Need timing help on a Chevy 350

[85_SS_302_Coupe]

Just need some pointers on setting the total timing on a 350. Who can help?

[85_SS_302_Coupe]

Nobody? I know there's some closet Chevy heads in here...

[leroy93lx]

What year are you working on? My tbi 1995 Tahoe 350 gets set to 0 degrees and the computer compensates.

[facemelter71]

If im not mistaken the total timing on a chevy 350 most likely with vacuum advance is going to be like 32-34.Thats total timing.If its a later model than its 0 initial.

[85_SS_302_Coupe]

This is a carbed 355 in an S10...we're just trying to bump up the total timing.

[Mista Bone]

34-38 depending on cam/fuel/heads etc.

[foxbodyfan]

SBC timing seems to be a "black art" to many folks, but it's really very simple to maximize the performance and fuel economy of a mild engine with just a bit of work. ANYONE can do this with a little care and the right tools. Figure on 2 hours to do this, and try to work undisturbed if possible. NOTE that a good dyno tune for $300+ will determine perfect timing, but this will get you 90% of the way there. This process assumes that you have an engine that is basically running with no significant issues.

Parts/Tools Needed

* Patience
* Willingness to get in and DO!
* China marker or other means of marking the balancer.
* Distributor advance kit. Any kit by a major manufacturer (Crane, Accel, Mr. Gasket, etc.) will work fine. The kit should be correct for your type of distributor (HEI or points) and include weights, springs and an advance limit bushing. I prefer this kit for 67-72: Mr. Gasket 927G for points-type, 929G for HEI. http://store.summitracing.com/partde...G&autoview=sku
* Adjustable vacuum advance. As above, any good one will work. I prefer this kit for the 67-72: Crane 99601-1 for points, 99600-1 for HEI http://store.summitracing.com/partde...1&autoview=sku
* Method for measuring advance. There are two basic ways to do this:
o Advance timing light. This type of timing light has a method to set advance at the LIGHT so that the balancer mark is always on the '0' pointer. This is by far the best approach if you can afford it. This is an example light; buy the best one you can afford if you work on many cars. Equus 3555 or similar. http://store.summitracing.com/partde...5&autoview=sku
o Timing tape. This is a tape that sticks the balancer and provides an advance reference. Clean the balancer with brake cleaner before applying. This kit has tapes for all different size balancers - MSD 8985 or similar http://store.summitracing.com/partde...5&autoview=sku


Process

1. Verify TDC. DO NOT SKIP THIS STEP - your success in this process is all based on accurate TDC reference.
* Buy or borrow a piston stop. These are cheap and likely available at your local parts store. Proform 66792 or similar http://store.summitracing.com/partde...5&autoview=sku
* Buy or borrow an easy way to rotate the engine. Generally, doing this with the balancer bolt is a bad idea -especially since we'll need to rotate the engine both directions. Here's a tool that turns the flywheel. NAPA 2270 or similar http://store.summitracing.com/partde...5&autoview=sku
* Pull the coil wire or if HEI, pull the B+ power wire.
* Pull the #1 spark plug (first on the RIGHT when FACING the engine)
* Put your finger over the spark plug hole, be SURE you are clear of anything that rotates, then have your friend (or remote starter switch) "bump" the engine with the starter until you feel the hole "burp" - this is the engine coming up on the compression stroke. If you don't have a remote starter switch, this may be the time to buy one - they're cheap and make this far easier.
* Screw the stop into #1 spark plug and turn the inside screw on the stop either until it stops or until flush with the outside plug.
* Rotate the engine one way with the flywheel tool - DO NOT use the starter - until the engine stops. Don't force it - it will come to a firm stop.
* Make a mark on the balancer directly opposite the '0' marking on the timing tab.
* Rotate the engine the other way until it stops and make another mark on the balancer directly opposite the '0' marking on the timing tab.
* TDC compression is EXACTLY 1/2 BETWEEN THESE TWO MARKS. Use a steel rule or tape measure to measure between these two marks and make a permement mark 1/2 between. If the mark is very close to the stock slot in the balancer, call it good enough. Accuracy with this method is about +/- 2 degrees - which ain't bad
* Turn the engine so that the TDC mark is opposite 10 or 12 degrees BTDC on the timing tab.
* Remove the piston stop and re-install the #1 spark plug.
* That wasn't hard, was it?
2. Mark the location of the #1 spark plug tower on the distributor body.
3. Remove the distributor cap.
4. Disconnect the vacuum advance.
5. Remove the distributor. DON'T try to do the rest of this process in the car...trust me
6. Chuck the distributor carefully in your vise.
7. Remove the rotor.
8. Remove the stock springs and weights and set them aside. If there is a limit bushing on the pin underneath the plate that the weights are on, remove it.
9. Install the limit bushing included in the advance kit. I generally give it a little squeeze with pliers to ensure a tight fit.
10. Install the weights included in the advance kit. Ensure they're clean of goo and move VERY easily. A little moly lube here is good.
11. Install the LIGHTEST springs in the advance kit. NOTE that every kit has different colors for their springs.
12. Install the adjustable vacuum advance and adjust as specified in the included instructions. Note that you may need to put a tube on the old advance unit to apply a vacuum (Mytyvac or your lungs ) to rotate the vacuum advance plate to get to the screws. You can manually rotate the plate as well.
13. Reinstall the rotor.
14. Reinstall the distributor. Note that the rotor will turn a little more than 2" as the drive gear engages the cam, so you'll want to start with the rotor about 2" behind the #1 mark you made on the distributor body. The distributor will be installed with the rotor pointing directly at the mark you made for the #1 tower with the vacuum advance pointing near the #4 cylinder (2nd on the LEFT side FACING the engine). If the distributor won't drop all the way in, the oil pump shaft is not aligned with the drive in the distributor - just carefully "bump" the engine until it drops.
15. Reinstall the cap.
16. Reinstall the coil wire or the HEI B+ power wire.
17. DO NOT reconnect the vacuum advance but ensure it is plugged.
18. The engine should start and run
19. Using your timing light or timing tape, ensure timing is fully advanced before 3000 RPM and adjust timing to 32-36 degrees at 3000 RPM.
20. Reset the idle to ~850 RPM and note the timing - this is your new initial timing;anything over 16 degrees requires additional debugging (PM me )
21. Driving test and adjustment
* Expect that with no vacuum advance, you may have poor part-throttle driveability. Ignore this for the purpose of this test.
* Make a few full-throttle runs. If you hear any pinging, replace the advance springs from the kit with the next heavier springs. This can easily be done with the distributor in the car, but don't drop 'em If you find you're "in between" two springs, it's OK to use two different springs to get it just right.
* Reconnect the vacuum advance and make some part-throttle runs. If you hear any pinging at part throttle, adjust the vacuum advance to provide less advance (the unit will come with instructions). In rare cases, a vacuum advance limiter may be required; the Crane kit above comes with this limiter if needed and instructions how to install.


That's it! Seems like a lot of work when every step is outlined, but you'll find this to be a very straightforward process that can be completed in a few hours...and you'll have improved driveability, throttle response an fuel economy.

[8banger]

34-38 depending on cam/fuel/heads etc.

Exactly....couple of Race SBC's I built liked 38 1@36 and 1 @ 40 degrees..

[Mista Bone]

Let me guess, the one that liked 40 total was alum. heads?

Not bad for a Honda Guy :)

I will note working on a Buick is alot easy with the distributor in the front, like a SBF.

[8banger]

Let me guess, the one that liked 40 total was alum. heads?

Not bad for a Honda Guy :)

I will note working on a Buick is alot easy with the distributor in the front, like a SBF.

Yep :D ...227 AFR full CNC heads 422SBC 13.1 :bigthumb

[RIXXX93GT]

I would help you but every time I try to adjust the timing on a chevy I cant find the friggin distributor. Where do they hide that thing?

[Mista Bone]

Yep :D ...227 AFR full CNC heads 422SBC 13.1 :bigthumb

cooler chambers = little more timing!


I would help you but every time I try to adjust the timing on a chevy I cant find the friggin distributor. Where do they hide that thing?

In the oil pan??????

:popcorn:

[85_SS_302_Coupe]

Yeah that's the stupidest thing about GM engines...it just makes it harder for the guy working on it.

My buddy seems to think that bumping his timing up from 32 degrees to 38 is going to drop 3 tenths off his ET so he's in the 12s and i think he's crazy, so we're gonna bump it up and see.

[8banger]

I don't know about 3 full tenths...but chevys do like 36 and up....for most part. :D
Personally I'd bump it 2 degrees each time up..make a pass and watch the MPH.....mph goes up(providing most conditions are the same)right direction .........MPH Goes down...turn it back..Then when the most MPH is acheived work on the jetting...the same way...(as long as its carbed).....