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chevy 305 timing and carb settings

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chevy 305 timing and carb settings

iremetal iremetal
New User | Posts: 8 | Joined: 10/04
Posted: 10/26/04
05:46 PM

my chevy 305 had an edelbrock performer non egr and a performer 600cfm 4bbl to match, bolt on mods only and no emissions crap.

Im timed to stock (4B) and the car runs slow and bogs when i punch it.

It was running faster when the timing was way advanced (off the scale). 

I went to fix my timing because i thought i heard ping (i was actually hearing a rocker in need of adjustment), and putting it back to 4B made it run slow.

Any suggestions?


User | Posts: 57 | Joined: 10/04
Posted: 10/27/04
12:04 AM

I'm guessing you set the intial advance somewhere around 4-6 degrees BTDC with idle around 650-700rpm. This doesn't take into account your total advance or how you get there ( vacuum advance, mechanical advance or both ).

Stock heads like around 40 degrees, sometimes more. Problem is most stock HEI distributors don't offer more than 20 degrees or so. When your foot is buried you shouldn't have much vacuum to activate the advance canister. If true then 20 degrees mechanical plus 6 degrees initial gives you only 26 degrees, not much when you need 40 ( more or less ).

You don't mention weather the engine bogs or pings during part throttle with light acceleration. And, you need to find out what your total advance is as it is currently tuned.

If your total advance  ( 3000 rpm with the vac adv. disconnected ) were in the 30 degrees plus range I would  advance the timing to around 10-12 degrees and see if it detonates or pings. That would put your toal advance in the correct range for your stock heads.

If your total advance is lower than 30 plus degrees when tested as discribed above you need to look in to a recurve kit/ adjustable vac adv. for your distributor.

send more info, does it have headers? dual exhuast? what kind of car? trans? rear end ratio?

Good Luck 


iremetal iremetal
New User | Posts: 8 | Joined: 10/04
Posted: 10/27/04
12:01 PM

I set idle timing to 10 degrees and it seems to run well. Summit technical told me not to go past 12 on the stock cam, as you said.

There is no ping.

still the total advance seems to be only 10 degrees. I ran the engine to 3000 rpm and timed it. my dial got to 10 degrees when the scale was at 0. Is there still something I should fix here?

The car has stock 305 exhaust manifolds, single exhaust. 1978 pontiac firebird. TH350 tranny, and stock rear end ratio: 3.08, 3.23, 2.56, or 2.41. Ill have to get back to you on that, i have to check it by spinning the rear wheel, i couldnt find the identification number on the rear axle.  



Edited 10/28/2004 11:02 am by iremetal  

User | Posts: 57 | Joined: 10/04
Posted: 10/28/04
01:16 PM

This is so funny, I have the same car, a '79 espirit.

I have lots of spares for chevy small block because thats all i mess with right now. I think it's likely to be your distributor weights frozen/rusted. even with no vac. adv., you should have at least 12 degrees plus the initial 10 for a total of 22. Thats still too low but you have nothing but initial adv.

There are two ways this could happen. The first is if you got a later model distributor for a car with electronic adv. ( mid eighties ) the other is if the weight springs were removed by someone during cleaning and not reinstalled. This would cause the weights to go out to full advance at idle and when you set the timing to 10 degrees that's it. Or, as stated above I have found frozen/ rusted weights that simply will not allow the advance mechanism to move smoothly if at all. This sometimes also causes errattic timing.

A rebuilt distributor forom the local retailer is around a hundred bucks. It usually comes with a new pick-up coil and module but no cap/rotor/coil/cover. It's quick, but I'd make sure you need it first by pulling the cap/coil/rotor and looking at your advance mechanism. 

Ultimately, the solution could be a new distributor from PAW/ Summitracing/ or other mail order house. All the things you will want like adjustable vaccum and mechanical advance are built in so you could tune your combo anytime you change it. You can add things but there isn't much money to save when it's all done because the aftermarket ones come with a matched coil/ module and that would be factored into the price of your DIY setup.

For what it's worth I'm still running the 2 barrel and manifold though I put in a 350 a couple years back. My wife was driving the car when a vavle lost the head and it stuck in the piston. Then it came up and poked the cylinder head. So my spare 350 was thrown in.

Good luck.

P.S. I have been through the whole car so feel free to ask questions about anything else.