318 MAX fuel economy builds?

[volaredon]

360? High mpg? Does not compute. Sorry.

In my case on my b body fury's 318 it will be getting a lean burn ectomy as it was starting to act goofy the last couple of years of crusin season (about 1500 mi/ year. A whole different engine is out of the question in my case, it may be a lil slow off the line but it'll cruise 70 happily all day long, as is, is really good on gas, (surprisingly so), and is the original engine in the car which has 56k original miles on it from new..... No way is that engine coming out of the car.

 

[Dmopower]

360? High mpg? Does not compute. Sorry.

In my case on my b body fury's 318 it will be getting a lean burn ectomy as it was starting to act goofy the last couple of years of crusin season (about 1500 mi/ year. A whole different engine is out of the question in my case, it may be a lil slow off the line but it'll cruise 70 happily all day long, as is, is really good on gas, (surprisingly so), and is the original engine in the car which has 56k original miles on it from new..... No way is that engine coming out of the car.

Challenge accepted. ;)

 

[273]

360? High mpg? Does not compute. Sorry.

In my case on my b body fury's 318 it will be getting a lean burn ectomy as it was starting to act goofy the last couple of years of crusin season (about 1500 mi/ year. A whole different engine is out of the question in my case, it may be a lil slow off the line but it'll cruise 70 happily all day long, as is, is really good on gas, (surprisingly so), and is the original engine in the car which has 56k original miles on it from new..... No way is that engine coming out of the car.

Larger engines don't necessarily mean more fuel plus he's looking for a power mpg balance, say it takes 20 hp to move your car down the road, it's gonna take a narrow range of fuel and air to make that 20 hp, so it depends on how efficiently you can make 20 hp at part throttle neither engine 318 vs 360 is using vastly different amounts of fuel and air is why you don't see huge differences in mileage.

 

[toolmanmike]

Larger engines don't necessarily mean more fuel plus he's looking for a power mpg balance, say it takes 20 hp to move your car down the road, it's gonna take a narrow range of fuel and air to make that 20 hp, so it depends on how efficiently you can make 20 hp at part throttle neither engine 318 vs 360 is using vastly different amounts of fuel and air is why you don't see huge differences in mileage.

A Briggs and Stratton cruise engine is what we need.

 

[Dmopower]

Larger engines don't necessarily mean more fuel plus he's looking for a power mpg balance, say it takes 20 hp to move your car down the road, it's gonna take a narrow range of fuel and air to make that 20 hp, so it depends on how efficiently you can make 20 hp at part throttle neither engine 318 vs 360 is using vastly different amounts of fuel and air is why you don't see huge differences in mileage.

My thought was that the 360 with a 1.7 rts ratio rather than the 1.85 and 40 more cubes would move the air faster through the carb and ports at lower rpm which would help the non FI engine atomize the fuel.

 

[rumblefish360]

360? High mpg? Does not compute. Sorry.

273 explained it pretty good. Of course, the larger the engine the harder it is to get good mileage. But before I go…

What do you consider good mileage?
And what’s good mileage out of a 360?

In my case on my b body fury's 318 it will be getting a lean burn ectomy as it was starting to act goofy the last couple of years.

Getting rid of the Leanburn should have been the very first thing you did when you got the car. Bar none.

My thought was that the 360 with a 1.7 rts ratio rather than the 1.85 and 40 more cubes would move the air faster through the carb and ports at lower rpm which would help the non FI engine atomize the fuel.

Super small potato chip crumbs!

 

[Bewy]

Dmopower,
I think your strategy is well thought out & do-able. Because mileage is made at lower rpms, I do not see any benefit from bushed rods if it is going cost $$ to buy/use them. The annular booster AVS is a good thought, but I think a small TQ would give better economy.

 

[Dmopower]

Dmopower,
I think your strategy is well thought out & do-able. Because mileage is made at lower rpms, I do not see any benefit from bushed rods if it is going cost $$ to buy/use them. The annular booster AVS is a good thought, but I think a small TQ would give better economy.

Thank you. The 273 rods were 25 bucks and they are lighter. Since i'm not looking to make 400 HP I thought why not lighten up the rotating mass with the lighter 273 rods. They just happen to be bushed from the factory. I already have the 1916 carb. If the 360 blocks don't check out I'll have the crank turned down and put in my 340 block which will lighten Things a tad more. I know there is someone on this site that ports 920 heads.

 

[Bewy]

I would be very careful with 'porting' heads where economy is the goal. If the ports are large enough & flow enough to support the intended rpm range, then removing metal could make the port sluggish...& hurt economy. Removing sharp edges, dags, & a valve job might be all that is needed.

 

[Dmopower]

I would be very careful with 'porting' heads where economy is the goal. If the ports are large enough & flow enough to support the intended rpm range, then removing metal could make the port sluggish...& hurt economy. Removing sharp edges, dags, & a valve job might be all that is needed.

The 920 273 heads have small ports and require porting and larger valves to get it to flow close to std J heads. Which is my goal to get them as close to J heads or better at .450" .5 lift. These smaller ports should help velocity and efficiency if I follow all of the good advice and pics this site has on the subject. But I'd be open to hiring it done. I know there are guys here that are far more skilled than I. I have a set of 920's on my 273 that I ported and they are working great. Just a mild bowl port and gasket match.

 

[273]

The 920 273 heads have small ports and require porting and larger valves to get it to flow close to std J heads. Which is my goal to get them as close to J heads or better at .450" .5 lift. These smaller ports should help velocity and efficiency if I follow all of the good advice and pics this site has on the subject. But I'd be open to hiring it done. I know there are guys here that are far more skilled than I. I have a set of 920's on my 273 that I ported and they are working great. Just a mild bowl port and gasket match.

Just spitballing not saying your wrong and or not partly true, but the main goal is to make the part throttle hp needed with less fuel and air, so less friction, less pumping loss so less restrictions from air inlet to exhaust tip, more cr, more efficient combustion, less heat waste, lighter rotational parts etc... Plus need less hp in the first place with less weight and aerodynamics.

Don't know if velocity gonna help much, the engine gonna have zero problem with the air requirements for the little hp needed, plus by time your done porting will there be that much difference between 920 and J heads? Heads are the number one way to make power look at LS and modern Hemis massive port flow small cam, cam choice can be one of the bigger mileage killers I'd still run better heads even if it cost slightly to mileage which I doubt would be noticeable and probably would be better cause you could run less cam for same or more hp.

 

[Bodyperson]

How does the lean burn system work? Its a carb.

 

[Dmopower]

Just spitballing not saying your wrong and or not partly true, but the main goal is to make the part throttle hp needed with less fuel and air, so less friction, less pumping loss so less restrictions from air inlet to exhaust tip, more cr, more efficient combustion, less heat waste, lighter rotational parts etc... Plus need less hp in the first place with less weight and aerodynamics.

Don't know if velocity gonna help much, the engine gonna have zero problem with the air requirements for the little hp needed, plus by time your done porting will there be that much difference between 920 and J heads? Heads are the number one way to make power look at LS and modern Hemis massive port flow small cam, cam choice can be one of the bigger mileage killers I'd still run better heads even if it cost slightly to mileage which I doubt would be noticeable and probably would be better cause you could run less cam for same or more hp.

You may be right. My thought was after reading posts from guys porting these 920 heads is that they are in the 135 cc port volume area. The j heads factory are in the 170 area. That last number may be wrong but assuming it is 170 that's 25% more volume moving the same cfm. Thats without calculating in the increase piston speed as little as it may be and I get heads capable of similar hp as factory J heads with a much more efficient 1000 to 3500 rpm and a much better quench allowing me to take advantage of as much timing as possible. No?

 

[273]

You may be right. My thought was after reading posts from guys porting these 920 heads is that they are in the 135 cc port volume area. The j heads factory are in the 170 area. That last number may be wrong but assuming it is 170 that's 25% more volume moving the same cfm. Thats without calculating in the increase piston speed as little as it may be and I get heads capable of similar hp as factory J heads with a much more efficient 1000 to 3500 rpm and a much better quench allowing me to take advantage of as much timing as possible. No?

For a full throttle run I'd say yes for the lower rpm but lower rpm don't matter much spend little time under 3500 rpm when getting on to it, but at part throttle the cylinders aren't even close to being filled and zero need to be, it's about needing less fuel and air to do the job. Don't know if velocity will help mpg much or at all maybe someone else can chime in my guess ported 920 vs stock j vs ported j wouldn't notice much difference.

The way I see it say you want 325hp, ported j heads would need the smallest cam to do so and get the best gas mileage cause of it and have the best powerband.

 

[rumblefish360]

I don’t see ported J heads or any ported head needed for this mileage build.

What I do see as far as cylinder heads go is a stock head given a awesome valve job and that’s it.

Induction wise above the head is any mild dual plane intake.
Carb, small primary unit. The small AVS II 650 is fine. I’m with Bewy on a small primary TQ.

Camshaft - Isky Mile-a-more Hyd

 

[Dmopower]

I don’t see ported J heads or any ported head needed for this mileage build.

What I do see as far as cylinder heads go is a stock head given a awesome valve job and that’s it.

Induction wise above the head is any mild dual plane intake.
Carb, small primary unit. The small AVS II 650 is fine. I’m with Bewy on a small primary TQ.

Camshaft - Isky Mile-a-more Hyd

I checked out those cams. They are pretty close to what I'm looking at after the Rhoads lifters reduce my duration 15 deg at .050. Kinda tells me I'm on the right path. I'm not porting J heads. The entire thread is about super high mileage. I'm hoping the increase velocity atomizes my fuel better than with the J heads and with superior quench maximizes the engines efficiency ay low rpm. I'm trying to get max mileage and still have a lil power from 3000 to 5000. If I don't get 325 hp that's fine. kinda. lol

 

[rumblefish360]

I understand that.

 

[toolmanmike]

A stock 2 barrel teen with a 2.xx rear gear will get you 20+. Keep your cruise rpm less than 2,000 and you will get there. That's one of the reasons why all the new cars have 6 and 8 speed transmissions, double overdrive and the like, to keep the cruise rpm down. If I was going for mileage and efficiency I wouldn't want to do much with those 920's other than a nice valve job, a back cut, a little bowl blend and may be port match. You can make them better without turning them into a J head.

 

[rumblefish360]

I never tried a ported head for mileage purposes.

 

[Dmopower]

I never tried a ported head for mileage purposes.

If you look at ANY new head they are all perfect ports. They get rid of the lumps and make them as efficient as possible. The Fuel injection and timing do their thing. My goal is to make the smaller port extremely efficient, let the carb, air-raid and performer manifold keep the air moving and the fuel atomized at lower rpm. Thats the reason for the smaller port. These things will keep the fuel moving fast and efficient. I'm thinking.

 

[volaredon]

I have a fresh set of '302 heads that need a little cleanup work (surprisingly they need more cleanup in areas that have nothing to do with how the engine runs like where the oil runs and drains back to the crankcase) and a set of '714 heads here that are "as removed" from the donor engine which was some kind of a reman engine as evidenced by the heat tabs glued onto the ends

 

[Dmopower]

I have a fresh set of '302 heads that need a little cleanup work (surprisingly they need more cleanup in areas that have nothing to do with how the engine runs like where the oil runs and drains back to the crankcase) and a set of '714 heads here that are "as removed" from the donor engine which was some kind of a reman engine as evidenced by the heat tabs glued onto the ends

Yup, I always debur my engines and parts for that reason. The 920 heads I bowl ported last year and are on my Cudas 273 were surprisingly clean ports compared to the BB heads I've ported from the 60's and 70's. I just did a light clean up in the bowl, back cut the valves and gasket matched the intake side. My car has a 904 with 2.94 gears and my carb was way too rich and it gets just over 15 mpg with the 275-60-15 rear tires on it turning about 2500 at 65 mph. It's not fast and the mileage isn't great. I think I can get this 360 to get over 20 and have some power when needed. I'm hoping anyway.

 

[rumblefish360]

If you look at ANY new head they are all perfect ports. They get rid of the lumps and make them as efficient as possible. The Fuel injection and timing do their thing. My goal is to make the smaller port extremely efficient, let the carb, air-raid and performer manifold keep the air moving and the fuel atomized at lower rpm. Thats the reason for the smaller port. These things will keep the fuel moving fast and efficient. I'm thinking.

I understand that and do see where you’re going with this but when you port the 318 head, it has me wondering. I read what you said earlier on equaling the cfm gain to be as close or equal a 360 head without the port being to large like the 360.

While I understand the thinking, I’m not 100% seeing this final head porting result in my head. When you make the bridge connection with modern cylinder heads, it doesn’t exactly connect in my head because of the layout of the modern cylinder head in its dimensions and shape.

I get that a modern cylinder head is a great idea and a way you’re seeing it as a help. While I agree, to a point, it’s that point I can’t see past. While a superior flowing cylinder head is a plus, I have to go back to what @273 was saying, your engine is only going to need XX amount of power to propel it down the road. It is easily achieved with a dead stock head.

I also understand that the porting will enable you to get some food top end. This, in my head becomes a catch 22. I am curious to see how this evolves and turns out.

I’m going to do some HEMI cylinder head homework for comparative purposes.

I think I can get this 360 to get over 20 and have some power when needed. I'm hoping anyway.

I’m going to go over this thread again for the particulars on the car. It’s weight rod one.

At the risk of repeating myself, I did get 20 mpg’s out of my 360 in a 3800 lbs B body. No headers, no camshaft change.
2.76 gears turning 235/60/15 tires. 904 trans, 625 AFB.

I’ve used Rhodes lifters before to bandaid a wrong camshaft for the job. They were the regular set. (Go for the top line adjustable units.) I have also used them on just the intake.

 

[rumblefish360]

Do you plan to dyno the engine?
What does the Cuda weigh in at with you in it and a full tank of gas?

I’d like to know that weight value as it is the worst case scenario to attempt to get the max mileage with. But only gets better as fuel is consumed .

 

[toolmanmike]

If you look at ANY new head they are all perfect ports. They get rid of the lumps and make them as efficient as possible. The Fuel injection and timing do their thing. My goal is to make the smaller port extremely efficient, let the carb, air-raid and performer manifold keep the air moving and the fuel atomized at lower rpm. Thats the reason for the smaller port. These things will keep the fuel moving fast and efficient. I'm thinking.

Port matched. Not big just happy.