305 vortec heads on a 350? Will they work? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 05-12-2004, 11:44 AM
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305 vortec heads on a 350? Will they work?

I just aquired a set of 305 vortec heads that are in good condition, for free, and am wonder if they will work on a mid '70s 350. The heads are off of a '95 half ton 4x4. They were replaced with GM performance heads. If they won't fit, I am just planning on using them to learn how to port and polish.

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Old 05-12-2004, 01:29 PM
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yes they`ll work, but you`ll still have to buy a intake and the other mods needed to use them, however, for performance I wouldn`t use them, they don`t come close to 350 vortec heads.
I wouldn`t use them as practice heads either, I`d stick them on ebay, since some looking to hop up there 305 are after them. These heads don`t have the bigger 170cc runners as the 350 vortecs do, they also have smaller combustion chambers and valves. It would shoot the compression ratio up on a 350, it would have explosive take off power, but would fall on it`s face at 4000 rpms.
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Old 05-12-2004, 05:39 PM
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Are you certain they are vortecs? I dont think true vortecs were made untill 96! for some reason alot of people seem to call the 87 to 95 yr heads all vortecs. They are all F.I. and they have a distinctive bolt pattern from the old heads but they are only vortec if they have only 4 intake bolt holes on each head instead of 6.
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Old 05-12-2004, 11:32 PM
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I was unaware of this. I'll have to check them out. I assumed they were vortec because of the way the intake was bolted on.


Yes, they do only have four intake bolt holes.
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Old 05-13-2004, 01:22 AM
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Then you have got the Vortec heads. If this motor isn't going to be raced then these heads will provide a fun, fast accelerating stoplight to stoplight ride. With a RV type mild cam they would be fine. Just make sure you have stock type or dished pistons tho!

By the way I like peoples slogans or phrases under their names!

I AM smiling, 70 bird!
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Old 05-20-2004, 09:11 AM
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What about on a 400 block? When I got it insured they said the vehicle code said this vin # came with a 400 ci. I've beed told these engines are junk and they have overheating problems. The person I bought it from said it has a 350 that was rebuilt about 15,000 miles ago. I need to check the #s. It is an original engine from the 70's (judging by the orange color with matching manifold and dirtyness even after a bath).

So my next question is, will the vortec heads work on a 400 ci block?
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Old 05-20-2004, 09:15 AM
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Yes, drill the steam holes. Don't use the 305 heads on a 400, it will fall on its face very early in your power band.

K
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Old 05-20-2004, 09:33 AM
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Don't use 305 heads on a 350 or 400, especially with a torque cam. You will have to run a really retarded (pun intended) timing curve to keep it from detonating. A 350 or 400 will never run up to it's potential with 305 heads on it. The only exception to these guidelines is if one uses pistons designed for using the 305 heads on a 350. Sealed Power and Silvolite have pistons for this use.
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Old 05-23-2004, 08:25 PM
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350-305

before we say we can't run 305 hd on a 350 let's do a little math,

A 305 hd @ 58cc on a 350 with factory dished pistons @ -15cc has a comp ratio of 9.65:1

58+15=73 Not much less than your tipacal 76cc smogger but enough to make a differance.

If the alternative is ruunnig 76cc somg heads (which are crap)
i'd bolt on the 305 head, it has to be a dished piston short block though.
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Old 05-24-2004, 02:33 AM
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I have a Q? Don't all GM iron Vortec heads have 64cc combustion chambers regardless of whether they're from a 305 or a 350? MSTom are u there?
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Old 05-24-2004, 03:50 AM
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I asked before about using 305 heads on a 350 and was told the same about it falling on it's face at 4000. well I have a 350 with flat top pistons comp 262H cam torker intake edl 600 carb, 3:73 rear th350 trans, 2200 stall in 81 Monte. (heads 64cc 202/1.6 valves valve area deshrouded, ported etc.) the launch is super and the thing pulls to 5200, no problem, never really pushed it more than that.

I like it

Ricers don't
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Old 05-25-2004, 12:31 AM
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what about on a 283? i was mentioning this combo to a dude at a local speed shop trying to get som info on what cam would be good for my motor, he said they wouldnt work on anything else then a 305 because the cooling flow is different or somthing like that. is this just BS?

i wanted to use them because i thought the smaller valves would be good for building a strong street 283, and the flow wouldnt be an issue, as its a smaller motor and wont see to high of RPMS, and they are super cheap from local head shops.
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Old 05-25-2004, 01:18 AM
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305 hed 283 sb

YGOC
The 283 that i had i ran comp cams 260h, She had a nice little lope to er a idle. I was runin the power pack heads back then, which has the 1,72 v/v.
I would think the bigger v/v 305 head would be supiorioer, Also i think the chambers cc out pretty close.
The Coolent flow thing sounds to me like malarky to me. If they changed the coolent flow in the 305 it would be news to me and a lot of other people!
I would agree about the air flow statment that you made.

One other thing, your rear gear choice should not be to tall, A good allround gear would be 3.50s
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Old 05-25-2004, 02:47 AM
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younguy I'd go with the World S/R Torquer 305 heads for your 283. Their combustion chambers are a nice tight 58cc and have the very effective and usable 1.94" intake valves. http://store.summitracing.com/defaul...&d=1&x=17&y=13
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Old 05-25-2004, 11:45 AM
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thanks guys
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