seventy77

Hey,

Here's my deal.I bought a 87 firebird auto.Originally a 2.8,but had a V8.(non-computer) I was told it was 350.Found out it was 307 produced from 69-73. It has a edelbrock performer intake,and 1406 carb.Don't know if the cam or anything else had been changed from stock.I bought a Accel dist with vac advance adjustable.I have not touched that.It came with 3 sets of curve springs,and one set already installed.I have no idea bout curve timing,or what springs to use,or set the timing at for this motor.The following springs curves are,gold: curve start 400 with total rmp 1600,silver:600-2800,black:600-4000.And the set on the dist i have no idea.Does anyone know what springs i should use,and what i should set timing at BTDC on this motor with what it has? It just a street car,and i'd like to get the best gas miliage,and performance i can with gas prices.Thanks Mark

Supervisor42

Wow. a 307. Are you sure? Mileage and performance they ain't. Use the gold springs. You want the timing all the way in at cruise 55-65 mph. Start with 6 degrees BTDC with the vacuum adv unplugged. Plug it back in and drive it and see how bad it pings. Add 2 degrees and repeat if it doesn't. Don't go higher than 12 degrees.
For mileage you want to run the timing as close to ping as you can get. (occasional is ok, just not sustained) The adjustable vacuum will help you because they come with a long stroke and will retard the timing a bunch when you put your foot in it keeping it from pinging.
The biggest thing you can do (since the ECM has been removed) is to get the torque converter clutch locking up again. That's an easy 2+ mpg for the price of a wire. Let's hope they didn't swap in a "vintage" tranny also...
We can tweak the adjustable advance later.
Is that 1406 an edelbrock squarebore?

seventy77

The cast numbers look to be for a 307.What do you mean by squarebore carb?

Supervisor42

All 4 bores the same, ie:non-Qjet.
What casting numbers do you have?

seventy77

The casting looks to be 3970024.I was hoping the last 1/2 #'s were off.Then it be a 350 lol.But i double checked.I think the bores are the same.If i understanding correctly.Oh and about the timing.Ive unplugged the vac canister to carb. Before i set the timing,but it don't change.The carb has no vac at idol.Atleast on the pass/side carb port.Is that normal? Thanks

Supervisor42

That's normal. It's ported vacuum. A lot of setups use the off-idle port to help popping in the exhaust when slowing down and tolerating the A/C load.

igotta355z28

iTrader: (1)

a 307 is 3.875 bore and 3.25 stroke....if u ever pull that motor just throw it in a river its not good for anything blocks are prone to cracking....

Supervisor42

Now, now. Those motors are perfectly good for pulling a pickup truck around the cow pasture on a farm. You wouldn't want to sentence a perfectly good 350 to a life of menial labor.
Besides, if he pulls it out, it should be responsibly recycled.
(77, are you sure you can't get a strong light on that casting number?)

seventy77

I can check it again lol.I did drop the gold springs in and timed it at 6.I'll have to wait til i drive for the outcome.That boat anchor will go at some point.Just wanted to use it for the summer.Yah! Great thing bout new england.4 Months of summer.It sucks! I do have a LT1 in my caprice i'm presently driving.The body may last one more winter,but the motor at 184,000 plus.Still runs sweet,and has plenty power.Thats a optionional swap.