best carburetor on the 87 2.5l

[ComancheCrusher9800]

What problems would I run into while putting a 1 barrel carbureter on the 87 2.5l tbi. I already have the adapter plate I just want to know what I would actually have to change

[Eagle]

The fuel pump. Carburetors need a maximum of around 7 psi (IIRC). If the pressure is too high, it will blow right past the needle valve and flood the float bowl. I think the best idea would be to scrap the OEM fuel pump and buy an aftermarket pump made for use with a carburetor.

 

You also need to find an appropriately sized carb. The carb used on the 2.5L Jeep engine in the '84 and '85 Cherokees was trash. If I were doing a carb conversion on a 2.5L (something I'm considering, actually), I'd look for a non-computer controlled carburetor. Back in the late 1960s, AMC had a 199 cubic inch version of the in-line 6 (the same basic engine as the 4.0L Jeep engine) that ran on a 1-barrel carb. A 199 c.i.d. is 3.2 liters, which isn't that much bigger, so a carb for that engine might work. I had a Rambler American back then. With the stock 199 engine, an more open air cleaner and a glasspack muffler, I routinely got 28 MPG on the highway.

[ComancheCrusher9800]

I had a carbureter on my last 87 mj and it was an aftermarket pump and my carb is the one I'm thinking about using is not computer wise at all

[Jeep Driver]

If you want the full benefit of a carb...........go with the MPI intake. 

 

 

Stock TBI intake is very restrictive............IOWs, they suck. 

 

 

Also, the MPI allows for a larger throated carb. 

 

Also, the heated intake............total myth, complete BS. 

 

 

[Jeep Driver]

Here is the adapter I made for mine, I don't have any pics that compare bore sizes, the MPI is about 40% larger. 

 

MPI intake flows extremely well............but you'll choke it up with the stock exhaust. 

 

 

 

 

 

I'm curious as to what distributor you plan to use?

 

 

 

 

 

 

 

http://www.jegs.com/i/Holley/510/12-881/10002/-1?CAWELAID=230006180039030301&CAGPSPN=pla&CAAGID=44693592161&CATCI=aud-224375369591:pla-193247796071&CATARGETID=230006180039218476&cadevice=c&gclid=CjwKEAjw4IjKBRDr6p752cCUm3kSJAC-eqRt1O_yT3nawAWykJ3rnNb_TWeY7SsuULe3ZrUwV0SO9BoCOB7w_wcB

 

I would keep the existing pump and plumb in a regulator...........return line is right next to the pressure line.

 

TBI fuel is regulated at 14lbs and the pump barely keeps up. I's also suggest a fuel pressure gauge.

 

[ComancheCrusher9800]

Well I have a 87 so I have unless I want to upgrade to ho I have to stick to the renix tbi system

 

Sent from my SM-G900V using Tapatalk

[Jeep Driver]

Well I have a 87 so I have unless I want to upgrade to ho I have to stick to the renix tbi system

 

Sent from my SM-G900V using Tapatalk

I have an '88 Renix. 

 

 

What am  I missing here?

[ComancheCrusher9800]

So your using an mpi intake? Whatd you use for the holes for the injectors

[ComancheCrusher9800]

Man I'm lost isn't mpi multi poet injection I don't even see any whole for the injectors in your intake. But that's a damn nice setup

 

Sent from my SM-G900V using Tapatalk

[ComancheCrusher9800]

Anyone know what carburetor would be best on the 87 2.5l? Non electrical and gets good on gas?

 

Sent from my SM-G900V using Tapatalk

[Eagle]

I thought you said in your other thread on this topic ( http://comancheclub.com/topic/53258-carbureter/) that you already have a carburetor.

 

:???:

[Eagle]

This calculator http://www.gtsparkplugs.com/CarbCFMCalc.htmlcomes out with needing 166 cfm if you want to keep 5,000 RPM as your redline.

 

Summit's on-line calculator https://www.summitracing.com/expertadviceandnews/calcsandtools/cfm-calculatorreports 187 cfm

 

Here's another calculator http://www.csgnetwork.com/cfmcalc.htmlthat reports 166 cfm.

 

So somewhere around 160 to 180 cfm is probably good. Too small will run well at low RPM but you'll be starving for power (which the 2.5L doesn't have an abundance of to begin with. Too big and you hurt fuel mileage. The third calculator I linked to above reports 220 cfm for 100% volumetric efficiency -- which would be a VERY high performance engine, and is basically impossible. So figure around 200 cfm as the maximum you'd want (I think).

[ComancheCrusher9800]

Do talks get up to 5k rpm? On a 2.5l? I've only ever gotten it to 4k. And I do have one It's just not good on gas

 

Sent from my SM-G900V using Tapatalk

[ComancheCrusher9800]

Does yalls?*

 

Sent from my SM-G900V using Tapatalk

[Jeep Driver]

Still curious as to what you have planned for a distributor?

 

How are you going to manage ignition timing?

 

If you are going to a carb to bypass Renix......????????...........you will still have to maintain Renix for ignition/timing.

 

If you cannot manage Renix, how are you going to tune a carb to sporadic ignition timing?

 

 

As far as I know, there are no non-electronic distributors for AMC/Chrysler 2.5s. 

[Jeep Driver]

Do talks get up to 5k rpm? On a 2.5l? I've only ever gotten it to 4k. And I do have one It's just not good on gas

 

Sent from my SM-G900V using Tapatalk

 

 

A carb alone is not going to give you a 5K 2.5.............clearly you missed my point regarding intake and exhaust. 

You cannot alter/swap/change one part or one part of a system WITHOUT altering/changing/swapping other parts of other systems. 

 

 

My 2.5 runs right on through 5K even with the pathetic TBI. 

[MuddFoot]

He used set screws to fill the holes for the injectors

 

Sent from my Z981 using Tapatalk

[HOrnbrod]

Caution - thread hijack!

 

 

 

 

Sure would like to see a pic or two if possible what the air intake through the grille looks like and how it's filtered .

[ComancheCrusher9800]

My fuel system went out on my last mj and all I did was put a different fuel pump and the carb on there and adjusted the carb and it worked fine. Same distributer I'm using renix for the ignition and timing

 

Sent from my SM-G900V using Tapatalk

[ComancheCrusher9800]

All I'm doing is taking the throttle body off and putting the adapter plate and carburetor on with a regulator on the fuel line

 

Sent from my SM-G900V using Tapatalk

[Jeep Driver]

All I'm doing is taking the throttle body off and putting the adapter plate and carburetor on with a regulator on the fuel line

 

Sent from my SM-G900V using Tapatalk

OK.

 

You are complaining that  you get poor gas mileage, correct?

 

Secondary complaint is that it will not rev very high or there is a loss of power in the upper RPMs, correct?

 

 

What are  you doing about TPS?

[Jeep Driver]

Look, I'll let you go here.........

 

 

I'm suggesting that you may have a timing problem.........I'm not sure how you manage that. 

 

I know that others have done what you have done, but the bottom line is you still have to manage ignition. And, I see no real benefit if you are not willing to explore intake and exhaust. 

 

I have not fiddled with a carb in twenty years and I would not look in that direction myself. I am looking to repower and I will go aftermarket fuel injection with a stand alone engine management system. 

 

2.5s are 100K to 150K engines........that's my opinion......after that...........I suspect you have low compression numbers, chain stretch has put retarded at the crank, you likely have some blow-by, and who know where your timing is, what sensors are bad......etc.......

 

 

You are looking for something out of a 2.5 that it just isn't willing to give you. I spent a lot of money and time and effort, it was a great learning experience, but I would not do it again. 

 

 

 

If you insist, I would look to small Weber 2 barrel, I would go the the MPI intake, I would make my own adapter. But, that will just lead to another chasing, more money, more time.....etc.......

[ComancheCrusher9800]

That's the reason I'm switching over. I'm having problems with it and it's pissing me off. I have all new ground I have c101 elimination. I just put a new map sensor and tps In. The tps worked for a day and then it went to crap again. Right now I'm having a problem with surging and bucking. Like at high speeds it will be a loss of power and taking off it will buck sometimes it doesn't have a pattern I can turn it on and off and it'll fix.for about a mile or two

 

Sent from my SM-G900V using Tapatalk

[ComancheCrusher9800]

And I've never gotten either one of my mjs above 4k rpms. Even when they were both running strong (ones totaled) but this one is the problem with all the bucking and crap and I'm willing to upgrade exhaust and intake I'm just 16 and on a limited budget since how I pay for all my own stuff and do my own work

 

Sent from my SM-G900V using Tapatalk

[Jeep Driver]

And I've never gotten either one of my mjs above 4k rpms. Even when they were both running strong (ones totaled) but this one is the problem with all the bucking and crap and I'm willing to upgrade exhaust and intake I'm just 16 and on a limited budget since how I pay for all my own stuff and do my own work

 

Sent from my SM-G900V using Tapatalk

OK, I understand. 

 

 

I've been dealing same frustration for 5 years. That's why I rebuilt and spent months looking for NOS or Mopar sensors........the best of every part I could find.........I went through all my wiring........etc......

 

Yeah, I get it.

 

 

Stick with it, it will be a learning experience for you too. 

 

 

Try the carb. I won't post links to other forums but there are others who have done the conversion, do a little more research and see what  you can learn from others. It' a very slow moving site but you might try 4bangerjp.com just 2.5 jeep guys there.