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Old 09-22-2003, 05:20 PM
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305 head on a 350 sbc

After hearing ppl saying so much sh#t about putting 305 heads on a 350 will boast compression depending on pistons.. and gain some low end.. but at the same time loose some top?? is this so?? im gona go bye the auto wrecker one day after work and pick up a set of heads to build up.. but not sure if i should go with 305 heads or 350 heads again... bye the way my motor is a 80-85 350 sbc.. and if i did go with the 305 heads.. wut would i look for.. a set off a 80-85 camaro? i no they had 305's.. thanx
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Old 09-22-2003, 05:56 PM
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What kind of pistons do you have? 305 heads on a 350 will raise your compression a good deal, maybe even too much for pump gas if you have flat tops or domed. I would go with 350 heads if I were you. If you have flat top pistons a set of 350 heads would be best.
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Old 09-22-2003, 06:01 PM
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My mate has the 305 heads on his 350 and the comp is high, good bottom and mid but no high end, even with a fair bit of port work, 286 comp cam, victor jnr it runs out at around 5500 rpm.
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Old 09-22-2003, 06:57 PM
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what about putting 305 heads on a 350?

sorry i ment puting 350 heads on a 305 sorry
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Old 09-22-2003, 07:02 PM
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technically it is possible.

But before you buy anything, go and find some heads and get the casting number off them. 305's came with different heads which had different valve sizes, intake runners, and combustion chambers.

If you get a set of heads with +64cc you should be able to run on pump gas with flat-tops, but not domed. Also, once you find a set of heads you can work with (valve sizes don't really matter because they can be punched out to 1.94/1.50 or 2.02/1.60 for pretty cheap), before you buy, ask if you can take them to a machine shop and have them magnafluxed and pressure checked for cracks, nothing worse than finding out the heads you just dumped hundreds of dollars on are just big paperweights.

The reason why the heads run our of top end are because the heads have smaller intake runners than the 350s so they run out of fuel to burn quicker. A victor junior intake, imo, is a bad choice for a set of 305 heads because it favours a high revving setup, which a 305 headed 350 definetly is not. You'd be better to go with a dual plane intake such as a Weiand Stealth or a Performer or Performer RPM intake.
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Old 09-22-2003, 07:55 PM
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I go with the 350 vortec heads, Then you will have the best of both worlds IMO. You need to update to a vortec style intake manifold. I have a 350 with 305 heads now.According to desktop dyno, the vortec heads would be an 80 hp improvement on my application....Just a thought....Jay
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Old 09-22-2003, 08:43 PM
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Well i baught the motor used.. it was all stock from the looks of it.. and feel.. with the exception of headers.. well bottom end is wut i want.. i never rev over 5500 in my truck anyhow.. so in a stock rebuild do they come with domed or flat? is there a way i can check without pulling the heads? say maybe bring it up to top dead cetner and stick a screw driver or somethin flexable to feel if it has a dome or not?? just a idea.. i also have a performer intake i put on.. shorty headers on now.. but gona go with LT's cuz one has a hole in it! so im goin for mosly bottom end power anyhow.. so i wana run +64cc then ?? ya i think its best i get some #'s off the heads.. where would i check these #'s tho?? can i get some #'s ahead of time so i no wut im looking for at the wrecker? thanx for the help
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Old 09-22-2003, 11:26 PM
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416 I believe is the # you want.I think thats the number of the ones I used.
Under the valve cover there will be a 6 or 7 digit # thats the casting # the last three digits are what your looking for.
Mine were off an 82 caprice they had 1.84/1.50 valves and 58cc chambers.
Torque out the *** but won't rev past 5000rpm.
A stock non hipo 350 rebuild should have dished pistons.If its a mid 70s and up non vette motor and your sure its a stock build then,I'd bet most likely it has dished.
The 58cc chambers and the dished pistons should net aprox 9.4-9.6:1 depending on gasket thickness.
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Old 09-23-2003, 07:57 AM
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78 Monte is correct, I'm running 416 heads on a 350 flat tops/ mild cam, at the strip low end is great, but won't do anything over 5000 rpm.

9.2 sec. at the 1/8 th 81 mph

14.9 sec. 1/4 at 93mph - 3.73 gears

motor just runs out of steam!!
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Old 09-23-2003, 02:46 PM
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if all you want is bottom end then the 305 heads will be a cheap and good addition. Just go to nastyz28.com or mortec.com and look up the casting numbers of 305 heads. That should give you the cc's and valve sizes. There's a lot of them tho, and some are better than others.
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Old 09-23-2003, 06:08 PM
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perfect.. thanx for the info and help guys, now i gota find a decent set..

Well a local guy just posted on this site saying he had a couple sets of heads he wants to get rid of..

354434 -- 75-80 -- 262/305 -- 1.71/1.5
3970126 -- 67-79 --327/350 -- 1.71/1.5

those are the #'s he posted.... now wut would i be better off for my motor?? would one give more performance then the other? like on the 305 heads they boast compression.. that means a bit more power right? well then wut would the 327/350 heads benifit?? same as my 624's i got on now?

Last edited by Trav; 09-23-2003 at 06:08 PM.
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Old 09-23-2003, 10:03 PM
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I had similar dragstrip times with the 416s 14.55@95 in 1/4 and 9.35 in 1/8.
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Old 09-23-2003, 10:20 PM
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same deal with those heads. The 262/305's will boost compression but will not flow as well as the 327/350 heads. Therefore limiting high end power. Well the 327/350 heads will have less bottom end due to lower compression ratio, but will flow better in the upper end.


Also, you could have the heads decked to increase compression ratio and have up to 2.02 intake valves and 1.60 exaust valves installed. The valve operation is actually pretty inexpensive and would more than make up for any difference in the lower compression.

Just before you pay for a used head, have it magnafluxed/pressure tested to make sure it's not cracked.
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Old 09-25-2003, 08:41 PM
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get a set of 305 high output heads smaller combustion chambers larger valves i have a set on a 350 with 55cc and 194 150valves runs great up to 6500 rpms
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Old 07-13-2005, 05:17 AM
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i'll just toss this out,if i was building a tow truck or the like (low end power,never revved past 5000)would 305 heads be good?
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