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For reference, my cam is a isky 256. 450/450, 202@.050 and 112 lobe sep.
I think a important thing to remember with mileage is that its more about the whole truck than the engine. Replacing the 9 in axles with 8.8s and the granny 4 speeds with the mazda 5 speeds im sure helped with mileage. the bullnose body style probably had something to do with it too.
Ill have to second C3H8's comment about the dirty intake vavles. I had my head apart last month after about 1 year of daily driving on propane and they were disgusting. I had thought it had more to do with the lack of any solvent qualities of propane compared to gasoline. Ive since bought a catch can but Im not sure itll help.
Nice cam, 4 degrees advanced I'd imagine, did you check it ? Sounds like this could be one of those engines with retard built into the timing gears.
You mention a catch can, is it breathing oil into the intake?
I talked to one of their tech guys and they said they build 3 degrees of advance in this cam. I took his word for it. As I understood it from the guys at fordsix.com, the efi plastic timing gears had some retard built into them. I installed the older steel gears with the cam.
The PCV always left a layer of oil in my intake. I thought that the catch can would help keep the intake valves clean.
For reference, my cam is a isky 256. 450/450, 202@.050 and 112 lobe sep.
I just looked that up and I think you have lobe separation (LSA) and Lobe Centreline Angle (LCA) mixed up. In all honesty I think the MILE-A-MOR or the Turbocycle-A are better alternatives. Why? Mile-a-mor is a single pattern fuel economy cam with a lower working rpm range from 1000-3800 rpm, the Turbocycle is a split (more duration and lift on the intake which should indicate to you how deficient the intake flow is on these things) pattern cam with a working rpm range of 1000-5000 rpm. Both of these work from 1000 rpm compared to the 256 cam which starts at 1500. Of course this is JMNSHO (Just My Not So Humble Opinion).
I thought about the mile-a-more but was scared off my its 108 lobe center. I was reading another post on here on how propane doesnt like tight cams as it tends to suck the intake charge out the exhaust. It probably makes more power, but I drive this truck 60 miles a day so mileage is important. I never seriously considered the turbocycle as it looks like it would be really asthmatic on a NA engine.
The PCV always left a layer of oil in my intake. I thought that the catch can would help keep the intake valves clean.
That's just an indication of an engine that is wearing or has to much clearance. Catch cans are a great idea but many people get a cheap unit that is to small for the engine.
I thought about the mile-a-more but was scared off my its 108 lobe center. I was reading another post on here on how propane doesnt like tight cams as it tends to suck the intake charge out the exhaust. It probably makes more power, but I drive this truck 60 miles a day so mileage is important.
All cams provide a certain amount of intake charge evacuation. 4 degree in a rotation of 360 is 0.9% and wouldn't add much if any increase in fuel economy. Running a cam that doesn't come on until 1500 rpm compared to one that comes on at 1000 rpm is a 50% increase in the time where the cam is inefficient.
I never seriously considered the turbocycle as it looks like it would be really asthmatic on a NA engine.
The turbo cam is a great indication of how asthmatic the naturally aspirated engine is on the intake side. When they add duration to the intake rather than the exhaust they obviously think the exhaust is up to the task of flowing a boosted engines burnt gasses. This indicates the efficiency of the intake port isn't great when the exhaust port can flow an extra 7 psi (approx 0.5 BAR or 50% more) of intake flow without adding to the exhaust duration compared to a naturally aspirated engine.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456
I thought about the mile-a-more but was scared off my its 108 lobe center. I was reading another post on here on how propane doesnt like tight cams as it tends to suck the intake charge out the exhaust. It probably makes more power, but I drive this truck 60 miles a day so mileage is important. I never seriously considered the turbocycle as it looks like it would be really asthmatic on a NA engine.
Goes the other way whilst you have any manifold vacuum which is most of the time, other than the misfires it causes it can still improve economy, think egr.
Still cam choice is related to the gear ratios you're running, you can cam and gear it to cruise at 3500 rpm if you can stand it, I like cruise set up for 2000 rpm or less but that probably requires more engine capacity for the weight you have to be practical.
I thought about the mile-a-more but was scared off my its 108 lobe center. I was reading another post on here on how propane doesnt like tight cams as it tends to suck the intake charge out the exhaust. It probably makes more power, but I drive this truck 60 miles a day so mileage is important. I never seriously considered the turbocycle as it looks like it would be really asthmatic on a NA engine.
Goes the other way whilst you have any manifold vacuum which is most of the time, other than the misfires it causes it can still improve economy, think egr.
Still cam choice is related to the gear ratios you're running, you can cam and gear it to cruise at 3500 rpm if you can stand it, I like cruise set up for 2000 rpm or less but that probably requires more engine capacity for the weight you have to be practical.
Wouldnt the cam-induced-egr theory only work with a horribly restricted exhaust? Any sort of free-flowing exhaust system should provide enough of a reduction of pumping losses to offset any mileage benefit of egr
The PCV always left a layer of oil in my intake. I thought that the catch can would help keep the intake valves clean.
That's just an indication of an engine that is wearing or has to much clearance. Catch cans are a great idea but many people get a cheap unit that is to small for the engine.
I thought about the mile-a-more but was scared off my its 108 lobe center. I was reading another post on here on how propane doesnt like tight cams as it tends to suck the intake charge out the exhaust. It probably makes more power, but I drive this truck 60 miles a day so mileage is important.
All cams provide a certain amount of intake charge evacuation. 4 degree in a rotation of 360 is 0.9% and wouldn't add much if any increase in fuel economy. Running a cam that doesn't come on until 1500 rpm compared to one that comes on at 1000 rpm is a 50% increase in the time where the cam is inefficient.
I never seriously considered the turbocycle as it looks like it would be really asthmatic on a NA engine.
The turbo cam is a great indication of how asthmatic the naturally aspirated engine is on the intake side. When they add duration to the intake rather than the exhaust they obviously think the exhaust is up to the task of flowing a boosted engines burnt gasses. This indicates the efficiency of the intake port isn't great when the exhaust port can flow an extra 7 psi (approx 0.5 BAR or 50% more) of intake flow without adding to the exhaust duration compared to a naturally aspirated engine.
My reasoning was my engine is almost always above 1500 if its in motion. If I towed more often, maybe, but it spends very little time between 1000 - 1500 rpm and the higher lift of the 256 would give me a stronger midrange.
Correct me If Im wrong, but I though the reason turbo cams have such short exhaust duration was to help prevent reversion caused by the high pre-turbine exhaust pressure?
Wouldnt the cam-induced-egr theory only work with a horribly restricted exhaust? Any sort of free-flowing exhaust system should provide enough of a reduction of pumping losses to offset any mileage benefit of egr
Just like "variable compression ratios" due to cam duration and overlap theory the "cam enduced egr" theory is a load of rubbish. EGR is exhaust gas recirculation, cams do not recirculate exhaust gas. The function of a cam is to hold open valves in order to let an engine fill the cylinder as best as can be and then to remove as much combusted gas as is possible. How well this is done depends on intake and exhaust flow as well as desired operational rpm range. Due to the nature of the beast (i.e. the internal combustion engine) it is impossible with the technology of these older engines to completely evacuate all the combusted gasses at all load and rpm points. If it were possible engines would be able to run at nearly 100% efficiency all the time.
My reasoning was my engine is almost always above 1500 if its in motion. If I towed more often, maybe, but it spends very little time between 1000 - 1500 rpm and the higher lift of the 256 would give me a stronger midrange.
Possibly but I doubt it would be anything you would be able to "feel".
Correct me If Im wrong, but I though the reason turbo cams have such short exhaust duration was to help prevent reversion caused by the high pre-turbine exhaust pressure?
Before I answer this I must say I am NOT a turbo expert.
If a turbo engine is suffering reversion from high pre-turbo exhaust pressure either the exhaust side of the turbo is to small or the post turbo exhaust pipe is to small. I am a member of another forum and another member of the other forum has as part of his signature something like (I'm paraphrasing to be polite) "The exhaust back pressure theory is rubbish, do you walk around any easier with a cork up your backside?". If you put more in you must take more out. Deliberately keeping combusted gasses in a system that is boosted is a great way to kill performance of any kind.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456
Wouldn't the cam-induced-egr theory only work with a horribly restricted exhaust? Any sort of free-flowing exhaust system should provide enough of a reduction of pumping losses to offset any mileage benefit of egr
Gas flows to lowest pressure, that's why the oil getting into your inlet tract gets burnt on to the back of the intake valve.
Everyone seems to have a different reason for my dirty valves. Im inclined to believe its from cylinder blowby, my machinist thinks its the valve seals (whitch I replaced twice), Tom68 says it my came from my cam, and C3H8 claims its inherent to this engine. Im not sure what the truth is.
Good camshaft discussion though guys. I noticed alot of threads on here revert back to cam theory, but Im alright with that. This stuff is fun to think about.
Everyone seems to have a different reason for my dirty valves. Im inclined to believe its from cylinder blowby, my machinist thinks its the valve seals (whitch I replaced twice), Tom68 says it my came from my cam, and C3H8 claims its inherent to this engine. Im not sure what the truth is.
C3H8 is a very clue guy, his advice and knowledge is spot on way more than 99% of the time. We don't see many 300 straight sexes in Australia (both myself and Tom are in Australia) most of our classic Effies are Cleveland or Windsor V8s. That doesn't mean we don't have or know about them but I'd trust C3H8's analysis as he has worked in LPG conversions for a very long time.
Having said all that there are some simple tests you can do. A cylinder leakage test will tell you where your cylinder pressures are going. If/when (assuming you haven't already done so) you pull the engine apart look for actual physical signs of oil movement. If it is blowby you'll see oil in the PCV hose and at the manifold port the PCV connects to. If it is the valve seals you will see signs of oil on the valve stems and in the valve guides. If it is the cam (I seriously doubt it myself simply because cams don't move oil around into cylinders) you will see some evidence of it.
Do a compression test, then do a cylinder leakage test, that will probably give you some idea as to where the oil is coming from.
Fuel flow requirements calculations
Engine air flow requirement calculation: CFM = Cubic Inches x RPM x Volumetric Efficiency (VE) ÷ 3456
I did a compression test a few months ago. I remember all cylinders were 120 or 115. I forgot to hold the throttle open when I did it and I live at 4000 ft, so actual numbers are probably quite a bit higher. The engine still delivers good mileage and power and doesn't smoke or make any weird noises, so I dont think a rebuild is necessary yet.
I can tell you that the catch can seems to catch just as much water as oil. I guess thats a byproduct of burning propane.
I did a compression test a few months ago. I remember all cylinders were 120 or 115. I forgot to hold the throttle open when I did it and I live at 4000 ft, so actual numbers are probably quite a bit higher. The engine still delivers good mileage and power and doesn't smoke or make any weird noises, so I dont think a rebuild is necessary yet.
I can tell you that the catch can seems to catch just as much water as oil. I guess thats a byproduct of burning propane.
Condensation to, everytime the engine cools moisture forms in the crankcase etc, as it warms it'll come out the pvc.
Thanks for the compliment storm, appreciate it. To clarify the valve build up issue. True story about a first generation 300 CI Ford (long time ago, 1980's). My dealer called me because a customer lost power on his engine. approximately 10,000KM's on it. When I got there we did a compression test and it was pretty low. We figured early valve recession possibly. He pulled the head under the warranty. Everything looked fine until we pulled an intake valve. On the valve was a perfect build up (think triangle) of hard carbon but looked very crystalized that was almost completely blocking the airflow into the cylinder. We scored it with a flat bladed screw driver on opposite sides and rapped it on the bench. The carbon broke off the back of the valve and valve stem into two perfect halves. Every intake had the same build up. As I stated earlier, when we asked IMPCO about it they said it was due to very slow airflow on 300's at idle. The dealer did check the valve stem seals and changed them just in case. We can't be sure but it appeared to be a mix of engine oil and propane heavy ends that caused the problem. Either way the dealer made it a point of running a chemical de-carbonizer through the engine when it came in for servicing and that seemed to eliminate the issue.
Well, it is a while since I visited and said anything !
I used to run twin carbs but they were essentially 'factory'
Twin Hitachi petroleum carbs, not twin Impco though
I fed these two barrels each babies from a 125 about 18" away
110 cubic inch flat four Subaru EA81 Brumby ( B.R.A.T. to most of you)
16/56 .235" lift OHV jobbie
I was tinkering with idea of a 125 on each head, mounted on a two barrel throttle body and manifold delete adaptors to run coolant and vacuum as well as a balance between both sides.Never came to fruition
What I had done earlier I think? was to forget the sizing charts in prep for my turbo OHC younger brother to OHV with twins
I knew my EA82T loved bigger than the J/ 125 combos that I had been using for years on the 1800 cc NA
I ran my Mongrel I call it - carb block, turbo twin port heads and turbo cams.
With twin port inlet EFI manifold and TB
Gave it the 200 /L combo, a little oversized it may seem, but it ran strong and delivered the best economy and power I have had from NA.
Almost achieved same economy from the turbo variant