318 Four Barrel Intake

-
M

MILLERSCAMP

Member
Joined
Feb 6, 2007
Messages
6
Reaction score
0
I am looking for a four barrel intake manifold for my 74 Scamp. It has the 318 V-8 in it. I would like to keep it somewhat stock so I am looking for a factory cast iron intake. What years did Plymouth offer a four barrel intake on the 318 that will fit my application? Any help would be greatly appreciated.
 
Mopar didn't offer 4 barrels on the LA318 until the late '70s. But I believe these motors also used 360 heads so the port of this intake will be larger than the ports on your 318 althought it will still bolt on to your motor. These intakes use the spreadbore type carb like Thermoquads or Q-jets.

If you find a 4 barrel intake off of a '66 - '68 273 it will match the ports of the 318. These intakes use a squarebore carb like a Carter AFB/AVS

Chuck
 
340Mopar pretty much covered it,but,if you aren't stuck on cast-iron, there was an "SP-2P" intake from Edelbrock that was a pretty good street intake for Square or Spreadbore carbs. Also, there was the LD4B,an older design and becoming a little hard to find. I think Offy used to make a 4bbl intake as well. As long as the ports are the small ones for the '66 and later 273/318 heads, you'll be fine. You can always paint the intake engine color to try and hide the aftermarket look. Keep checking e-bay and the like and one will show up. The '66-67 273 factory 4 bbl intakes are getting scarce and expensive!!!

Hope this helps...
 
340mopar said:
Mopar didn't offer 4 barrels on the LA318 until the late '70s. But I believe these motors also used 360 heads so the port of this intake will be larger than the ports on your 318 althought it will still bolt on to your motor. These intakes use the spreadbore type carb like Thermoquads or Q-jets.

If you find a 4 barrel intake off of a '66 - '68 273 it will match the ports of the 318. These intakes use a squarebore carb like a Carter AFB/AVS

Chuck
Click to expand...

Correct info. The 3184bbls used 360 top ends. I would look for an edelbrock LD4B as my first choice, looks pretty much stock 2nd choice would be a Performer. These are bolth small port intakes.
 
I have to agree with what's been said. I wouldn't bother with the stock 273 4 bbl. manifold unless you find one dirt cheap. They're not much of a manifold. Pretty much a low rise, single plane 2 bbl. manifold with a mounting pad big enough for a 4 bbl. I had one & it was better than having a 2bbl. but that's about all that can be said.
 
hi, mopar offered one 4bbl intake for 318 in late 70's. they were used with the 360 heads and cam for the HP version, the regular 318 used a smaller cam and 318 heads, the intake and carb are the same as used on the 360 motors. casting # are, 4095080,4100340,4173915.
 
All good advise thus far, just thought I would chime in on the port mis-match. Way, way back when, 30 plus years ago, I read all the Mopar factory books (Hustle Stuff/Direct Connection) and thought what they said was gospel. They always said do not use 340 manifold on a 273/318 under any circumstance due to the severe port mis-match. SO, I spent big bucks (at the time over $300) for an Edelbrock Streetmaster 318 and AFB 500 carb. Worked great, went from a stock 17.4 et down to 16.2et. Very pleased untill I saw others with $15 junkyard 340 intakes (that was $15 for the intake and AVS or Thermoquad) on their otherwise stock 318's running deep into the 15's. They just shook their head at me for spending so much money. Also remember how the same books went into great detail describing the proper way to notch the bore so that a 273 could then be able to accept 340 heads. Many years later I found out, you can just bolt them on, "factory book" be damned. Through the years I found many other discrepancies from the factory experts (big block/hemi too), but those just starting out would correctly assume that the factory knows best. Haven't looked at one of those books in years. Sorry if I strayed a bit off topic but I still get mad every time I see the "port mis-match" mentioned.

Just remembered:::eek:n my '81 Ram 360 I swapped out the original thermoquad and 4bbl intake for a stock 318 intake and 2bbl carb just to get better fuel mileage. Works great:::been on there for 17 years and guess what? "severe port mis-match" again.
 
Just remembered::n my '81 Ram 360 I swapped out the original thermoquad and 4bbl intake for a stock 318 intake and 2bbl carb just to get better fuel mileage. Works great:::been on there for 17 years and guess what? "severe port mis-match" again.
Click to expand...
But the port mismatch is your favor because the intakes ports are smaller than the heads ports. If it were reversed, then I would say theres a problem. The air and fuel crash into the head and then try and go into the port.

Your move is a smart one. The reverse would not be.
 
Very true, but go back and read my post again about the 340 intakes on 318 ports. Bottom line is while agreed there will be an impediment to flow, it will "work" forever, it won't hurt anything and the car will likely go quicker for less money. I sold my original Ram 4bbl intake/thermoquad to a co-worker with a '73 318 powered motorhome, he simply wanted more power. Again, port mis-match but he was thrilled with the power increase and will not sell the combo back to me. He would have spent far more money to get a "proper" intake to match his ports, and would have ended up with less power as well. I currently have a very well ported set of RB heads in combination with a stock 440-6bbl intake, there is indeed a mis-match but I did not want to alter my original 6bbl intake. Heads alone gave me .70et and 8mph and I can't imagine careful matching of the ports giving the performance increase to justify the time involved. Not saying it wouldn't give an increase but it could also have taken a lot of time and not given anything. I am sure there are many Max Wedge "clones" out there running the correct crossram setup but with only stock B/RB heads. Again, port mis-match but even so it will likely outperform any other 4bbl or 6bbl intake combo, port mis-match be damned. Just saying you don't have to have matching ports to acheive desired results be they economic/appearance/performance.
 
OK, I'm with that roy. It is a proven upgrade. Been there done that.

A 340 intake on 318 head will work. Just shooting for better. That's all.

Didn't mean to sound mean or other to you.
 
May I follow this thread up with a question? I recently picked up a '72 Duster which had a 318 laying in the engine compartment. It has a 4bbl intake on it, #4100340. My plans are (were) to put it on a new long block that I just picked up - nothing special, just a "regular" 318 long block. My goal is only a nice reliable daily driver, good gas mileage and a little pep. Would I get better mileage with a 2bbl - assuming I kept my foot out of the 4bbl?
Thanks,
C
 
Using a good 500 cfm AFB ,tuned properly, you'll get better mileage with the 4 barrel, keeping your foot out of the 4 barrel's. I don't have any info on that 4 barrel intake you quoted, but stay with a small port ,dual plane intake to maintain good port velocity and fuel atomization. Stay away from the large port 340/360 intakes.

That's just my $0.02 CDN....
 
I have found the 2bbl has always given the best mileage and it removes any temptation to open it up. You can still open it up, but when you don't get the pleasure out of hearing those back barrels open up, you just say to yourself "whats the use?" and then you just quit doing it. I have gotten 21.5mpg with a '74 Newport 400/707/2bbl, 21.5 with '75 Duster 318/4spd/4bbl;23.5 same car as a 2bbl, 22.5 with '81 Ram 318 2bbl/A833 o.d., 14.5 with '81 Ram 360/4spd/4bbl/4wd;16.0 with same truck as a 2bbl and back in the day could get 16.2 from a '68 GTS 340 4bbl/4spd/3.55, 15.8 out of a '71 Charger R/T 440 4bbl/727/3.55 using the "keep your foot out of it" method. Could easily get 8mpg out of either of those last 2 as well by not using "the method". With gas looking like it soon again reach $3/gallon I will do whatever it takes to save a few drops.
 
Since 2bbl's and 4bbl's are rated at different pressure drops, or vacuum readings, what you really need to look at is the size of the barrels. If you could get both cabs on a flow bench and compare, that would help. But since we do not have these in our garages................

The 2 bbl. is good on gas. Period. Like Roy said, you can't give into temptation and floor it for more. However, while driving on the road at a moderate speed, only the front primary should be open. The size of the small 500 cfm carbs primarys are smaller than a 2bbl.'s. This should help increase fuel mileage. The velocity through the carbs smaller throttle bores will remain high and keep the air and fuel moving rapidly and well atomized.
This is where the mileage comes in.

Other improvements in the intake, exhaust. Easy in, easy out free up power. A better ignition system would also provided more mileage by getting more power. Or bang out of the air and fuel charge. A complete burn of the air/fuel charge in the cyclinder rather than most.

Things I have done in the past to improve mileage were;

Open air cleaner
K&N filters or equal
new, smaller carb
better intakes
headers
free flowing exhaust, duals
upgrade ignitions from start to finish
remove accer.'s not used on the engine including fan. Went to an electric

And tune tune tune that carb.
 
By Roy;
Just remembered::n my '81 Ram 360 I swapped out the original thermoquad and 4bbl intake for a stock 318 intake and 2bbl carb just to get better fuel mileage. Works great:::been on there for 17 years and guess what? "severe port mis-match" again.
Click to expand...

Here Roy makes a claim. It is easy to believe. I know this will work. A poor running T-Q is a fuel burner and in a time past, rebuilding them wasn't easy, part wise. There easy carbs to rebuild.

Though the T-Q's primarys are smaller, the 360 is a larger engine and pulled air and fuel accordingly. Through the 318 2bbl and smaller runner intake. The air and fuel was going very fast for atomizing.

The port mismatch he talks about is one that leans to his bennifit. The intake port are smaller than the heads port window. No problems.
The problem (And not a big one) is when a larger window intake (340/360) is used on the smaller windowed head. ( 318 )
The air and fuel crash into the head and tumble into the port. Fuel can reform into droplets and not burn well.

Now yuo all must understand that even in the high speed of this happening, even the smallest things show up and will effect power, mileage and emissions. Sounds crazy, but look at what the auto manufactures are doing today. Big difference from years past.

By Roy again;
I sold my original Ram 4bbl intake/thermoquad to a co-worker with a '73 318 powered motorhome, he simply wanted more power. Again, port mis-match but he was thrilled with the power increase/ He would have spent far more money to get a "proper" intake to match his ports, and would have ended up with less power as well.
Click to expand...

Here the engine is seeing a big increase in air and fuel delivery. This is why power jumped. A port matching intake would have made more power.
Price of the proper port sized power vs. cheap bolt on power? Your wallet may be the deciding factor. But you'll get it ethier way.
If you use the 360 sized intake, port match the 318 heads to the 340/360 head.

Who remembers Mr. Tony West's web page?
The kicker of the link is when he dyno'd the engine. You should read through it all so you know the whole deal of what was done and going on. At the end, here is further proof of what happens when parts are matched up. Now it's up to you or your wallet.

Click this!
http://www.geocities.com/alwest_83/318

(Performer intakes can be cheap at swap meets, but factory 4bbl's should be a fraction of the cost. Up-sizing the 318's port isn't going to kill the heads performance. If done right, it will still make more power than a stock port and valve sized 360 head. The important areas to match would be the roof and side walls, center divider on the inner pair.)
 
roycrown said:
the same books went into great detail describing the proper way to notch the bore so that a 273 could then be able to accept 340 heads. Many years later I found out, you can just bolt them on, "factory book" be damned. .
Click to expand...

roycrown, is this true? Have you actually done this? Tell me more. I know this post is about 4 barrels on 318's but I have never heard of anyone doing this before w/o a notch. pm me if you need to.

kev
 
Do the math. The valves are in line and the bore space is.....
I have not ever had a 273, so test fit before fireing is allways the order of the day.

2.02 + 1.60 = 3.62
1.88 + 1.6 = 3.48

273 cid bore, stock, 3.63

3.63 - 3.62 = no way.
3.48 - 3.63 = 0.15 or yikes, whoa and other.

The issue with the smaller vale (1.88) is shrouding. Also the valve can wiggle a tad. A valve hitting the cylinder wall is more than bad.

Both do not included space between the valves. No matter how small.
I think BJR can answer this and other head work best.
 
hi, the 1.88 int will not hit the bores, the 2.02 will hit. the 1.88 is only .050 bigger toward cylinder bore.plenty of room. as for port mismatch, when air flows from a smaller port into a bigger port ,it slows down and will fill the space, then continue on. there is a loss of velocity in the port. just some info from superflow.
 
perfacar, and is that worse or better than a 340 intake on a 318 head?
Tell the crowd.
 
i have a 87 318 with a ederblock 4 bbl and intake i am look to go back to a stock 2 bbl. I will sell cheep.
 
I've got 2 older stock cast iron 4 brl intakes here. Aplication unknown. If you can get casting numbers of what you seek I'll compare them. I will say both intakes have EGR ports and one of those ports is turned up sideways.
 
Kooltool and Redfish;

You do realize this thread is over 1 and 1/2 years old right?

Welcome aboard anyways Kooltool!
 
You must log in or register to reply here.
-

Back
Top