Late model 305 Chevy Truck heads on one of our 305? (mine is an 81 Monte)

J

Jeff

Not-quite-so-new-guy
Apr 29, 2017
5
3
I heard heads from a late model 305 in this case from a 1998 Chevy truck will fit on one of our blocks. And if you upgrade Cam, Intake and Carb you will flow enough to get 300 horse power. I would like to get 300 HP out of my 81 Monte on a budget. Anyone have details on this working or am I sadly mistaken. Thank you for your time. Jeff
 
Streetbu

Streetbu

Royal Smart Person
Supporting Member
May 22, 2011
1,585
113
Central NY
350 heads will fit on your 305. Don't use the Vortec 305 heads, you won't notice much of a difference. Use the 350 heads. Casting numbers ending in 062 or 906 are the good ones
 
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olds307 and 403

olds307 and 403

Geezer
Oct 14, 2008
5,596
113
Melville,Saskatchewan
Aren't the Vortec heads nearly as crack prone as the Dodge Magnum heads? Either buy new or get them pressure checked. Also what is the chamber size vs 305 stock heads?
 
MrSony

MrSony

Geezer
Nov 15, 2014
5,375
113
Des Moines, Iowa
300hp budget 305 parts list:

1. 9.5:1 vortec head 350
2. See #1
 
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Doug Chahoy

Royal Smart Person
Nov 21, 2016
1,817
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The factory hp on the stock 350 was 260 from 96-99. That would be the better way to go. My 99 Tahoe REALLY came alive with a K&N filter charger short headers and a complete Magnaflow exhaust with their cats. I wouldn’t waste the time and money on a 305.
 
DRIVEN

DRIVEN

Geezer
Apr 25, 2009
6,582
113
*CENSORED*
No real need for two threads on the same subject. Yes, Vortec heads will "work" on an old 305. Whether you use Vortec 305 or Vortec 350 (they are quite different heads) either will be an improvement over the '81 305 heads.
However, as stated already, you're farther ahead to just find an L31 Vortec 350, both to reach your 300hp goal and also probably financially. Either way, you'll need a Vortec specific intake manifold.

We're all on a budget of some sort. My advice is not to spend any money on a 305. The ROI just isn't there. They were a compromise design that was intended primarilywfor fuel economy and lower emissions. The bore to stroke ratio is more conducive to building torque rather than horsepower.
 
TURNA

TURNA

Rocket Powered Basset Hound
Jul 24, 2009
10,441
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Socialist NY
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gnvair

gnvair

G-Body Guru
Sep 1, 2018
566
93
Southern New Jersey near Philly
I have a local engine core supplier that I have been buying rebuilable engines from for years. He will no longer sell 906/062 Vortecs because they are almost always cracked. Either buy new GM or look into the Engine Quest replacements.
One other detail is that 305s typically have small combustion Chambers to keep the compression up. The 906/062 Vortecs have a larger chamber. Putting them on a 305 will lower the compression.
 
olds307 and 403

olds307 and 403

Geezer
Oct 14, 2008
5,596
113
Melville,Saskatchewan
I have a local engine core supplier that I have been buying rebuilable engines from for years. He will no longer sell 906/062 Vortecs because they are almost always cracked. Either buy new GM or look into the Engine Quest replacements.
One other detail is that 305s typically have small combustion Chambers to keep the compression up. The 906/062 Vortecs have a larger chamber. Putting them on a 305 will lower the compression.
Exactly my point, lower compression. Without out a converter and gear change, 305 Vortec heads might be better. I was told the same thing from a wrecker about Dodge Magnum heads, they would not sell them even if they had them because of cracks. So I bought the Ram EQ heads. Hopefully the EQ Vortec heads don't have sticking valves like the EQ Magnum heads. I bought the Hughes modified EQ heads with bronze guides, 0 issues.
 

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