest of the engine(headers, cam?, compression) so we can better suggest fixes.

zedpapa

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1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

I agree that 12" hg is LOW vac reading for idling... did you adjusted your valves right? what cam do you have there?

Anyways, due to the symptoms you describe, it seems to me that you have too much primary jets. I'd start from 53 and a 8.5 power valve. A 61 jet in a 350 cfm carb (with near 36 mm of htrottle bore at the base IIRC) is like having a 500 CFM (near 40 mm throttle bore at the base) carb with #70 jets... just TOO MUCH jetting for a /6.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

thanks

The engine cam out of a running car ( '63 valiant pushbutton) - I drove it before the seller pulled it, and it had a lot more balls than my stock 198. the guy said when he bought it he was told it had a shaved head, oversize valves, and a radical cam, but that he didn't really know anything for sure. The price was right, and I knew it had compression, so I was sure I could make it work.

it is a late head (not hydro, but no plug tubes) engine with headers, 3" collector, 2 1/2" pipe with flowmaster 40. Im running 61 jets and 65 power valve. The cam is almost certainly aftermarket but the rocker lash is still set .010 and .020.

It came with 3" pipe all the way back and 69 jets in a 6221-2 inverse idle 2300 series inverse idle carb (replacement carb for 70-72 ford) The motor had points ignition which I changed over to my "73 electronic ignition.

I investigated a tiny bit when I had the 63 oilpan off the motor to switch to 73 oilpan, and when I switched to the new carb. The oilpan had homemade baffles welded in, and the intake was ground to match the opening of the two barrel adapter to allow flow.

I think my biggest challenge is that the car has a real low rear end ratio and the power band is much higher and stronger than with my 198 (old soldier). The new motor is pulling hard from 2500-4000 rpm. The vac. reading is steady and when the car is warmed up it idles at 750 in drive with the brake on @ 12.5" of vac. At cruise it pulls 20-30" vac. It pulls smoothly from cruise vac to around 7", then it doesn't lose all power like before with the 85 valve but WOT isn't strong like it should be, and throttle response should be much crisper.

The car definitely has a hesitation off idle and sometimes feels like it is loading up when I first come off the highway. My first full tank yielded 12mpg, but I drive 80mph to and from work a lot It's my daily driver so I can't afford to guess lean and drive all day, I guess I'll start with a 58 and buy a couple sizes inbetween that and the 54s I already bought but am afraid to put in. Whattaya think?

Kevin

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madam im adam

if you're pulling 7" vacuum at WOT, then you need to switch to a four barrel carb. don't rejet until you have some way of knowing how its running now.

zedpapa

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1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

You may want to try loosening up the valve lash before getting into the carb, that could improve idle vacuum and throttle responce. Most performance cams take more lash then the factory's .010 & .020 setting.
Also try more initial timing advance, again, that improves idle vacuum.

Manifold vacuum has a direct impact on the carb's ability to do it's job so be sure you have maximized your idle vacuum reading before recalibrating the carb.

After doing all the vacuum checks and improvementst, go to the carb and try leaner jets. Accelerator pump shot may also need adjustment. Another area of adjustment is the power valve oriface, the holes that meter the PV fuel once the PV opens. This is a tricky adjustment because you have to drill-out the carb. body, then it's hard to "go back" if it is not correct.
DD

You mentioned it before, but the PA weather has been so crappy I didn't do them yet... They will be next.

Thanks to everybody who helped me out with ideas- the car has decent street manners now and fine tuning for optimum power is not gonna make me pull my hair out.

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madam im adam

Don't not if this is relavent. when they are talking about valve lash, my cam card, 268 cam, told me that I should .016 intake and .018 exhaust.

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225+0.080 at 10:1
268cam
holley 390
clifford headers
8 3/4 355's lsd
kh brakes
electronic ing