Thread: mileage

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Hi Guys,
I know many of you aren't the right people to ask, but here's my questions:
I'm planning to build a 305 SBC for mileage only. Power is secondary, 200HP are easily enough. I want to make 16-17 mpg in a lbs 5000 G20. I know it's possible, people before me have also managed.
I just want to know which of these statements are true:
1. roller rockers decrease internal friction
2. lighter rods and pistons save gas because they decrease the weight the engine has to accelerate in different directions all the time
3. a shorter stroke slows down the piston speed and gives the same effect as #2.
4. porting, headers, large manifold chambers increase the airflow, the engine has to do less "pumping" so less efficiency is lost this way
5. balancing the crankshaft will stabilize the whole engine and cause less energy to be lost in vibrations
6. Aluminum heads will dissipate the heat better but will not help in getting mileage
7. Aluminum block and heads will save weight, but not enough to make a difference in mileage
8. decreasing vibrations, internal friction and the weight of accelerated parts (also in the valve train) will get me higher efficiency and slightly higher power, but lower torque.
9. going for low RPMs at mid compression (under 9.5:1) is going to be more efficient than running high RPMs in high compression (over 10:1).
9. so I go with Aluminum pistons, forged conrods, a stock 305 block and ported heads, an EFI, high octane fuel (I'm planning on 105 octane LPG) and a cam designed for efficiency.

Is that going to get me good mileage?
Please tell me which of these assumptions are wrong, gas costs $5 per Gallon here in Germany and I want to keep my V8 van. (And I need something new to play with )
Thanks a lot, MadMax

I just want to know which of these statements are true:

1. roller rockers decrease internal friction - YES

2. lighter rods and pistons save gas because they decrease the weight the engine has to accelerate in different directions all the time - NO

3. a shorter stroke slows down the piston speed and gives the same effect as #2. - I would adjust rod ratio, make stroke whatever you desire and build around it.

4. porting, headers, large manifold chambers increase the airflow, the engine has to do less "pumping" so less efficiency is lost this way - To big of port is lazy, a lazy port will drop the fuel from the air resulting sucky performance. Intake port needs to be mated to engine requirements. Exhaust port needs to be as smooth and large as reasonably achievable. Its less important to work on a good ex port, the intake port has 2 times the effect on an engine. But a hogged out intake is as bad as a choked intake port. Right is right.

5. balancing the crankshaft will stabilize the whole engine and cause less energy to be lost in vibrations - Not sure about energy loss, but it will be smoother and longer lasting. Its easier on parts and adds long life.

6. Aluminum heads will dissipate the heat better but will not help in getting mileage - Allum heads absorb heat, this takes heat energy out of combustion and costs you power. An allum head needs to have increased compression to compensate over the same engine with iron heads.

7. Aluminum block and heads will save weight, but not enough to make a difference in mileage - Any saved weight on the chassis may make a change, but the change may be .2 MPG change by saving 300 lbs in a 6500 LB van. Is that worth going to an allum block/heads if you dont own them? No.

8. decreasing vibrations, internal friction and the weight of accelerated parts (also in the valve train) will get me higher efficiency and slightly higher power, but lower torque. I doubt it will be measurable. This is a stock style engine not a top fuel dragster. Its not a concern, really.

9. going for low RPMs at mid compression (under 9.5:1) is going to be more efficient than running high RPMs in high compression (over 10:1). - This is common sense. You are biulding an engine for a 3/4 ton van, you need to maximize the engines cam for the cruise RPM of your van and that is based on gearing/tire size/and speed that you travel at cruise. What good is a NHRA capable 9000 RPM engine in a van that travels at 3200 RPM on the street?

9. so I go with Aluminum pistons, forged conrods, a stock 305 block and ported heads, an EFI, high octane fuel (I'm planning on 105 octane LPG) and a cam designed for efficiency. - All pistons are allum, but are you wanting good, better, or best? That would be Cast, hypers, or forged. Stock rods are more than fine, anything else is a waste. Stock block is fine, spend money on blueprinting it, get it all straight and true and it will spin easier and live longer. Porting heads is always a great idea, but the intake can be severly messed up by porting it with the hog and hope method. Learn, read, ask, learn more...and finally make a plan and stick to it.

I wouldn't consider putting a 305 nothing in a 5000 lb. truck and expect it to do nothing but drank gas. you gonna work that motor to death. that's my story and im sticking to it.

OK, seems like larry got some points there, my main question is, what do I leave stock because cost would simply be too high for the increase in mileage (no use spending a thousand bucks on cam and lifters if that saves 200 bucks gas in a lifetime) and what do I change because I will see real increase?
From what I gather from all the answers put together is:
-get a near new 350. (which I have)
-take it apart and have it blueprinted (what do you mean by that, never had a blueprint done so far?)
-put in forged pistons
-port the heads to match intake manifold or other way round
-port ex runners (headers)
-go for FI rather than carb
- what FI? Holley or Edelbrock? TB or Port?

Is this overall correct?
Why would a 305 be killed in a truck that heavy? I've seen those vans being moved with the small V6s and they run OK (but I want a V8)
In all, I'm building this engine to later save money on gas. I know many of you think I might be off my head and why don't I buy a toyota starlet if I want to save gas, but the thing is, this is what I want to do just as much as you want to get 600 HP out of an SBC. But I don't want the engine to cost all that much either.
My main problem is that almost all upgrades you can buy will get you more power, but that's not what I want, I want upgrades that will decrease consumption, if that brings more power it's OK, if not, also OK.
Have any of you tried this before? Do you happen to know other things that will decrease my consumption?
Thanks,
Mad

[QUOTE]Originally posted by MadMax
[B]OK, seems like larry got some points there, my main question is, what do I leave stock because cost would simply be too high for the increase in mileage (no use spending a thousand bucks on cam and lifters if that saves 200 bucks gas in a lifetime) and what do I change because I will see real increase?
From what I gather from all the answers put together is:
-get a near new 350. (which I have)
-take it apart and have it blueprinted (what do you mean by that, never had a blueprint done so far?)
-put in forged pistons
-port the heads to match intake manifold or other way round
-port ex runners (headers)
-go for FI rather than carb
- what FI? Holley or Edelbrock? TB or Port?

Is this overall correct?
Why would a 305 be killed in a truck that heavy? I've seen those vans being moved with the small V6s and they run OK (but I want a V8)
In all, I'm building this engine to later save money on gas. I know many of you think I might be off my head and why don't I buy a toyota starlet if I want to save gas, but the thing is, this is what I want to do just as much as you want to get 600 HP out of an SBC. But I don't want the engine to cost all that much either.
My main problem is that almost all upgrades you can buy will get you more power, but that's not what I want, I want upgrades that will decrease consumption, if that brings more power it's OK, if not, also OK.





in a 5000 lb. truck you increase cu. in. to decrease comsumption.
the thing im relating this to is when i was a mech. at the olds. dealership early 70s, olds had these heavy stationwagon that they sold a bunch of and you could get a small v8 or the big v8, so everybody went for gas milige instead of power and there was a lot of unhappy people driving small motor, heavy wagons up and down the rd. put 6 people with the big motor in the car and it was fun to drive, because it had a little power left over, it got better gas miles because it wasent being lugged around all of the time and got more miles out of the car because it wasnt over worked. the people with the bigger was happy and the ones with the small motor was very unhappy.

Originally posted by MadMax
OK, seems like larry got some points there, my main question is, what do I leave stock because cost would simply be too high for the increase in mileage (no use spending a thousand bucks on cam and lifters if that saves 200 bucks gas in a lifetime) and what do I change because I will see real increase?
From what I gather from all the answers put together is:
-get a near new 350. (which I have)
-take it apart and have it blueprinted (what do you mean by that, never had a blueprint done so far?)
-put in forged pistons
-port the heads to match intake manifold or other way round
-port ex runners (headers)
-go for FI rather than carb
- what FI? Holley or Edelbrock? TB or Port?

Is this overall correct?
Why would a 305 be killed in a truck that heavy? I've seen those vans being moved with the small V6s and they run OK (but I want a V8)

OK, this is only one opinion, and its only my opinion, but to try to reply directly to your questions:
What to leave stock - Leave crank and rods stock. The pistons you suggested going to forged, that is most likely overkill, you will be all set if you get a hyper, just dont get the cast junk. I like a file fit ring, but set your ring end gap as per the towing/RV gap. THis will allow your rings to take the heat of lugging around that brick of a van without butting end to end and destroying the piston.

Now, here is where your disposable income comes into play. You can save internal losses due to friction by making all things you can ride on bearings. Go to a hydraulic roller lifter set up, I like Crane Cams. Go to a roller rocker arm set up, once more I like Crane Cams and I really like the gold series with the oil restrictors that spray the oil directly at the fulcrum and then bleed the oil out over the roller tip. If you call Crane call 386-252-1151 and ask for extension 4211, this is Pat, he is my rep and he is a great guy. He can help you choose a cam.

As far as the 305/350/383 your going to get your best economy out of a 383 I would suspect. Just like it was discussed, a engine that is running in the "bog" or "lugging" area is running in a very unefficiant way. Get a nice 383 package and cam it with a cam that makes good grunt down low and your going to have plenty of power where its needed for the engine to run on the least fuel. A 305 will have to work harder to pull the weight, it will lug itself much more. If you drive primarily on flat open roads a 305 will give you better mileage because your not using the start out power much, your in the cruise power and even a 305 is OK there. But, if your in hills and mountain area, or not on open roads a 305 will have to work double hard to do the job. Think about it, plain physics say it takes a given amount of energy to move a given mass, your engine has a hard time making the energy that a 350 or a 383 makes so it requires more fuel, more air, and more RPM's to get the energy to be equal.

Blue printing is a generic term. In the case of what I like to do, I like to have the mains re centered, have the cam re centered, and the mains are done with torque plates on the block to simulate the heads. This is called line boring or align boring, depends on who your talking to...lol. Then when you do the cylinder bores you do the same thing, use tq plates so that the cylinders are actually round once the engine is bolted together. THere is more that can be done if your picky, like have the bore stop at .008 from finished size and bring it in with the hine machine, this is done race engines to get a smoother finish on the bores.

Another thing that you can do based on finances is ceramic coat the tops of the pistons to stop heat absorbtion and you can also do the cumbustion chambers. Do the anti-friction coating on the sides of the pistons to make things more slippery.

The thing is, how much are you willing to spend to gain 2-5 MPG? Assuming you can gain 5, how many years will this old van have to last at your average miles per year to pay for the engine? If you spend and extra grand on the rebuild to gain 5 mpg and you drive 20K a year..... you could make back 1200 the first year, but what if you only gain 2 mpg? than you make back 600 bucks, so you need 2 years to break even.

OK, always gasket match your heads and intake. Take the new gasket and a sharpie marker and hold the gasket in place centered over the bolts and mark the metal that is showing inside tha gasket port holes. Use a dremel or die grinder and make a nice smooth funnel like transition from the original port to the gasket size. Do this on all gasketed surfaces of intake and exhaust, on manifolds (both intake and exhaust) and heads.

A well tuned carb will make as good power as a FI system, only if you travel to extreme conditions of temps or elevations a carb is not going to self adjust. A FI system will keep itself adjusted from pikes peak in winter to death valley in summer.

You think a 383 is going to get me better mileage than a 350? I find that hard to belive. I live in mainly flat area, but do use the car in town a lot, so going for the bigger engine might be a good idea. But I never even thought of building a 383, surely the longer stroke will increase my comp ratio and need higher RPMs to run well, or isn't that true? I haven't spent much time on 383s yet. And I don't know where to have cam and crank aligned either, I live in Germany, where many people just buy a different car and not very many fiddle around with things, so there isn't such a thing as a "local machine shop". And I asked about having my crankshaft balanced and it would have cost around 600 bucks, and that's going a bit far (but I have only asked at one place so far).
How much would you expect a bluprinted block to cost? Is that better and straighter than buying a new one?
I've asked at Holley and Edelbrock and they say with a well set FI you can gain about 12-15% in mileage over a well tuned carb, I guess that would be the single most important thing to do. I have been fiddling with my carb a bit (rods and jets) and it sometimes does seem to make a difference, but not really in mileage. I guess I'll just wait for a few more answers and start looking things out, which might fit my plans...
Just another idea: can a BBC make the same milage as an SBC? If all of you say the bigger the better, but there's a limit somewhere. But I probably couldn't fit a BB into the engine comp of my van anyway.
Let's see how far this project goes...

At the point your at, and being in Europe, it would be easier to buy the an entire ballanced rotating assembly from the US and have it sent to you. The 600 ballance charge is alot, it should cost 200. I doubt a BBC would fit easily, nor do I think it would get better MPG. A good tight 350 crate engine may be the ticket for you and just swap to a Holley fuel injection system. Its tough to do these things from outside the US, I work some Sweedish and German guys that collect parts when they come state side and ship them home to themselves. They say things are much cheaper here. Question, being in Europe, cant you find a nice turbo diesel 6 cylinder that would fit in there? Change tranny with it adn have a drive shaft made and weld up a new crossmember and your in. That would be best. Isn't your cost for gas about $9 u.s. per gallon?

I've thought of the TurboDiesel, too. In fact, I thought about it a lot. Gas is about $5 here BTW :-) I don't know whether you've heard of LPG-gas? It's a mixture of butane and propane and you can get it easily here in Germany. There are about a million (that's the real number at the moment) cars in Germany running on it and it's very easy to convert from a petrol to gas. I say gas here because it's real gas, not a fluid :-) Costs about 2000 bucks to install, fits every petrol engine and halves your fuel costs. It has about 105 octane, and doesn't create any soot, or wash oil off your walls when cold, so the engine lives longer. But you can only do that with petrol, not with diesel engines. That's the overall plan. And I like a V8. I like the sound, the feel, the torque it has... And I like fiddling around with things :-) That's what it's all about. Seeing as I'm a student and build cars as a hobby only (no race or anything) I'm not much into the power building business. BTW, I just read your long thread on 383 building, that looks like a good job well done! I would like to hear what mileage you get from that, if you're ever going to work it out, I guess mileage isn't really a concern with the fuel price being so low :-)
And I'll have to find a nice block-machining shop, too.
I know things are cheaper over your side of the lake, I often buy my trans-parts from transmissionpartsusa. Seem to be quite cheap (about half the price I would pay here and that's including the postage and tax) Sometime i would like to build a really good, stock engine (everything balanced, everything fits ...), the one I have now runs OK, but it was rebuilt in Germany by a shop that didn't even manage to get the oilpan gasket in straight (there was about a ton of RTV all round the engine and it still leaked), but that was before I bought it and changed all the gaskets myself. Ah well, I've been blathering a lot, I notice, Hope you don't mind :-) I wish you the best of luck for your 383, and will get on planning my project...
CU,
Madmax