billybob6110

what would cause timing to go past the setpoint? I have a 355 sbc, and I adjusted the weights and springs in dist to come in all by 3300rpm. the timing comes in at 36 degrees at 3300 if I rev engine higher the timing mark will slowly creep up farther. totaling up t0 43 drgrees. how do I make it stay at 36 without advancing past that point?

sofakingdom

iTrader: (1)

Vac adv disconnected while making this test?

If not, do so and re-test.

If so, then your "total" timing isn't 36° @ 3300; it's 43° @ some higher RPM.

zraffz

I'd just like to add in if the later part of sofakingdom's post is indeed correct, you need a lighter set of springs.

billybob6110

I don't have vac advance at all on car. so ill have to change the springs to make it stay below 36*?

billybob6110

vac advance isn't on car. so what would be best way to keep it at 36*?

midias

What problems is the car exhibiting?

What distributor do you have?

You have two options rotate the distributor so total timing is 36 and initial is less. Or put in the correct springs and weights to make it advance the correct speed and total amount. On some distributors there is a bushing to control total advance.

sofakingdom

iTrader: (1)

Does it matter? (that is, does the car run better at the one setting than the other?)

Is your instrumentation ACCURATE? for example, timing mark/pointer verified, and marks (such as tape for example) used on the damper and NOT a "dial-back" timing light?

AlkyIROC

Springs control how fast the timing advances. Weights and center cam change how much mechanical advance is in the distributor. Initial/base timing plus mechanical equals total.

If for example, you set your base timing for 12* and you want a total of 36* then the distributor needs 24* of mechanical advance. Since the mechanical advance needs to be changed with components, if you move your base timing, your total timing will move the same amount.

Best base timing depends on the cam grind. Once the base timing is set for the cam grind, you should never have to change it. If you don't get the proper amount of total advance then the distributor needs to be recurved.

As mentioned already, sounds like your total timing is 43* providing it doesn't go any higher. You can adjust the springs to bring that total timing down to 3300 where you wanted it. Lighter springs will allow the timing to occur sooner and you can mix and match light and heavy springs to get the desired results. If you have 2 lightest springs installed and it still reaches total above your desired rpm range then it should be professionally recurved. Once the rpm range is reached, you can change the weights and/or center cam to change how much it advances. Again, if you can't get the desired mechanical advance with parts you have, it may need to be professionally setup. Junkyard hunting can also provide spare parts but many times you'll be finding worn out parts. I pulled a cap off an old 70's firebird once and the weights were seized. I wondered if the last owner before it was junked complained about poor performance all the time.

A distributor setup machine makes it a lot easier. You tell them you want full advance at 3300 and exactly how much mechanical advance you want and they'll do it. Hardest part is finding someone with a distributor recurve machine. Not too many cars now need this done.

billybob6110

car runs great, cool, and lots of power. might need to verify the timing pointer and true tdc

sofakingdom

iTrader: (1)

Then why worry about it?

If I may paraphrase the wisdom of one of The Greatest Ones in a completely unrelated field:

"If it RUNS good, it IS good".

AlkyIROC

Finding true TDC is a must. Many years ago, my engine was somewhere around 42* total timing and still wanted more. Shortly after that, I used a degree wheel and a piston stop to find out the timing mark was retarded 8* so that 42* was really 34*. No wonder it kept wanting more timing.

I now use a Milodon fixed idler timing gear set. It's quiet and will never change like a stretched chain. The balancer has all the degree marks engraved in it and the timing pointer is adjustable. I had to determine exactly where TDC was to adjust the timing pointer to index the camshaft. My distributor is locked out at 37* and my ignition has a start retard to get the engine started. No guesswork. Everything needs to be set exactly. It's a race engine. It's a little overkill for a street engine but power can still be made if you check all the measurements.

Never depend on OEM markings. They can be wildly inaccurate.