Carburetor & Intake Compatibility Question

I'm sure someone on here can help me with a question I have before I make another purchase of a wrong part.

I have a stock 318-2V in my 1969 Satellite that I am going to swap out for a 4V set up. The existing 2V carb is shot, but instead of spending time & money on the 2V for a motor that I had planned to have rebuilt next year, I figured I would put the new 4V on now to drive the car this summer. I've gathered the parts I needed, or so I thought, but when I finally went to dig into the project I discovered that the carb I bought a couple of years ago doesn't fit the intake I bought.

The carb is a brand new, 500 cfm, Carter AFB 9511 that was still in the plastic wrap inside the box & the intake manifold is a stock, Chrysler cast iron piece for a 340, from 1972-73 I believe. I don't have the casting number handy but the intake manifold has the wider gap between the two front primaries for a Theromquad carb. The Carter AFB I have is much smaller & the throttle plates are closer together so they hit the intake manifold.

I see that the older 340 intakes have the front openings closer together. Will the Carter AFB 9511 I have fit this intake?

(see photo)

Would it be better to hunt for & use an intake for a 1966-67 273-4V?

I really don't want to drop $350 or more on a new carb that will fit the 340 intake I have. It seems that replacing the intake is a much cheaper alternative. I'd consider a spacer/adapter, but then I get into height issues & don't want to have to rig linkages or end up with hood clearance problems.

Thanks.

You will need an adapter to go from the spread bore manifold to the square bore carburetor or find an early 340 intake. The intake you have has larger ports than your 318 heads. It will work, but won't be ideal. If you are going to stick with the 318, at the very least you should add 360 heads when you rebuild it to match the ports. I do have a '69 340 intake that I am selling, but shipping from California would be about the same as what I want for the manifold...

The 340 and 360 intake ports on the heads and intake manifold are larger than the 318 heads and intake ports which will cause reversion
Sell the Thermoquad intake and buy a AFB style 318 intake so the motor will like your changes

That is really a non-issue except in a max effort engine build and you wouldn't being doing that to a 318 anyway. I don't know why people keep bringing that old chestnut up, got any dyno pulls to prove it is an issue?

All that said, I ran the factory spreadbore intake on my otherwise stock 87 2bbl 318, yes the small port heads with zero reversion issues. Ran an Edelbrock 1406 carb on it without an adapter. What I did was run a thick (~3/8") carb base gasket. Don't have a PN though, I just picked it off the shelf back when there were speed shops and carb mounting gaskets to look at. Might look at Edelbrock Carburetor Adapters 2732, it's about as thin an adapter as you will see, probably thinner than my thick gasket trick.

You will also need the kickdown linkage addressed as the 2bbl stuff doesn't play so well with a 4bbl, did you get the adapter for the throttle and kickdown linkage as well?

Just thinking out loud. what about building a 360 (or even a stroked 360) on the side. It'd minimize your down time when it came time to swap & there'd be a significant gain in torque which you could definitely use.

The Carter AFB 9511 that I have may be a square bore, but the front primaries are smaller & not as far apart as the openings on the 340 manifold. The ideal adapter would be a wide to narrow spread bore if such a thing exists. The fear with adding an adapter is linkage issues & hood clearance because the 340 manifold is already substantially taller than the 318-2V manifold on there now.

I did see your ad & agree that the shipping would be crazy. I was hoping to score something local or even meet someone at Carlisle to pick it up.





Been looking for a different intake that's reasonable but no luck yet.






Years ago I did the same swap on my 318 Scamp for almost the exact same reason, to not spend money on a beat 2V knowing I was going to switch to a 4V anyway. It ran fine with the stock 318 with an Edelbrock Performer & a Holley 600. When I had the motor rebuilt a year later with a bigger cam & some other mods I reused the same intake & carb & it ran a 15 second quarter with the 7-1/4" rear & 2.76 gears.

I do have that same 2732 adapter but it's not going to fix my issue. I need more even height to clear the cast iron between the two openings. That's why I was mainly asking if anyone knows whether the carb will fit on an older 340 manifold. Of all the things I've been reading the carb I have is for the 273 Commando.

I am aware of the linkage differences & had found what I needed in a junkyard back then. This time the parts were available new & I bought them from Mancini.

Thanks guys.

I'm always looking at local ads for some kind of small block in running condition but I'd like to avoid the additional expense & save it for other improvements later. When I bought a package deal of parts a couple of years ago for things needed on my son's Coronet & my Scamp, it also included the 340 intake. I later got the new carb, brackets, linkages, gaskets, filter, etc., but wrongly assumed the carb would fit.

I'm running a Thermoquad intake with a square based Holley. I am using a square bore spacer about 1/2 inch thick and it works perfect. I also have a small block Thermoquad intake with the small intake runners. They were used on 318 and 360 engines around 80-83 and possibly later. I am planning on using it for a 318 in a Dart.

Any reason you cant just take a die grinder to the offending metal?

Just buy the adapter and be done if you want to go 4bbl route.

Good to know, thanks.




I'm afraid of sparks.

Seriously, that's not a bad idea & I will take a look at the intake this weekend.




You know I had 3 or 4 of these adapters in a box years ago that came wirh a variety of cars & parts over the years. I put them out at a swap meet & gave one to a friend & wish I had kept one to try out to make sure clearance would be okay.

As Alchemi said, that was my thought: open up the intake. Use a carb base gasket for a pattern.

Since this swap is not a rush at the moment, I decided to rummage through some boxes of parts hidden in my basement to see if I still had any of the spacers / adapters I used to have. Unfortunately I am sure I sold or gave all of them away.

But I did find one on ebay over the weekend for $9 & free shipping.

So I ordered it & will probably have it in a few days to try out & see if clearance is an issue or if I have to do something to the linkage. I'm not going to rule out getting a different intake or grinding off part of the one I have, I'm just going to try the quickest & easiest first. And for $9 it's no big deal, I'll just drink one or two less beers.

Thanks for the input.

Why don't you find a decent Thermoquad, put a kit in it. You will be money and performance ahead of anything mentioned!

Dude, do you know what your talking about?
The early 273/318 heads had a lot smaller intake port than the 1968 to 1974 340 and 360 heads had, a lot smaller
I'm not sure what year Mopar started offering the 318 motors with the smaller 318 heads and then the larger 360 smog heads with cast iron intakes made for those specific heads with a Thermoquad carb., maybe 1976 or 1978 era
I have made the mistake of putting a stock cast iron 1968 340 AVS intake on a near stock 318 motor with a bigger cam and stock heads, talk about reversion and harm to the throttle response, that motor had it
As far as how many dyno pulls and test sessions I've have been involved with on legal SB Mopar V8 NHRA stocker motors it is over hundred so far, how about you?

I agree w Cab, for a few years Edelbrock made a 4 bbl 318 manifold w 318 sized ports....I have one of these on an otherwise stock engine w headers and it runs better, has throttle response like no other 318 I've ever had. It will effortlessly spin a rear tire on my Challenger vert. Keeping the velocity in the intake ports up is very important for good torque and cylinder filling.

Same number as you've done with the big port intake on the small port heads, which was the question asked.

This isn't the race forum where you turd polish an engine to rules complying perfection and if you had issues with the big port intake on the small port heads my experiences running them ON THE STREET doesn't match yours. It has always been an improvement over the 2bbl setup. Which is exactly what the OP is asking about.

As an aside, Edelbrock still makes a 4bbl intake with small ports, it's called the Performer and running one of those on my 318 is exactly the same as running a stock 4bbl intake on small port 318. BTDT.

I'm 56 yrs old and my 1st engine was a 318 I modified that engine with 340/360 intake carb and headers and it was a dog compared to the 318 small port intake on the current 318 in the Chally vert., I've owned many 318's in my 30 yrs of driving mopars and a big port intake on a 318 sucks. I know from experience.

The Edelbrock Performer DOES have the smaller intake ports. I have 3 of them in my shop. The small block RPM intake has the larger ports to match 340/360 heads.I ran a regular Performer intake on a 360 I had and didn't like the way it ran. Going to a stock 360 spreadbore intake made a big difference. The only reason I can see for running the larger port intake on small port 273/318 heads, would be if you have nothing else. As I stated earlier, the factory made small port spreadbore intakes and used them on both 318 and 360 engines in the 80's. Cab, I think you were referring to the early LD4B(small ports) or the LD340(large ports).

I used to run a stock 360, 2 bbl intake and carb on a stock 318. Got it to run 14.40 so while it isn't optimal, it also isn't that bad. Since the OP only wants to run this for the summer it should be fine.

Your correct, thanks for the help
Maybe the DP4B was a 361,383 or 413 426street or a early 440 intake

Yes, the DP4B is a low deck intake and the CH4B was the RB counterpart.

At full throttle the reversion problem is minimized, and the diff between big and small port is no big deal. The place a small port manifold excels is in throttle response and part throttle power. The small port 4 bbl manifold, makes my current 318 more fun to drive than any other 318 I've ever had. It has immediate throttle response w tons of torque, will spin a tire w ease at much less than full throttle. You can build engines like me your whole life before you find a combo like this. Ever put headers on an old Ford 360-390 ? same kind of deal amazing results for minimal effort.

clear things up here..on a SB 2v-318 it has the small ports & never used a 4-v intake on them. 273 had a open plenum low rise 4 hole intake with the small ports. this is what fits the 318 best as a stock OEM intake.

a factory 4-v 318 came with the 1.88/1.60 valve 360 heads large port heads. IMHO.. a 2.02/1.60 X head on a 318 cyl bore shrouds the valve.

a edelbrock 318/340/360 performer is a stock OEM cast iron replacement and has the spredbore flange as well as a square flange ** use of a edelbrock flat adaptor plate is the best fit over the thicker spacer adaptors IMHO.

in the instruction sheet it clearly says it has the large 340/360 runnners BUT NECKS DOWN to a 318 port size. also states that if used on a 340/360 head to gasket match the first 1" into the runner this makes the intake a large port 340/360 intake ONLY after gasket matching

so when looking for a used one check the runner for porting.

LD4B is a 318 small port reverse copy of a large port LD340 the LD4B is one of the best duel plane small port intakes for a 273/318 small port head.

LD340 is a high rise duel plane intake with large port/runners and does not give up very much compared to a edelbrock RPM & RPM air-gap intakes

edlebrock RPM & air-gap RPM are the best newer intakes but only slightly better than the 40-50 yr old LD series of intakes

Holley STREET dominator is a low rise, single plane, spredbore intake with small port/runners for a 273/318 head works very well on a street engine to be a single plane intake. I like mine as a daily driver.

Holley STRIP dominator has the 340/360 port/runner size and is another low rise single plane intake that works well for the strip. this is what I remember 340 engines getting back in the day.

no need to talk about the small port sp2p gas miser intakes they are not for HP performance


I have a
LD4B on a 318 #302 heads
Holley STREET dominator on a 318 #302 heads
RPM air-gap 318 360 heads

all have the hughes whiplash roller cam and run rather well as daily drivers in my mid 80s trucks

IMHO cant go wrong with any of these intakes.

The LD4B is what I have.....why they ever stopped making these I'll never know....best intake for a 318 ever by FAR !

I have had the LD4B on a 360 engine and a couple 318s with the 360 heads. the small runner/ports keep the velocity up going from small to large port and worked rather well on the street daily driving.

I have been dropping 360 heads on 318s since I was 15 and now I am 56 don't care what negatives people SAY it has as it works and makes up for it in the mid to top end RPM range. exactly why Ma Mopar did it in 85 for the 318. and it got a bump in CR to the 9.0 to 1 and used the q-jet/intake.

FYI...

stock 318 2v = 150 HP @ 4800 rpm

stock 360 headed 318 4v "police engine" = 177HP @ 4800 rpm 85-91

now the "police engine" did run a better cam with the 360 heads/q-jet

Ma Mopar did a few good things for the teen from 85-91 and sure made plenty of them.

I open the bowls up and clean up the runners home porting the heads and install pistons backwards to change piston rod offset and use about 214*/228* dur @ .050 with .485/.500 lift and my little 318s are screamers in daily traffic. run mid 13s 1/4 mile track 4000lb truck.

old skool tricks still work for the poor man 318 daily driver.

I've been making it part of my daily routine to look here on Moparts, Ebay & Craigslist for intakes. I spotted a few that were decent deals, but the shipping is always a killer on the old cast iron & most will require a massive amount of cleaning to get the carbon out from inside. I saw a clean one for $75 that was VERY tempting, but it was a 2-1/2 hour drive one way. I told myself to just wait until the Carlisle show because there's bound to be a bunch of them there & I've carried heavy crap across the fairgrounds all the way up the hill to where my truck is before.

This past weekend there was a new ad on eBay for a brand new Edelbrock Performer for $140 & $38 for shipping. I thought about it, passed on it & went to bed. After laying there looking at the ceiling & thinking about how a crusty old intake needs to be cleaned up, I turned my phone back on & went right to eBay & clicked the "BUY IT NOW" button. I have this same intake on my Scamp & did the same 2V to 4V swap ages ago so for roughly $50 to $75 more than what I planned on spending, this will save me a bunch of grief.

Thanks for all the ideas that were posted.

I did the same on a 318 in a 76 Charger SE.... ran fine on the street, daily driver, work car, etc. never took it to the track but it ran better than with the original 318 intake and carb.

The 4bbl 318's ran the same cam as the 2bbl 318's. Difference was the 4bbl 318's never got a roller cam, they stayed flat tappet.

4bbl 318's were never 9.0:1 compression ratio, advertised or otherwise, the 2bbl did get an advertised 9:1 ratio though but that was with the 302 head.

As said by those that have actually done it, putting a stock 4bbl intake on a 2bbl 318 is an improvement, period.

Just a follow up in case anyone was wondering.

New is nice, but it's nicer when it's cheap. I'm into this entire set up so far for about $375 including the intake, the carb, all the linkage pieces, brackets & gaskets to do it. Now I just need to find the time to actually swap it all.

I will hold onto the stock, cast iron intake for now since I still have another 318-2V engine kicking around in my Coronet convertible that one day may get redone.