Time to tune

[plumkrazee70]

Hello everyone!

As stated in a previous thread, I got the rebuilt 340 up and running yesterday. Despite all the hurdles, everything seems to be going well.

I'm going to start tuning this week and wanted a little advice. Here is what I have 68 340 bored .040 over, MSD 6A box with their billet distributor (no vacuum advance) Comp .454 cam. Edelbrock 650 Thunder AVS carb vacuum secondaries. J heads. The car is going to be street only.

From what I have read and researched:

Timing:
Warm engine. Set idle and get a vacuum gauge and tune for max vacuum minus 2". Check initial timing. Raise RPM to 2500 - 3000 and check total timing. Take total minus initial = * of mechanical advance. Adjust springs to suit curve.

Does this sound about right?
Anything I missed or should look out for?
Is the 2500 - 3000 RPM range too high to check total Or should should I increase the RPM until timing stops advancing?


Thanks again for the help. If I missed some info on motor let me know.

 

[crackedback]

A bushing determines the amount of mechanical advance in your distributor. It should have a blue 21* on it now. That may be OK depending on how much total you run. If you run anywhere from ~33-38 it may be OK. If the starter will handle more initial, you could put the black 18* bushing on it.

Springs that tend to work well are a light silver and med blue

I only back off timing to get a 1" drop in vacuum. Make sure you keep idle speed same when doing this. You may have a situation where the vacuum gauge method gives too much initial for the starter to handle. Use either the vacuum method or wherever the starer kickback.

 

[plumkrazee70]

A bushing determines the amount of mechanical advance in your distributor. It should have a blue 21* on it now. That may be OK depending on how much total you run. If you run anywhere from ~33-38 it may be OK. If the starter will handle more initial, you could put the black 18* bushing on it.

Springs that tend to work well are a light silver and med blue

I only back off timing to get a 1" drop in vacuum. Make sure you keep idle speed same when doing this. You may have a situation where the vacuum gauge method gives too much initial for the starter to handle. Use either the vacuum method or wherever the starer kickback.

Awesome. I will have to wait until I get my radiator fixed/ replaced first. Great info.