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305 cylinder head upgrade?

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Old 05-16-2011, 06:55 AM   #1
briaineo
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Default 305 cylinder head upgrade?

Was wondering whats the best heads to get more power from my 1978, 305. With the original heads.

Not looking to break the bank!

The intake manifold was changed by the P.O. to an Edelbrock Performer

I've since installed a 750 cfm, Mechanical Secondary Double Pumper.

Have a nitrous kit, not installed.

What power output improvement could I hope for by changing the heads?
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Old 05-16-2011, 07:33 AM   #2
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AFAIK ... 350 is only size available 1978 ... not 305.

Is yours a L48 (cast dished piston w/ low compression)? ... or ...
L82 (forged flattop w/ higher comp)?

Automatic trans or 4spd?
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Old 05-16-2011, 08:37 AM   #3
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Quote:
Originally Posted by jackson View Post
AFAIK ... 350 is only size available 1978 ... not 305.

Is yours a L48 (cast dished piston w/ low compression)? ... or ...
L82 (forged flattop w/ higher comp)?

Automatic trans or 4spd?
Hi

heres the engine number: T1024CEJ

I presume that its either one of the options below:

Went with the 78 because the heads were dated from that year.


CEJ 1978 305 145 2
CEJ 1980 305 155 4

Car has a manual transmission not sure if its the original didn't check the numbers yet.
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Old 05-16-2011, 08:52 AM   #4
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Neither one of those are original to Corvettes. They are both listed as 305 motors. The 305 is not a really good performance motor but being that it is a SB chevy it will respond to mods like most of them. The 750 DP carb is really to much carb for a very mild 305. I would not go spending big bucks on a worn out 305. Save your money so you can put something decent in there. The 305 was never meant to be a performer.
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Old 05-16-2011, 09:19 AM   #5
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Hey Gordon

Its not a corvette engine as far as i can find out its from a camaro.

not gonna spend much on it, anything i do spend i'd like it to be reusable on a future engine.

Wanted to find out what horsepower increase i could expect from changing the heads?
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Old 05-16-2011, 09:42 AM   #6
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A head change will definitly help. The 305 heads were terrible at best. Install a decent cam while you are changing the heads and you could see a nice HP increase. The cams are also terrible in the 305. You could easily get a 50HP increase with a head and cam change. Maybe more depending on you head and cam selection. Also consider what transmission and rear gear you are running.
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Old 05-16-2011, 11:20 AM   #7
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Here's an article that you might find interesting.

http://www.popularhotrodding.com/eng...cks/index.html
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Old 05-16-2011, 12:07 PM   #8
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Quote:
Originally Posted by Gordonm View Post
A head change will definitly help. The 305 heads were terrible at best. Install a decent cam while you are changing the heads and you could see a nice HP increase. The cams are also terrible in the 305. You could easily get a 50HP increase with a head and cam change. Maybe more depending on you head and cam selection. Also consider what transmission and rear gear you are running.
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Old 05-16-2011, 12:11 PM   #9
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A 750 Holley is extreme overkill for that small engine. Unless it is supercharged, you wouldn't need anything over 650 cfm. The best carb for your application would be a Q-Jet, as it is a "demand" carb and will work on any engine up to the limit of its capabilities.

Just about any modern heads for a 305 engine would be better than what is presently on it. But keep enough compression chamber volume so that compression ratio doesn't exceed 8.5-9.0 or you will have to use premium fuel. If you want higher compression, you will have to have access to premium fuel and/or use octane additives for it to run well.
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Old 05-16-2011, 12:35 PM   #10
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suggest acquire a core iron-head 5.7L 350 Vortec motor to build up ... 8'th character in trucks vans vin code is "R" about 1996-2000. G'luck
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Old 05-17-2011, 01:21 PM   #11
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GM 5 litre's really didn't catch on like Ford 5.0's, but are pretty decent and did come stock in some California Vette's for emission reason's. I personally wouldn't bother, if looking to spend money on head's, ext. Drop in a well set up 355, 383, 406, and keep the 305 for your daily grocery getter. It's your money, but just a bit of advice in helping you spend it in another direction.
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Old 05-17-2011, 02:04 PM   #12
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It's going to be REALLY HARD to find heads that will work with a 305. The 305 has a narrow bore and the same stroke as a 350.

This means the piston bore will most likely interfere with the valves.

The article linked is using Vortec heads. If you're really scraping dollars together to make power and are DYING to have a new engine, this is a good way to **** money away.

However, if your goal is big, ultimate power, skip the Vortec heads and the 305 and go on to bigger and better things. That article is lying - sure, you can put Vortec heads onto a 350 block, but their limits will be hit very quickly.
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