318 carburetor question...

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Chryslerkid

Chryslerkid

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Hi again y'all,

I know that for a stock 318 engine, a 600 cfm four barrel carburetor is not too big, but would a Holley 390 cfm four barrel carburetor be too small? What's the range that I should stay within in order to give the engine to right amount of gas? Again, I have a completely stock 318 with a two barrel carburetor and I'm trying to put a four barrel on top. Thanks guys.
 
ive never seen or heard of a holley 390 four barrel. get you an edelbrock performer dual plane 4 barrel intake. i see them all the time for 100 bucks or so. get you a 1405 or 1406 edelbrock carb or a holley 600. this engine was a 2 barrel 318, with nothing more than an intake/carb and headers added to it. you would be suprised how much get-up this little engine has....
 

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yes..they made a 390 holley 4 barrel....i would go with the 600 as long it is a vacuum secondary.
 
I agree with 73AbodEE I have never heard of a Holley 390 I have a stock 318 with an edelbrock intake and a edelbrock 1406 600cfm 4 barrel and it has plenty of get up
 
they do make a holley 390 cfm carb .there are 2 atop the tunnel ram on my 340.however i do agree with the other posts that a 600 cfm would work well and give you room to grow.
 
340 8BBL said:
they do make a holley 390 cfm carb .there are 2 atop the tunnel ram on my 340.however i do agree with the other posts that a 600 cfm would work well and give you room to grow.
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can you post a pic for informational purposes? ive never seen one. ive seen plenty of 2 barrels that size.
 
My iPad won't allow me to upload the pics of my Holley 390 cfm carburetor. But for informational purposes, it just looks like a regular four barrel Holley carburetor jus has smaller jets and sprayers.
 
Chryslerkid said:
My iPad won't allow me to upload the pics of my Holley 390 cfm carburetor. But for informational purposes, it just looks like a regular four barrel Holley carburetor jus has smaller jets and sprayers.
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And smaller venturis. MUCH smaller. lol Hold it next to a 600. You'll see.
 
There really isn't much use for a 390 up top a 318 even if otherwise, dead stock. And if it were a dead stock engine, a 500 is as small as I would go. (OK, actually, I wouldn't myself....)
 
interesting little carbs. i guess they would work well with a couple atop a tunnel ram, but not near enough for even a little 318. i have a 600 holley atop my 360 and that seems to be the ideal CFM for a stock / mild cam. it will run good with a 625 or 650. i tried a 750 DP but that was too much carb for my stock 318.
 
73AbodEE said:
interesting little carbs. i guess they would work well with a couple atop a tunnel ram, but not near enough for even a little 318. i have a 600 holley atop my 360 and that seems to be the ideal CFM for a stock / mild cam. it will run good with a 625 or 650. i tried a 750 DP but that was too much carb for my stock 318.
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I agree with the 750 being a bit large. Not so great throttle response when the engine is mild and the gears are still Hwy.-ish. Even on a mild 360, the smaller carb works great.

I checked out Bobby's link to Summit racing to look at the 390's. I am not into circle track. So I was surprised they cam in 2bbl. flange. I also did not know they have a 4150 model. ( http://www.summitracing.com/parts/HLY-0-80507-1/ )
I think a pair of these on a small runner T-ram would be cool stuff.
 
Copy that. I'll go ahead and look for a 600 edelbrock then. Sweet! Thanks everyone.
 
Well Ed (805MoparKid) removed a 390 from his SLANT and put on a 650 and sped up. It even sped up yet again when he put on a 750. What's that tell ya? lol
 
StrokerScamp said:
Well Ed (805MoparKid) removed a 390 from his SLANT and put on a 650 and sped up. It even sped up yet again when he put on a 750. What's that tell ya? lol
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lol go figure huh? you would think the 750 on slant would kill it. im guessing he has a great build to support it. i dont know what cfm a little single throat 2 barrel bbd is, but the stock 318 is a complete turd running one. word on the street is that with only an intake and 4 barrel , the 318 doesnt benefit much, but i REALLY beg to differ. a little bump in the timing and the extra cfm, my little 'teen will roast the tires and it gained a huge amount of top end. with headers of course
 
Ed's got a hot little *****. His girlfriend ain't bad either. LOL
 
Chryslerkid said:
Copy that. I'll go ahead and look for a 600 edelbrock then. Sweet! Thanks everyone.
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There are great deals to be had on these Carburetors. I got my EnduraShine for around $ 200. Runs like a dream on my 318.
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Stock two barrel intake and carb.

$60 for mainifold off Craigslist (Dual plane 318/360 Performer)
$40 Pick and pull find Eddie 1406 with electric choke (Like new):D
$30 or so for gaskets for the intake and carb base.

Still dialing everything in, but it'll get there.
 

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exactly! i paid 75$ shipped for the same intake from a member here, i paid 60$ for the 1406 off of CL , and 140 shipped for the headers that included reducers, gaskets and bolts. bolt on performance on the CHEAP and it runs GREAT and sounds healthy
 
I think people are to worried about over carburation too much, 2 and 4 barrels are measured different levels of vacuum so 390 cfm 2 and 4 barrel not the same. 2 barrel is measured at 3" Hg and 4 barrel is 1.5" Hg cause they assume those are levels that a 2 and 4 barrel engine are gonna produce at full throttle. So the lower the vacuum at full throttle your cfm quickly shrinks to check if your too over or under carbed use a vacuum gauge, on a street car your looking for 1.5" Hg on a street strip car no less than 1" Hg full race lowest that will work for you. I think drivability more depends on how well your carb set up, I seen a write up on a warmed over 383 they dynoed like a 650,750,850,950 and a dominator all made more power without a loss on torque now they didn't drive each one on the street to check drivability.
 
Everybody says "go big", then when the price of gas goes over $4/gal, they fuss about "only 8 mpg". A 390 cfm is a better fit for a slant six, and they are rare and more expensive than most 600 cfm carbs. The 2 bbl Carter BBD is actually great for street driving, where most people notice low end torque more. That is why most V-8's shipped with a 2 bbl. If you want the high rpm power of a 4 barrel and good mileage, the Thermoquad and Quadrajet were the best.

One interesting choice is the "dual port" intake by Offenhauser, with small dedicated runners for the primaries. I have one to try on my BB. TBI or MPFI is the best way to get performance and mileage, and if you document what you pay for gas in a daily driver, the seemingly high cost might pay off in a year or two. Even NASCAR is going EFI.
 
More expensive, yes. Rare, no. You can buy them new at Summit everyday.
 
What's the opinion on a four barrel afb 650 cfm carburetor for the stock 318? Pro' and cons please everyone?
 
Would probably work pretty well.
 
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