F-Body Demon

iTrader: (1)

Hey fellas, heres the bit. Im sure im not the only one who noticed that gas is almost back to the $3 mark. And with that, I was thinking of pursuing a project I have wanted to get into for quite some time. Now all of this is going to apply to a 3.23 rear gear and a 700R4, as well as a full exhaust using 1 1/2" to 2.5" Long tubes and a X-Pipe with turbo mufflers on the back, unless someone can tell me a better way to get it done. But im wanting to stick to the 3.23 for the better off the line if possible, however like I said im open for reasonable discussion.

That being said the engine (and discussion piece) would be a "Low" cubic inch SBC that runs very well and is good on gas (21 City 30 Hwy). All this to be done in a form that favors reliability over trick parts, as well as being budget conscious, but will still roast tires and nail you with some serious grin factor.

My Plan
L31 Block
L99 Rods and Crankshaft
Hyper-U pistons with floating wristpin
416 Heads with port work and valves
LG4 Intake manifold with port matching
1" 4 hole poly spacer
Tuned Q-Jet non CC
Summit HEI w/Controller
And maybe someone with a bit more camshaft time can help me pick a proper cam to match the selection. But I would need to stick to roller.

Like I said the Idea is a 290-310 CI SBC that makes 250hp 350tq and gets good gas milage.

Any other ideas?

EDIT: Note the L99 I refer to is the Baby LT1 L99 not the new Camaro engine haha.

gregsz-28

iTrader: (1)

Why don't you want to use a CC q-jet? I got more mpg with the CC q-jet then I did with a non CC q-jet.

Quinny

I would be going for something like this:

*Eagle rotating assembly - crank & I beam rods with Keith Black pistons - 10:1 comp
*Trickflow alloy 175cc heads
*Comp XE276HR hyd roller cam 230/236, .520", 110LSA (retro-fit)
*Edelbrock Performer RPM Air-Gap intake
*Holley 650 carb
*MSD billet HEI distributor
*1.6:1 roller rockers

Should make 350+hp, 350+ft-lbs. Don't really care about gas milage - as long as it puts a smile on my face.

Oh, and for the record - gas prices in Australia are much higher than in the US. You are paying about $3 per gallon, we pay about $1.25 per litre (3.79 litres per US gallon) for regular unleaded.

Shadow Z

iTrader: (2)

If you're looking for gas mileage, just make the car lighter. T-5 or T-56 swap, a Carbon Fiber driveshaft, fiberglass fenders and doors. Acceleration is what really kills city gas mileage, when combined with a lot of weight. 2,000+ RPM's is what will kill highway mileage. I'd go for a lower gear, 2.73's?

There's always the option of custom carbon fiber serpentine pulleys. Removing all of that unnecessary unsprung weight will give you a nice bump in gas mileage. I don't see any reason of why a 350 with forged internals, combined with the right gears and transmission wouldn't yield 30 MPG's. It's not like we drive tanks, our cars are relatively light. Possibly an LS1 to take off even more weight?

Lighter wheels will save you a heap at the gas pump, also. I know that single stripe IROC wheels weigh 25 pounds, and magnesium C5 Corvette wheels weigh 17/21.

I don't see any need to go for less cubes, but if that's what you like, go for it.

Orr89RocZ

iTrader: (20)

Sounds like a bolt on 305 TPI car with a stick, taller gearing and well tuned ECM. No need to build a new motor with all those parts. Just need a fresh 305 TPI LB9

That torque is hard to make with intakes other than TPI


Else do a 302 clone, 4" bore short stroke with L98 aluminum heads, ZZ4 type cam, and make 300Hp easy while getting that mileage with a tune

gregsz-28

iTrader: (1)

Don't listen to this advice, sure it would help, but there are many more important places to spend money first. A CF DS, 'glass doors and fenders, CF pulleys, and corvette magnesium wheels will cost at least $3000, and might get you 1 MPG more.
Instead, spend that $3000+ on the already mentioned t56 swap, headers/exhaust, tires, and gears, and that will make a real difference.
My '72 Pontiac got about 9 mpg, and my Camaro, after all the modifications I made, got about 18-19 mpg. Sure, the Camaro is a couple hundred pounds lighter, but it also has a smaller, more efficient engine, and overdrive.
CF pulleys. Really? That's ridiculous. Since when are pulleys unsprung weight? Sure, they are less rotating weight, maybe a couple pounds, but I bet you could get headers for less money and they would probably increase engine efficiency more than 50x than what CF pulleys would.
Lighter wheels won't make a noticeable difference, either. Tire width and diameter are much more important. Get narrow, taller tires.

Like Orr said, you should be able to accomplish what you want with your TPI, much easier than you could with a carb.

Rolling Thunder

Personally if i could do it any way i wanted.....

302 short block
vortec heads
TPI intake
with a relatively tame cam depending on the rest of the build and as much compressions as possible

My reasoning, the 302 is well known for its big bore short stroke combo which is nice. Also the larger bore allows the use of larger valves as its the same bore as a 350. Really the best motor that would be in that range of displacements in my oppinion. The vortec heads are dirt cheap and perform great no explination really needed there. The TPI intake is what really makes it all come together though. At the time GM boasted that gains of 30% in fuel economy, hp, and torque would be realized by swapping this intake onto exsisting carbed motors of the time. Today i still feel its one of the best fuel injection intakes for the GEN 1 SBCs for street use. They have great economy and gobs of torque. Also being that this is a smaller motor it wont be so restictive as the factory TPI is designed around the 305s air flow data. Now although it may seem crazy to swap on a TPI when you look under the hood of a factory TPI car and see what a mess it is of hoses and wires but keep in mind a vast amount of all that is emmissions related stuff that could be eliminated. The bare essentials of what a TPI intake needs to run are actually fairly simple and can be bought fairly cheap used. Not as cheap as a carb of course but to me the the advantages would outweigh the cost difference. The big expence would be the intake base if you went with vortecs as that would be like 400 but you could always go with the 416s instead. Something like this i would guess would be good for a low 300 hp number but with great economy and torque while maintaining some nice top end. As far as the drive line the rear 3.23s would be good especially with TPI as its a torque monster and likes lower gears than other motors. I would go stick shift as you will see a slight gain in MPGs. Although at this rate your probably better off just getting an LB9 as its a lot easier to fine a 305 than find or build a 302 and it would already have TPI on it. You might even be able to pick up a wrecked camaro or firebird cheap and just use it as a doner. Or at that rate you might just be able to find a LB9 equiped camaro/firebird and be done with it all together lol.

Shadow Z

iTrader: (2)

Don't listen to this advice. This guy does not comprehend that overall less rotating mass leads to more efficiency. I'm not telling him what to do, I'm telling him that there ARE other options than a small cubic inch engine, such as shaping the body around the engine, in order to reach that goal, gas mileage wise.

Lighter wheels won't make a difference? You may as well go back, and erase that post, to save yourself the embarrassment, what a noob-ish thing to say. So I guess all of them guys out there running forged wheels, and carbon fiber wheels aren't shaving off tenths in the quarter, just from less rotating mass? You're fooling yourself, that is absolute non-sense.

What you just did, is took my advice, and turned it into complete non-sense BS. T-56, yeah, I mentioned that, so you mention it also. It is obvious that you're rambling on, with no personal accounts or experience behind what you say.

Headers make a drivetrain more efficient than lighter pulleys would? No. Headers offer better flow, and more of a scavenging affect, which may yield a whole 5 peak HP, NOT efficiency. Drivetrain efficiency is what counts with getting decent gas mileage, such as putting less power into spinning an alternator pulley. Getting more of that power that's ALREADY THERE to the wheels helps with gas mileage.

I suggest you take your little cocky attitude, and misinformation BS elsewhere.

Quinny

If you want to improve your fuel consumption, then reducing unsprung weight is a very good way to do it. However, it comes at a cost.

Replacing body panels with fibreglass or carbon fibre can be expensive, as can magnesium wheels, carbon fibre or titanium engine/driveline parts.

Then again, building an engine and replacing the gearbox is pretty pricey too.

If you want a good engine which is efficient, I would be looking at an LS1 swap - it is all alloy so it is lighter, and it will be more efficient than an older small block, especially when given a proper tune. Combined with the T56 or 4L60 overdrive trans to keep the revs down, should make a good difference in economy.

Another option is to buy a cheaper small car and leave the Camaro at home for your normal running around, and bring the Camaro out on the weekends.

Shadow Z

iTrader: (2)

+1

Finally someone who actually thinks, and doesn't imply that piling more power on is the way of efficiency. You sir, made my day, by just letting me know there's still a bunch of smart people out there.

I really think an LS1/T-56 combo, combined with weight reduction would be the way to go for him, if he wants decent power and gas mileage.

Look at Corvettes, a lot of the C5's are getting nearly 30 MPG's, which is more than most Hondas, powered by sub 2 liter engines. Sometimes less cubes isn't the way to go for efficiency. Decent sized engines with good amounts of torque lower in the power band will yield most likely the best gas mileage, other than any hybrid, electric, or Diesel powered car, of course. The only limiting factor is drag coefficient, and of course weight. Which will really, really hurt city mileage.

I agree more with just getting a smaller more practical car though. Third Gens are very practical for daily use, but it'd be horrible to see one turned into a machine that's purpose built for gas mileage.

Somehow in my mind, F Body doesn't = Econobox.

However, it will be neat to see one getting great gas mileage, while having 300+ Horsepower. Good luck if you go along with your small engine build.

gregsz-28

iTrader: (1)

Headers do increase efficiency, giving more HP and more MPG. I would expect at least 10% better efficiency with headers. That scavenging effect not only makes more power, but since you aren't using any power to get that effect, it is free HP, and it also helps efficiency. Anyone that has real numbers about how much efficiency is gained from headers or pulleys will agree with me. I know less rotating mass makes the engine more efficiect, I even mentioned that, and you quoted me, but I am saying for the cost of CF pulleys, you could build a new shortblock, or get headers/aftermarket exhaust, or new gears, etc, for less money, and see much greater results.
I have had a few different sets of wheels on my Camaro, I even borrowed some light aftermarket wheels from a friend for a while, and they never made any noticeable difference in fuel economy. Sure, lighter wheels do help efficiency, but there are many other things you can do for less money that will have greater results.
BTW, have you ever weighed a 'glass fender? I haven't either, and I haven't ever weighed a stock fender either, but I really doubt 'glass fenders would save more than 10 pounds, which isn't worth the few hundred $ they cost to most people.
'Glass doors? Have fun with that on a street car. I like being safe and having functional windows.
You are right to say I have no experience with a t56 swap. But, i do know that my truck with a 5 speed and 3.73:1 gears gets 25.8 mpg, and my Camaro never got that, with an auto, and with the 3.42 or the 3.08 gears.

At least I'm not the one that thinks pulley are unsprung weight.

Quinny

Just as a side note, my old LS1 made 417rwhp, ran 11.89 in a full weight (all 3800lbs of it) street car with T56 and 3.9 gears has seen up to 26mpg on the highway. It is all in the tuning.

Shadow Z

iTrader: (2)

"At least I'm not the one that thinks pulley are unsprung weight."

I made a small mistake, I sometimes confuse unsprung weight, and rotating mass, is that such a crime? I don't think so.

You make some very good points, that are more practical than most that I have listed, with the exception of the T-56/LS1 swap and lower gears, that is a very practical idea, which will increase gas mileage.

You're forgetting that the aim would be efficiency, efficiency does not include stacking on more power, efficiency is using the power that is already available, as in a more efficient serpentine system, and drivetrain.

Then again, at least I'm not the one who thinks headers give HP. Last time I checked, Horsepower was a measurement, and that Torque is the actual force behind the crankshaft, transmission, driveshaft, rear, and axle, combined with time, in the form of RPM's, to create that measurement.

Horsepower = Torque X Engine RPM / 5,252.

Just kiddin'.

gregsz-28

iTrader: (1)

...
I think we all can agree that an LS1 and T56 will increase efficiency, but the OP was talking about about gen 1's and a 700r4.

I'll say it for you again, headers don't just increase HP, they increase engine efficiency.

Yes, and since they increase torque, they also increase HP

Example:
1 X 1000 / 5252 = .19
2 X 1000 / 5252 = .38

Quinny

By fitting pulleys which are lighter than standard - does it not decrease both rotating mass and unsprung weight?

By fitting a lightened flywheel which is 5lbs lighter than standard, you are not only increasing rotating efficiency, but you have also decreased the overall weight of your car by 5lbs.... The same goes for fitting titanium conrods, valves, carbon fibre pulleys, chromoly tailshaft, light magnesium or carbon fibre wheels and even titanium wheelnuts etc.

Shadow Z

iTrader: (2)

That was my main point, and it's a very good one. I've read that rotating mass will affect a vehicle's drivetrain efficiency and power wise 8 times more than the weight of the actual body. EDIT: Let me rephrase that, 8 times more than sprung mass, that's be a tad more correct in technical terms.

Needless to say, unsprung/rotating mass is extremely important when it comes to efficiency, yet the price of forged and carbon fiber materials usually steer people away, to the simple method, which is adding more power. Resulting in poor gas mileage.

Possibly the point will not get through.

gregsz-28

iTrader: (1)

No, it doesn't decrease unsprung weight. It reduces sprung weight and rotating weight.

All those things you listed do increase efficiency, but they are expensive, and aren't as effective as other methods. Sure, new Corvettes have all those trick parts, and they get an amazing 600+ HP and 30 mpg. But, they also cost $150,000.

It is more important to first focus on the things that will yeild greater results, such as tuning, headers, and gear ratios better suited to your driving style, then it is to get titanium lug nuts and CF pulleys

Shadow Z

iTrader: (2)

No one mentioned Corvette ZR1's. ZR1's cost right over $100,000, not $150,000, and they also only get 20 MPG's. I mentioned C5's. C5 LS1 Corvettes get nearly 30 highway MPG's.

Orr89RocZ

iTrader: (20)

For relatively cheap, I think you could pull out a 4.8 L truck motor, swap on LS1 intake/oil pan/etc to make it fit in the 3rd gen fbody platform for less than or equal to the 290-310 sbc build, unless you have a good 305 shortblock/longblock. Maybe just re-ring and go over the bearings to make sure the motor is fresh and you'll be good to go. you can pick up 4.8's for pennys these days.

They easily will make 300hp and get near 30mpg in a fbody with the right gearing and tune.

Rolling Thunder

Theres alot of things that could be done but these are the facts. It takes energy to accelerate a mass and it takes energy to overcome the forces or aerodynamic drag. Then theres the efficency at which the motor can turn the chemical energy into mechanical energy.

1. The motor effects gas mileage under all driving conditions

2. Driving at a steady pace (highway driving) weigh has very little to do with economy here aerodynamics is very important.

3. Stop and go driving (city driving) is effected by weight mostly as most of the energy you motor uses goes into accelerating the car which is then waited in braking.

What this means is dropping all the weight imaginable would have extremely little advantages in terms of highway driving and only helps the stop and go. Furthermore although decreasing the weight helps a lot of these examples would never make a return on the investment. I mean thats the point of it all isnt really? Spend some now to spend less later? If you shave off 5 lbs on a fender how many miles would you have to drive (let alone they have to be miles you were accelerating as weight plays virtually no role in constant speed fuel economy) to make these fenders pay for themselves? Another mention is adding more power equals worse gas mileage. Motors by there nature are horribly inefficient. So to build performance theirs only 2 ways of really doing this. 1 being increase the volume 2 being to make it more efficient. For example increaseing compression increases performance and fuel economy because it increases the efficiency of the motor. Also the motors efficency varies widely over the rev range so building a motor you want to build its peek efficiency where you typically spend most of your time. For example a modded 305 whos peek efficiency was at 3 or 4 k rpms might do better on the highway than the same car whos peek efficiency was at 2 k rpms if it was a car with no overdrive and a steep rear and constantly cruised at 3.5k.

Irockz

iTrader: (1)

I really like the notion you have,I have ran that rotating assembly through my head a million times.Other than a piston that may or may not be hard to come by,you have an affordable rotating assembly using proven GM parts.
I am with the crowd,the vortecs are going to be the cylinder head of choice,I might even consider reusing the L31 camshaft.In the end,I really can't tell you from any experiance what kind of MPG you could expect,but it should knock down good MPG,run pretty sporty and answer some of the questions in my own mind.My thoughts on this are,if it doesn't get the MPG you hoped for,I bet a fresh,roller capable 30r 1 piece rear main seal engine would bring good coin,especially if topped with vortec heads.It's an experiment,so theres always a chance it won't work out,but this is one that you could likely recoup what you've spent.Remember,the infamous 5.0 Mustang ran this same bore/stroke combo,and got good MPG as well as being fun to drive.
On one last tangent,the 4.3 V8,in its LT1 form,isn't all that bad a little engine.I have no idea what the HP/torque #s are for it,bit it's not a terrible performer.I swapped one into a 55 Bel Air a couple of years ago for a guy who liked to drive to a lot of distant car shows.I was pretty impressed with it's performance for such a little fella,and he later told me he was knocking down 24mpg on the highway,and that is in a heavy old brick.They are cheaply aquired,might be worth your time to test drive a Caprice,etc. with that engine,see if it would ever meet your needs.I bet in something as aerodynamic as our Camaros,it would get real close to 30 MPG,look pretty neat under the hood,and swapping them in place of a traditional SB isn't too much of a chore.
In any case,let us know what you do and how it works out,I love the idea of a realistic,fun 3rd gen.I've been shooting them in a straight line as hard as I can for so long now,that the idea of a fun DD is back to being interesting to me.

Rolling Thunder

Also this is still very incorrect. Maybe as a general ruel of thumb someone came up with this number it dosnt even look reasonable to me so im thinking it may have been for some specific example like wheels or something. Reason is imagin a driveshaft with an infinetly small diamater it would have no difference rotating mass vs sprung mass in terms of reducing weight. A flywheel on the other hand has a much larger diameter and would have a pretty serious effect. Its not just some constant not even close it depends not only on the diameter but also the weight distribution of that item. For example drive shafts have most of there wight on the outside as there hollow. A rotating mass with the same shape and weight whose mass was more distributed in the center would have less of an effect on the rotational mass.

gregsz-28

iTrader: (1)

7X, 8X, or 10X, is just a common generalization, which I have used before, but that still doesn't make it very accurate. But, in addition to distribution of the weight, gear ratios need to be considered. For example, if the DS and axles weighed the same, and had the same weight distribution, a reduction in the weight of the axles would have far less effect then a equal reduction in the weight of the DS. Also, the wieght of the DS has far less effect than the rotating weight of the engine, except in drive, where it has an equal effect, and in OD, where changes in DS weight will have more effect than changes in engine rotating weight.

Quinny

I love the way that this has turned from a conversation about building a small capacity engine to a high school physics lesson... interesting read.

dimented24x7

iTrader: (2)

If your looking to save gas, stick with EFI. The setup above w/ a mild roller should easily be able to hit all your perf. targets without any exotic weight reduction or anything like that. I know my old vortec did with ease. But, there are some things you can do with EFI that you cant do with a carb, like lean cruise. Even with a cam, Ive noticed that setting the engine to run around 15.5-16:1 at steady speeds and at idle saves quite a bit of gas. Since its EFI, the engine still runs at 14.7 under normal accel, and 13-12:1 under high load, depending on the conditions. Cant do that with a carb.

Guest

I think you're going to have a hard (likely impossible) time getting 21 city with a V8. 30 highway, thats possible with the right tune and parts. It would make more sense to live with what you can for city mileage and alter your driving habits rather than your car to get the most out of it in the city.

As far as weight, decreasing rotating mass isnt going to affect highway mileage much if any. Refer to Newton's first law. If you are not accelerating the object, then the mass is not a factor. This is generally why highway mileage is so much different than city mileage, because there is little to no acceleration of the rotating mass.

"But, there are some things you can do with EFI that you cant do with a carb, like lean cruise."

Actually you can, but its a lot simpler with EFI.

Just for your reference, I have a carbed 302 that the best I've ever gotten in the city is 18. Its a very light car with a bunch of lightweight parts, that is why I think your 21 city is not realistic. Not with a V8. I dont think EFI is going to help much either. I have gotten as much as 32 highway, and its a little less aerodynamic than a thirdgen. Usually I get about 30 highway. So if you shoot for 18/30 I think you will get it. Otherwise, I'd suggest going with a V6.

ericjon262

I like your build plan, I've wanted to have a 302 in my camaro to confuse the ford guys!

Do you plan to keep it emissions legal?
You need nitrous!

Orr89RocZ

iTrader: (20)

My bolt on L98 got around 18mpg mixed driving..mostly city type drives with stop and gos, but not like heavy traffic, but this also had alot of hard driving as well. Baby it around abit more, and 20-21 may be achieveable and this was with little tuning to the motor. That car made 254whp and ran high 12's.
I think its very doable in a 305 based car. Rather see a 302 for the 4" bore for heads that can use a bigger valve

dimented24x7

iTrader: (2)

A mild, stock type cam with no overlap, good compression (at least 9.5:1), heads with good, high swirl CCs like the vortecs, lean AFRs, and tuning (EFI, no carbs) are how you get good fuel economy in the city. Even with a 350, you can still get good fuel economy if you stick to using 5w-30 synthetic to minimize friction. Another part of the fuel economy that gets overlooked is driving habits. You can only get good fuel economy if you ensure that the engine isn't run hard in stop and go driving conditions. Basically stay off the gas and try to coast from light to light. I know my 3.5L gets up to 25 MPG in the city when its driven properly.

RED_DRAGON_85

i agree with dimented24x7.
one thing that is forgotten is that you can put the best cam in the world in an engine with shitty heads and it will run like... cr@p
take that same engine and put good heads on it with the stock cam and it will do wonders.

to the OP
buy a 4" bore block, and the best heads you can afford.
swept volume is what eats gas, so get yourself a 3" or 3.25" stroke crank
remeber that a 3" crank will make your cam choices harder because a cam designed for a 350 will be more radical on a 302.

get your heads worked on to maximize flow and use big valves, especially exhaust valves. your intake will probably be ok stock.

reduce as much reciprocating and rotating weight as possible as it will have a much larger effect on the whole picture, but anything you can do to remove weight is good.

big wide tires look good, but are heavy and have a big effect on aerodynamics.
215 tires will give you all the grip you need if you get the right compound (i recommend bfg KDW and G-Force Sport line). get the lightest wheels you can get in your size. eineke (sp) makes a good 15x7 wheel and it is very very light weight.

if you go with an automatic, keep your stall speed as low as possible. keep lockup working and tune it to turn on around 30 mph.
you want your rear gears to put you at cruising speed midway between your torque peak and vacuum peak (an approximation for peak BSFC. if you can get this value from a dyno, use it instead)

if you run a manual transmission, i would think that a t-5 would be sufficient and is light weight at only around 80 lbs. a t-56 is heavier but will give you more flexibility in gearing.

keep your compression high as you can without compromising your timing.


as said above, aerodynamics will get you mileage on the highway, efficiency will get you mileage around town.
keep your efficiency as high as you can by wasting as little power as possible.

ericjon262

if you can swing it, get an L99 and an LT1 and swap the cranks. you get the big bore of the Lt1, with the shorter stroke of the L99, with all the benefits of the Gen II motor.

Hippie

Lot's of good ideas posted. I've spent a fair amount of time investigating this type of build for myself and there are countless ways to do it. I think what you are planning will work or at least come very close but I think there's an easier way, let me just throw this out for you to chew on.........

L30 305 Vortec engine
'395 Marine roller cam ( also used in the Ramjet 350 and HT383 crate motors, "new" crate motor takeouts are about $80 on eBay )
Performer, GMPP or similar brand name intake (don't waste your money on those cheap knock offs)
1-1/2" Tri-Y headers
March underdrive pulleys

As much as I like QuadraJets I have to agree with the general consensus that you'll get better mileage and driveability with some form of EFI, TPI on this would be sweet. Just my $.02 FWIW.

InfernalVortex

iTrader: (4)

I think the premise of your post is wrong. A 305 doesnt get better gas mileage than a 350. If they are setup to make the same peak hp, the 305 will get worse gas mileage than a 350. If they are setup to get the same mileage, then the 350 will make more power.

Displacement isnt what eats fuel, it's horsepower that eats fuel. Some engines do it more efficiently than others due to all the factors previously mentioned on this thread, but I dont think you're really helping much by going to a short stroke motor. smallblock chevys are already extremely oversquare, I dont think cutting the stroke a half inch is really going to make very much of a difference.

Instead of putting together this expensive science project that's castrated from conception, just get an LS1. It's lighter, more powerful, comes with excellent EFI, and gets fantastic gas mileage. It's a much more efficient engine. They've been proven to make power while saving you gas.

bjankuski

I need to comment on this, a 305 will get better mileage then a 350 if all things are equal. The frictional losses are less with a 305 (frictional include pumping loss and drag). It takes x amount of hp to keep a car moving and if both engines are set-up the same (efficincy in the power band it is being used) the 305 will get better mileage and still be able to make 250 HP and 350 TQ. (Sure a 350 will make more power but it will use a little more fuel).

My opinion:
-305 CI
- 10 to 10.5 CR with alum heads (Corvette heads) or TFS 175cc heads, if you stay with cast iron use vortec heads, and limit the CR to 9.5 to 1.
-small cam like a ZZ-4
-1-5/8 headers os similar
-I strongly recommend FI like the factory TPI with a ported base and some large tube runners.
-A carb may work OK but it will be difficult to get good AFR (14.7) all the time, so mileage will suffer.


I had a 305 with the above combination and vortec heads and it made 257 RWHP and 317 RWTQ and was able to get 30 MPG on the highway. I have somce changed to a more aggressive 355 and it still get good mileage but not as good as a properly built 305 could obtain.

1989GTATransAm

iTrader: (3)

If I was going to build one I would use the new Dart SHP block as a base with the 4.125" bore. Then buy a light weight crank of the appropriate stroke. Buy the longest rod that would fit without getting into the rings. Then purchase the best heads I can buy. For 91 octane I would use a compression ratio of 11:1 with somewhere around a .035 quench. Next up I would talk to Mike Jones for a camshaft. Next up would be a custom oil pan with all the goodies for a high rpm operation. That would form the basis of the motor I would build.

Orr89RocZ

iTrader: (20)

Yep, i'd do it somewhat like this, but probably keep it on a 4" bore and just use a splayed 4bolt GM block. Rev it to 7K rpm, still keeping it hydraulic roller. Expensive valvetrain, using AFR heads so they are light weight but I'd go with titanium retainers, their 8019 springs shimmed up alittle, and a nice cam. Stealth ram or similar, keep compression as high as i can get, and let it eat.

It would be a fun small inch motor thats for sure, and still get decent mileage all tuned up for it

five7kid

iTrader: (14)

Hey, Marine, where are you???

35 replies over 8 days, the OP hasn't come back in.

This smells of the proverbial grenade tossed in the room and walking away.

F-Demon, if you're serious about this thread, PM me and I'll reopen it.