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Unread 05-25-2012, 06:56 PM   #1
DryerDog
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HEI conversion Buick 225 doesn't want to run on 6

I recently finished up the build of a 1961 CJ5 with a Buick 225 engine. Engine was bored and rebuilt. After close to 40 hrs on the distributor install I still can't get the odd fire HEI distributor going right. It's been five years since my last build and that was a Chevy SB, so hopefully I'm just overlooking something really easy. It was going for a while on 3 cylinders, and sounded pretty good after a lot of backfiring and misfiring, but probably only because the passenger plugs fouled up on me... I'm thinking I didn't have the terminals correct on the OF cap... 50/50 chance? and I didn't check 'em. So I've read install guide after guide on the 225 HEI conversion and think I have a pretty good understanding of the little guy, but still can't get it to fire up on all 6. The engine does have a new Offy intake and a Holly truck avenger 470 carb... Here's some pictures to show how I've installed the HEI. I found #1 TDC, I put the rotor in a position where it was pointing at the #1 terminal on the cap... The attempt in the photo has #1 on the cap as a long terminal, followed by a short #6, short #5, long #4, medium #3, medium #2. The pole piece tip under the rotor lines up perfectly with a big section point of the stator. I believe this setup should cause #1 to fire at TDC (or about 10 degrees before if i spin the housing CC a little). Then #6 fires 150 degrees later; then #5 90 degrees after 6; and so on... I've pulled the distributor 20+ times and tried starting #1 at every position on the cap and still it's backfiring and misfiring every time I get it started. On top of all this, when I do get it running poorly and I hook my timing light up, I see my timing mark is way too far advanced (like 40 last time I tried it). So that plus the fact that I can keep it running on some cylinders tells me I've still got it in wrong. I have the vacuum advance line from the carb off and plugged. Also, I can't keep it going at anything less than about 1400 RPMs. (I've got engine at TDC and I'm holding my #1 in the photo)
Any ideas what could be going on here?


Last edited by DryerDog; 05-30-2012 at 08:04 AM.. Reason: Those pictures were too big so I removed them...
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Unread 05-26-2012, 09:15 AM   #2
badbird17x
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Interesting, I've never seen these before. I did a little google work, it appears there is a couple firing orders for the different years? Also read about an odd fire rotor? Just a couple stabs in the dark, but hopefully it helps.
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Unread 05-26-2012, 10:46 AM   #3
jeepdaddy2000
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Silly Question here....
Did you happen to adjust the idle mixture? Stock 225 intakes feed 3 cylinders per barrel. For aftermarket intakes, these are usually on the opposite side of the engine from the offending barrel (you can look down your intake and find out for sure). If the idle mixture is off, or if the float bowl is flooding into one of the barrels, then the cylinders feeding off that barrel will starve/foul.
As far as the dist goes, the cap should be marked with the #1 cylinder. the firing order is 165432. Rotation is clockwise. Timing should be started a 5 BTDC (you will probably bump this up once the engine is running right).
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Unread 05-26-2012, 05:59 PM   #4
DryerDog
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I haven't adjusted the idle mixture. I haven't really touched the carb except for the idle speed screw... For some reason my cap isn't marked with #1... I was under some time pressure to get it running so I just ordered cap, distributor, and rotor through autozone. When I line up a purple mark on the gear with the purple mark on the housing of the remanufactured distributor I would think the rotor should point to the #1 terminal since the cap only goes on one way... This could be assuming too much. It does point to a terminal that has the right spacing (150 degrees rotation of crank 75 degrees rotation of rotor) to the next terminal #6. Today I swapped back in the old socket distributor and I'm having the same issues... It is firing on most cylinders now as far as I can tell, but I'm getting a lot of misfires on both sides and my timing light tells me I'm 60 degrees advanced when I get it spun to a point where it will keep running.

I checked out the rotor on the HEI today and found it's the same part number as an even fire rotor... I was hoping I just had the wrong rotor. I talked with a mechanic at Napa today and showed him the HEI and he thought my distributor and rotor looked like the right system, but that they didn't line up with the cap I have... I'm hoping to have a different cap to try sometime next week.

Thanks for the replies.
I'll keep y'all posted on my progress.
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Unread 05-27-2012, 12:46 AM   #5
jeepdaddy2000
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I stand corrected. The #1 cylinder is marked on the snap on plug wire retainer.
The # 1 terminal should be the one directly to the left of the power/tach inputs, when looking at the cap from above.
The rotor is standard Gm. It is the cap that is different.
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Unread 05-27-2012, 05:39 AM   #6
wushaw
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I don't intend to insult your mech ability so please don't take any of it as such, sometime we miss something simple.

Motor timed right?
Your 12v ign wire going to the coil is 12ga straight from the ign switch with no ballast of any sort?
#1 cyl is on compression stroke, and your on the right cyl?
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Unread 05-28-2012, 03:48 PM   #7
DryerDog
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Here's the update for today:
Now I've got the old distributor in that was working before I had the engine rebuilt; I've put the HEI aside for now. I'm getting sparks down every plug wire. If i start timing at 5 BTDC I can barely keep the engine running and it sounds like it's backfiring at least once on every rotation. Big explosion sounds happen. When I spin the housing so that the timing ends up at about 30 BTDC the engine runs pretty well but backfires and misfires pretty randomly. I retard the timing any more than that and it just gets worse and worse. I'm still hoping I'm putting the distributor in wrong, so here's the process of what I've been doing:

I find TDC on the compression stroke for #1. I put the distributor in with the rotor pointing towards where number 1 will be on the housing. I spin the housing clockwise until the points are closed and then counter-clockwise until the points just barely open with the rotor still pointing at where #1 will be on the cap. I then clamp it down to the point that I can still spin it. If it's to the point that it can run poorly I throw the timing light on and see its at 30 BTDC. The vacuum advance is not hooked up. It's probably going at about 1400 RPMs but no tach is hooked up to the old distributor.

I did check to make sure the new cam was odd fire-- it is.

The new intake manifold part number is Offenhauser 6035DP. Here's the marketing info on it: Offenhauser Dual Port intake manifolds feature completely separate runner systems for the primaries and secondaries. At low-load, the primaries feed the fuel-air charge through the smaller bottom passages at near sonic speed, improving power and efficiency. When the secondaries open, their charge goes through the bigger, cooler upper passages. Then, in turn, it is rammed into the cylinders when it encounters the high-velocity mix from the primaries. The result is better fuel economy and a 15-30 percent power increase across the whole rpm range.

The new carb part number is Holley 0-90470. It's the 470 cfm truck avenger. Here's the marketing on that: The carburetor gurus at Holley built these carbs with you truck guys in mind. Features include maximum low-end torque and horsepower output, exceptional fuel control over rough terrain, steep angle idle, spring-loaded needles and seats, four vacuum ports, a one piece fuel bowl vent tube, vacuum secondaries, and a electric choke.

My mech abilities are limited at best so no offense taken wushaw. As far as I can tell the motor itself is timed right. The guy that rebuilt the engine is very old and has apparently done of 225s in the past, he did good work on a 350 Chevy SB for me 5 years ago. To double check that it is an odd fire cam in there I looked at the order the rockers go down when I turn the engine. I should mention that once the #1 rocker arm compresses the spring and I keep turning the engine to go to TDC it seems like I have to turn it a long way before I see my timing mark for TDC...

When I was trying the HEI I had a 10 gauge wire going to the coil straight from the battery from relay on a keyed switch.

I'm still thinking I have #1 on the compression stroke and I'm treating the front driver side cylinder as #1. I do remember messing this up and trying the exhaust stroke first when I did the SB Chevy 5 years ago. I pulled it out found TDC on the compression, put the HEI back in and that motor fired up right away. I had a friend who was a mechanic help me out with that distributor install though.

I've seen a lot of threads now where people had similar issues due to a dirty carb. Is there any chance I'm dealing with a carb issue? Jeepdaddy2000 do you think I should lean out the idle mixture? Or is the carb just too aggressive for this application? I thought it fell within the range for cfm on the spec sheet that came with the new intake manifold. I'm having a lot of trouble understanding how carb issues would make it want to run best at 30 degrees BTDC.
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Unread 05-28-2012, 07:53 PM   #8
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It sounds like the harmonic ballance may have slipped, I don't see how it would start at 30deg BTDC. You are doing everything correct as far as installing the distributor. There is something terribly wrong for it to be misfiring & backfiring like it is though.

Any mechanic friends that can take a look?
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Unread 05-29-2012, 10:01 PM   #9
DryerDog
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Yeah, It's getting to the point where I'll have to get a mechanic over. I'd like to find someone who's worked on odd fire engines before though.

This morning I tried pulling it and putting it back in a couple times and I still have the same problems with backfiring and the timing is best between 40 and 60. It seemed pretty good at 25 when I first tried, and spark plugs 2 and 6 were fresh. (I'm on my 5th set of spark plugs and I've started replacing just the bad looking ones. #6 is consistently the worst... dark black... and number 2 is often pretty dark. 1,3, and 5 seem to stay pretty clean, and 4 usually looks alright too.)

Tonight I tried switching the plug wires one position on the old distributor so #1 starts at 6 marked on the cap. It sounds much better this way, there is minimal backfiring, and I can get the idle way down and keep it alive. It honestly sounds good. It is pretty obvious it's only running on three cylinders though because pulling 2, 4, or 6 makes no difference. This makes sense... 1, 3, and 5 would still be firing at the right time based on the rotor position but 2, 4, and 6 would be sparking when the rotor is 30 degrees early. This let me run it for a couple minutes longer than i usually do. Usually I just put the distributor in, fire it up, check the timing and try to rotate it so it's less than 40-60 degrees BTDC, and kill it because of all the backfiring all within about 20-30 seconds.

Letting it run like this without all the misfires and backfires I think I heard the hissing of a terrible vacuum leak. It's hard to tell because I have Hooker max flow mufflers on her, which are way too loud. I was going to spray brake cleaner around the intake and see if it would stall, but since I'm only running on 1,3, and 5 and I suspect the leak is on the passenger side I thought it wouldn't tell me much. If i switch it back so 2,4, and 6 get sparks at the right time it's painful to keep running anyway and it sounds so inconsistent I wouldn't be able to tell if it stalls. Tomorrow I'll try blowing smoke in one of the vacuum lines and see if it comes out around the intake manifold on the passenger side? I used a FelPro gasket kit and silicone in the corners, but considering all the other leaks I had at first I wouldn't be surprised if the intake manifold is leaking like crazy.

Could a bad vacuum leak where the intake manifold isn't sealed cause the symptoms I'm experiencing?
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Unread 05-30-2012, 09:42 AM   #10
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Not the backfiring. It will cause raised RPMs.
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Unread 05-30-2012, 10:36 AM   #11
DryerDog
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The boys at Offenhauser were real clever and decided to put a super secret hidden vacuum hole right on the back of the intake manifold in plain view next to the other vacuum port holes I had plugged. That 1/8" open hole under the carb really had me thinking odd fire distributors were tricky. I'm surprised I had it running so well on 1,3, and 5, and I still can't believe I could get it running 60 degrees off.

Now the jeep is running strong on all six. I'll be switching to HEI tomorrow.

Thanks for the help!
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Unread 05-30-2012, 12:42 PM   #12
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Now clean all the fouled plugs with a wire brush or bead blaster you have laying around and keep em for future use.
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