vacum or mechanical? choke or no choke?Hello

Discussion of the 331-354-392 HEMIs.

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mrossbach
Posts: 8
Joined: Tue Oct 13, 2009 8:44 am

vacum or mechanical? choke or no choke?Hello

Post by mrossbach »

Hello again...I have the carb figured out...now...how do you determine if you need vacum or mechanical...electric choke or no choke?
354 hemi...dur= .050 230 230
adv 300 300
lift 480 480
lobe 108
30 over...mallory dist
vac at idle 10......
thanks....mike
polyspheric
Posts: 57
Joined: Wed Apr 09, 2008 1:03 pm

Re: vacum or mechanical? choke or no choke?Hello

Post by polyspheric »

vacum or mechanical what?
NE57
Posts: 192
Joined: Fri Mar 27, 2009 12:54 pm

Re: vacum or mechanical? choke or no choke?Hello

Post by NE57 »

If yours is a street car, where you have all kinds of different loads and conditions i think you'll find better driveability with an electric choke and vacuum secondaries.

While its true you could adjust opening time on mechanical secondaries you know you're going to put your foot all the way in it every time so the adjustment might not mean much. Adjusting the opening of secondaries is a kind of fail safe option. Once tuned right, they will never open until the extra flow is demanded by the motor... no bog. You wanna enjoy driving it, right?
NE57
Posts: 192
Joined: Fri Mar 27, 2009 12:54 pm

Re: vacum or mechanical? choke or no choke?Hello

Post by NE57 »

>Adjusting the opening of secondaries is a kind of fail safe option.

here I meant VACUUM secondaries.
392heminut
Posts: 488
Joined: Sat Nov 30, 2002 2:16 pm

Re: vacum or mechanical? choke or no choke?Hello

Post by 392heminut »

polyspheric wrote:vacum or mechanical what?
secondaries! :roll:
Owner of the Poor Man's Hemi Cuda
mrossbach
Posts: 8
Joined: Tue Oct 13, 2009 8:44 am

Re: vacum or mechanical? choke or no choke?Hello

Post by mrossbach »

Thanks..I went with a all aluminum street avenger 650, vac 2nds,electric choke...bolt it on monday...bought from Holleytv.com
should have checked Jegs first....much better deal ohwel!!!
thanks for all the info guys...will post pics soon.....
oldngood
Posts: 121
Joined: Thu Mar 13, 2008 5:14 pm

Re: vacum or mechanical? choke or no choke?Hello

Post by oldngood »

mrossbach wrote:Hello again...I have the carb figured out...now...how do you determine if you need vacum or mechanical...electric choke or no choke?
354 hemi...dur= .050 230 230
adv 300 300
lift 480 480
lobe 108
30 over...mallory dist
vac at idle 10......
thanks....mike

you definitely should run a vacuum advance AND a mechanical advance together, because vacuum goes away and mechanical takes over at RPM WOT

if you run vac advance, it will pick up your idle and help tame that big cam

run as much initial timing as you can without making the engine hard to crank over, and run as much total timing as you can at high rpm without pinging- timing tames a big cam for the street

to be honest, that's a big cam for a 354- let me relate this story

I ran a 308/320 advertised duration, 230/240 @ .050", .520" lift cam in a "brand x" 406 motor- it took some work to tune it, had to use 1 step richer metering rod, and also a weaker metering rod spring, to get it to idle and not be lean

I took that same cam, put it in a 350, and it was a BEAR to tune- it was so lean it blew flames out of the carb when it was cold

I'd recommend a smaller cam for a 354 for a street car, say 200 degrees @ 050"

basically look at what other 350 engines run for cams, and choose a cam with those specs and performance level- such as a 340/360 Mopar cam specs- if I was building a 354 I would not put a 230 @ .050" cam in it, unless it was a stick with 4.33 gears, or an automatic with 3000 stall converter. My 230 duration cams were dead below 3000 rpm, they hit like a sledgehammer right at 3000 rpm, and pulled to 5500
mrossbach
Posts: 8
Joined: Tue Oct 13, 2009 8:44 am

Re: vacum or mechanical? choke or no choke?Hello

Post by mrossbach »

oldngood wrote:
mrossbach wrote:Hello again...I have the carb figured out...now...how do you determine if you need vacum or mechanical...electric choke or no choke?
354 hemi...dur= .050 230 230
adv 300 300
lift 480 480
lobe 108
30 over...mallory dist
vac at idle 10......
thanks....mike

you definitely should run a vacuum advance AND a mechanical advance together, because vacuum goes away and mechanical takes over at RPM WOT

if you run vac advance, it will pick up your idle and help tame that big cam

run as much initial timing as you can without making the engine hard to crank over, and run as much total timing as you can at high rpm without pinging- timing tames a big cam for the street

to be honest, that's a big cam for a 354- let me relate this story

I ran a 308/320 advertised duration, 230/240 @ .050", .520" lift cam in a "brand x" 406 motor- it took some work to tune it, had to use 1 step richer metering rod, and also a weaker metering rod spring, to get it to idle and not be lean

I took that same cam, put it in a 350, and it was a BEAR to tune- it was so lean it blew flames out of the carb when it was cold

I'd recommend a smaller cam for a 354 for a street car, say 200 degrees @ 050"

basically look at what other 350 engines run for cams, and choose a cam with those specs and performance level- such as a 340/360 Mopar cam specs- if I was building a 354 I would not put a 230 @ .050" cam in it, unless it was a stick with 4.33 gears, or an automatic with 3000 stall converter. My 230 duration cams were dead below 3000 rpm, they hit like a sledgehammer right at 3000 rpm, and pulled to 5500
Hello thanks for the info. I was just going to sell the engine afterI built it. However I found a nice 46 studebaker p/u. I have a 700r4 w o/d trans, dana 61 with 456 gears, 33 15s rr tires...airbag susp....I just put a Holley, aluminum, 650 ,vac secds, electric choke.
It runs much better now. The carb I had was used for 1/4 mile...it was not really set up for street use..ok thanks again...mike r. mich
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