318 - Intake, 4BBL, Cam - Who regrets the upgrade?

[moreada]

I have read a few posts online from some folks who made the above small upgrades to their 2BBL 318. While the consensus is that you will gain some power, there has also been some posts concerning a drastic decrease in mileage. A few mentioned wanting to go back. I suppose my question is who out there has done these mods and come to regret it and wished to go back? Is there a primary reason you chose to do so? Thanks in advance

 

[Cordoba1]

Changing the intake and upgrading to a 4BBL shouldn't affect your mileage too seriously -- if you keep your foot out of it! If you use your new-found power at every stoplight, yeah, you're going to drop quite a few MPG. But the math is plain: To make more power, you need more fuel. I don't know too many people who regret having more power, though. Just use it judiciously.

 

[aspen77rt]

I went from the stock 2bbl setup with a mild cam, to a 625 street demon/ edelbrock performer. I didn't have the stock setup long enough for a mileage comparison. However, the street demon has small primaries and huge secondaries (Like the TQ). Throttle response and cruise manners are excellent.

No, I wouldn't go back.

 

[Aspen500]

I think the trick is to get the carb calibrated correctly and mpg's should at least be equal, depending on how often the secondaries are open that is! Pretty much need a wide band A/F gauge to get it right. Seat of the pants,,,,,,,,,,it might seem fine but chances are it'll end up too rich that way. Running an aftermarket carb "out of the box" on a stock/mild 318 it WILL be rich. Just my experience for what it's worth.

 

[Master M]

I looked at a 1987 5th ave awhile back that was for sale locally. The car had been converted to an Edelbrock 4bbl set up. I saw the receipt for the work at the cost of $1800.00. The owner had just taken a road trip and was not happy getting 3-4 mpg worse than stock. I don't know how the carb was tuned, or if he was just enjoying the gas pedal a bit too much.

 

[Aspen500]

One hiccup is most, if not all, aftermarket 4 barrel intakes have 340/360 size ports and you can get fuel deatomization when it hits the step into the head ports, and that'll cause reduced mpg and power. Insead of entering the chamber as atomized fuel, it goes in as big drops which don't burn and end up going out the exhaust. It also messes up the air flow into the chamber which makes things even worse. Now, doing port matching and tapering the transition into the head port an inch or so would work good. In THEORY the air/fuel charge flow would speed up from the venutri effect(?)

What I mean is, just tossing a cam, intake and carb onto an engine and leaving the heads alone leaves a lot on the table for power and efficiency.

 

[kkritsilas]

I think, and may be completely wrong, but the Performer (not Performer RPM, or Performer RPM Air-Gap) have 318-2 barrel sized runners. If I am wrong, then you may want to look around for early 318 4 barrel intakes, or other earlier manifolds (SP2P or others of that time period) that were around when the 318 4 barrel still used 318 heads. It was relatively later that they put the 360 heads on the 318, so any 4 barrel 318 intakes that were around during that time would work. More than a few knowledgeable guys on this board have said that the factory 4 barrel intakes were actually really good.

The other way is to put 360 heads on your 318.

 

[mirada80]

Aspen77rt how do you like the Demon carb, I just bought one for my Mirada to replace the Thermoquad, I have heard good things about it.

 

[moreada]

Good tips. Thanks. My neighbour came over and we were doing some talking. He knew a decent amount about JBodies and the options etc. Got me to thinking I may upgrade. I also think I understand what you mean now about the way the car won't open up and be hungry for gas until you want it to be - when you floor it, secondaries open letting in much more fuel?

As for an A/F gauge, I am guessing the benefit is in being able to adjust it accordingly for the conditions and not just guessing how its running. I see the benefit in this and depending on driving could pay for itself quickly. The wideband ones I see online run about $200, so I will factor this into a 4bbl swap along with an intake from a 340. Does my factory air cleaner still work?

Is a cam upgrade usually done in conjunction? The articles I read said that I can employ the cam from a 340 as well? Will I need to source this from a Dodge dealer or can used ones be... used? Lol

 

[aspen77rt]

I think, and may be completely wrong, but the Performer (not Perfromer RPM, or Performner RPM AIr-Gap) have 318-2 barrel sized runners.. If I am wrong, then you may want to look around for early 318 4 barrel intakes, or other earlier manifolds (SP2P or others of theat time period) that were around when the 318 4 barrel still used 318 heads. It was relatively later that they put the 360 heads on the 318, so any 4 barrel 318 intakes that were around during that time would work. More than a few knowledgeable guys on this board have said that the factory 4 barrell intakes were actually really good.

THe other way is to put 360 heads on your 318.

Yip the performer has 273/318 size ports outta the box.

 

[aspen77rt]

Aspen77rt how do you like the Demon carb, I just bought one for my Mirada to replace the Thermoquad, I have heard good things about it.

I have the 625cfm on the Mirada and like it. Nice throttle response and cruise. For gas mileage who knows it's not my DD. Go to the demon site about air cleaners not all will work apparently. The 625 will come off for the E-Street EFI this winter.

I have the 750cfm SD version in the box for the aspen. I have not put my cars on the track so no report there.

I posted a couple of vids in another thread.

https://www.youtube.com/watch?v=00RMploSTmM
https://www.youtube.com/watch?v=fb6byZ3KcAk

 

[Aspen500]

Yip the performer has 273/318 size ports outta the box.

As Johnny Carson always used to say, "I did not know that!"

 

[aspen77rt]

As Johnny Carson always used to say, "I did not know that!"

Box stock performer

The same performer intake opened to 340/360 size

 

[aspen77rt]

I think, and may be completely wrong, but the Performer (not Perfromer RPM, or Performner RPM AIr-Gap) have 318-2 barrel sized runners.. If I am wrong, then you may want to look around for early 318 4 barrel intakes, or other earlier manifolds (SP2P or others of theat time period) that were around when the 318 4 barrel still used 318 heads. It was relatively later that they put the 360 heads on the 318, so any 4 barrel 318 intakes that were around during that time would work. More than a few knowledgeable guys on this board have said that the factory 4 barrell intakes were actually really good.

The other way is to put 360 heads on your 318.

Another small port after market is the old Holley Street Doninator. Very similar but apparently better

than the 273 cast single plane. The Holley is not a high rise and was designed for stock or mildly modded engines.
http://www.moparchat.com/forums/archive/index.php?t-49672.html

Here's the one from in my garage

 

[moreada]

Thanks for the tips... its sounding like I may be out to lunch. Do i uderstand correctly that I am better off doing the above mods with a head swap to 360 heads? Or its just the matching of port size I want? Part of me wonders how far down this rabbit hole goes in my case.

I am off to the wrecker to try to find a part... and while on phone he mentioned he had an edelbrock intake that may work on my car...

... the rub is I believe I am a Lean Burn victim and totally unsure now how to proceed in going forward. I know the Lean Burn ain't cool and its likely gotta go. Will look for a thread on how to remove it. That will hopefully answer some questions in the meantime. Thanks for all the advice folks.

 

[jasperjacko]

Don't put 360 heads on. You will lose compression.

 

[moreada]

Now that you mention it, I recall reading that about losing compression too! Haha. Weird how things come back. When it comes to 318/340/360 talk I get a bit confused and its likely because I am trying to learn too much at once. I have decided to get it running with the Lean Burn, pending it doesn't require any substantial investment. Then I will carefully plan swapping it out with a thought out system. It would seem inevitable that if I am to lose the Lean Burn I will need to swap in a new carb and intake... and ignition as well?

I was at the wrecker but they only had a '78 Cordoba with a Lean Burn. Nothing to poach. When there I tried to look at wheels but am unsure the offset of the Mirada wheels - so he wasn't really able to show me without knowing what I needed.

The wheel thing sidetracked me and I totally forgot to ask about the Edelbrock intake though - DOH! On my way out tho he told me of a wrecker who has a lot of Mopar stuff I will contact tomorrow and see what he may have based on my list of things to find.

 

[double a ron]

I have a parts car with factory 4bbl lean burn, what are peoples thoughts about replacing my 2bbl with this carb, or just ditch the lean burn and move to an eldebrock set up?

Moreada would love to get your wrecker contacts on mopar stuff, I am in Calgary as well.

 

[kkritsilas]

double a ron:

I live in Calgary, too.

In Canada, just like California (only) we got the 318 with the 4 barrel. The US outside of California didn't have it available; only the 318 2 barrel.

Locally, sometimes the Pick-n-Pull on Barlow Trail has older Mopar stuff. Last year, they actually had a Cordoba with a 340/727 and 8 3/4" rear end come in. Too late for me to grab anything, but did get the tubular exhaust headers from it.

 

[double a ron]

Well you should both email me at triallison@gmail.com to share resources. I have a tank and gas sender in decent shape for you moreada.