1966 170 timing/overheating

[tailpipe]

This may be more of a discussion than it is a question, but I would like to hear your thoughts and experiences. Please note this is my first time dealing with a 170 (had lots of 300s in my day). So the story goes like this; I rebuilt my original 170 from my October built 66. It was a full rebuild with all the machining, even had to go .060 on the cylinders to get them cleaned up. I rebuilt the original carb and original dizzy too. Once I finally got it all together and started her up everything was good; driving (putting a load on her) was a different story. Within 3 miles of driving the temp would get up to 200-205 and climbing, but at an idle in the garage it wouldn't get higher that 180. After chasing the typical "overheating" components nothing seemed to work. Here's the point, the book says timing should be set at 4 degrees BTDC, but guys over at fordsix were saying the 170 is happy at 10-12. I gave it a shot and bam! Fixed the running temperature, sowhat gives? Why would the book say 4 and reality is 10-12, thats a big difference imo?

 

[oldiron]

Others more educated than myself can probably explain this better than me but I'll give it a shot.
Late timing i.e. 4 deg. coupled with todays fuel (or fuel blends) can mean that the combustion process is still happening after the piston has reached BDC and on it's way up for the next event. This puts a lot of heat in the engine without any real benefit/power added, it can make headers glow cherry red since your actually pushing fire out the exhaust valve instead of spent gasses.
Advance the timing and the combustion process is completed sooner, you run cooler, and you get all the energy available from the fuel instead of releasing it out the exhaust.
Hope that helps
Greg

 

[B RON CO]

Hi, as you discovered, your engine, as do most engines, run better with more initial timing. If the timing is retarded, the engines will run hot. When a guy says my engine seems to run hot the one of the first things to do is check the timing.
Your engine will also make more power with the timing advanced. My feeling is you can advance the timing as long as it does not ping or knock under load. My test is go up a hill in second gear. If it pings, I retard the timing a little.
So you know about the old style Load-o-matic distributor and Spark control valve on the carb. I ran my 66 Bronco like that for years with no trouble.
But you should check out two things to see if you can get the Bronco to run better. If you have a timing light, raise the RPMs and see the timing mark go up under the water pump. This will tell you if the vacuum advance is doing anything. If the timing mark doesn't move, there is no vacuum advance (these distributors have no mechanical advance).
The other thing is the old saying: dwell affects timing, but timing does not affect dwell. You need to get the point gap perfect before you set the timing. I would go for .025 point gap or 40* dwell. This also tells you as the rubbing block on the points wears, the timing changes (did you lube the distributor cam).
Good luck

 

[tailpipe]

Thanks for the replies. I have learned a lot during this process, especially concerning points, dwell and the likes (yes dizzy cam lubed). Everything make sense as I have been going through the process, but I just could not figure out why the "book" timing was so different to reality. The comment above about today's fuel must be considered. I am running non ethanol gas but who knows what that really means. I'll keep tinkering to find that sweet spot. Thanks again guys!

 

[B RON CO]

Hi, the shape of the combustion chamber has an effect on the timing story. I've read that if the mixture is in a turbulant state, like a tornado in the combustion chamber, the engine won't need a lot of initial timing. If the mixture is more like a lazy river the engine will run better with more initial timing.
The Ford timing specs are another story. They may have wanted the engine to run hotter because a hotter engine will run cleaner. The Ford V8 distributors from the late 60s had a vacuum retard and a vacuum advance. Under certain conditions the vacuum would retard the timing for cleaner emissions.
Good luck

 

[DirtDonk]

Why would the book say 4 and reality is 10-12, thats a big difference imo?

Everything make sense as I have been going through the process, but I just could not figure out why the "book" timing was so different to reality.

Simple. Because this is no longer "reality Greg";D (as they said in the movie ET). As far as the book is concerned, this is no longer the engine it was written for.
The book stopped having anything to do with reality the moment you changed your engine so drastically. And by that I mean that even with a six, a .060" overbore is a LOT of material removed from the cylinder walls.
And that alone could be the single source of your change.

Even without a cam change, or intake or exhaust change, your dynamics have changed enough that your ignition timing needs have changed.
And remember, the factory settings are not necessarily for optimum performance, but for general use in thousands of different conditions, by thousands of different types of owners (from grannies to gear-grinders, surfers to ranchers) along with fuel economy and emissions.
A lot of Ford owners found out decades ago that boring a 351W to .060" was a craps shoot as to whether you'd even be able to use it anymore. Much less race it!
While your engine is not the same, the concepts are. Thinner cylinder walls promote more heat transmission into the coolant passages. Especially in the form of localized hot spots that can turn into steam pockets. Which in turn turn into self-propelling heat sources as steam forms and can't help dissipate combustion heat anymore, because steam is not liquid.
More timing reduces this heat buildup in the combustion chamber as more goes out the exhaust more completely burned, as was said.
Not saying this is the only thing that could be doing this, but it's high on my list of probabilities.

Maybe your distributor rebuild included different springs, weights or other internals? If just bushings then nothing changed with timing, but if you changed the advance plate, or any of the related bits, then you could have changed your particular engine's tolerance for heat. Maybe it's not advancing fast enough now, so you need more initial?

No matter what though, sure glad you got it dialed in to the point it does not run hot anymore. That can be a very frustrating thing on a new engine.
I'd be curious how hot it would get. That 200+ is not overheating until you get into the 240 range. But anything over 220 would seem to be at least out of control of the cooling system. I know you said "and climbing" so keeping it below 200 is a good thing.

Have fun with it.

Paul

 

[patterdale]

This may be more of a discussion than it is a question, but I would like to hear your thoughts and experiences. Please note this is my first time dealing with a 170 (had lots of 300s in my day). So the story goes like this; I rebuilt my original 170 from my October built 66. It was a full rebuild with all the machining, even had to go .060 on the cylinders to get them cleaned up. I rebuilt the original carb and original dizzy too. Once I finally got it all together and started her up everything was good; driving (putting a load on her) was a different story. Within 3 miles of driving the temp would get up to 200-205 and climbing, but at an idle in the garage it wouldn't get higher that 180. After chasing the typical "overheating" components nothing seemed to work. Here's the point, the book says timing should be set at 4 degrees BTDC, but guys over at fordsix were saying the 170 is happy at 10-12. I gave it a shot and bam! Fixed the running temperature, sowhat gives? Why would the book say 4 and reality is 10-12, thats a big difference imo?

Not on a EB but similar type situation. We had a focus wagon that was totally undrivable on ice/snow. Dealer said it was totally in spec. Took it to an alignment shop and they said," we can fix that". They did, could do a scary 60-65 mph on ice no problem. When I saw the fix it was equally as scary. Long story short, it was a ztw model wagon that they tried to put a performance suspension in the rear. Deadly great on dry pavement but shyte on wet or I y roads. Bottom line. Alignment is alignment. They can list specs and then for liability reasons have to stick with them. Physics are physics. No matter the design from model to model or brand to brand. The front and rear tires have to meet the pavement within certain parameters no matter the engineer's beliefs or ego for good highway driving.