The Stovebolt Site Forums The Shop Area The HiPo Shop 350 Small block timing.

I hope some of our resident engine gurus see this.

I currently have an '81 C3 Corvette 350 in my truck,I'm having trouble getting a definitive optimum timing setting for it.

My Haynes Corvette manual says: Refer to spec plate on car.....

The timing settings varied wildly over the years before and after this year,or so it seems according to the book.
I have no previous info on this engine as it was cut out a fire damaged C3 and the engine ID number points to a possible replacement in previous years.

Engine # is: VO809800
All searches done have come up blank.

Afaik it's a non EGR with HEI,4 bolt main with a stock cam and some basic modifications,i.e. block hugger headers and an Edelbrock 1406 Vac-sec carb.

Can anyone out there point me in the right direction with a ballpark figure to aim for?

I haven't driven my truck in three weeks and i'm having some serious withdrawals!

With the vacuum advance disconnected, set the timing around 10 to 12 degrees advanced. If it doesn't crank over like a dead battery, or ping when you accelerate you should be good to go (if not just retard the timing a couple of degrees at a time till it's O.K.). Also have your vacuum advance hooked to full manifold vacuum. Depending on compression and quality of the fuel you're using, this should get you going.

Brian

Hy jockbolter50, in my Motor manual there is only one engine listed for a Corvette in 1981, as 55 SHAKER has said remove the hose at the distributor advance unit, but plug it so there is no leakage. If your truck has an automatic set the timing at between 500 and 600RPM in drive, if your truck has a standard transmission set the timing between 700 and 800 RPM in neutral. Timing should be set at 6 degrees BTDC for either transmission, hope that helps.

Here's a video, if you want to learn about total advance, and running a curve on your distributor (fine tuning your ignition).
Hope this helps.


Brian

If you have access to a delay-flash timing light, try setting the timing to 35-36 degrees at 2500 RPM with the vacuum advance disconnected. That should put the initial advance at startup somewhere in the 10-12 degree range. You'll get another 10 degrees or so from the vacuum advance for light-throttle cruise and improved gas mileage. I've done a few hundred dynamometer runs on Chevy 350's, and almost every one got its best full-throttle power with centrifugal advance in the low to mid 30 degree range, regardless of camshaft or compression ratio. The only reason not to run that amount of high speed advance would be if it's difficult to crank the engine due to too-early spark timing.
Jerry

I timed my '56 with a 350 by Jerry's method and it runs great.

Thanks for the input fellas,i'll let you know how it goes.

UPDATE:
Tbh I've been dragging my heels on this but yesterday I decided to change out the distributor,the advance weights on the one in the engine are fubar.
Set #1 cylinder to TDC on the compression stroke,marked the rotor arm position relative to the distibutor body.
I then removed the unit.

I then tried to install the rebuilt unit (original to that engine) and when the bevel gear and oil pump drive meshed it put #1 approx 45 degrees out from the marked position.

Can the oil pump drive rotate when the unit is removed,I was very careful not to turn the engine when the dizzy was out so what gives?

Can I simply refit the plug wires relative to the 'new' #1 position......i'm confused. HELP!

UPDATE on the UPDATE: I found out from a friend I can rotate the oil pump drive to correspond with the distributor drive position,I didn't want to touch anything 'til i'd checked.
I just wasn't sure if it would totally knock everything out of whack.

It looks like you've got the problem under control for now, but here's a little suggestion for the next time you remove a distributor- - - - -Take a long screwdriver and reach down to the pump drive, and rotate the shaft very slightly counterclockwise. This will allow the distributor shaft to engage the slot in the pump drive easily without catching the wrong gear tooth on the camshaft. Also, remember to start the dizzy into position with the rotor about halfway between the #2 and #1 spark plug towers, as it rotates CW toward #1 as the gears mesh.
Jerry

Thanks Jerry,I got it sussed,I'm also beginning to suspect some bad gas. (In the truck that is)

I flattened the battery turning it over this morning so i'm just waiting for it to charge up and then back to the garage.

Got myself an all singing all dancing Snap-On timing light so will give your tuning tip a try,once again thanks for your input.


UPDATE: I got it started and basically it was running same as before.
I'd reset everything from scratch,drained the gas tank a put in 2 gallons of fresh fuel.

2/3 minutes later it stumbled a bit and then settled down to a nice V8 burble.
Whatever residual fuel left in the lines had passed through and it cleared right away.
Let it warm up and reset the timing as per your instructions Jerry.

Suffice to say it's running like a champ and i'd even say better than before.

Thank you to everyone for your valued advice and input.
Once again Stovebolt.com has bailed me out!

Good lesson in timing..Brian..thanks for the video link. Pretty much spot on with Jerry's advice, just a little higher RPM's for total advance. Jock...at some point you will have to enlighten us on the Scot's contribution to mankind. Off the top..Scotch,Golf (ok enough said)... Haggis,Bagpipes,Manskirts,...

Haha Allen,I didn't issue that statement,I just happened to agree with it.
Here's a few for starters......
Bear in mind 'our' engineering contribution to the world as well,shipbuilding,steam locomotives etc,many of which are still in use today.

I AM biased of course!

My Scot-Irish ancestors arrived in the colonies in 1763, in South Carolina. By the 1820's they had reached the center of the Universe, Tennessee. They brought with them the secret for eternal happiness, the recipie for Scotch whiskey. Once they figured out they dicn't need to barbecue the ingredients by smoking them over peat, and started using heirloom white dent corn sprouted in running water for the grain component, Tennessee corn whiskey was born!
Jerry

Dang Hotrod, I've often wondered about that Whiskey. Who would of thunk I got educated on whiskey in a timing thread for SBC. I love this forum.

So you're decended from some of the original rednecks Jerry?
Many of them came from just south of me in Galloway and of course Ireland.

Typical Celts though if,there's grain available they'd find a way to make booze with it....!

Redneck and proud of it, Jock! Of course, a little Cherokee from my great-grandmother makes me a really wild child!

Jerry

That's some good genes ya got right there Jerry,you're made of some tough stuff!