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Unread 09-21-2009, 04:56 PM   #1
cpvarner
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1977 CJ5 
 
Join Date: Sep 2009
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DUI HEI 304 timing problems

Hello All:
I'm a new guy to this forum, so I hope I got this right, here is my problem, any help, ideas, suggestions would be most appreciated!!!

I have a 77 Jeep CJ5 304 w/edelbrock 1406 4bbl, edelbrock performer intake, headers, 64 IH T18 trans, and a new DUI HEI distributor. All pollution devices have been removed.

I just installed a new DUI HEI and I'm having real problems getting the timing dialed in, I've tried the advance @ from 12 down to 7 BTDC with the idle high and low, and the mix rich and lean. Every time it seems to idle fine with full vacuum, with the 12 advance it literally purrred, never heard it sound so good. It sounds even better when I rev it up while in neutral. But once it's on the road it's really rough with misses & stutters as I go through the gears and seems to be holding back if that makes any sense.
Thx,
ChrisV

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Unread 09-21-2009, 06:32 PM   #2
John N
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I've have a DUI on my 360 and tried that carb, at one time. Are you plugging the vacuum advance while you set the timing? If not, then you aren't setting the timing where you think you are. IIRC, 8 BTDC is the spec and has worked well for me.
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'81 Scrambler w/ FI 360 AMC, 33x12.50 BFG M/T's, 5" of lift, ARB'd Dana 44's F & R, Dana 300 clocked & twin sticked w/4:1, Warn XD9000i, etc...
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Unread 09-21-2009, 06:51 PM   #3
cpvarner
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Quote:
Originally Posted by John N View Post
I've have a DUI on my 360 and tried that carb, at one time. Are you plugging the vacuum advance while you set the timing? If not, then you aren't setting the timing where you think you are. IIRC, 8 BTDC is the spec and has worked well for me.
Thank you very much I will give it a go @ 8BTDC with the vac advance plugged.
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Unread 09-21-2009, 06:56 PM   #4
John N
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Quote:
Originally Posted by cpvarner View Post
Thank you very much I will give it a go @ 8BTDC with the vac advance plugged.
Be sure you plug the line to the carb, so it doesn't have a vacuum leak. The distributor doesn't need to be plugged.
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'81 Scrambler w/ FI 360 AMC, 33x12.50 BFG M/T's, 5" of lift, ARB'd Dana 44's F & R, Dana 300 clocked & twin sticked w/4:1, Warn XD9000i, etc...
2002 Grand Cherokee Limited, 2008 Overland Grand Cherokee, a 1976 CJ-7 in pieces and 3 more off-brand 4x4s...............
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Unread 09-22-2009, 06:59 AM   #5
cpvarner
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You bet, I will be out there in a few minutes. We have some xlnt weather here in Arizonza this morning, about 67 right now!!

Thx again for you help, I hope it works
ChrisV
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Unread 09-22-2009, 07:31 AM   #6
JeepHammer
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Don't just 'Remove' the vacuum line from the distributor,
Remove and PLUG the line.

If you don't plug the line, it's a vacuum leak and will effect the fuel mixture and timing.
A golf 'T' works well for a plug, and I don't go anywhere without one when I'm doing ignition work.
Bright colored ones also help you remember to put them back in the box when done!
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Unread 09-22-2009, 10:45 AM   #7
cpvarner
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I plugged it good, thx. I went to the spark vac (no vac @ idle) and set the initial time @ 8 btdc and it's almost there. It still kind of stutters / hesitates a bit when I punch it. So I think I will advance it abit more. I have the idle set at about 750 rpm.

Thx for your help, I really appreciate it
ChrisV
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Unread 09-22-2009, 12:07 PM   #8
Fjguercio
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How about a little less advance. Not sure of the HEI DUI but most others have too much advance for the Jeeps. Would not suprize me if you have to got to the 5 range or little less. Your own distributor insertion could have this value change some the initial advance setting.

Since you are are driving on road to test, accelerating, etc, this is under load. You said it did not run too well, I think too much advance.

Less advance not more....

Fred
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Unread 09-22-2009, 01:46 PM   #9
Andy5150
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Its best to have a dial-back timing light so you can see how much centrifugal advance your dist is bringing in ,and how soon rpm wise. Its common belief that HEI,s have too much advance for jeep engines. This may be true, although the Proform HEI I put in my 360 was curved way too slow; it didn,t start advancing until about 2500 rpm, and didn,t reach its full range until about 3500. You also need to check how much vacuum advance your,e getting; on a DUI, its probably adjustable. Theres a bit of trial and error involved. My 360/w performer plus cam, 600 holley runs best with 15 degree intial, and a total of 35 degrees in by 2200 rpm. Theres also 12 degrees vacuum advance hooked to manifold. This is what works best with my combination; yours will probably be different.
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Unread 09-22-2009, 02:28 PM   #10
Fjguercio
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Quote:
Originally Posted by Andy5150 View Post
Its best to have a dial-back timing light so you can see how much centrifugal advance your dist is bringing in ,and how soon rpm wise. Its common belief that HEI,s have too much advance for jeep engines. This may be true, although the Proform HEI I put in my 360 was curved way too slow; it didn,t start advancing until about 2500 rpm, and didn,t reach its full range until about 3500. You also need to check how much vacuum advance your,e getting; on a DUI, its probably adjustable. Theres a bit of trial and error involved. My 360/w performer plus cam, 600 holley runs best with 15 degree intial, and a total of 35 degrees in by 2200 rpm. Theres also 12 degrees vacuum advance hooked to manifold. This is what works best with my combination; yours will probably be different.

Andy,

I think 15 deg of initial advance ( alot 2x normal) and 35 deg advance by 2200 rpm should scare you. You are also using Manifold Vac rather than the normaly ported.

You have a very odd set up, maybe 1 of 1000 or 10,000 might match you. This set up is not something to publish for others to copy. IMO

You also have a after market cam and that changes the time curve for that engine and will no longer be stock curve.

AMC engineers made the stock advance curves because that is what works well in the AMC engines. These engineers forgot more than we will ever learn about advance curves. We can bring them in a little quicker for a snapy response but we are still following the curves for the most part. We have published the Jeep FSM Advance Curves several times here on JF. You might have something that works but think how well it could work if you have the correct curves.

You also had a thread asking about gears it was 4-5 pages long. So you are well familar with the pitfalls and problems with HEI Distributors in Jeeps.

Fred
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Unread 09-22-2009, 05:32 PM   #11
cpvarner
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Just found out from the DUI folks that the base timing for the 304 is between 10 & 15 deg BTDC
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Unread 09-22-2009, 05:39 PM   #12
73jeep
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Factory advance timing has a lot more to do with emissions than anything else. My Stock 258 is running 12 at idle and up 42 at full advance. for you hei haters i have 15k on a junkyard hei (coverted efi) with factory v8 drive gear. These engines do well with a little more timing than stock.

i set the idle by adjusting it till i get the best idle quality, then adjust the advance curve to prevent pinging. Summit has spring kits for around 15 bucks.
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Unread 09-22-2009, 05:43 PM   #13
Andy5150
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The aftermarket cam; maybe thats the key.If it has more duration than a stock cam, it may reduce static compression ratio, and require more initial timing. Iv,e set the dist. several times ranging from 2000 to 3500 rpm for total advance. The current setting(35 degrees@2200rpm) work best for my engine as far as fuel economy, throttle response, and cool running. Same goes for my initial setting(15degrees),and the can of worms I was afraid to open,manifold sourced vacuum advance.I tried ported vacuum, and the motor heated up at idle, and lost 2" vacuum(19to 17). My motor idles smooth and cool, never kicks back against the starter, has great power and throttle response,and went from 10 to 12 mpg. in town. Not bad for a cj-7 /w 360, 4.10 gears, no overdrive(t-18) and only 32" tires. As for thr HEI, I read about the problems after I already bought it, so I used the MSD gear, checked for proper installed play(up and down), and as of 3 days ago it still look new after 10000 plus miles.All I can say is, it works for me!
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Unread 09-23-2009, 07:42 AM   #14
cpvarner
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Performance Distributors tunes each of their HEI units before shipping, based on the info provided by the customer, i.e. engine, cam, carb, trans etc.. They calibrated mine to 24 degrees @ 3000. I will be re-checking all the plugs, the cables and the electrical hook-ups, also according to them their HEI requires a min of 12 volts but really likes a voltage of 14+
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Unread 09-23-2009, 08:11 AM   #15
JeepHammer
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Hesitation/Shudder (also called 'bog') when you 'Punch' the throttle is probably a accelerator pump issue...
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