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post #1 of (permalink) Old 07-09-2001, 04:47 PM
jeepfreak
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4.0 head conversion with carb...whos done it?

I was wondering how many here have used a carb with their 4.0 head conversion. Thats is how I am doing mine and I am having a problem getting my newly rebuilt 258 to start. Here is what I have: 258 bored 060 over. 97 4.0 HO head. Cliffard Performance intake for a 91 head and Cliffard Performance headers. I am trying to start this motor for the first time and its not wanting to start. It fires every once in a while while im turning it over but that as much as it does. Ive double checked that the distributor was set to number 1 during compression and it looks to be...both valves are closed. The coil and spark plugs are getting spark. Ive also checked fuel and the new holly its getting gas and there was some gas in the cylinder when I took the spark plug out. Does anyone else have any suggestions that I could look for?

JACOB
81 cj5 WITH SOA/SR/302
2000 TJ with 4" lift
Confuscious said:
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post #2 of (permalink) Old 07-09-2001, 05:40 PM
 
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Re: 4.0 head conversion with carb...whos done it?

if you dump a little gas down the carb, will it run a little longer? or, try to keep it running on WD-40 (its better than starting fluid on the engine). is the Holley new? rebuilt? 2bbl? 4bbl? have you tried to adjust the float? try turning the idle screws all the way in and then back out about 2 turns. you may want to triple check that the timing is correct. matt

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post #3 of (permalink) Old 07-09-2001, 06:34 PM
jeepfreak
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Re: 4.0 head conversion with carb...whos done it?

Yes the carb is new..It is a Holly 390 CFM. It doesnt seem to run longer with gas or starting fluid. It seems that it must be the timing. The only thing I can think of at this point is that maybe I screwed up when I installed the cam. How could I tell if that is the case?

JACOB
81 cj5 WITH SOA/SR/302
2000 TJ with 4" lift
Confuscious said:
"The wise man takes the path of least resistance"
I say:
"Confucious didn't know jack about Jeeps"
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post #4 of (permalink) Old 07-09-2001, 06:53 PM
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Re: 4.0 head conversion with carb...whos done it?

sounds like an eletrical ignition problem
like your starting circut is enabled but your continuioius running circut is bad
i dont know much but that seems like a logical assumption


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schaan

1980 CJ7 83.2% completed
1969 Early Bronco 43% completed
post #5 of (permalink) Old 07-09-2001, 08:53 PM
 
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Re: 4.0 head conversion with carb...whos done it?

Yep, it does sound like it's either a start/run wiring problem
(this is when the coil gets juice while cranking but it's turned off in 'run' mode
OR it sounds like it could be you may have mistook the correct timeing chain alignment.
But first check to see if you haven't set up your plug wires to the wrong rotation. It should be clockwise starting with #1 ... check the dist. rotor at TDC ... the rotor shold be about 1/4" PAST (accounts for timing advance) the #1 on the cap.
Hint: the start/run thing is easy to check ... just put a voltmeter on the primary ignition circuit and see if the juice goes to 'o' after you come off the 'start' position on your keyed ignition switch ...
You should be able to check the cam timing by turning over to TDC + 8* on the compression stroke (valves still - confirmed ignition on) of the #1 cylinder then loosening the dist and rotating it back and forth to see if you're getting any spark on the #1 plug wire.
Hope you find the probem ... it's usually a brain fart thing... [img]/wwwthreads_images/icons/smile.gif[/img]




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post #6 of (permalink) Old 07-09-2001, 10:24 PM
jeepfreak
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Re: 4.0 head conversion with carb...whos done it?

Thanks for the replys, I will double check all this again. The other thing that I was thinking might be a problem is that I'm using a carb on a head that was designed for feul injection. Does anyone have any thoughts on this? Has anyone else used a carb on a 4.0 HO head?

JACOB
81 cj5 WITH SOA/SR/302
2000 TJ with 4" lift
Confuscious said:
"The wise man takes the path of least resistance"
I say:
"Confucious didn't know jack about Jeeps"
post #7 of (permalink) Old 07-10-2001, 01:38 AM
 
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Re: 4.0 head conversion with carb...whos done it?

It should fire.
Because it's just popping means the plugs are firing at the wrong time or in the wrong order or the cam postition to crank stroke is wrong...
unless anyone can suggest anything else ...?

JAF
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post #8 of (permalink) Old 07-10-2001, 03:54 AM
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Re: 4.0 head conversion with carb...whos done it?

Have you checked for vacuum leaks. I did the 4.0 head conversion last month and ran into similar problems. After ironing out the computer nightmare with the "nutter bypass" I found I could only get the motor to pop off for a second or two. It turns out I had a massive intake manifold vacuum leak and wasn't producing enough vacuum at idle. I had to retorque the manifold bolts in a three part circular pattern to get it to seal. I am currently running a Clifford intake with an edelbrock 500 cfm 4bbl. It runs great. I have also tried the Holley 2300 and a motorcraft 2100 that I had laying around. I have found that the 4bbl works the best. I was told by Clifford that the head breathes much better than stock and really needs a 500 cfm carb. Perhaps they were trying to sell a carb but it seems to work really well.

By the way. I was told by the boys at Clifford performance that the recently dynoed a 258 bored .30 over with their intake and header, stock ignition and an Edelbrock 500 cfm carb. They said it made 224hp and 290 ftlb of torque. I don't know what mine makes but it will set you back in your seat now.

David

'84 CJ7 258 .30 over,4.0 head (lots of fun head work done), Clifford intake & header, edelbrock 500cfm, MSD6A, Team Rush Ignition upgrade. Etc, Etc.
post #9 of (permalink) Old 07-10-2001, 08:58 PM
jeepfreak
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Re: 4.0 head conversion with carb...whos done it?

Hmm that gives me somthing else to think about...now that I'm not using the old computer maybe I should wire my distributer directly to a hot lead to see if it will run. I cant remember off hand where that lead comes from but maybe it is throwing the timing off. Thanks for you input. Also them dyno numbers are awsome...I hope mine makes that kind of horsepower. I wonder what cam the used.

JACOB
81 cj5 WITH SOA/SR/302
2000 TJ with 4" lift
Confuscious said:
"The wise man takes the path of least resistance"
I say:
"Confucious didn't know jack about Jeeps"
post #10 of (permalink) Old 07-12-2001, 09:48 AM
mindbender
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Re: 4.0 head conversion with carb...whos done it?

David: I sent you a private email, but neglected to signin, so it probably didn't get to you. Well, anyway. I was curious about the performance of your jeep after the conversion. What numbers are you turning in RPMS? What might your power curve look like based on your experience with its performance? What kind of gas mileage on the road? Gearing in diffs and tire size?

I did the conversion to a 4.0HO and significant head work based on specs by Cliffords. But, still running the 32/36 Weber. After the head work the gas mileage dropped from 18.5 to 15.0. Very low end torque seemed delayed, but then it increases significantly. It will run down the highway at 65, but struggles to push much over 70/75. Hills give it some problem. Still trying to sort out the issues with the conversion.

Appreciate hearing about your experience.

Mindbender 85CJ7 I258 [img]/wwwthreads_images/icons/smile.gif[/img] 40 head ported polished [img]/wwwthreads_images/icons/smile.gif[/img]
Jacobs [img]/wwwthreads_images/icons/smile.gif[/img] 31" [img]/wwwthreads_images/icons/smile.gif[/img] 999 insulated hard top
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