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305 v 350-What would you do? Edited

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by AussieK5, Sep 10, 2001.

  1. AussieK5

    AussieK5 1/2 ton status

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    I just bought a K20 (still have my K5) and am about to go on a parts swappin' bender. I have always had 350s and I don't know squat about 305s, except some people don't seem to like em. Now, if I was to use the 305 (because its fresh) what parts are interchangable/similar with 350s (fairly common around here), how do they rate for durability (towing etc), and do they respond as well as 350s to usual the power upgrades (absolutely no smog laws for my year model). What do you think?
    PS Do 305 heads have hardened valves seats standard?]

    Edited part
    I crunched the numbers on my K5 engine (with thanks to Dorians links) and found I actually have a 68-69 327 block. I'll be keeping it anyhow until its done a bit more time then drop in a 383. Thanks for the advice.

    &lt;P ID="edit"&gt;&lt;FONT class="small"&gt;&lt;EM&gt;Edited by AussieK5 on 09/13/01 06:50 PM.&lt;/EM&gt;&lt;/FONT&gt;&lt;/P&gt;<P ID="edit"><FONT class="small">Edited by AussieK5 on 09/13/01 06:54 PM.</FONT></P>
     
  2. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    Re: 305 v 350-What would you do?

    i dont know what the cubes would be but stroke the 305.
    Grant

    1974 Chevy Blazer Cheyanne. but it is on 33's now, with saggy old springs. i am in Yuma Arizona if ya got any parts for me.
     
  3. DesertDueler

    DesertDueler 1/2 ton status

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    Re: 305 v 350-What would you do?

    I would put the 305 heads on your 350. It will bump up the compression and give you more power. Other than that I would keep your 350. The 305s cost too much to make them have decent power.

    86 Jimmy 4"lift 35"MTRs Other cars 69Firebird w/525 hp,and 70GTO live in PHX,AZ<a target="_blank" href=http://www.geocities.com/modifierperformance>My vehicles</a>
     
  4. WOODYJ

    WOODYJ 1/2 ton status

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    Re: 305 v 350-What would you do?

    I know that the 305 heads are good for pulling torque out of an engine. The 305 heads, i'm sure are all fitted with hard seats. If you get a 350 and just put the 305 heads on it, you will have gobs more torque than the regular 350. You will sacrifice a few r's with the 305 heads, but the extra power and torque will much outweigh the difference. I run 305 heads on my 383 and you talk about a torque monster. Hope this helps.

    k5woody I Don't Understand The Jeep Thing Either!!!
     
  5. Neil

    Neil 1/2 ton status

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    Re: 305 v 350-What would you do?

    The 350 has naturally more torque. The 350 and 305 have the same carnk/stroke. The bore is much smaller on the 305. If you had a set of lightly ported 305 heads, that would be a good setup to go on a 350. Most 305s heads did not come with hardened exhaust valve seats, Only the H.O heads with 1.94/1.50 valves. Never use 882 or 624 casting 350 heads if you can help it due to overheating problems if you plan on hard running off road.

    Neil H. Alabama.. "It's a full size thang, Jeep owners don't understand!!" '78 K5 400ci 4x4 AT,AC,PW Cheyenne., '74 C10 4x2
     
  6. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Re: 305 v 350-What would you do?

    305 heads suck. It hurts me to put them on a 305. They don't flow worth a darn. I can't believe someone would put them on a 383. In fact, 305 heads are THE REASON everyone hates 305s so much. Quite possibly the most poorly designed head ever.

    Not to say power can't be made with a 305--mine is well beyond a stock 350's output.

    Tim
    '84 Chevy K10, lifted, loud, fast, and 3/4 ton axles
     
  7. CaptCrunch

    CaptCrunch 1/2 ton status

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    Re: 305 v 350-What would you do?

    cubes cubes cubes...

    I have to say 350 all the way and the 305 making more torque? I don't think so. 305 heads aren't very good, but can be made to flow much better w/ some port work. I'm not a big fan of the 305 swap because it will raise the compression through the roof. Prem gas would be needed and the power increase I think is overated. IMO all the carb heads of the mid 70's on engines pretty much suck canal water. I would try and find some older camel humps, go aftermarket alum heads, or even the SR torques cast heads will make much more power. Actually have had very good luck in the past w/ those on 350's for mild performance. Very reasonalbly priced too... the vortech head is also another awsome choice.

    -Mikey
    1987 Chevy K5 Blazer- 350 TBI
    <a target="_blank" href=http://coloradok5.com/gallery/captcrunch>http://coloradok5.com/gallery/captcrunch</a>
     
  8. AussieK5

    AussieK5 1/2 ton status

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    Re: 305 v 350-What would you do?

    I run straight propane and would not be adverse to raising the compression a bit (to 10:1), what cc are 305 heads? BTW the engine apparently came from a 88 corvette, could be BS.
     
  9. NorthernRedNeck

    NorthernRedNeck Registered Member

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    Re: 305 v 350-What would you do?

    I would definetely stick with the 350, and keep the 305 for an E-brake in the back! Seriously, it's not that the 305 wouldn't work, but if it's all 'bout spankin' ass, definetely use the extra cubes for the torque, hp and durability gains. The only time I would consider using the 305 heads is if you were not going to need rpm's, they will choke it- big time! I had a set on a 400-they were there when I bought it- and gotta say gobs of low rpm torque, but the motor was suffocating by 3500.

    '89 Jimmy SLE 350/700, sadly 2 close to stock, much lighter thanx to salted winter roads!
     
  10. Neil

    Neil 1/2 ton status

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    Re: 305 v 350-What would you do?

    305 heads usually do have small chambers, due to the small bore size of the 305. they are 76cc some and down to 60.5cc on some.Most have the 1.71 intk/1.50exhst valves also. you just have to see what ya got. Most of them also have the double heat riser passages and are prone to crack in heated conditions. So, cutting all the tech. crap, I would not use 305 heads if given an option. 305s are smog compliant V8 motors basically.

    Neil H. Alabama.. "It's a full size thang, Jeep owners don't understand!!" '78 K5 400ci 4x4 AT,AC,PW Cheyenne., '74 C10 4x2<P ID="edit"><FONT class="small">Edited by Neil on 09/11/01 06:05 AM.</FONT></P>
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: 305 v 350-What would you do?

    Toss the 305 and go 350. it is not worth the time, effort OR money to make a 305 perform, when the exact same mods on a 350 will net you more power in the first place, and reliably, since the engine doesn't have to work as hard. 305 heads are fine on a 305, but other than that.. : )

    I think PAW makes a kit for a 334, but again, I ask *why*!
    : )

    As to hardened seats, I'd be surprised if anything after about '71 DIDN'T have them, since the hardened seats were necessary after US Federal Law banned leaded gas for new vehicles.

    I was told however, (by a shop that delas a lot with Vortecs) that there are two types of Vortec heads, one set (bad) with hardened head castings in the valve seat area, and ones with actual seat "inserts" like most heads have. Thats just what I heard one time though, so I'm not sure as to the validity of the Vortec statement.

    Wouldn't put it past GM to try and save money like that.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  12. AussieK5

    AussieK5 1/2 ton status

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    Re: 305 v 350-What would you do?

    Thanks for the excellent advice guys, I'll be sticking with my 350 all the way.
    I have to say waking up to what I saw on the TV today seemed like a bad dream. I hope your government catches the elements responsible and makes a example of them and anybody they're associated with. Everbody I know really feels for what your going through, I hope the whole world joins in and these mindless atrocities are stamped out forever.
     
  13. Neil

    Neil 1/2 ton status

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    Re: 305 v 350-What would you do?

    Thanks. I believe we all can agree on that. I feel so bad for all those families in NY and DC and abroad.

    Neil H. Alabama.. "It's a full size thang, Jeep owners don't understand!!" '78 K5 400ci 4x4 AT,AC,PW Cheyenne., '74 C10 4x2
     
  14. MUDNUTT

    MUDNUTT 1/2 ton status

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    Re: 305 v 350-What would you do?

    <font color=blue>if youve got the 350 why even consider the 305. yes parts interchange like the distibutor, waterpump, brackets, carb, alt, starter etc, but as the saying goes "theres no replacment for displacment". use the 350 and keep the 305 for parts

    <font color=blue>DRIVE IT LIKE YOU STOLE IT [​IMG]
    <font color=red>PROUD TO BE AMERICAN [​IMG]














    [
     
  15. chevyracing

    chevyracing 1/2 ton status

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    Re: 305 v 350-What would you do?

    Why would anyone put a boat anchor (305) in a blazer???????

    Like to go sloppin' 'round in da mud in a rapid fashion....=)
     
  16. Emmettology 101

    Emmettology 101 3/4 ton status

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    Re: 305 v 350-What would you do?

    Definately go 350. The 305 was GM 's try at a fuel efficent engine and they definately failed!

    Mike

    <font color=green>"My K5 is purdyr than your sister!"</font color=green>

    <a target="_blank" href=http://www.geocities.com/emmettology101>www.geocities.com/emmettology101</a>
     
  17. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Re: 305 v 350-What would you do?

    I'll throw some more wood onto the fire.....

    It really doesn't sound as if too many people have actually listed a real legitimate reason why 305's should not be used. Sure, if you compare the same year truck 305 versus truck 350, then of course the 350 will make more power. But compare anywhere from a late 70's to mid-80's carburated 350 out of a truck to a '96 or newer Vortec 305....I'm sorry but the 305 in this case would blow away the 350 in both power and gas mileage. I'm also not sure about the power output, but I would also guess that even a earlier TBI 305 would outperform the older carbed truck 350. Let's not even talk about the TPI 305's in Camaro (sure, compared to the newer TPI 350's they were that impressive.....but a huge step over what was in the trucks).

    Basically what I'm saying is that you have to make sure you are comparing apples to apples. Sure, if I had an '86 305 and an '86 350 I would use the 350......if I had a fresh 305 and a 350 that needed a complete rebuild that might be another story. Spend the money that it would cost for a stock rebuild on the 350 and invest in performance parts for the 305 and I'm sure it would outperform the stock 350 by a noticable amount. Of course rebuilding the 350 and then adding the same performacne parts would yield more overall power, but at a higher price.
     
  18. dyeager535

    dyeager535 1 ton status Premium Member

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    Re: 305 v 350-What would you do?

    The legitimate reason is that a bigger motor will make more power with the same components. Do all the work you can to a 305 and a 350, and the 350 will always come out on top. With the exact same cam, heads, intake, exhaust, etc., the 350 will always be on top.

    And this from a guy with a 379CID motor as his name :)

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
    No anti-theft measures on your truck? No pity when its stolen
     
  19. jwduke

    jwduke 1/2 ton status

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    Re: 305 v 350-What would you do?

    Don't 305 heads have a problem of "cracking"???

    1 ton '87 Chevy SWB in the making!
     
  20. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Re: 305 v 350-What would you do?

    Great reply, you basically just reiterated what I said. If you would have taken the time to read the original post carefully, it stated that the 305 was "fresh" which goes along with my statement about spending the money it would cost on a rebuild for performance parts. I'm pretty sure it wouldn't take much to make a 305 exceed that awesome tire shredding output of 160 h.p. that the old carbed 350's made.

    I will not argue with you that with everything else equal, the bigger engine will put out more power (which I stated previously).......but just because it's a 350 c.i. does not mean it's always better than a 305 c.i. engine when it comes to power output.

    Also, what's with your last comment. Do you think that because I got a great deal on a K5 with a 6.2 in it, and that it works pretty good on the trails, that I don't have right to make a statement about other engines????
     

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