Hello Guys,
Working on my 56 BA & I'm trying to eliminate a "slight" intermittent miss / stutter while cruising 55mph @ 2100 rpm and would like your input. It doesn't do it all the time and sometimes you have to really feel for it.
Specs -- 1968 327 with 461 heads, TRW Forged Flat tops, Crane 284 cam, set 4 degree advanced with 1.60 roller tip rockers, NEW 600 Holley Carb, with MSD 6A, Pro Billet 85551 dist. (NO Vacuum Adv.) Blaster 2 coil, NGK V-power xr5 spark plugs (heat range 5) gapped to 45 per MSD. dist. is running the 18 degree bushing with light blue springs & 16 initial timing to put me @ 34 total and all in around 2800--3000 rpm. I ONLY run BP 93 & Car starts great, hot or cold and i don't have any pinging at high rpm. 4- speed tranny, manual Disc brakes, 160 thermostat, 1 5/8" Headers.
Things i have already done--
- lowered timing, seem to make it worse so i put it back.
- changed spark plugs from AC 43 --- the NGK's did seem to do better, also bumped gap UP to 45.
- marked, pulled & inspected plugs, the lower side (closest to piston) is a white/vanillaish clean color.....however, the top side (closest to valves) is dark, black, wettish color.
- Replaced pick up modue, dist. cap and rotor button.
- set air fuel mixture. both are turned OUT 1 turn to get a maximum vacuum of 12-13 inches.
- looked for stray sparks under hood at Night with engine rev'd up pretty good. - none found.
- Checked for vacuum leaks -- none found.
- Checked with timing light, while rev'n up the rpm's.....occasionally the timing line will fluctuate, indicating the miss.....BUT not noticeable by ear, just sitting at idle.
On the to do list--
- GOING to change dist. springs from blue to Silver (the lightest to allow to come in sooner)
- Pulling plugs back out for one more review -- NOTE these have been Fouled Once and were cleaned and re-used.
- Verify line on Harmonic balancer is correct for TDC
This complete MSD 6A ignition system (likely now out dated) was purchased a long time ago and then suddenly the project came to halt, (family reasons). Originally i had planned to just take it drag strip as a race "toy" hence the NO Vacuum Dist. BUT not now, as my intentions are to just DRIVE IT / Cruise around and enjoy..... NO drag strip.... just an "occasional Heavy FOOT between red lights" while the boys in Blue are having doughnuts.
So here are my questions--
- Considering this is now more of a weekend driver and less WOT --- would a vacuum advanced type dist. be a better option? the one i'm looking at is MSD 8361 as this will plug right into my current box.
- Do i even need a MSD box, in other words perhaps go to a small cap version distributor with a Pertronix unit or something similar? I do NOT want points and need a dist. with small style cap to clear firewall.
- increase or decrease spark Plug -- HEAT Range and or GAP??
- could it still be a spark plug wire breaking down, even though i don't see any sparks under hood? The reason i ask, is these are OLD and have a couple nics on them.
- Increased or decrease timing
Sorry for the Lengthy post, but had to get it ALL out there.
Thanks in Advance,
Ed