What headers will fit an 84 Chrysler 5th ave? I want to make it as fuel efficiant as possible.

Also what would be best a 360 2bbl or a 4bbl intake for the 318? Thanks

I would use the Street Dominator that I have for sale or use a Eddy performer if I was going new..
Not sure on the headers.

I would ditch the cats/y-pipe for 2 1/4" pipes off of manifolds following stock routing then a 2-into-1 collector from summit 3" single pipe back to muff and 3" tail pipe on a 5th ave/dippy/fury.

this works bestest IMHO,the headers (flowtech) will be the one fits all A-body header that has the 3 tubes down under the tierods. APITA to install and have no ground clearance unless you crank up the t-bars,have to strip/plug off all smog stuff. (which I just block at the manifolds or remove it all with headers) did I mention fitment sux?

I would go with a stock 4-v intake/q-jet,a999 HS-LU trans,2.94 gear,235/75/15 tires. if this gets 19 mpg in my 85 truck it should be great in a 5th ave with better ride comfort.

I have Hedman 78050 A body headers on my Mirada which is the same as 5th ave basically.

The driver side is a pain to install, but they clear everything fine and you can still use the stock starter and get it in/out without messing with the headers.

As mentioned 3 tubes go under the steering linkage on the driver side and you WILL scrape them now and then. And the air injection ports in the heads will need to be tapped and plugged.

For an intake I would just find a used Eddy performer or a stock intake if you are using a Tquad/Q jet, and a Eddy RPM/Crosswind copy if using a squarebore.

Keep in mind a 'standard' 318 in a 5th will have 318 heads with smaller ports, so a 318-4 intake (aka a 360 intake) will have larger ports, giving you a discontinuity/neck-down at the cyl head port.

For mpg, I think the payout on headers would take a while. Other parts would be of better benefit. Search for a HotRodDave MPG thread.

Stock iron manifold with a QJet or Tquad will net you the best mileage.

Sheldon

Scratch 235s are a bit big for it.
I thought letting the motor breathe better helps with mileage etc so why would stock manifold be a better choice than headers?

Iron intake manifold. Headers seem to always add MPG.

Sheldon

gotcha. I need to read slower

I need to type more!

Sheldon

had both hedman and summit brand A body headers on mine, worked good, never bottomed them out.

go 4bbl on the 318. have never driven a 360 that wasn't a pig in the fuel economy department.

I installed some shortys from edelbrock that work great. They don't take up much space, come out exactly where the Y pipe comes out so it is to attach. It isn't hard to install and look good. I would do it again on the 85 dippy I have.

Well my main reason for getting the best fuel economy is Ill be driving this car at least 4 days a week 60miles round trip around the end of may beginning of June.
Im not sure the size of tank but it drove almost 100miles and used almost a half tank driving 70 with puny 195s. Im hoping that's good. I swear my of 5th got around 20mph. I plan to go back to 205s but if 215s clear wich Im sure they will Ill run them. I plan to add overdrive when Im able to aswell.
What would be best a 500 or 600 cfm? I have a factory 4bbl carbon from a 85 W150. I would think the 500 would be best

best mileage with my 5th aves (had an '86 and '88) I got was when they were stock with lean burn. I'd get 22-25mpg on the highway, 13 around town, and about 18 mixed.

when I modded the '86 with a mild 360 (stock long block, eddie 600, eddie air gap, comp XE262, headers), & 3.55 rear I got about 11 in town, 15 highway, 13 mixed. I replaced the 998 tranny with an A500 (OD), and that brought it to 11 in town, and about 17-18 highway, 15 mixed.

then I replaced the 360 with the original reringed 318 shortblock wearing magnum heads, the same intake and headers/exhaust as the 360, and had the factory roller cam reground to 259adv/208@.050/127@.2"/.316" lobe lift/.506"@ the valve, and mileage increased to about 13-14 in town, 20 highway, and 17.5 mixed. power felt about the same as the 360....either would hang with a 2005 300C AWD (so, realistically mid 14's car)

tires were either 205/75R15 or 255/50R17 (both 27" tall).

then I sold it and bought a 2011 charger R/T, which is faster, more comfortable, and I've been averaging 23mpg in mixed driving....

as an aside, I honestly think I coulda gotten the 5th ave's mileage up another 2-3mpg had I swapped the air gap/eddie AFB combo (which I tuned with an LM1 wide band O2 for optimal mixure...was way too rich OOTB) with a small t-quad on a modded LD340 intake, or had tried one of the new thermoquad style demon carbs

http://www.demoncarbs.com/Types/Street%20Demon.asp

Like patrick, I don't get great mileage with the single, cat-less exhaust system. Cherry bomb straight through muffler. Don't think headers will make that much difference. Lean burn though, I don't like that idea. Right now with the carburator problems I am having, even with the carb running lean, it isn't going to make that much difference. I thought about pulling the engine/transmission and putting in the new 5.7 hemi with the eco system. Power and mileage with the new engine would be sweet. But, that adds more money to it. Maybe the 3.5 v6 from a wrecked charger/300m. Mmm!

mine had a custom built (by me and a friend) all 409 stainless 3" mandrel bent system off the headers, BTW....

well, almost all stainless...they dynomax 17769 muffler and 3" summit glasspack in the tail pipe as a resonator were both aluminized.

What do you guys think of using HP 340 exhaust manifolds with a 2-1/4 dual exhaust all the way to the back would do on bone stock 318 or 360?

Magnus manifold I've been told flow better than the 340 ones.
Important pretty sure my old 5th ave I had 4-5yrs ago got around 20mph. That was with leanburn delete and we pitched the cat and later had dual put on. Important thinking the headers and kit listed on the dippy forum will be the ticket as it'll cost more just to have a shop run the exhaust from headers back than it will for me to buy headers and kit and do it myself. Its under $400 for the setup. Shops charge that or more from the manifold back.
Its almost at a half tank now an has about 118 miles on the trip odometer. So mileage is looking better on her but want better