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vortec 350 heads on a 305

Discussion in 'The Garage' started by lunchbox, Jun 29, 2006.

  1. lunchbox

    lunchbox 1/2 ton status

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    I have a nother motor questioin (sorry). Ive oppted to stick to a 305 but i was wondering if i could run 350 vortec heads from a 1997 silverado on my 1987 305. I know i'd have to change the intake manifold. but would this work? thank you
     
  2. b454rat

    b454rat 1/2 ton status Premium Member

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    Don't see why it wouldn't, your changing the intake. Compression might change, but really depends on what CC the 305 heads are. Make sure you get the correct style rocker arms for Vortecs, they are self aligning, stock ones won't work.
     
  3. 96RAM85CHEVY

    96RAM85CHEVY Registered Member

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    keep in mind,most 305s have 58 cc chamber heads,and vortecs are 64 cc,so your going to lose compression.

    what kind of 305 is this? if its possibly a highoutput {which i doubt} it'll be 9.5 to 1 Compression stock,if its the low output with dished pistons,it'll be 8.5 or 8.7 to 1

    tossing vortecs on the highoutput motor would probably be tolerable,but it would be absurdly low on the lowoutput motor,although then it would be perfect for boost :D

    so to sersiously answer your question,yes they will bolt on and and it will run,but the performance gain by swapping to vortecs,might be lost in the drop in compression.
     
  4. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    I would be worried about the large valves hitting the small cylinder bore of a 305.
     
  5. 96RAM85CHEVY

    96RAM85CHEVY Registered Member

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    there 1.94 intake and 1.50 exhaust,they will clear a 305's bore,be careful on the valve lift with flat top pistons.
     
  6. lunchbox

    lunchbox 1/2 ton status

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    how could i increase compression? I forgot to add that i was going to do a federal mogual rebuilt kit when i do all of this.
     
  7. lunchbox

    lunchbox 1/2 ton status

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    i know ive asked this before but if i shouldnt do the vortedh heads what is a way i can make power out of the 305 when i rebuild it, im not looking for monster power gains im just hopeing to make it a little less sluggish. thanks for all your guy's help.
     
  8. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    I recomend a Lunati Voodoo Cam and an Action+ intake manifold. That should wake your 305 up a bit. Also run a higher compression by using dome pistons and those vortec heads. Should be a pretty good combo.
     
  9. 96RAM85CHEVY

    96RAM85CHEVY Registered Member

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    if i were you,order the kit for a factory high output motor,code L69

    factory rated 9.5 to 1 and 190 hp STOCK,very good starting point.

    these have 416 casting cyl heads,which are A VERY good casting,and respond beautifully to porting,im used to the fbody world{camaro-transams}so im not sure if your 87 305 will be roller,if not im sure its one peice rear,and at least has the spider holes drilled in the valley for the conversion to roller cam/lifters.

    if it has these,id suggest going roller cam,if your motors a lowoutput it will have dished 4 valve relief pistons,hwen you order your rebuild kit,order one for a HO motor,it will have the flat top pistons{which will minimize your CR loss if you do the vortec swap} personally,unless you have the heads already,i wouldnt bother,grab a set of 416 casting cyl heads and either port them yourself if you can,or have someone do it,you wont be dissatisfied.

    i ran a 305 HO with a comp XE 284 cam,weiand single plane intake,holley 650 double pumper,headers and exhaust in my transam when my 350 blew up,the 305 was a SCREAMER,and threw down 294 rwhp to boot.

    you could always do the vortec swap,and use a domed piston to keep your compression at 9.5 to 1,or possibly go larger in CR.its all up to you really and what YOU want the engine to do. gimme some more info and ill give you my thoughts and opinions.

    and also,if you are going to search for the 416 casting heads,just about every 82-86 305 powered camaro/z28/transam/firebird had them,just pop a valve cover and confirm it before you yank em off.

    i forgot to mention,do NOT run a cam with over .460 lift on stock vortec heads,you will regret it.

    comp beehive springs are about the easiest way to increase valve lift capabilitys in vortecs. the stock ones suck pretty bad,and you will float a valve if you go above and beyond the 5k rpm mark very much.

    heres a few pics of my personal stuff to give you an idea of vortec ports

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
    this intake works VERY well,and is cheap,had it for about 3 years now,zero problems,look on ebay for professional products cyclone? something like that.
    [​IMG]
    these pistons are what i used on the 305 i jsut tossed together for my transam after my good motor blew up,from speedpro there 2 valve relief skirt coated flat tops,keeps the compression the same if you swap to a 64 cc head from a 58 cc 305 based head.

    i never got a chance to dyno after i tossed the vortecs on the 305,but i gaurantee it was ALOT more then even the 416s put out.

    also,vortecs respond the most to exhaust porting,you will pickup a few ponies from the intake ports,by gasket matching,but nothing like you will if you base your time working the exhaust side of the ports.

    sorry for the huge rant,hopefully i helped someone with some good info,any more questions just ask,ill chime in my .02
     
  10. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    what is the difference between that intake and the power+ ???
    I have the power+ and got it new for $120.. sure better price than edelbrocks $245 price at summitracing:wink1:
     
  11. 96RAM85CHEVY

    96RAM85CHEVY Registered Member

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    yeah i got my fully polished cyclone,which ias basically a edelbrock RPM air gap,for 145 shipped to my door. they might be cheap,but htey make good products.

    the power plus is is also a professional products intake aint it root?
     
  12. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    The Action+ is a Weiand manifold and the Power+ is a profesional Products manifold. I don't really know much more about the two. But what I do know is that my Action+ got me what feels like 20hp more. I'd recomend that manifold to anyone.

    96RAM85CHEVY: My 305 is an HO from a 83 Firebird that originally had the X-Fire injection so the code is LU5. The PO swapped this motor into my truck and put a carb on it. I have those 416 casting heads and I thought they were crap? But I guess they aren't that bad if ported?

    I know my 305 has more power than most people expect. I have a 600cfm Holley, Action+ intake, 2 1/4in true duel exhaust, Pertonix distributor.

    My next upgade is going to be Doug Thorley headers. If $$ allows I want to send out the heads and get a valve job done and have them ported and polished. Along with the heads I would do a cam most likely a Lunati Voodoo cam.

    Quick question, what would be the stock cam specs for my 305? Also can the stock heads accept 1.6 roller rockers or do they need to be machined?
     
  13. 96RAM85CHEVY

    96RAM85CHEVY Registered Member

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    since all LU5 cfi motors were automatics,your cam is

    .403 lift intake,.415 exhaust ,202* dur intake,206* dur exhaust,on a 114.5 lobe seperation.

    your LU5 is CONSIDERED the medium output motor,but the longblock is the same,the fuel delivery is what constricted the output,very piss poor design.

    so you have a good starting base, 9.5 to 1 shortblock with flat top pistons,rather large {for 80s specs} camshaft,and a good set of heads.

    if I were you,i wouldnt mess with the vortecs,unless you plan on building something bigger in the future.

    either yourself,or someone you know is good at porting,hog those 416's out,slap 1.94 intake valves in them,good set of 1.6 roller rockers,good set of valve springs,i would stay away from a cam with excessive duration,as it will take away the torque somewhat,comp XE 4X4 270ish would be perfect.

    this is no bull****,on a basic BASIC rebuild of the 84 L69 i just tossed together for my 84 transam,it would spin up 6500+ rpm all day long,and flat hauled serious ass for a 305,alot of people dont like them,hell i dont like them,but they serve t here purpose sometimes. there tough little engines,properly built they will give a 350 a run for its money.

    the other thing DONT get to wild on the exhaust for a 305,they do need a bit of backpressure,keeps the scavaging effect up,youll lose alot of low end with a large set of headers,i gaurantee it.

    the other thing is,if you already have headers on your motor,with a carb you should be WELL above the 175 hp your lu5 was rated stock.

    put it this way,and i have this on dyno video to prove.

    with my 305,basic rebuilt longblock,ported heads,comp XE cam,i forget the duration,but it was i beleive 270 or 280ish something{its been awhile}
    with the bone stock log manifolds and STOCK exhaust system with the ****ty cat,and 2 muffler setup they had in 82-84,i put down 200.4 rwhp and 260 something torque. that was with 2 inch exhaust, SINGLE exhaust

    after my header swap,and catback swap with no cats,and a holley carb it put down 290 something at the rear wheel,when i put on my hooker 1 3/4 headers on,i lost 15 hp.


    and yah,the stock heads can take 1.6 rockers with nothing needed,provided you stay within the lift limits of the stock springs,or you might bind them.

    these are some older vids of jsut crap i tossed together for some dyno runs in my car club. ive never uploaded a video onto photobucket,so if these dont work,let me know lol

    first ones the 305 i tossed into one of my t/a's jsut to make it to the dyno,spun it 6600 rpm on that run,gimme some time and i can get you the actual a/f ratio graph,and the hp and tq curves.

    [​IMG]

    this video is the transam i currently own,stock L69 with nothing but a weiand intake,and holley doubler pumper,71k original miles. its currently my pro touring LS1 twin turbo car :D

    [​IMG]
     
  14. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    The 2nd video is impressive that you can do that with a near stock L69 :bow:

    You say you lost 15hp with Hooker Headers, well the Doug Thorley headers are designed for stock and mild engines and are a tri-y design. I don't think i will have any problems with scavenging.

    Oh yeah I also removed every piece of restrictive emissions equiptment including the cat. That in itself is a good almount of power gained right there.


    What do you think of this cam: http://store.summitracing.com/partdetail.asp?part=LUN%2D60103&N=400421+314473+4294887485+4294908216+4294840138+4294925044+115&autoview=sku
     
  15. beater_k20

    beater_k20 Banned

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    dont waste your money on making a 305 work with Vortecs. build the 350. it'll be cheaper, easier to find parts for, and will make more power to boot.
    the combustion chambers on Vortec heads are designed to be most efficient with flat top pistons. going to a domed piston would actually decrease their efficiency, and would adversely effect performance.
     
  16. lunchbox

    lunchbox 1/2 ton status

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    i dont really know what im doing yet, i want to find a core so that i can still drive the truck while im making an engine.And i want to learn more about how to build an engine and do a swap first.
     
  17. beater_k20

    beater_k20 Banned

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    while its a nice car, and i'll bet it runs real good... i can powerbrake a 4 cylinder S10 just the same.

    my '86 TA with a 250hp 350 would light the tires on command, stopped, rolling, whatever. would not hook up until you let off. 2.73 gears are great for that. hell my '86 C10 would do the same thing with a stock 305 and 2.73s. the car ran 13.50s all day long, had i put a set of gears in , and a set of sticky tires it i would've been in the 12s easy.

    just out of curiousity, what gears are you running in that car?
     
  18. 96RAM85CHEVY

    96RAM85CHEVY Registered Member

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    i would have to disagree,about putting the money into a 305. first off,he might not have a block,or the money to spend on fully machining one.

    granted 350 would be cheaper,IF you have the block already,and get good deals on machine work. i wont dispute it would make more power,everything being equal.

    and you would also be correct about them being designed for flat top pistons.


    heres my final recomendation unless this thread continues,if you already have either vortec heads,or a vortec intake,toss them on the 305 and be done with it,run it until funds permit a full 350 buildup,then swap the topend onto the 350,you cant lose with that situation if your budget limited.

    if you have neither the heads,nor the intake,id just focus on your 416 heads and basic longblock for now,if you cant afford to go with a 350,blah blah,everyone will tell you toss a 350 in,sometimes its just not feasable,nor economical enough to do so.
     
  19. 96RAM85CHEVY

    96RAM85CHEVY Registered Member

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    obviously your 86 t/a isnt stock.

    i didnt post that video to try to convert people to a 305. just posted it for the hell of it lol.

    and in that video i was running the stock 3.23 posi rear drum 10 bolt,it currently has a t56 tranny,and 4.10 geared 12 bolt disc rear.

    and bythewayi didnt powerbrake it,1500 rpm launch and feathered it from there.i did accidently trip the linelock though,but i clicked it off right after i hit it.

    if your saying your 86 t/a ran 13.50s all day with 250 HP,im gonna call BS. even 250 RWHP, let alone 250 crank hp,wont push a thirdgen into the 13.5 range,unless you had NO interior,and serious weight reduction.

    what induction are/were you running? tpi?carb?tbi?

    again,im not trying to start ****,but 250 hp,gears,and some slicks simply will NOT push a 3rd gen into the 12s,even a 12.99,ive had probably 10 of these vehicles,still own 2 of them,and ive had countless engine combos/tranny combos/rearend combos,and i gaurantee it takes ALOT more then that to run a 12.9 or better. in reality,there a horrible car to drag,there insanely heavy being the biggest downfall. the suspension setup is top notch,even stock.
     
  20. lunchbox

    lunchbox 1/2 ton status

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    i just dont have the money to do a 350 swap
     

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