Tech / General Engine Is your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!

timing on 350 with 305 heads

Thread Tools
 
Search this Thread
 
Old 08-16-2011, 11:20 PM
  #1  
Member
Thread Starter
iTrader: (3)
 
0pyders's Avatar
 
Join Date: Nov 2009
Location: Saint Louis, MO
Posts: 453
Likes: 0
Received 0 Likes on 0 Posts
Car: 86 Firebird LG4
Engine: 350
Transmission: 700r4
Axle/Gears: 3.23 limited slip
timing on 350 with 305 heads

My carb and distributor are computer controlled.
Should I just time the engine with what the sticker says on my hood and let the computer take care of the rest or should I bump it down a couple degrees since the compression's a little higher than stock?
Old 08-17-2011, 12:03 AM
  #2  
Supreme Member

iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 25,749
Received 368 Likes on 297 Posts
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: Strange 12 bolt 3.42
Re: timing on 350 with 305 heads

Compression is gonna be higher so I'd maybe look at bumping it down alittle for now and see how it likes it. IF you had datalogging equipment you can monitor for knock counts or spark retard. You can also add premium 93 gas to be safer.
Old 08-17-2011, 12:33 AM
  #3  
Member
 
Seven_MPG's Avatar
 
Join Date: Jun 2011
Location: King George,VA
Posts: 227
Likes: 0
Received 0 Likes on 0 Posts
Car: 1985 Z28
Engine: '69 350 4 Bolt Main .30 Over
Transmission: 700r4/B&M Shift Kit and Flywheel
Axle/Gears: GM 10 Bolt 3.23 Gears
Re: timing on 350 with 305 heads

Is there any advantage in running 305 heads on a 350?
Old 08-17-2011, 01:16 AM
  #4  
Member

iTrader: (1)
 
gwarren007's Avatar
 
Join Date: Jun 2010
Location: Safford, AZ
Posts: 409
Received 14 Likes on 12 Posts
Car: 1992 RS
Engine: 305 (LO3)
Transmission: 700R4
Axle/Gears: 2.73?
Re: timing on 350 with 305 heads

not really. You get a bump in compression (up to ~10:1, but then you get smaller valves for less top end. A better bet would be aluminum L98 heads or vortecs.
Old 08-17-2011, 01:57 AM
  #5  
Senior Member

iTrader: (1)
 
GTA Sammy's Avatar
 
Join Date: May 2005
Location: Winnipeg, Manitoba. Canada
Posts: 971
Received 8 Likes on 6 Posts
Car: 1989 T-Top GTA
Engine: 5.7L TPI> 6.2L
Transmission: 700R-4
Axle/Gears: 3.27
Re: timing on 350 with 305 heads

You can find World S/R Torquer 305 heads with the 1.94/1.50" valves and 170cc Intake runners and good exhaust ports...
with a max lift of .560"! You won't get that out of a stock head...
http://www.summitracing.com/parts/WRL-042650-1/

I had a pair that I was gonna throw on my 350 (once upon a time)
But I decided to spend the extra $$$ and went with the AFR's instead...
I don't think that you can go wrong... especially if you have them already!

or do you have stock 305 heads...?
Old 08-17-2011, 03:03 AM
  #6  
Junior Member
 
84ws6ta's Avatar
 
Join Date: Mar 2010
Location: Titusville, Fl
Posts: 70
Likes: 0
Received 0 Likes on 0 Posts
Car: 1984 Trans Am
Engine: 350
Transmission: JW Performance 700R4
Axle/Gears: Borg Warner 9-bolt, 3.08 gears
Re: timing on 350 with 305 heads

If you are running the stock comuputer controlled distributor, there is no adjustment in timing that you can make. The stock setting is not going to hurt the engine. The compression ratio depends on size of the combustion chambers, type of pistons, decking of the block and thickness of the head gaskets used. Some 305s had 58cc chambers, while others used 60cc chambers. So depending on the combination, you may be at 9.5:1 or 10:1 or something else. The stock 305 L69 (G) engines were 9.5:1 compression and ran fine on 91 octane. You will see a bit more power with the 350 lower end, but you won't get full advantage of it until you put on 350 heads with larger valves.
Old 08-17-2011, 08:24 AM
  #7  
Supreme Member

iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 25,749
Received 368 Likes on 297 Posts
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: Strange 12 bolt 3.42
Re: timing on 350 with 305 heads

You can still set base timing lower than stock which will affect timing across the board.
Old 08-17-2011, 11:19 AM
  #8  
Member
Thread Starter
iTrader: (3)
 
0pyders's Avatar
 
Join Date: Nov 2009
Location: Saint Louis, MO
Posts: 453
Likes: 0
Received 0 Likes on 0 Posts
Car: 86 Firebird LG4
Engine: 350
Transmission: 700r4
Axle/Gears: 3.23 limited slip
Re: timing on 350 with 305 heads

I know using 305 heads on a 350 isn't the smartest move but it's all I had and this whole project is pretty much just about learning and not spending a ton of money because I didn't want to ruin any nice parts lol. Next time I'll just get a new crate 350 and drop it in, much easier.

More on the 305 head thing: I read that it increases a little bit of low end torque but craps out on you at like 4500 rpm. (I guess it makes sense because of the higher compression/smaller valves part).
Old 08-17-2011, 11:23 AM
  #9  
Supreme Member

iTrader: (1)
 
Sonix's Avatar
 
Join Date: Jul 2004
Location: Calgary, AB, Canada
Posts: 10,763
Likes: 0
Received 4 Likes on 4 Posts
Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Re: timing on 350 with 305 heads

Originally Posted by Seven_MPG
Is there any advantage in running 305 heads on a 350?
Depends on what 350 heads you're comparing it to. They have smaller chambers and arguably better ports than the '70s smog heads. They have more meat to port, and when done up, can be a very competitive head. I run 416 305 castings on my 350.
Old 01-17-2012, 08:41 PM
  #10  
Junior Member
 
Code1racing's Avatar
 
Join Date: Mar 2007
Posts: 22
Likes: 0
Received 0 Likes on 0 Posts
Car: 1989 Rs
Engine: 355
Transmission: 700R4
Axle/Gears: 3.42 Gear
Re: timing on 350 with 305 heads

Originally Posted by Sonix
Depends on what 350 heads you're comparing it to. They have smaller chambers and arguably better ports than the '70s smog heads. They have more meat to port, and when done up, can be a very competitive head. I run 416 305 castings on my 350.
I run the very same 416 cast heads on my 350 & man do I love it. With a decent cam youll be very impressed. It even ripped my "bullet proof" 700r4 to shreads. Because of that Im using my tax money to get a bowtie overdrive stage 3 700r4.
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
MustangBeater20
TBI
11
10-29-2022 09:20 PM
BlueIroc-Z
Camaros for Sale
7
06-09-2019 03:22 AM
camaro71633
Tech / General Engine
39
09-01-2015 10:24 AM
NinjaNife
Tech / General Engine
27
08-23-2015 11:49 AM
st.evel07
Engine Swap
5
08-13-2015 06:15 PM



Quick Reply: timing on 350 with 305 heads



All times are GMT -5. The time now is 04:37 PM.