4-barrel Conversion 1988 Chrysler Fifth Avenue

Outlining all the mods to convert to 4-bbl carb on my '88 5th Ave. 318 V-8 with factory roller cam and fast-burn #302 casting heads. Rebuilt '70s ThermoQuad carb on top of an Edelbrock Performer manifold.

[@macdrew77]

Therrrmoquaaad. Love it man, once these become smog exempt in CA i want one

[@nastybastardatlive]

The AFB is better. Very similar, but made of aluminum instead of plastic.

[@mark0decker827]

Beautiful

[@kennesbit6987]

Im doing 4bbl conversion on my 87 Fifthave but keepin it smog leagel have lean burn Thermoqaud same one used on 82 New Yorker also have Eldbrock Intake Manifold

[@kennesbit6987]

Im doing same on my 87 did you switch to vacum advanced distrib how u hooked up the vacum on distriburator

[@carlorocky]

Great job man! Did you know that the police interceptor dodge diplomat which is the same car, came with 4bbl quadrajet? Also, they had a much better gear ratio, 2.96 vs. the 2.26 gear that you have now. Try to find the entire rear end, it’s much stronger and bolts right in. When I was a teenager my friend had an ‘86, we did everything we could to create a sleeper. The rear end is single best upgrade for serious performance increases. I always loved those cars. Nice job guy!

[@mopartron3030]

Thanks! I actually sold this car almost a year ago but one of the first mods I did was swap in an 8.25" rear out of a Jeep Cherokee with 3.07 gears, definitely woke it up. Now i'm working on my '70 Duster again hopefully i'll have more videos of that soon.

[@HyperRidemx]

was that axle from the Cherokee a direct bolt in? I just picked up a '88 5th Ave and was thinking of changing the rear axle to a Jeep, but was not sure on the width.

[@pkranz937]

The police 8.25 rear was 2.94 from '82 - '89, SureGrip opt. The idea of using a shorter gear ratio is misleading. In a heavier vehicle with a torquey engine, shorter gears tend to create more of a "noise maker" situation - all show, not much more go. The 2.94 ratio was considered a split between the 2.76 and 3.23 ratio.

[@patrickfansler4760]

What did you do with your egr valve and idle control motor? I want to do a 2 barrel to 4 swap on my 89 d150 it’s got same 318 motor but Idk What parts or where to start, please help!

[@mopartron3030]

Your truck has the TBI setup which is totally different I haven't messed with those myself. Cars with the 318 kept using a carb all the way to the end in 1989.

[@fabianramirez8534]

Sounds nice what exhaust is on it ?

[@flimflam6547]

^

[@DADSGETNDOWN]

Oh, 302 Heads huh ? Will that manifold work on the stock 318 heads, and if so, which intake is that, as in part number and or what vehicle do they sell it for ? Lastly, what did you do to the exhaust ? Stock manifolds right ? What else ? Remove Converters? Just run duel all the way out ? I am doing this stuff right now to my '86...

[@mopartron3030]

302 heads have the same bolt pattern as any other LA head so any LA intake will work, this is just your garden-variety Edelbrock Performer for SBM LA engines. Exhaust I just ran homemade 2 1/4" duals off the stock manifolds (with 2" downpipes for the first couple feet to keep the velocity up) and ditched the cats; luckily I sold it to a guy in Wyoming because we have emissions testing here and it would have failed without cats lol. You might have to get creative with the pipe routing though those cars weren't designed to have dual exhaust, gas tank is offset to one side.

[@nastybastardatlive]

These 140hp 318s just need a cam, intake, and exhaust to make 300hp. They're basically underpowered 340s. I heard Aspen/Volare headers work on the Diplomat/Fury.

[@DADSGETNDOWN]

@@nastybastardatlive lol. "Just".

[@kennesbit6987]

@@mopartron3030 im gonna have my fuel tank moved over n filler pipe exstended headers x pipe dynatech cats borla mufflers and dual outlet tips

[@KevBehindACamera]

I had one similar to this. It was very slow as all cars from the 80s were.I want the trading it for a 1983 Trans Am which had a v-8 but was slow as well..they do have fuel injection conversion for these. That would be interesting to see

[@nastybastardatlive]

Fuel injection wouldn't effect horsepower. This 318 needs a cam swap.

[@mopartron3030]

The 2.2x gears are what really kill them, that made the biggest difference in my car going to 3.07s. Free up the exhaust with some true duals or free-flow 3" single, get a distributor in there with a performance mechanical advance curve and put a 4-barrel on it you'll pick up at least 30-40 HP. Gas mileage also didn't change much for me after I did those mods, still averaged around 20 MPG.

[@kennesbit6987]

Thats what plan do with my 87 but wanna keep it emmision legal as have friend in Cali n wanna go their someday so will use eldbrock emmission legal carb btw mine missing that spring on kick down so far ive change spark plug wires to 8 mm summit racing wires taylor cap n rotor fast coil and E3 spark plugs

[@mopartron3030]

Biggest things to keep it emissions-legal would be to keep the air pump and at least keep the Lean-Burn air cleaner so it *looks* like the computer is still there. I'm not sure if you could get away with dual exhaust even if you put in a pair of cats, they might be dickwads like here in CO and require factory-replacement CARB-legal cats. I'd contact your local emissions test station and ask them to be sure.

[@carfixer5194]

How much of a problem did you have removing the EFCS and the Holley 6280? Looking to possibly replace the 6280 with a 2280 (non electric feedback version of the stock 6280).. Going 4bbl is not economical - or HEI.. Just wanting to either bypass the EFCS or get it running right.

[@mopartron3030]

Car Fixer you can't bypass the EFCS without swapping the distributor and converting to regular ignition unfortunately, check out a channel called Tyler's Neighborhood Garage he goes into great detail about the conversion, way more than I do.

[@carfixer5194]

EngineNerd451 will do!! Thanks! I’ve seen his carburetor work - I’ll check out the rest!

[@pkranz937]

There is no reason to replace the Lean Burn system unless the computer tests bad. Then it's cheaper to replace the computer. There's no performance to be gained by eliminating the Lean Burn system.

[@nastybastardatlive]

Why didn't you swap in a cam?

[@2_Idiots_Shooting]

also whats up with your speedometer going to 125? that wasn't a police edition was it? mine stops at 85

[@mopartron3030]

Logan Hammond yeah it's a cop speedo, previous owner installed it

[@pkranz937]

Fifth Avenue and Diplomat SE were not offered in the AHB police package

[@danr9584]

Is here a Ballast resistor that you had to Add or remove when you did that Ignition coil swap?

[@mopartron3030]

No ballast resistor, MSD box requires its own type of coil altogether

[@mr.b2107]

These models had a built in resistor in the coil. So they did not have a external resistor

[@2_Idiots_Shooting]

how did you get rid of that lean burn computer crap? i can never figure it out on my 85 fifth.

[@mopartron3030]

Logan Hammond I literally gutted it and replaced it with non-lean-burn distributor, ignition and carb

[@pkranz937]

It's cheaper to figure out what is actually wrong, and fix it. The computer is rarely the problem. Even if the computer is proven bad, a replacement is far cheaper than hacking your car up for a new intake, carb, and ignition. Plus, you gain absolutely zero in power and fuel economy.

[@junkiejackflash]

@@pkranz937 that's been my main concern with putting a carb on. They make it sound easy, but you lose fuel economy, and I can find a new lean burn for $80. Probably less if I cruise the junkyards

[@assadsmagicalmysterytour]

Where can I get a proper diff for one of these?

[@mopartron3030]

Find an 8-1/4" rear end and swap that in, pretty easy to find parts for those

[@matthewnorton4529]

Was the ac easy to keep with this intake

[@mopartron3030]

Yeah it's pretty much just an aluminum copy of the factory 4-bbl intake

[@chargerman426]

Does your cruise control still work?

[@mopartron3030]

Sort-of, I have since sold this car but at the time it did work but I had to mess with the buttons a lot to get it to activate. I think the module just needed to be disassembled and cleaned/lubed.

[@matthewnorton4529]

What did you do for linkage and trans kick down

[@mopartron3030]

Just modified the stock 2-bbl parts, if I did it again though I would probably get Lokar KD and throttle cables they're worth the money. It took lots of trial-and-error to get the stock linkage to work.

[@matthewnorton4529]

@@mopartron3030 do you know which intake you used model

[@matthewnorton4529]

Also could you please share link to correct lokar kickdown and throttle cable I suck at searching the web

[@matthewnorton4529]

@@mopartron3030 I have 85 fifth avenue so I need lokar kd and cable for 904 trans

[@matthewnorton4529]

What dizzg did you use

[@mopartron3030]

Just a stock replacement electronic distributor from any 70s-80s Mopar WITHOUT Lean-Burn

[@junkiejackflash]

Hey, I bought an 88 Fifth Ave, and know nothing about cars. But I love this one and I wanna learn. Could you do an update video showing how you did this?

[@mopartron3030]

Hey sorry for the late reply, I have long since sold this car and don't remember all the details but in the near future I will be starting to put out content all about how to get older American cars running the best they can and what are good mods to do for power and fuel economy. Most of it will be based around my 1970 Plymouth Duster which I have rebuilt pretty much everything on, sometimes multiple times lol.

[@HyperRidemx]

nice, what it should have come with from the factory!

[@pkranz937]

QJet after 1984 ...

[@nathaniellynch8980]

Where's ur computer?

[@mopartron3030]

The car is long gone at this point but I ditched the computer, converted it to traditional setup with vacuum-advance distributor and non-feedback carb

[@nathaniellynch8980]

How do I do that?

[@mopartron3030]

@@nathaniellynch8980 I mean I kind of outline it in the video. Get a 4-bbl carb and intake for a 318 and an electronic vacuum advance distributor from a non-Lean Burn engine and just swap it all out. The computer is only connected to the carb and distributor you can just pull it out and all the stuff that goes with it and convert the engine to 'as it would be' for an early-mid '70s Mopar.

[@mr.b2107]

I didn't much care for some of the thermoquad commentary. They are usually all rebuildable unless throttle shaft is worn and if you are experienced with the carbs. Why do I say this? Because it doesn't take 8 to make one good one, thats nonsense.

[@mopartron3030]

Have you rebuilt one recently? It's not easy to find parts for rebuilding or tuning and for the cost of getting one in good shape imo it's better just to go with a new design that's still in production. It's a great carb but lack of parts availability as well as performance-oriented spread-bore manifolds makes them kind of a "niche" carb to me.

[@corycarpenter5873]

Cut the cats off