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Old 02-13-2004, 04:52 PM
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Exclamation how to build a really fuel efficient SBC for gas at $5/gal.???

Hi guys,
Im posting for the first time here although Ive been reading a lot here for a couple of months already. Would like to thank you all for some really excellent posts. I thought I knew a fair bit about engines until I started researching stuff here .

I moved to Berlin Germany with my family and 55 Bel Air 3 years ago. Im pretty isolated from other car people so I was really glad to find this board. However, building a gas miser is not normally a big priority with you guys but I have seen some pointers I can use. But I cant put it all together in a real concept. Now to my problem:

Gas costs friggin 5 (five) bucks a gallon here!! So I spend a lot of time just looking at my car in the garage rather than driving it. Which is a bloody shame . Now my tired old 283 runs on 7 cylinders and really needs replacing and I want to take advantage of every conceivable trick to build a really efficient SBC so I can afford to drive it more often...
The car weighs in at nearly 4000 lbs. (Its so heavy because of A/C a 2nd battery for a cooler, lots of sound deadener, contikit, etc. etc.) so Ill need a 350 or better yet a 383. I have a performer intake and edelbrock 500 CFM and a 600 too. Id like to use them if possible, but not necessarily. The car has:
a 2004R tranny with lockup and 3:73 gears
headers
dual exhaust (2.5 inch pipes)
no posi

As for my expectations, I just cruise with it. I want to get 0-60 in under 10 seconds (which it managed with the 283), its not for racing. The best mileage I got with it on the highway was about 17-18, which is just too expensive (like if you were getting about 3-4mpg). Please dont tell me to put a diesel in it or a 6 banger!
I think the 283 had too little torque to be able to cruise efficiently.
What should I do? Roller cam? What pattern? 350 or 383? Vortec or old style heads? Small valves on big engine for torque? Has anyone tried those Turbulator exhaust tips (supposed to help low end torque and thus mileage). Maybe go back to iron manifolds and a single pipe? How about Direkt Hits ignition (extreme high voltage for better economy)? TBI?
Someone here said the L31 is powerful and efficient, any opinion on that? What other combination would fit the bill?
Thanks a lot
PS the photo was taken a month ago on the set of Kevin Spaceys new movie about Bobby Darin (Beyond the Sea). A lot of it was filmed here in Berlin, my car was used on the set
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Old 02-13-2004, 04:56 PM
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5 dollars a gallon i would leave germany.
just kidding.
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Old 02-13-2004, 05:43 PM
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If gas mileage is what your after, then I would stick with the 283. It`s hard to move up the performance mark in cubic inches and retain mileage. I would rebuild the 283 with the following pieces:
Flat Top pistons with the correct compression height, with the quench distance set at .040
A comp cams 240H camshaft, made for small cubic inch engines with high axle ratio`s, it`s RPM band is idle to 4600.
I would use the edelbrock performer intake
I would also suggest the use of a Rochester Quadrajet carb, It`s small primary`s are ideal for low end torque and fuel efficientcey.
I would retain the headers and exhaust, but I would add a crossover pipe with the size about 75% of the overall pipe size and add it to the hottest section of the exhaust.
Upgrade the iginition system with top components, such as a HEI with a pertronix flame thrower coil and module, and add a set of Spiral core spark plug wires, take your time and route them correctly. if your running a points ignition, throw it in the trash and make sure you route a new wire for the HEI that has a solid 12 volts.
Use a K&N air filter.
Fill the rear diff with royal purple gear lube, this will cut rolling resistance. Repack the front wheel bearings with sythetic grease.
Lower cruise RPM`s equal better mileage, and i`m betting with this combo, you`ll reach around the 21 MPG mark or better.
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Old 02-13-2004, 09:14 PM
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350 Chevy tuned to about 250-300 HP@5000rpm and a set of 3.0 gears for the back. The bigger cubes will get that weight moving and the rear gears should get you into the 20's for mileage. Use a Quadrajet if you can, they are great mileage carbs.

Forget about 30MPG, not going to happen unless you go diesel. Whats wrong with a turbodiesel Benz V8 or BMW? Probably lying around the junkyards there, they would probably still get you into the 10's from 0-60.
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Old 02-13-2004, 11:13 PM
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Good looking ride!

Pricewise, rebuilding a 350 is cheaper than a 283, but those cubes also require more petrol. I would check PAW for 283 parts. They're about the only one I can think of right now that probably still handles 283 parts.

Whatever your choice, I would try to stay in the 8.5:1 compression ratio area, with cam with no more than 200-210 duration range. The Comp Cams' XE252 might be a good choice. I would also keep the dual exhausts.

I agree with the above comments about a Q-Jet. It's economical if you can stay out of the secondaries. With your 200R4 and a lower (numerically) rear end, you should see better mileage.
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Old 02-14-2004, 01:00 AM
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How about a later factory hydraulic roller 350 with Vortec heads, Q-jet (or EFI), & a tiny roller cam such as this one:
http://sdpc2000.com/cart.asp?action=...d=989&pid=2146
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Old 02-14-2004, 01:33 AM
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Hi guys, thanks for the input so far. I have a few things to add to my posting:
I have an HEI and will upgrade to Pertronix or Direct Hits (a similar product)
I will use all synthetic oils and fluids.
Have a K&N filter.

Have had experience with a 69 olds with 350 ci (stock, with highway gears) no overdrive or lockup that got consistant 19 mpg on the highway. With an overdrive and lockup it would have been in the low 20s. So a Q-jet is a good idea.

Gasoline is much higher quality here than in the US. Regular and Super is nearly the same price so Ill run Super. That means 9.5:1 compression will be used.

My goal is 23-25 mpg. Diesel is not an option because of very high annual licence fees for diesel powered vehicles, plus I just dont like them. The swap would be much too difficult too.

Wouldnt a lower diff (say 3:08 or so) cause the engine to lug or cause a too slow air velocity through the carb to be efficient?

How do you determine the hottest part of the exhaust pipe (for the crossover pipe)?

Id like to hear from folks that have switched to roller cams and vortec heads, whether that impacted economy. What heads would be best for my purpose?

Thanks again.
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Old 02-14-2004, 02:19 AM
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You can use a gun that you just point and pull the trigger and it will give you the temperature of the targeted item. There is also a paint you can put on the pipes that will turn different colors signifying different heats. Its about 1:30 am here and the names of both products has escaped me. I have never used the paint however I do have the temperature gun and it works great.

I used to live in Ireland so I know what you mean about petrol prices.
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Old 02-14-2004, 09:01 AM
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I live in the states but my Olds 455 in my 81 Cutlass is drinking alot of gas. I'm getting tired of 10 mpg! So, I'm in the process of gathering the parts together for a TBI system. They are all over the place, resting quietly in the junk yards and they look like a carb. No one will ever know that you have fuel injection (except for a wiring harness that will snake away from under your air cleaner). You and I both know good fuel milage isn't just highway cruising. There's the start up and then stop and go driving both of which simply can't be managed perfectly with the carb...including the "Q-jet". I've gathered 75 percent of the parts that I need for my TBI conversion and plan to do everything for about 500 bucks. I really think TBI would be perfect for what you're trying to achieve! Anyway, I'm going to try it...good luck.
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Old 02-14-2004, 09:52 AM
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Hello Bel Air,

I am going to point out the obvious and suggest EFI. There are several DIY(do it yourself) controllers that can be used with junk yard parts to build a very cheap EFI system. You can get more information on two controllers here:
http://www.bgsoflex.com/megasquirt.html
http://www.squirrelpf.com/msavr/

The first is the original Megasquirt and the second is a newly stemed project. The first only does fuel control and is available cheaper and with firware that is proven. The second is bleeding edge new and is what I am working on myself right now.

If you do not mind spending some money Holley and Edelbrock both make some very nice bolt on systems. Unless you are a master tuner, you will never see the mileage that you will get with EFI. EFI can monitor fuel ratio and constantly adjust it while cruising which is where you will really get the good mileage.

I agree with most of the above information about engine dynamics. You want to keep lsa high and duration low to maintain good cylinder pressure in the low RPM range. Also, you do not want to go overboard on the heads port size. Keep compression as high as possible on the fuel you have available. With EFI, you can get away with a little more because you can more easily monitor and tune around it. Optimize everthing else as for a performance engine so the engine will be as efficient as possible.

Chris
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Old 02-14-2004, 02:07 PM
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Nice 55 Bel Aire!!! I'm with Kevin on the EFI. Edelbrock makes a total package Pro Flo with 2 barrell air valve that will give you at least 6 MPG over anything you can build with a carb on it. Roller cam, rockers and lifters will decreas the friction in your valve train drastically and that translates into more hp or fuel economy. The vortec heads will help your fuel economy also. They are just more efficient. Throw your total package together on the little 283 and I can see 25 MPG as atttainable. Get a summit catalogue and look at what Edelbrock offers and even go on line (edelbrock.com) to their tech services and address your questions to Gary. I have the bigger setup on a 383 motor that is producing 475 HP and I'm getting 21.5 MPG and still tuning for economey(think I can squeeze out another 2.5). Course its in a 2700# vehicle, but we are talking 100 more cubic inches and a 1000 CFM air valve vice the 600 CFM two barrel air valve.

Trees
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Old 02-14-2004, 04:51 PM
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edelbrock advertises some pretty good increases in HP and economy. Honestly, you want smallish port heads with small, efficient combustion chambers. Get roller everything, cam, rockers etc. Not to disagree, but its not the fact that they reduce very much friction that makes them so desireable, its that the ramp designs can be more efficient because they're not limited by angle that makes roller valve gear so desireable, its a common misconception. You can underdrive your pulleys, you can get rid of your fan and put an electric one on there, and you can get a two in one water pump alternator if you want to really go for it. K&N filter all the way. Do some searching on what carb to use, I'm not sure a quad is the best way to go. I'm sure they're great if you're going to keep your foot out of it all the time, but they hog it down pretty good if you ever get into it. In fact, most of them are rated 780 and higher CFM, which is quite a lot for that motor. You don't need anything bigger than 600 (and don't let anybody tell you otherwise).

K
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Old 02-15-2004, 01:38 AM
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A Quadrajet will not "overcarburate" your engine. It has small primaries with extra "booster" venturis, which is good for mileage due to better fuel atomization. If the motor doesn't need the full 750cfm of air flow, the secondaries just won't open all the way. EFI would still be better. As far as rear end gearing, my 3700lb '88 T-bird w/302, tiny roller cam (~180*@.050), high-swirl heads, & EFI came with a 2.73 rear end & AOD overdrive trans, & it got nearly 30mpg (highway) when it had an intact body. Cruised comfortably at ~1800rpm at 70mph. Severe front end damage knocked off about 4mpg. A 3.45 gear knocked off 2 or 3 more. 0-60 was ~12sec., now it's ~11.

The temperature paint is called Tempilaq, but you have to know at what temperature you want it to melt. It costs ~$12/bottle, & comes in several melt temperatures from 400* to 1500*.

http://www.brownells.com/aspx/NS/sto...le=TEMPILAQ%7e
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Old 02-15-2004, 03:47 AM
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I would put a nice 355 in there with Castiron Vortec heads. Use the stock crank (maybe get it cut) stock rods (very good rods) and put in some hyperutectic pistons. A nice comp cam 1500-6000 rpm. A hydrolic should do the trick I dont think you need a roller. I'd top if off with a Performer RPM intake (airgap if you wana spend a little more and look cooool) I had a similiar motor in my Nova a year or 2 ago and it went pretty good. You could probably drop that rearend gear to some 3.08 or 3.55's because this motor will make enough torque to get ya moving down low. A friend of mine has a 355 iron headed vortec motor and is high 7's in the 1/8th mile all motor in a 97 fbod (pump gas). Not the lightest car either. With an overdrive trans and highway gear you should have good gas mileage and still be able to get going when you gotta.

Also..these motors generally put out 375-425 hp. Compression,carb size, and head work are the variables. And roller cam or not. The 383 stroker with vortec heads was putting out 500hp+ with a hydrolic roller cam on 94 octane pump gas about 10.1 compression.
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Old 02-15-2004, 06:47 AM
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i live in Denmark where gas prices are about the same as our southern neighbour. and let me tell you "its not the miles, but the smiles per gallon that count" i wouldnt expect more that 23 miles per gallon (10L/100km) with such a heavy and aerodynamically-dysfuncional car. In my opinion a lt1/lt4 engine out of an 91-94 camaro with fuelinjection is your best bet for performance and mileage. they cost arround 3300 euro with wireing loom and cpu. they will definately get you from 0-60 faster than a MB 320 CDI and run just as smooth.
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