Timing gear considerations on 1978 Ford 460

Propane, Butane, LPG, GPL, C3H8, C4H10
storm
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Location: NSW, Australia

Re: Timing gear considerations on 1978 Ford 460

Post by storm »

Over the last few years I have learned that each engine is different. That is why I now say give each engine what it wants and can cope with. The 460 is a decent engine, not as good as the earlier 427-428 but still a good engine in its own right. They weren't designed for mid to high rpm performance by any stretch of the imagination but rather were designed for low end torque. If it is ok with 20 degrees idle timing +15 mechanical then that's fine. Just ensure your starter is coping with the extra load of more timing and that your engine is not detonating under load. Until you can get a datalog or verify acceleration times you are going to be tuning by the old butt dyno which is notorious for its inaccuracy.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

Lou
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Joined: Mon Feb 22, 2021 3:24 pm

Re: Timing gear considerations on 1978 Ford 460

Post by Lou »

I think storm has some great advice for you . Your low compression engine is not ideal for propane but that doesnt mean you cant get it too run somewhat better . it takes time patients especially with out a chassis dyno. i thought all the roads in saskatchewan were good.

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Timing gear considerations on 1978 Ford 460

Post by evranch »

Yup thanks to everyone for their input on this one. I'm hoping to get fuel tanks mounted this weekend and hit the highway for some better testing. Might even make 10MPG cruising on the pavement.

I'm ordering a 3-keyway timing set which should actually boost compression by getting the intake valve closed on time. Might try the advance keyway for 4 degrees more of camshaft advance as apparently that will get me even more low end (and that's what I need in this truck, as mentioned these are not high RPM engines). And I just picked up a set of good used dual exhaust pipes with blue bottles that should get the exhaust flowing properly. Hoping these will help get my mileage up a little, at least they are low cost upgrades.

Tom68
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Location: Australia

Re: Timing gear considerations on 1978 Ford 460

Post by Tom68 »

evranch wrote:
Wed Jun 16, 2021 3:41 pm
Yup thanks to everyone for their input on this one. I'm hoping to get fuel tanks mounted this weekend and hit the highway for some better testing. Might even make 10MPG cruising on the pavement.

I'm ordering a 3-keyway timing set which should actually boost compression by getting the intake valve closed on time. Might try the advance keyway for 4 degrees more of camshaft advance as apparently that will get me even more low end (and that's what I need in this truck, as mentioned these are not high RPM engines). And I just picked up a set of good used dual exhaust pipes with blue bottles that should get the exhaust flowing properly. Hoping these will help get my mileage up a little, at least they are low cost upgrades.
4 degrees cam advance is good, most street aftermarket cams are keyed to be 4 degrees advanced from straight up.

As you are aware 70's era engines had all sorts of weird cam phasing angles in an effort to meet emissions targets.

As for closing the intake valve early to increase trapped volume at low engine speeds, make sure you know your cam timing numbers including lobe centres, a small cam won't need much advance over straight up.

P.S. Apologies for asking questions on things you'd already stated in your first post, hopefully I haven't missed your cam specs. :oops:
Last edited by Tom68 on Fri Jun 18, 2021 2:51 am, edited 1 time in total.

storm
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Re: Timing gear considerations on 1978 Ford 460

Post by storm »

"Cam timing" is often spoken about as though there is some dark secret cam grinders and oem manufacturers have deliberately hidden from everyone. The specs written on a cam card are there simply so the installer can verify the grind is what is advertised. Where the cam is actually installed is, and always has been, totally up to the person installing it. No dark secret, no hidden agenda, no BS, no problems. People who know this don't talk about "dark secrets" they dispel the myth and install cams where they calculate it will work most efficiently for them.

The concept of "dynamic compression" I have said it before and will say it again, there is no such thing. Compression ratios are a direct result of swept volume and remaining volume. It is a purely static mechanical relationship. The cam does have an effect on cylinder pressure, through pressure bleed off etc, but it does not have an effect on compression ratios.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

Lou
Posts: 4
Joined: Mon Feb 22, 2021 3:24 pm

Re: Timing gear considerations on 1978 Ford 460

Post by Lou »

Just wondering if you have tried advancing your cam yet. I feel it would be difficult to get decent power and economy out of a engine designed for regular gas. Maybe advancing the cam would help build up cylinder pressure. Hopefully it helps you out somewhat.

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Timing gear considerations on 1978 Ford 460

Post by evranch »

Unfortunately I have not, it's harvest time so I got a set of 200L tanks installed and have just been using the truck at 7mpg. A working truck is more valuable than a truck pulled apart and since the rad has to come out to change the timing gears, it's looking like a winter project. Once I have it apart I'm trying to get a set of the famous D0VE heads to drop on which should significantly improve compression. I could also go to flat top pistons to hit around 12:1 with the D0VE heads but don't feel like taking the engine apart that much. It's a farm truck and not a race car after all.

At least propane is so cheap (0.50 vs 1.30) that cost-wise it's the equivalent of about 18mpg, which is pretty good for a heavy truck.

Interestingly this is not even that bad of mileage for these trucks on gasoline: https://www.fuelly.com/car/ford/f-350/1979
These years were known for their poor economy due to low compression and goofy valve timing.

Another odd thing about my truck is the manifold is not ported for EGR, which means it uses more fuel at lean cruise than it otherwise would. I've kicked around ideas to perform the same function of filling some of the cylinder with inert gas like water injection - but that's something to play with when everything else is done.

I also gave up on getting the vacuum advance set up properly at the moment. The truck runs fine unloaded with vac advance but put a heavy trailer behind it and it's knock city. I'll either have to pin it, swap for an adjustable can, or back off my base timing to get it to work. Also even if I get it working well I'm considering using a solenoid and switch to manually turn it on when I'm cruising. For now I'm just running with it plugged off, base + mech @ 35. No starter issues at all, starts great even hot. Plugs are showing slight signs of excess timing heating but they are the stock plugs, probably time to drop a heat range.

I did just receive my order of tach, vac and EGT gauges to install in the cab when I have some time, all of which should be helpful in trying to get a good tune on the road.

Tom68
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Location: Australia

Re: Timing gear considerations on 1978 Ford 460

Post by Tom68 »

evranch wrote:
Mon Aug 30, 2021 11:19 pm


I also gave up on getting the vacuum advance set up properly at the moment. The truck runs fine unloaded with vac advance but put a heavy trailer behind it and it's knock city. I'll either have to pin it, swap for an adjustable can, or back off my base timing to get it to work. Also even if I get it working well I'm considering using a solenoid and switch to manually turn it on when I'm cruising. For now I'm just running with it plugged off, base + mech @ 35. No starter issues at all, starts great even hot. Plugs are showing slight signs of excess timing heating but they are the stock plugs, probably time to drop a heat range.
I'd run Vac under throttle blades and back off base timing at this point. you get the base timing and more back when the engine can use it and it all drops out when ping inducing load comes on.

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Timing gear considerations on 1978 Ford 460

Post by evranch »

By vac under throttle blades I assume you mean non-ported i.e. full manifold vacuum? That's a pretty good idea because as you say it will be effectively in as part of the base timing unless the engine is under load. Maybe next time I have it in the shop I'll dial back base to get all in with vac around 35-40 and see how it does.

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Timing gear considerations on 1978 Ford 460

Post by evranch »

Finally had time to work on the truck. Haven't changed the cam timing yet but I think I have the spark timing dialled in properly now. Finally upgraded to a dial-back timing light which was very helpful in isolating the contribution from each component, as well as having a tach readout directly on the timing light which is a godsend. To anyone else coming to LPG from gasoline, don't delay, buy a better timing light right away.

Found my mechanical was contributing significantly more than 15 degrees at higher RPM when the stiffer spring came into play. Added a piece of heatshrink over the stop, got it down to 15 degrees max, tweaked the stiff spring post back a little so it came back into play earlier. 10 degrees @ 2000, 15 degrees @ 3000, could come in a little lower, I'm not taking it apart again before some road time because it's a pain.

Confirmed that the Duraspark 2 vac advance can has an adjustable spring. Cranked it as stiff as possible for a maximum contribution of 18 degrees at idle, the least I can get without pinning it. Put it on full manifold vacuum instead of ported, which gets rid of the advance spike on tip-in and greatly improves the idle.

Set my base timing back to 15 degrees now that I have the vacuum can in play. At idle with the vacuum can hooked up it's sitting around 30-32 degrees. Turned the idle speed screw in several turns, because it idles that much higher. Now I don't have to hold my foot on the throttle to warm it up, it will start and idle on its own.

Overall I'm now running more advance in more situations, but without the risk of spiking into the 40 degree range I had before. The sound of the truck on the road is totally different, much more "modern" without the classic burble everyone loves despite the fact that it comes from poor combustion. It coasts nicely when I let off the throttle and I can tell it will be using less fuel just from the sound and road feel. It used to engine brake so hard it would snap your neck. Haven't tried pulling a heavy trailer yet, though.

Hoping to get those 0 degree timing gears installed in December as well as the dual exhaust and then... the truck is done I guess!

storm
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Re: Timing gear considerations on 1978 Ford 460

Post by storm »

Thanks for letting us know how you have been going with it. Just remember the lower the timing (closer to TDC) for the same output the more efficient the engine.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Timing gear considerations on 1978 Ford 460

Post by evranch »

Well, I finally got the new timing set installed. The old chain had a ton of slack in it, though the nylon was still attached to the gear at least. I could push the chain in over an inch without trying. The new double roller chain slides on nice but you can't deflect it at all with your thumb.

I decided to go for the advance keyway as it seems most recommend adding cam advance to these motors. Hopefully that's the right decision as it's a huge pain accessing the timing gears, with the coolant running through the timing cover for some reason. Would be nice if they just put two hoses on the pump instead of 4 gaskets in a stack!

I was surprised to find my base timing up to almost 30 degrees when I started the truck and thought I might have skipped a tooth somehow, since that's a gain of almost 15 degrees. But when I did the math, I added 8 degrees of crankshaft timing (removing the -4 of retard and adding another +4 advance), and skipping a tooth represents 8 or more degrees of crank advance. So that means I couldn't have skipped a tooth, or I should have been over 30 degrees... and guys are saying the factory chain/nylon gears can lose up to 10 degrees during the life of the truck. With the amount of slop in the factory chain that wouldn't surprise me to have lost 5-7 degrees.

Besides the truck runs too well for it to be out an entire tooth. After setting the base timing back to 15 degrees, it starts and idles beautifully and picks up nicely with the pedal down, though it definitely takes more from the starter. Cylinder pressures are definitely up. The motor runs cool and quiet compared to before. Unfortunately initial testing is not showing any economy gains, but the truck is not really set up for portable tanks now, and I was starving it for fuel running vapour from cold tanks on the test run I made... I'll have to get a longer hose to get liquid into it and try again on a nice day instead of with -10C propane in a bottle.

Probably will start from scratch on the ignition timing now too since it's a significant change. Vacuum readings are rock solid now without the backlash in the factory chain, and the vacuum climbs rapidly when I add base timing in a quick test. Probably will take that heatshrink off the distributor post and start running more mech advance again, it actually seemed to perform best in the past with 35 degrees total and no vac.

C3H8
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Re: Timing gear considerations on 1978 Ford 460

Post by C3H8 »

I presume your running a 425 on this truck. The 425 has a different gas valve available for the F600, 700, 800 series to improve economy. The part number is Av1-1644. IMPCO purposely designed this valve to run a little leaner in the mid ranges and would not significantly richen up until the throttle was depressed past the 80% mark. Heavier vehicles tended to go rich sooner then required and this gas valve kept the engine from gobbling fuel to soon. Your truck is smaller then these, however it's still pretty heavy and there is a possibility it could help this design of engine for economy. Operators have to be aware though that the feel is quite different. It takes a lot more throttle to accelerate compared to the standard AV1-16-2 gas valve. That was done on purpose to maximize fuel economy for HD vehicles driving around urban stop and go conditions. The mixtures would only truly richen up during really heavy footed operation and when the engine reached a little higher RPM's.

evranch
Posts: 53
Joined: Thu Dec 13, 2018 11:11 am
Location: Saskatchewan, Canada

Re: Timing gear considerations on 1978 Ford 460

Post by evranch »

Hi C3H8, good to see you back on the forum. I've wanted to try one of those gas valves since I built the truck! I've called a bunch of suppliers in Canada and they seem scarce. Ebay vendors of course charge a fortune to ship to Canada and overprice them to start, making the gas valve worth as much as an entire mixer assembly once it's delivered. Century themselves will only ship UPS which always hits me for $80-100 in customs. Unless you know a shop in Canada that would be likely to have one?

I read that the high CFM that a large displacement motor uses will push the regular valve into the enrichment portion of the curve and that's why this lean cruise valve is a good choice. Would be interesting to try.

I put the timing back to 20 base+15 mech+vac, cobbled together some hose and took the truck out for a 20km run on my hilly gravel roads and managed to just squeak under 40L/100km. That's around 7.2mpg which is about as good as a truck of this vintage would get on gasoline, plus it's heavy with the steel tilt deck and terrible aerodynamics from the remaining grain box front so that's definitely an improvement. Drivability is much better than with the old timing set for sure, powerful and quiet running, very little pedal needed to cruise and way less heat thrown off the motor, plugs show no evidence of excess timing heat.

At least if I can make under 40L/100 I should be able to make it to the city and back without worrying about running low. Only one station with LPG on the route and it's out of the way.

Something I've always wondered, when a vehicle tank is stamped with a volume (i.e. 202L on this tank) is that the usable volume at 80% full, or the total volume of the tank? I've never filled it from empty. That 20% would make a difference of 100km in total range.

C3H8
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Re: Timing gear considerations on 1978 Ford 460

Post by C3H8 »

Usually the dat plate gives the capacity with the letters in front of it stamped as WC which stands for water capacity or 100%. So your 202L is actually only capable of being filled to 161L + or minus a few either way. I'll look into the 1644 gas valve and see if I can dig one up and let you know.

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