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Technical MOTOR, Chevy 305...Mighty Mouse in Underdog's costume!!

Discussion in 'The Hokey Ass Message Board' started by Fat Hack, Sep 19, 2003.

  1. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    I'm kinda surprised at how most gearheads view the 305 Chevy engine! It's been around since 1976, and was essentially the base V8 in many GM models up into the 90s, so there are plenty of them around, and available on the cheap!

    The 305 is really just a small bore 350, with the 3.48" stroke common to both of them. This gave GM an engine that would save them a little bit on their Corporate Average Fuel Economy ratings, yet still deliver enough torque to get their vehicles moving! The 305 really strikes an ideal balance between performance and economy.

    From a performance standpoint, the 305 rates very well. It's very responsive to common-sense engine modifications and as I stated in another post, and it makes a great street supercharger motor if boost levels are kept within reason! By fate or by design, I've owned, modified and tuned many 305 Chevys, and here are some of the things I observed.

    Case 1: The Malibu:

    A stock intake works okay, but the 305 really loves the basic Edelbrock Performer. The dual plane design maximizes the engine's efficiency at rpm levels below 5500, and actually INCREASES fuel economy by a considerable margin over a stock cast iron intake and two barrel carb when equipped with a 600cfm Holley. I had the chance to observe and note the effects of manifold swaps on my old "dyno mule" Malibu, and here is what I found.

    Baseline: Stock 1977 305 2v................17.30s and 12mpg
    Performer intake w/ Holley 600 carb........16.50s and 17mpg
    Recurved stock HEI and added Supercoil.....16.30s and 17mpg
    Headers w/ turbo mufflers dumped at axle...15.70s and 20mpg
    Mufflers removed, 3ft tubes on headers.....15.50s and 21mpg
    TRW #274 cam, new chain, flex fan..........15.00s and 23mpg
    Full duals from headers Dynomax mufflers...15.10a and 23mpg
    K$N stub stack, softer secondary spring....14.90s and 22mpg
    Magnum roller tip rockers, 1.52 ratio......14.80s and 24mpg
    Magnum 1.6 rockers on exhaust side.........14.80s and 25mpg

    <img src=>

    At that point, I was VERY satisfied with the way the car performed at the track and drove on the street. You really had to DRIVE the car to appreciate 60mph on the freeway, the weight of your shoe was enough throttle to keep the car humming along! The combination was so efficient, it was scary! All this in a hulking four door with stock tranny and rear gears...and 120,000 miles on the clock to boot! My buddy drove the car and was impressed to no end by it's INSTANT throttle response and the way it just "jumped" when you hit the gas!

    The logic behind slipping the 1.6 ratio rockers on the exhaust side only was to try and recover what little I had lost by having a full set of duals run on the car. (I drove it on the street for MONTHS with just the three foot extensions on the header collectors!). A friend worked at a speed shop and gave me a set of like-new Magnum roller-tip rockers in 1.6:1 after I bought the 1.52 ones from him.

    Case 2: The Pontiac:

    The engine was removed from that 1977 Malibu and dropped into a 1970 Pontiac LeMans Sport to replace a screwed up 350 Chevy that was in the car when I bought it. Curiously, the lighter Pontiac was slower than the Malibu, yet it got the same mileage figures! All going to show you just how vital the ENTIRE combination is to gaining maximum results from your vehicle! The Malibu had a 2.73 axle, and the Pontiac had a 3.31 rearend. In theory, the Pontiac shoulda been faster, but never made it!

    <img src=>

    Baseline: Malibu engine into Pontiac.....17.80s and 19mpg
    Fixed shift cable, fuel line, new plugs..15.30s and 21mpg
    Torker 2 intake, carb re-tune............15.20s and 21mpg
    750cfm carb, electric fan................15.00s and 18mpg

    That's where I stopped messing with that car. The Torker 2 intake moved the powerband up and killed some of the wheelspin off the line. 60 foot times were quicker, but the ET didn't change much. On the street, the Performer intake "felt" better...and had snappier throttle response and tire-burning ability! In hindsight, I shoulda left the Performer on and softened the rear springs and bought better tires...the car had stiff rear shocks and springs with garabage Formula One Super Stocks...the Malibu would squat and go...the Pontiac hazed the one tire off the line! Oh well...lesson learned!

    I also tried out a Weiand Team G intake on the Pontiac with an 800cfm double pumper, but never ran it at the track with that set-up. It had a healthier top end charge, and felt about the same as with the Torker 2 off the line. It might have cracked the 14.90 barrier, but we'll never know!

    Later on, a Comp Cams 270H Magnum cam was installed and the rear springs were replaced. I added Olds rally wheels and good radials and a cool can for the fuel. This didn't feel any different around town but seat-of-the-pants feel can be deceiving. It never made it to the track in this configuration either.

    Case 3: 1977 Caprice Classic:

    This one almost mirrored the Malibu Project, with the one odd addition of ANOTHER 200,000 miles! That's right...I got the car with a bona fide 309,000 miles on it from the second owner. The original owner was an old mechanic with family in Seattle who racked up all those miles, yet the engine was never rebuilt! By the time I got it, it smoked a wee bit, but still ran pretty good! I figured why not have some fun with this one, too??!!

    Baseline: Stock 305 2v.....................17.50s and 14mpg
    Edelbrock Performer RPM intake/600 Holley..16.40s and 17mpg
    TRW #274 cam, new chain....................15.50s and 17mpg
    Headers, turbo mufflers dumped at axle.....15.10s and 19mpg
    HEI re-curve, Supercoil, Stub Stack, fan...15.00s and 19mpg

    This car was just a daily driver, and it ate up spark plugs due to oil consumption, but even with all those miles under it's belt, the motor ran flawlessly and the car continued to cruise the neighborhood like a big black crop-duster for a few years after I sold it! My buddy at the parts joint sold me plugs for 50 cents each, so i always had an extra set or two in the glovebox. I'd drive to the track, pop in fresh spark plugs, and run it all night!

    Okay, so high 14s and low 15s in 70s era mullet-monsters isn't gonna set the world on fire, but these were heavy stockers with stock torque converters, trannys and rear gears. I seriously dobt that a 350 would have done much, if any better...and I doubt that the 350 would have delivered the fuel economy numbers indicated.

    (All MPG figures were observed highway mileage recorded while driving the car to and from Milan Dragway where all testing was done on test-n-tune nights. These cars also went on long trips where the same numbers were observed.)

    So...if you were to score a cheap or free 305 from somewhere, and build it as I've outlined here...what do you suppose you'd see in...say, a Model A coupe with an 2500rpm converter, shift kit, 3.90 gears and slicks? We're talking about a vastly lighter vehicle here with better gearing and superior traction. My "test mules" were just warmed over transportation specials in full (heavy!) street trim! Imagine a car that weighed almost half as much with drag-oriented gearing!

    All this post is really designed to do is to show you that the ill-respected 305 is a very capable performer that is far too often passed over by rodders. Don't let the smaller bore fool you, they can run with their 350 siblings and do it for less money while returning better fuel mileage!

    Who gives a shit about fuel economy in a hot rod? The guy who has to watch his budget, yet still wants to have a fun to drive car that he can build dirt cheap! A 305 powered rod will be mild enough for daily driving, reliable enough to drive to events across a few states, and fast enough to have fun doing it!

    By contrast, my first car was a 1969 Chevelle with a 350. Stock engine, trans and gears with a 302 Z28 intake, headers, Holley 780cfm carb and single point distributor with Accel points. It ran 15.20s and got 16mpg. This car was similar in size and weight to the 1970 Poncho, and you see the numbers! They look close enough to conclude that a 305 runs about as good as a 350, but gets better mileage...just what GM was hoping for when they introduced the down-sized mouse motor!

    So, find you a 305 that nobody else wants, hit it with the bolt on parts I mentioned, stick a low buck Saginaw four speed behind it, and slip that combo into your hot rod project! You'll get alot of bang for very few bucks! Ain't that what home-brewed hot rodding is all about?

    Let the goldchainers pay alot more for a 350 crate engine and a Muncie trans...they won't go much (if any) faster, and they can brag about how much more money they spent than you did!!

    [​IMG] [​IMG]'s YOUR money, I'm just trying to help you save some of it!

    [​IMG] [​IMG]

  2. Jimv
    Joined: Dec 5, 2001
    Posts: 2,928


    I'm running a 305 in my T bucket.Its got stock heads &amp; pistons with a comp 280H cam &amp; lifters,1.6 alumn roller rockers (its alittle over cammed),I'm running a Offy 3 duece setup with all primary carbs, that don't really give me any trouble.I also just have blockhugger headers with a 2.80 ford 8 inch.
    I have to admit the car is really snappy, doesn't ahve much low end for about 50 ft.But after that it come on really strong &amp; holds it thru the gears(TH350)
    great motors I won't trade it for the world.Next yr I'm going to put in a slightly milder cam,2600 stall&amp; do some head work.
    One thing though is the mileage isn't that great but I do have my foot in it alot.
  3. McGrath
    Joined: Apr 15, 2002
    Posts: 1,415


    I am surprised at the lack of interest in 305's too, especially in the Street and Rat Rodding groups. You can easily get respectable power with good fuel economy, just the thing for a "Driver". I think one would be great in a T Bucket.

    And Jimv, you have the same problem I have...too much Cam. But I like it that way. I'm running a 292-.505 in my 355 and through the 3" exhaust it sounds like one bad assed, slobberin sum' bitch. You can still hear the cam at 2,000 rpm,which is second gear cruising speed in town.

    I wouldn't win many races though because its in a 4,000lb '65 F100. Runs like a 2 stroke, even with the 2500 stall. No bottom end, but once you get into the powerband shit starts happenin'.

    Anybody with a decent Holeshot would blow my doors off though, so I don't bother with Street racing. Just Cruise around sounding bad Assed.....
  4. Great post, Hack. Thanks for the info. I'm back to running the 305 in my Stude. I built a 350, only to loose two cams in a row this spring. I put valve seals in the 160K 305 and stuck her back in. Doubbled my gas milage, and the little motor goes like hell. I get the same shit, everyone tells me not to wast the time and money on rebuilding the 305. Fuck um, when it really needs it (another 50 K or so) I'll build it. The 350 can go in my 33. Come to think of it, I just happen to have a saginaw 4 speed sittin on the shelf. Maybe I can get a little respect after all.
    Register now to get rid of these ads!

  5. my ol work truck has been on runs to haul projects as far away as Torronto Ontario and gets 10 mpg loaded and about 15 empty[lost three mpg when I de computered it with a quadrajet and hei ign.]but I hate not being able to trouble shoot with just my wits and what tools are in the truck. I hauled this two ton cab over down the hiway at 70 miles per hour.....shoulda seen the looks!!!! [​IMG]
  6. One big drawback of the small bore 305 is valve shrouding. There's just not much room in a 3 and 7/8ths hole to put valves without getting really close to the cylinder walls. That's why supercharging is such a great idea with a 305/307 chevy. I don't know why turbocharging isn't more widely used with these little engines. A steel big journal 327 crank and some low compression forged pistons would be steps in the right direction to make a little 307/305 a holy terror! Throw on the factory port injection with some hi-flow injectors and the GNX guys wouldn't know what hit 'em.
  7. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    Right you are, Rocky! Big valve heads are a no-go on 305 engines! One trick is to install the larger 1.60 exhaust valve, but leave the 1.94 intake valve in tact. I've seen guys notch the cylinder edges for this, too...but I don't feel right about that!

    The good news is that the small valve heads work really well on a 305 to begin with! They like velocity more than volume, which is another reason that they respond so well to mild supercharging. A simple B&amp;M Forced Induction or a 4-71 blower make real monsters out of 305 engines!

    As far as head mods, most guys I've taked with who've modified 305s say to do little more than gasket match the ports in the intake to those in the head and run a good 3-angle valve job. Excessive porting or bowl work isn't neccessary, and small tube headers work just fine.

  8. panheadpete
    Joined: Jan 27, 2002
    Posts: 55


  9. Chuck Fish
    Joined: Oct 29, 2001
    Posts: 112

    Chuck Fish

    My work truck is a 96 extended cab pickup with a 305 in it.It has 123,000 on the clock.It had 98,000 on it when I got it. I'm the 3rd. owner [​IMG].I use it to haul everything from groceries to fire wood. It does a very respectable job at whatever I ask of it. I'm getting ready to put a cold air intake system on it with a hiperf.mass air sensor,and dusl exh. Ithink that will really wake it up without hurting the low end performance. I may also go to a small tube header system. I'm getting 15mpg around town,but only 17 to 18 mpg on the hywy,cruising at 65 or 70 mph.,with a 3:73 rear.

    Do you 305 guru's think I'm headed in the right direction.I don't want to go hawg wild with it,just get a little more grunt,when I tow my car trailer,and such.

    Chuck Fish
  10. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    Sounds like a plan, Chuck.

    There are complete performance exhaust systems available for your truck along with headers, all designed to work in harmony. In my experience, the 305s like a free flowing exhaust as much as any othe rengine does!

    Edelbrock also makes a Performer intake manifold for throttle body injected small block Chevys. Blueprinted throttle bodies are also available. Those mods plus a cold air kit and a K&amp;N filtercharger will wake your truck up a little more!

    You can also bump up to a slightly hotter cam without affecting the ECM function, but the basic bolt-ons mentioned above should get you where you want to be with your hauler!

    Joined: Jun 2, 2002
    Posts: 9,639

    Classified's Moderator

    <font color="green">GOOD POST HACK!!!!

    I copied the other one pertaining to this also.

    Mama's 59 came to her with a 305 with tired heads and a tired cam. I put a stock aluminum Iroc intake and Edelbrock 600 on it and redid the rest of the fuel system.

    it has a 350 and we think 4:11 gears in it.

    I took it down the track at the H.A.M.B. drags and it pulled 17.00. I was surprised it did that well.

    I think I will put that cam you mentioned in and maybe a set of Vortec heads.

    have to do the math and see if that would be worth it.

    If I go the Vortecs I will probably get a cam, that will max out the heads.

    the one you mention is almost there.

    RASHY </font>
  12. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    About the TRW #274 cam;

    I don't know if that's STILL the valid part number, but it used to be, and I don't see why they'd change it. It's a stock replacement cam for 350 engines sold through better parts stores. There is a different part number for 305 and smaller engines, but the 274 cam is a FAR better bet!

    Idle quality is smooth as silk, and low end performance is excellent with all other components of the puzzle in tact! It makes for a very efficient engine, which translates to better mileage AND more torque...good things for a street motor!

    I don't recall the specs offhand, but they can be found in a TRW catalog. They are really quite mild, as this IS just a stock 350/400 cam. I worked at a parts joint that sold these things, and I always gave them to guys who came in wanting to put a new cam and lifters in their 305 or 262. They were impressed at how well their cars ran afterwards, and I never sold even ONE 305 cam to anyone!

    The Magnum Roller Tip rocker arms from Competition Cams actually feature a 1.52:1 ratio (vs stock 1.50:1) so they can help you out by giving you a wee bit more cam, and by reducing friction as well! In addition, they are far more consistent than stock rockers, which can varry from about 1.48:1 to 1.51:1 on the same engine! Using 1.6:1 Magnum Roller Tips adds a little more lift and resulting duration, but also increases side load on the valve stems and CAN potentially increase valve guide wear. I only ran 1.6 rockers on the exhaust side to compensate for running a full, closed exhaust system, and it worked fine with no obvious wear issues after LOTS of miles on an engine that ALREADY had over 120,000 miles on it before I began tinkering with it!

    Good pushrods are a nice idea, too. I just used TRW replacements, and one of their timing sets for older 350 engines as well.

  13. 286merc
    Joined: Mar 3, 2001
    Posts: 1,795

    from Pelham, NH

    So without getting inside what would you suggest for trailer hauling 85-8 Caprice wagons? The ones we have all have a QJ.

    As I said in the other thread we can cruise fine at 60-65 with a 5K trailer. The only real issue is going up hills where its down to the floor and losing speed.

    Would a RV manifold be better than the Performer for us? How about ignition and exhaust mods; any benefit at low rpm?

    And what about heads, just curious as Ive no plans on pulling them for now. Is there any head difference over the years? I have a complete 60K original '79 2v out in the trailer just in case.

    All our wagons have 180-250K on them and Im just amazed at how well they run; we put 500-1000 miles a week on a few. They are almost free out here, Havent paid over $500 for any and the 89 Buick mentioned below was $200; everything works and even blows cold air.

    Oh, one smokes a bit but after throwing in some NGK platinums there hasnt been a trace of fouling.

    Now if ONLY there was something that would wake up a 307 Olds! The 89 Buick Estate wagon can sure use some help; even with no trailer and only 5-600 lbs in the back its a dog.
  14. Nads
    Joined: Mar 5, 2001
    Posts: 11,495

    from Hypocrisy

    Damn good post bub. Who knew?
    My pal's got a '57 283 with 305 heads. Someone said this was the hot set up, can you shed some light on this.
  15. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    The Performer intake with a small four barrel is a DYNAMITE choice for a towing/station wagon application! I used 600cfm square-bore Holley carbs with vacuum secondaries and electric chokes right out of the box. Never even changed jets or power valves...they seemed to be right on the money as they came from Holley. The only things I ever changed were the secondary springs (going one lighter for better drag strip times), and I fooled with the accelerator pump cams a little, but all that did was affect the gas really made no difference in the ET).

    The Holley 600 on the Performer intake with the TRW 274 cam makes for an engine that delivers INSTANT throttle response and strong low end! Just the ticket for a heavy vehicle or tow car!

    The stock cast iron four barrel intake with a stock older (pre feedback) Q-jet is also a stellar performer on a mild 305. I've not had any luck with the stock 2v carbs, though. They tend to leak, get lousy mileage and just don't run worth a shit! Rebuilds and tuning didn't help, so I gave up messing with them at all and concentrated on the four barrel set-ups. When driving a car equipped with a vacuum secondaries 4v, you are using the small primaries most of the time. This contributes to great off-idle performance and great mileage figures. The dumpy GM two barrel is a gas waster and a power robber in my experience, although some of the roundy-round racers really modify the shit out of 'em for impressive power with NO thought towards fuel economy!

    I can see putting 305 heads on a 283. They probably flow better than the average standard 293 head did, and they will have hardened seats for use with unleaded fuel. It sounds like a smart move! The combustion chambers might be larger on the 305 heads, lowering compression somewhat, but the difference is probably slight, and the gains from better flow and hardened seats likely outweigh the minimal (if any) loss in compression.

  16. I just have to put in my 2 cents here...back in high school a buddy of mine had a '71 Malibu 307 plain jane. Stock right down to the gold paint and hub caps. He started messing with the car and did the usual intake/cam/headers/duals thing. That car HAULED! I was so amazed the first time he took me for a ride, that I have forever had a new found respect for that little motor. I had a 396 '71 Chevelle SS at the time, and I was more impressed with his car! He beat on that car relentlessly for about 2 years, with lots of weekend street racing and such, and that motor held up to the abuse. Didn't even have hardened valve seats... [​IMG]
  17. HotRodMicky
    Joined: Oct 14, 2001
    Posts: 1,637


    Has anyone tried an Edelbrock Perfomer Camshaft??
    I have a 305 with an Edelbrock Perfomer Intake an 600cfm
    Carb an looking for Cam "update". I have a 4-speed and
    3.00 Gears.
  18. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    I remember looking at the specs for the Performer cams years ago and thinking that it'd be a decent cam for a street 305. You're running a four speed and a four barrel on a Performer intake now, so I think it'd work okay. Just don't go too crazy with cam selection and those 3.00 gears, or you'll kill off some of your low end pull and end up going slower in the quarter mile!
  19. Rocknrod
    Joined: Jan 2, 2003
    Posts: 649

    from NC, USA

    I'm building a 350 currently...

    This threads a-helpin me quite a bit...

    Whats the thought on the Vortec heads on them? I've heard they alone can increase the gasmilage by quite a bit! [​IMG]
  20. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    Can't help ya there...never used Vortec heads on my Chevs!

    (Never had any that NEW! [​IMG])

    They're popular enough, so they must be pretty good...try 'em out and tell us how they work!

  21. tomslik
    Joined: Mar 3, 2001
    Posts: 2,171


    fathack, the 305's had 58cc chambers, think they'd be a good choice on a 283(watch the gas quality!)
    better flow than powerpacks?

    BTW, guys,305's had a problem with flat cams, worse than the "supposed"prob with 307's

    i'll STILL stand by my statement that it's MORE cost effective to build a 350.
    price stuff out before you build!
  22. Anyone have any comments about so-called RV type cams for 305's? Are they any good, do they give good low end and mid range response? Will they help gas mileage?
  23. tommy
    Joined: Mar 3, 2001
    Posts: 14,761


    Here's mine. Paid 450 for a 45k wrecked ugly Monte Carlo. I got 500$ for parts so I came out with a positive cash flow. It'll move my Deuce p/u down the road as fast as I want to go. My highly technical cam selection was #2 on the Summit list. [​IMG] I tried throwing a dart at the book but I couldn't even hit the book. [​IMG]
  24. I'm gonna run a 305 in my PU, and the TH200R4 that came attached to it (overdrive), the combo came out of a hearse but I'm using an 8 inch with 3.50 gears, hope I get decent mileage out of it as gas is worth it's weigth in liquer here these days. I'm gonna use 2 97's on it and a mechanical advance dual point Mallory, we'll see what gives.
  25. Fat Hack
    Joined: Nov 30, 2002
    Posts: 7,716

    Fat Hack
    from Detroit

    RV cams are designed to produce low rpm torque and smooth driveability. That's essentially what the TRW #274 cam is in a 305...a strong stump-puller!

    I used a Melling RV grind in a 460 Ford for my Torino project to make a good thing even better! Sold the car to a buddy, and he dropped the motor into a truck for a tow vehicle!

  26. motor mikey
    Joined: Jul 17, 2002
    Posts: 261

    motor mikey
    from hanover pa

    Hey rocknrod, Vortec heads are a very good choice on a 350. If you check into a 330 horse crate motor from GM, that is what they come with. The engine is a very tame one at that. Small cam and barely 9-1 compression. Basically use a set of flat top pistons and a cam with around .450 lift, 230 duration and you will have a screamer.
  27. colorado51
    Joined: Feb 24, 2003
    Posts: 1,578


    Hi guys,

    Here are some loose numbers that I ran through my dyno software. A stock 305 with a 2bbl carb, and say, 8.0-1 compression puts out 157HP at 3500rpm, and 258 ft lbs at 2500 rpm.

    Ok, if you add bolt-ons (dual plane manifold, a 750 cfm 4bbl, and a set of headers), you get 187HP at 4000rpm, 290 ft lbs at 2500rpm.

    Now, if you add a hot hydraulic cam and a good set of heads (porting and large valves) to the above bolt-ons, you get 298HP at 5500rpm, 310 ft lbs at 4500rpm.

    Lastly, if you bump the compression to 9.5-1 to the above, you get 325HP at 6000rpm, 332 ft lbs at 4500rpm.

    Again, the numbers are fairly loose, but it gives you something to think about!
  28. olds vroom
    Joined: Jan 29, 2010
    Posts: 644

    olds vroom

    I found a good 305 for cheap but it's a throttle body , can I switch the intake to put a carb on it? Or is the bolt pattern different?

    They told me it couldn't be done... So I'll try it.

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