I am dialing in my 68 350 in my 80. The HEI was from a 80 4.3.

My note to upgrading the ignition system, verify the clerance and type of the plug but the Spark Plug Gap should correspond with the ignition system.

The 68 used a .030 gap on Champion RJ18YC, points ignition (not HEI)
80, .060 gap on Champion RJ18YC6 HEI.

I am using .060

Comments?

 

You might consider running R46SX and gap them to .060. The timing on the HEI will also be higher, I like to set it to 34* at what ever RPM it stops at, without vacuum advance connected. Leave the base timing to whatever it falls to.

 

I am dialing, so, what is the pro on the R46SX


Spark Plug:

AC Delco R46SX @ .060 the cross ref to Champion -> RJ18YC8 @ .80


Timing:

Clarity, instead of my base (1000rpm vac adv plugged) @ 14° go to 34°
I did realize the motor like the advanced timing.

The motor is pieced together from various models. I did finally put on the timing mark piece and verified the TDC mark on the harmonic balancer to the #1 cylinder to " 0 " zero on the numbered timing mark. I had never used a timing light. So "dialing in", I wanted to see where the light/mark was. I could not see it. I had to back off the timing way off/down. The mark was up under the water pump, advanced, maybe @ 24°.

I have ordered a timing light with advance.


Q-Jet:
800 CFM MDL# 17058230


Thanks for your comments!

 

With a dial back timing light, set your timing at 34* with the engine running at 3400 RPM (or at the RPM the timing stops advancing), vacuum advance disconnected. Then see what your base timing is, it'll be somewhere between where is now or higher.

I prefer the AC spark plugs over champion, and I don't like running a .080 gap.

 

Large gaps like that put extra stress on secondary ignition components like the spark plug wires, secondary windings in the coil, cap, rotor, etc. I don't see any reason for running spark plug gaps any larger than .045 max.

Are you sure the 68 called for a RJ18YC? That is a hot plug. My 70 called for a RJ12YC or R45S. I would think about lowering the heat range and the gap.

 

Are you sure the 68 called for a RJ18YC? Yes, it used points and a coil.

The 77 350 with HEI does call for the RJ18YC6

But, I am not sure, for sure. I used the Champion link and Autozone and they both had the same plug.

The plug seems the same. The gap seems to be the difference.



Alternative spark plugs for AC DELCO - R45S -> Champion: RJ18YC

http://www.sparkplug-crossreference..../AC_DELCO/R45S

 

I have HEI on my 72 350 cutlass and I changed my plug gap to 45 from 35 and it seems to run very rough. I'm going to change to 40 and see how it runs. I'm so confused, Do I have to run a special plug with the HEI system with a bigger gap. That's what it sounds like everyone is doing.
barb.

 

Yes Barb, you want to run the correct plugs for HEI, say a '76 350. .080 is the spec, but I agree this might be excessive. I have mine at .060.

 

RMOTHS: "it seems to run very rough"

Explain-> at idle, mid, top end or all of the time.

Thought, maybe wires? Timing?

Mine runs great on Champion: RJ18YC at .060
I do plan to buy a set of AC DELCO - R45S to compare.

 

I have AC Delco R45S plugs in now, do you think I need to gap it more than 45.
I'm going to reset the gap back to 35 and see what happens, If no change I'll try like 50 just to see if it runs different. Barb.

 

Gap to the Engine, not the Ignition. Your 68 motor was over 9 to 1 compression...late model HEI motors more like 8 to 1 comp. Use the narrower gap to avoid stressing the components of the system as was stated earlier.

Just look at our race motors, we run lots of Voltage in electronic ignitions, but you won't see plug gaps over .040...I run .035.

Just my experience..hope this helps.

Danny

 

Thanks Danny. I'll go back to 35 and will see how it works, ( Or runs better).
Barb.

 

Went back to 35 and it runs better.
Thanks Danny. Barb.

 

I don't see how running a .060 gap on an ignition system that was designed for .080 is going to stress the components. I also don't see how a bigger spark using the correct plugs for a later ignition system on an older motor is a bad thing. Not arguing with your setup on your car Danny, I don't have a car in the tens, but if .035 is better than .060, then why wouldn't .010 be even better? And is your ignition MSD, e.g. MULTIPLE sparks per power stroke, e.g. even MORE stress? Wouldn't THIS be the reason for a smaller gap in your case? MSD recommends gaps for their systems that are different than the OEM recommended gap. I WOULD agree that .060 on a points system would be ill-advised. My '70 455 with a '76 HEI and '76 HEI plugs gapped at .060 (.030 wider than 1970 spec) runs superbly well, with 25% less stress on the ignition components than the '76 ignition gap spec. I've also never had a stress-related ignition component failure... I guess my main point is, if you're running a race-only car, there may be different things to consider than if you're running a mostly stock motor with a later factory ignition. Just my opinion.

 

I think .045" is better on higher compression with HEI. Heat range is important, higher compresson, colder plug.

 

Barb:

Glad your car runs better.

Mike:

I ran a Pertronix HEI with the Coil in the Cap and NO MSD in the car in my sig. line and ran down into the mid 11 second range before several upgrades and YES moving to MSD. About 10.0 to 1 compression and .035 gapped plugs. In those days I was told to gap to the motor specs and not the ignition. And you are correct that there are lots of variables and diffs. between street and purely strip cars. Now the compression in my 9 sec '70 race car likes the gaps smaller, but I do know the old .080 gaps were on the pathetically low compressioned cars of yore.

Hey, plugs are easy to change and a good tuning tool so why not experiment when looking for a weekend excuse to get out of the house and wrench? I'm glad youre happy with your set-up and I'll bet you have turned a few heads with the big motor in your car. Who knows?? Maybe I'll try .010 sometime.

Good thread...what are some of you other guys running?

Danny

 

Carb-
800 CFM, rebuilt last weekend. It is better, but not there. The rough idle which feels like a cam, is still there.

The passenger side idling screw ports seems to be clogged. I turn it all the way in and there is no change. Out no change. Drivers side, I turn it in, the car dies. Deduction, passenger side is blocked.

*****
The 'cam' feeling is gone! I opened it back up, ran a small wire through the inlets, sprayed some cleaner and put it back together. To add to the mix, the needle clamp was also not seated on the float. It was lying in the bottom of the bowl.
*****

Plugs -
Champion: RJ18YC at .060 -> "I will try the .045"

Distributer -
HEI, maybe stock. This weekend after I put my new cap and plug wires on, I went for a RIDE.

Timing -
I started off at 14°, then to 16° back down to 12°.

Team, It feels like something is holding it back until I get to 2500-3000 RPM. Then it takes off, like changing gears. I want that on takeoff sooner. Thoughts?

-BREAK-

After half a day of play time I had to leave it alone so I replaced the battery.... I was getting frustrated.



Thoughts?
Question, maybe a new HEI, if so suggestions?

 

Did you get a dial back timing light? What is your timing at 3500 rpm with the vacuum disconnected?

 

dial back timing light? On order
digital tach, on order.

Without a factory mechanical start point/mark, I am shooting blanks!

I have installed a bracket and scratched a small tick mark on the side of the distributor at the point I have deducted to be 14°. I am creeping the timing advanced (1/16") at a time. I think I am around 20° advanced for base timing, no vac.

I read I can advance up until I get a miss-fire and/or difficulty when starting then back it back.

My stuff should be here, soon.

Thoughts?