HEI conversion 250 distributor gear problem

[bretcopsey]

This project just keeps snowballing. Decided to convert the 250 in-line six cylinder to HEI distributor. Picked up a distributor at Advanced Auto for a 1975 Camaro. I got the wiring replaced all the way back to the junction block on the firewall, and just pulled out the original distributor. The distributor gear on the original compared to the HEI unit are reverse from one another. At first I thought I could just swap out the gears, however the original is about 1/8-3/16 of an inch shorter than the new one. This leaves excessive slop in the distributor shaft, and I'm not sure that I should try to make it up with shims. Any quick fixes for this?

[hamjet]

From what I see all L6 dizzys physically look the same, If the drive gear was on the opposite way you have the wrong one.

['68OrangeSunshine]

That is weird. I'm about to put a new HEI in my L6 292. I'll have to check on that. I can't think of any application where the distributor would have a reverse firing order. I thought AC/Delco distributors were used in GM, AMC, Studebaker and IH L6s. I have no experience with other makes, though.
Definitely take it back to the parts store, with your OEM distributor, for a re-check.

[bretcopsey]

Well, that's part of the problem. Advanced Auto near me (or any other parts stores) doesn't carry a distributor in stock for a 1975 Camaro with a six cylinder. So I ordered this and had it shipped to home. I'm sure I can take it into the store to return it, however I'm going to have to wait so many days for another one to come in to compare. I'm weighing my options now, may just break down and use the Pertronix conversion kit. Was really hoping to have this buttoned up this weekend.

['68OrangeSunshine]

I'm moving to HEI, because the Pertronix Ignitor II and Flamethrower II coil in an Accel Blueprint [reman] AC/Delco distributor was cutting out at freeway speeds. Ignition blackout -- crankcase turning at 2800 RPM not firing -- Clutch in, slow to 55 key off/ key on/ pop start. It got annoying. And there's always some yuppie up my tailpipe when ever it happened.
Ran fine for 7 years, then zilch.
We pulled the distributor, added a shim [on the theory that the reluctor was rising with high RPM and signal was off phase in the mag pick up] Didn't work, and now the distributor has a weird wobble.
Also the water pump is going out, but that's been soldiering on since 1/98 -- swapped over from the last engine, so it's run out its time.
'68 C/10 Stepside, L6 292 [.030 over Badger pistons, Crane 260H cam, 1.84 intake valves, Offy intake, Edelbrock 1404 500 CFM 4 BBl, Clifford headers, SM465 3.73 Eaton posi 12-Bolt corp rear.]

[bretcopsey]

That's not encouraging. I converted my 51 project to Pertronix.


Maybe I'm over simplifying things, but would a distributor really care which direction it rotates as long as it's in sync with the engine's firing order? Seems like swapping the gear on this HEI would be pretty straight forward. All of the pics I'm finding for 6 cyl Camaro HEI show the gear like what I have.

['68OrangeSunshine]

Rotation is critical. If the helical sweep of the distributor gear does not match the sweep of the gears on the cam it'll be catastrophic. I'm not sure if the V8s and V6s have an opposite rotation from the L6s. If they do that would explain how some starving Chinese or Mexican orphan put a V6 gear on your L6 distributor, keeping her production quota up with the rest of the girls on the line, or get beaten.
If you have a Pertronix kit on the shelf, go for it. At least you're not 'down' awaiting parts. I live in the Desert, so maybe the electronics 'cooked' after 7 years in the heat.
I just got a NIB L6 HEI from EBay for $65. Made by Assault Racing w/ 65K coil.
www.assaultracing.com

[bretcopsey]

Originally Posted by '68OrangeSunshine

Rotation is critical. If the helical sweep of the distributor gear does not match the sweep of the gears on the cam it'll be catastrophic.

Yes, sorry I should have been more clear. What I meant was as long as I find a gear the fits the HEI but matches the points distributor gear, I should be good?

['68OrangeSunshine]

Yes. IIRC the V8s have the same shaft diameter [.500"]. But if the helical sweep is opposite, that gets us nowhere. Call the techs at Summit or Jegs. They don't print much L6 stuff in their catalogs, but I hear they stock it. Somebody might know. Or try Tom Langton at www.stoveboltengineco.com He's an L6 specialist. Even has his own line of mini-heis for the 235/261s.
I'm gonna go outside in the 105* sunshine and see what the V8 and L6 gears look like.
My digital cam went belly up from battery corrosion, and I lost the cable that connects my cellphone to the laptop, so I'm blind there, too, but I'll have a look and get back.

['68OrangeSunshine]

OK. I got the right dope:

///////V8//////

\\\\\\\L6\\\\\\\

Also the V8 gear is 1/8'' longer than the L6 gear. I don' know nuffin' about no V6s. but we might speculate it differs from the V8 [which has a shrouded slot blade for the oil pump which is integral with the gear]. The L6 gear is set 1-7/8" -2" further up the shaft.
So, yeah, some famished and/or fatigued overseas factory worker gave you a V6 helical gear.
FD.
Take it back.

BTW the sweep and length of my new Assault Racing HEI looked good. Matched the AC/Delco points units' gear set exactly.

Does your Advance Auto distributor have a variable vacuum can?

[bretcopsey]

Thanks for all your help! Back to Advance in the morning. Variable vacuum can has the hex shaped front, correct? That is what I got.

[bretcopsey]

With discounts applied I paid about the same as you did, and it seems the assault unit is a better deal. I think I'm going to pull the trigger on that and take this one back for a return.

[factorystock]

I bought a new HEI for a 250 6 cyl few years ago, haven't installed it yet, here is the gear that was on it.

['68OrangeSunshine]

Originally Posted by bretcopsey

Thanks for all your help! Back to Advance in the morning. Variable vacuum can has the hex shaped front, correct? That is what I got.

Yes. Hex can is adjustable/variable.
They say you can tailor your vac-actuated acceleration curve best thru the variability of the vac cam and liberal use of different springs in the mech adv and variable tuning with a 3/32 allen key in the hole.
I'm so far off on the V8 350 w/ a Mallory delco-style HEI, that I'm almost ready to buy a fixed Vac Can for a '75 K/5 HEI, then I don't have to guess. But I have a post on the '71 Jimmy's V8 re-curve gripes and other engine gripes on the Engine and Driveline section, so it would be bad form to hijack here.
Looks like you're on the right track.
Happy to help a Brother Inliner.

['68OrangeSunshine]

Here are some pix I shot yesterday of distributors and drive gears:
1] New HEI L6
2] Stock L6 points
3] " " " OEM to my '68 292
4] V8 HEI

[Custom/Ten]

Why not get a hei distributor for a 1980 c-10 with a 250?

[RichardJ]

From the first post.

Do not shim the gear on the bench without also checking it in the engine block. In some cases if it is shimmed too tight, the shaft can be pushing down on the oil pump gear. Put the distributor in the block without the gasket. If the housing isn't sitting solidly on the block without at least .001 - .002 on the shaft, you have it shimmed too tight. The gaskets come in different thicknesses and remember they do compress.

Better to be way too loose than pushing down on the oil pump.

[pritch]

I'll bet that dizzy is for a boat. A boat with twin 250's and one has reverse rotation. That was a fairly common set-up back in the day. Probably just put in the wrong box at the factory.

[trac209]

Bottom line is they gave you wrong one its a direct swap

[RichardJ]

I didn't read the entire SuperChevy article, but I did catch this.

>>Early HEIs were infamous for giving up at speeds above 5,000 rpm-so many avoided them. <<

The problem wasn't with the HEI. The problem was that in 1975 GM was stupidly suggesting plug Gaps of .065" At that wide of a gap you get very erratic firing and misfires.

Before 1975, engines needed regular 10,000 - 15,000 mile tune-ups for points and plugs. After '75 they still needed regular tune-ups, but for plug wires, caps and rotors. The higher voltage capability of the HEI caused the electrons to try and find any alternative path to ground instead of jumping that .065" plug gap.

One good thing that followed was whole new generations of much improved plug wires.

By 1980, GM pulled the HEI plug gaps down to .045". By the end of the '80s GM dropped the gap to .035" in many HEI applications.

.035" gap has more consistent firing, fewer misfires for less unburned gas going out the tailpipe for better fuel economy and lower emissions.

This is a '75 6 cyl HEI with external coil. Plugs gaped at .035"

['68OrangeSunshine]

Thanks for the insight, Richard. I gap @ .045 for HEI and Pertronix and always used .035 for points.
Where did you get the remote coil and lowboy cap? I don't have A/C in the '68 w/L6 292, but my '71 Jimmy w/350 is 4x4, and there is very little headroom between the firewall and the V8 HEI cap. A short cap would take up less space and a remote coil on the firewall would stay cooler.

[RichardJ]

6 cyl has only six posts. That could be a problem with a V8. MSD does sell a very low profile distributor.

That cap clocks differently than the 6 cyl coil-in-cap. The key slot in the housing is in a different location on the external coil distributor housing. That coil is an original GM that I pulled off a 250 along with the distributor.

[bretcopsey]

Well, I followed 68orangesunshine's lead and ordered the Assault HEI. It arrived earlier this week and I got it dropped in today.

Now another problem has cropped up. Sometime during the week while I was at work my son took off the gas cap and said there was a loud wooshing sound. I noticed there was fuel all over the intake, so I decided to pull the carb and the intake was full of gas. The plugs were wet too. Drained the oil which was full of gas.


So, now looking at a carb rebuild.

['68OrangeSunshine]

Originally Posted by bretcopsey

Well, I followed 68orangesunshine's lead and ordered the Assault HEI. It arrived earlier this week and I got it dropped in today.

You're ahead of me. Mine is still on the bench. First the '68 Stepside gets a new water pump, new heater- and radiator- hoses and coolant. Then I'll deal with ignition.

['68OrangeSunshine]

Well, yeah, I knew the difference between 6 and 8 cylinders. I was hoping there was a parallel unit for V8s. I'll look up MSD. They merged recently with Mallory who are all owned by Mr Gasket, including Accel. I looked at the MSD Blaster HEI coil at O'Reilly's.
They wanted $82 for a Chicom coil.
I wonder why the low cap clocks differently than the coil-in cap? If you snap the #1 plug wire on the first terminal closest to Cyl #1, and follow 1-5-3-6-2-4 clockwise with the successive plugwires, isn't the effect the same? Or does that put the Vac Can out of position? So you are saying the Coil-in-cap base is different and incompatible with the lowboy external coil cap?
Or is it that the V8 cap has a different index notch than the L6 caps? Might make more sense.
Do they use the same HEI caps for L6s and V6s? The base would be different from the 'Late' L6 since the 231 V6 is a cut down 3/4 of the SBC. GMC big V6s likely have an even different distributor configuration. Who knows?