[vatalaro]

I am having trouble setting my ignition timing. I recently installed an HEI distributor (new) and new 8mm wires and new spark plugs gapped at .045. I set the timing at 9 degrees btdc with the engine fully warmed up and at idle. However the timing seems to move after I have driven it. I recheck the timing and it has moved from 9 degrees to say off the scale. What could be the problem? I also read an article by Larry Maggio on how to upgrade to an HEI system for the older 258 engines and he sets the timing at 9 degrees btdc at 1600 rpms. Is that a misprint or is that how your supposed to set the timing? Can someone please help.

Julius

[jadams68]

Are you tightening down the distributor bolt enough?
Maybe your timing chain is worn and requires replacement.

[Geer_hed]

That 9 degrees @ 1600 RPM is the OEM spec for 1985 Jeep w/Auto Trans. I'm still not sure why it's necessary to run the engine at 1600 RPM to set timing. The HEI excludes the OEM EECU and any dizzy vac is capped anyway.

If you timed it at Normal Operating Temperature (which you said you did) and the timing is still variable, then I would look at something like what Jadams is suggesting. Note Jadams also has a HEI Writeup that doesn't mention setting timing at 1600 RPMs... Wonder if that caused him any problems... I'm thinking not.

Definitely make sure that your distributor can not be rotated by hand after you've set the idle. If after a short drive, the timing has gone from 9 degrees to off the scale, something is definitely up.

[jadams68]

Actually that is one of our garage buddy's jeep.
I run TFI and I had to adjust my timing somewhere between 8 and 10 degrees.

[Geer_hed]

yeah I knew you ran TFI, but I thought if it was important you would've made sure it was in the writeup, ya know? I just can't think of a reason why it would be.

[jadams68]

I'll get right on that....

[dawgates]

I'm shotting from the hip here, but hear me out.
We I was race drag cars. we set the timing at total timimg degrees of 32 (350 Chevy).
You do this at 2500 RPM that way the advance curve in the dist. is at full advance (whether vaccum or weights), your total timing. The basic timig for the engine (turning the dist. the timing was around 12 degrees when finshed).
So, at 1600 RPM your HEI dist. could be at full advance. He's telling you the correct way to set your timing at 9 degrees.
And as jadams68 says, make sure you tighten the dist. bolt. This does happen even to the best of us.

[Geer_hed]

Originally Posted by jadams68

I'll get right on that....

could you have possibly missed my point any more? I was trying to say that if you or one of your "clowns" thought it was a necessary step in the install that you probably would've included it in the writeup. Sorry, I won't give you that much credit or use your writeup as a good example again. better? whatever....

dgates.. forgot about the dizzy spring advance being in the equation for setting idle ignition timing. hmmm... All things being relative, does timing at full spring advance more likely to be accurate than timing at idle with the engine @ Norm OP temp... That's interesting...

[vatalaro]

Thanks guys for the help. I really appreciate it

Julius

[jeepmor]

But it's true. The oil pump drive flange at the bottom of the distributor needs to be filed. It is too long. Not the screwdriver like tip itself, but the tip needs to be made longer with a rat tail file where it transitions to the round shaft shaft. Grind this up another 1/6" or so towards the distributor.

I had this exact problem on my first HEI install. And I ended up breaking the clampdown flange on the casting before I figured it out, cost me a second distributor.

Simple enough to fix, but what a bugger to troubleshoot. Tighten and you'll notice you can still turn it by hand. If this is the case, it's this, not your mechanical timing. Mechanical timing will get sloppy and make you run rough, but it won't change from test drive to test drive.

GOOD LUCK, I BET THIS IS IT!

jeepmor

[jadams68]

Wow, the internet is hard to decipher intent I guess. I actually did mean, that I'd get right on that and fix it...

Originally Posted by Geer_hed

could you have possibly missed my point any more? I was trying to say that if you or one of your "clowns" thought it was a necessary step in the install that you probably would've included it in the writeup. Sorry, I won't give you that much credit or use your writeup as a good example again. better? whatever....

dgates.. forgot about the dizzy spring advance being in the equation for setting idle ignition timing. hmmm... All things being relative, does timing at full spring advance more likely to be accurate than timing at idle with the engine @ Norm OP temp... That's interesting...

[dawgates]

Yes at RPM you will get a better reading. All the moving parts in the engine are under stress, just like driving.
Example: at idle your timing chain will be lose. At speed it will be tight from the stress of the RPM.
How do you think a Dyno machine works. The engine is under stress when they take the max torque and horsepower readings.

[Geer_hed]

Originally Posted by jadams68

Wow, the internet is hard to decipher intent I guess. I actually did mean, that I'd get right on that and fix it...

Well then my apologies. I thought you were trying to get "smart" for what appeared to be no reason at all. You have to admit, it was a pretty abrupt response (especially when I was hoping you'd agree that it wasn't necessary ) that could've been taken a couple of different ways. Sorry if I took the wrong one.

Dawgates~ Torque / Horsepower and Timing are way different. I'm sure you probably know that. A dyno calculating torque isn't the best metaphor, but I think I see what you're getting at. I agree that the pull on the chain at higher RPM will probably tighten the timing chain more than it would be at idle, but the timing gears turn at a constant ratio regardless of RPM. Frequency is directly proportional to RPM, but I can't see how slack in the chain (with the exception of a jumped tooth) would adversely impact timing. If there is variation in timing values between say, 700 and 1600 RPM, depending on the degree of variation, there probably is an issue, but how would that be avoided by setting time @ 1600 rpm? You'd still have to compromise that timing value with a value more appropriate for curb idle if there was really that big a difference between the two, right? I guess what I'm getting at is there shouldn't be that big of a difference between timing at idle and timing at say 1600 RPM. I guess I'll have to go outside and prove myself wrong later...

[jadams68]

not a problem... oh and i'm going to use your diagnosis page to help me figure out why my battery is dead every 2 or 3 days... Looks like I have a serious draw.

[rcsutton]

What is the "Juice Box" TFI of HEI Differance?

Jadams & Geer hed you guys are the best.