Timing question, Searched didn't give me much help

[xero_gto]

I know this is asked atleast 100 times a year, but i couldn't find much in the way of my situation with the search function.

Basically what im trying to do is ensure my initial timing is set correctly. I know the truck starts and idles fine, has some blow by coming from my breather. As soon as you put it into gear it idles horribly, drops to around 400 from 650-700rpm it shakes, and while under a load and accelerating it has a pinging coming from the hood. Which makes me beleive the timing is off. both initial and full advanced. I got a timing light from summit, and im trying to figure out what i should be running. Chiltions say's 4deg BTDC for a 70 350 with points, but the previous owner put a HEI in the truck, he also mentioned the engine was from a 74 i beleive. So i looked up for the first year HEI in the chiltons and it says 8deg BTDC. I'm trying to figure out if thats right considering im running long tube headers. have an edel dual plane intake, and a summit carb. Any input or just a WAG (WILD A** GUESS) would be appreciated. Thank you.

[pat 70/71]

I run my 350 @ 8 degrees with 34 as a total. runs fine (no pinging) on regular fuel hope this helps, cheers, Pat

[Shyguy]

I have heard a lot of people like to bump the timing up to 10-12 degrees on 350's. That is what my son does and it works for his engines.

[DaSchlange]

Well I have my 454 set on about 9 degrees right now. Learned a little something though while doing it from a friend of mine. If your distributor has a vacuum advance that goes to your carburetor, take it off your carb and plug it off. Then time it to around 8 to start out with. See what works best for your motor. I would also moderately adjust the idle position on your carb as well, that could be part of the problem.

[69 longhorn]

Originally Posted by pat 70/71

I run my 350 @ 8 degrees with 34 as a total. runs fine (no pinging) on regular fuel hope this helps, cheers, Pat

The 34 total is what I like to run, but with my dist, I run 14 Initial. Forget about initial timing for a bit.....focus on total timing set the ol bioch, where she 'lites off best",then look @ the total. On pump fuel,set tween 32-36 degrees(where it runs the sweetest). I would call "all in" around 2800-3200.....then set the vac can(normally, you can run 10-12 vac timing @ the crank).....a little more on some apps. Play with it, give the ol bioch what she LIKES! Go roast some rubber, & have fun....crazy AL

[hayhauler71]

Originally Posted by 69 longhorn

The 34 total is what I like to run, but with my dist, I run 14 Initial. Forget about initial timing for a bit.....focus on total timing set the ol bioch, where she 'lites off best",then look @ the total. On pump fuel,set tween 32-36 degrees(where it runs the sweetest). I would call "all in" around 2800-3200.....then set the vac can(normally, you can run 10-12 vac timing @ the crank).....a little more on some apps. Play with it, give the ol bioch what she LIKES! Go roast some rubber, & have fun....crazy AL

what crazy al said 36 all in at 3000 rpm but i use no vac advance

[Myself]

It's very hard just to say " set it at 8 degrees initial". Every engine build will require a little different setting. You need to warm the engine up to operating temp and unhook the vac advance. Advance the distributor a little at a time to get your maximum rpm then back it off just a little. Shut it off then try to restart it without giving it any gas. It should start right back up. If it goes woh...woh...woh then it's still advanced a little too far. Back it off some more and try starting it again. When it starts right off, and shuts back down with no dieseling or hic-up, lock it down. Now look at it with your timing light to see where you're at. Now you can work on setting the mechanical and vac advance. As said above smallblock Chevys like 32-36 degrees all in by 3000 rpm. After that you can work on vac advance. It depends on your gearing and cruise rpm, as well as how heavy the vehicle is and compression ratio. Try starting with around 15 extra degrees advance with the vacuum. Then drive it a little at cruise rpm and up some hills. If it piings then you need less vac advance. My little S10 Blazer with a smallblock only wants about 6 more degrees on the vac advance. But it lugs a little at 55mph and sits at about 9.5:1 compression. If I turn the vac advance up a bit it pings every time I start uphill! Once you get this all dialed in you can accurately set your carb and you'll be all smiles every time you drive it.

[xero_gto]

think i found the problem, timing was set at roughly 20 degrees BTDC with vac adv unplugged. Turned it back to around 8-10 degrees. Runs alot better now.

[Shyguy]

Originally Posted by xero_gto

think i found the problem, timing was set at roughly 20 degrees BTDC with vac adv unplugged. Turned it back to around 8-10 degrees. Runs alot better now.

Great! Glad to hear that it is running better. Thank you for letting us know.