• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

67 GTX Timing, Advance and Plugs

67GTX440

67GTX440

Well-Known Member
Local time
3:01 PM
Joined
Nov 29, 2012
Messages
1,014
Reaction score
424
Location
Jacksonville, FL
Since I have about exhausted all cooling system causes of my car running at just over 200 degrees, I am looking at the timing, advance and A/F tomorrow.

Car is a 440 with a replacement Edelbrock 4 bbl carb and the engine was rebuilt pretty much stock with minor modifications to better run off unleaded gas. It has had a Pertronix electric ignition conversion added to the distributor. I run it on standard 93 octane unleaded from Shell. No knocking at all. I do not know the specifics of the rebuild. Car starts first bump of the starter after sitting for weeks and drops into a decent idle immediately. Exhaust looks clean. Car seems to run fine and has done so without touching the carb or distributor the past four years.

My question is regarding the specs from the shop manual. Should all of these settings for timing, advance, plug type and plug gap still be where I want it set? Would any of these be different as a result of premium unleaded now being the fuel source as opposed to premium leaded in 1967?

12.5 degrees BTC at set at idle
0 degrees advance at 325 to 425 RPM
0 to 4 degrees advance at 425 RPM
4.5 to 6.5 degrees advance at 640 RPM
8.5 to 10.5 degrees advance at 2200 RPM

Is J-11Y Champion or P3-3P Mopar plugs gapped at .035

Thanks!

Don
Jacksonville, FL
 
More advanced timing the cooler it will run, vacuum advance will make it run even cooler at cruising speeds.
Richer af ratio will run cooler and ngk plugs is the way go
 
Last edited:
67GTX440 said:
Since I have about exhausted all cooling system causes of my car running at just over 200 degrees, I am looking at the timing, advance and A/F tomorrow.

Car is a 440 with a replacement Edelbrock 4 bbl carb and the engine was rebuilt pretty much stock with minor modifications to better run off unleaded gas. It has had a Pertronix electric ignition conversion added to the distributor. I run it on standard 93 octane unleaded from Shell. No knocking at all. I do not know the specifics of the rebuild. Car starts first bump of the starter after sitting for weeks and drops into a decent idle immediately. Exhaust looks clean. Car seems to run fine and has done so without touching the carb or distributor the past four years.

My question is regarding the specs from the shop manual. Should all of these settings for timing, advance, plug type and plug gap still be where I want it set? Would any of these be different as a result of premium unleaded now being the fuel source as opposed to premium leaded in 1967?

12.5 degrees BTC at set at idle
0 degrees advance at 325 to 425 RPM
0 to 4 degrees advance at 425 RPM
4.5 to 6.5 degrees advance at 640 RPM
8.5 to 10.5 degrees advance at 2200 RPM

Is J-11Y Champion or P3-3P Mopar plugs gapped at .035

Thanks!

Don
Jacksonville, FL
Click to expand...

I'm assuming that the advance degrees in your post are at distributor rpm and have to be doubled for crank speed. That would give you 12.5 + 21 deg + 33.5 total initial and mechanical. You can probably bump the initial timing to about 14 or 15 and stay around 36 deg total.

However, the distributor in the car may not be original to it and may not resemble those figures at all. The only way to find out is to find someone with an old SUN distributor machine or get a dial-back timing light and map the curve yourself. The bushings were worn in my old 440 and I bought a NAPA rebuilt distributor to put in as my old one did not appear correct to the motor. Well, the NAPA one was even worse and pretty much confirmed that rebuilder just disassemble everything and throw the parts into big piles and just randomly select parts to rebuild from. No telling what you will get from them. The NAPA unit I got had about 28 or 30 degrees of centrifugal advance in it (crank rpm) which meant I could only run 6 to 8 deg initial timing and the car ran like a dog at low speed. I finally welded up the advance slots in the plate and filed them out to allow a total of 20 degrees centrifugal advance and I run initial advance of 16 degrees + vacuum advance. That pretty much transformed the engine.

Today's gas shouldn't really affect any of the tuning. It gets compensated for when you adjust the idle mixture and if it pings a little under load, the initial timing get backed off a little. Most problems with todays gas is increased volatility and drying out the fuel bowls if it sits for a couple weeks without being started. Todays gas as compares to 60s gas also seems to be at least as much, if not more so, subject to vapor locking from engine heat.
 
i've run thru all the timing scenarios trying to get my r/t to run cooler and absolutely nothing made any difference no matter the curve, initial, vacuum advance or anything.
 
My timing light is an antique and does not show RPM and I have no way to check A/F ratio. I called the local Precision Tune yesterday and asked if they had equipment to check my timing, advance and A/F ratio. The owner said sure and I made an appointment for 8 AM this morning.

I told the owner the car runs and starts great and I just wanted to check the specs without changing anything on the distributor or carb first and to let me know if anything was out of spec. I provided him with the settings recommended in the service manual. The tech pulled the car in the shop and I had the same discussion with the tech.

I sat there for about 20 minutes while they never opened the hood and the owner came back to me and said he had been on the phone with the area manager. He said 205 in the heat with A/C on did not sound unreasonable to him and that what I was asking the tech to do (verify existing timing, advance and A/F ratio) was a little above his pay grade. Really? He must be really sub minimum wage. He said he did not want to take my money for something they could not do.

I thanked him for being upfront about his tech's level of knowledge and beat a path out of there. Jesus, what do they do at Precision Tune all day? Just screw in new plugs and call it good?

I guess I need to buy a new decent timing light or find a shop with an old Sun Machine and an old tech who knows how to use it. Do auto parts store have a decent timing light with a tach they loan or would a tool rental place have one? I have not had a need for one for the four years I have owned this car or about 25 years before that.
 
67GTX440 said:
My timing light is an antique and does not show RPM and I have no way to check A/F ratio. I called the local Precision Tune yesterday and asked if they had equipment to check my timing, advance and A/F ratio. The owner said sure and I made an appointment for 8 AM this morning.

I told the owner the car runs and starts great and I just wanted to check the specs without changing anything on the distributor or carb first and to let me know if anything was out of spec. I provided him with the settings recommended in the service manual. The tech pulled the car in the shop and I had the same discussion with the tech.

I sat there for about 20 minutes while they never opened the hood and the owner came back to me and said he had been on the phone with the area manager. He said 205 in the heat with A/C on did not sound unreasonable to him and that what I was asking the tech to do (verify existing timing, advance and A/F ratio) was a little above his pay grade. Really? He must be really sub minimum wage. He said he did not want to take my money for something they could not do.

I thanked him for being upfront about his tech's level of knowledge and beat a path out of there. Jesus, what do they do at Precision Tune all day? Just screw in new plugs and call it good?

I guess I need to buy a new decent timing light or find a shop with an old Sun Machine and an old tech who knows how to use it. Do auto parts store have a decent timing light with a tach they loan or would a tool rental place have one? I have not had a need for one for the four years I have owned this car or about 25 years before that.
Click to expand...

This sounds very familiar. Most regular car repair chains today have no experience with older cars unless you luck out and there is a tech who happens to be a real car guy. I went through this with more than one of my cars. Are there any shops in your area that specialize in building / maintaining muscle cars or hot rods? That doesn't guarantee they will be any good at it so you have to check em out but at least there is a better chance they will have the knowledge.
 
TxDon said:
This sounds very familiar. Most regular car repair chains today have no experience with older cars unless you luck out and there is a tech who happens to be a real car guy. I went through this with more than one of my cars. Are there any shops in your area that specialize in building / maintaining muscle cars or hot rods? That doesn't guarantee they will be any good at it so you have to check em out but at least there is a better chance they will have the knowledge.
Click to expand...

I need to try the one that replaced my leaf springs and shocks. The first place said the bolts would not come loose and gave up. The next place just cut everything off and said they did not know they came off an old car any other way. They considered my 67 a new car compared to most of the mid 50's cars they work on.

I have a shop that is good, just not real convenient. They did have a really slick Miller Light casket for sale along with a bunch of pretty sweet old cars last time I was there. Not many Mopars, but they seem to be able to do about anything.
 
I was lucky and found a shop that does the right kind of work and is close by. They were also used and recommended by a number of the guys at the Cars & Breakfast groups I go to. I just had them do a clutch and trans rebuild which I'm describing in my project thread, it was a good experience and I will go back.

To get back on your topic, the first thing I had them do was the same type of timing check you wanted. They had the dialback light with tachometer and did the job in about ten minutes, wound up with 36 degrees total and 13 degrees initial. From what most guys say on here it sounds like limiting the centrifugal degrees and increasing initial is the way to go for performance, although I'm not so sure about that being a cooling cure. If the timing was a cause for overheating then every car came that way from the factory set to stock specs...
 
I have one similar to this that works well.

https://www.summitracing.com/parts/sum-g1059/overview/

But Summit has a number of models available. You just need to get one with advance timing or dial-back timing so you can map the advance curve.

It's pretty hard to find anyone with a working Sun Distributor machine anymore - maybe an older speed shop if there's one around. I doubt Precision Tune had any idea what they were looking at with a 67 GTX or anyone who could replace points.

I would stay with the .035 inch plug gap.
 
67GTX440 said:
I guess I need to buy a new decent timing light or find a shop with an old Sun Machine and an old tech who knows how to use it. Do auto parts store have a decent timing light with a tach they loan or would a tool rental place have one? I have not had a need for one for the four years I have owned this car or about 25 years before that.
Click to expand...
67GTX440 if you're ever
20140211_182843.jpg
in the area you're welcome to throw your distributor on the old SUN 506 and map the advance curve.
 
I'm 67,so yes I know how to use one.LOL. Easiest way to tuneup a Mopar was to just yank distrib out and set points on the Sun.no gear teeth to mesh like the "other" guys. Change advance springs and watch what they do--Great
 
You must log in or register to reply here.

Similar threads

J
Looking for Some advice
Replies
6
Views
1K
Joel Talka
J
Kern Dog
What is your timing curve?
3 4 5
Replies
84
Views
3K
moparedtn
moparedtn
D
Timing mark jumping around
Replies
19
Views
2K
Black_Sheep
Black_Sheep
funknut
Help me pick a distributor!
2
Replies
22
Views
2K
XCELLR8
X
K
Detonation after distributor cap install.
2 3 4
Replies
67
Views
4K
LowBikeMike
LowBikeMike
Auto Transport Service
Back
Top