340hp dist curve

[jim cear]

After reviewing past posts on dist. mapping(Dukes) I checked mine. 63 340hp 097 cam,correct vac can, new springs and weights. This resulted in a map very similar to the 30-30 cam engines of past posts and not to 63 manual specs for a 63/340. Full centrifugal advance was all in at 2500 rpm,about 32 degrees (rather than at 4600 per spec)initial is set at 8 BTC. I will/have it correctly curved. Question is could this have caused any issues? (no audible detonation detected)Thanks. JIM

[Mike McKown]

Re: 340hp dist curve

I think it will run better the way it is than the way it is supposed to be.

[Duke W.]

Re: 340hp dist curve

The '63 advance map was not very well optimized for SHP/FI engines, but it was okay for the 250/300 HP engines. The vacuum can in particular is ill-suited because there is not enough idle vacuum to pull it to the limit at idle, which causes idle instability.

I recommend that the '63 SHP/FI map be modified to equal '64-'65 SHP/FI maps.

Start with the vacuum can, then with 12 degrees initial, install lighter springs until you hit the low rev detonation limit.

I modified my 340 dist. to the these specs (with '65 spec parts from Chevrolet parts) in the late sixties, and ran up to 16 degrees initial, but I don't think you will be able to run this much initial on today's pump premium.

Duke