69 camaro missing after a few upgrades this weekend

[wd69ss]

I need some ignition help with my sbc I just got going this past weekend. I tore it down and put in new cam, lifters, roller rockers, heads, and torque converter. It runs good at idle and seems to run good at wot but when I'm just cruising, 1500 to 2500 rpm, it has a miss. It also has a slight hesitation in it when I punch it, but I believe thats carb issues. Initial timing is 12 degrees btdc and I have the 2 blue (light) springs in the distributer. What should timing be?

Heres the setup:
AFR 195cc heads
Lunati 284/292 .525" .546"
Lunati 1.6 rockers
Coan 2800 stall
Holley 650DP mechanical secondaries
MSD 6AL
MSD Blaster 2 coil
MSD Pro billet distributer
MSD 8.5 Super wires

[Red67Mustang]

Try putting a timing light on it at 2000-2500 rpm to verify what your total timing is at that RPM and that the timing is stable.

Just a hunch, but with 12 degrees initial you may be getting too far advanced at cruise rpm with no load (not much gas to burn) but be alright at idle (no centrifical advance) and a wot (lots of gas to burn). Just one thing to check out...

[wd69ss]

ok ill do that. This is my first motor to be doing all the work on so im new. Is it not best to set the timing at full advance instead of at idle? I just set it initially to 12 at idle to get it running and cam broke in. So now do I throttle it until it stops advancing and time it on that end and then change springs and stop bushings until I get the curve I want?

What you said sounds exactly right. Thanks for the help

[WidowMaker68]

I have a tempest so it's a bit different but I unhooked the vacuum advance and plugged it to do my initial timing. I believe I was 8 degrees btdc and it runs great.

[wd69ss]

Mine is mechanical advance and my setup doesn't make good power until higher rpm so do I want a steeper advance curve that advances quickly and then flattens out at a lower rpm or do I want a flatter curve that spreads more across the chart and not be full advance until higher rpm?

[sam 74]

try total timing between 34*-36*, with timing light rev up to about 2500 or so depending on your advance springs and check your timing advance, to tune your timing you'll need a bushing kit from MSD so you can tailor the timing curve to what you need. the general rule of thumb is to run as much initial as you can without issues. i have a custom made stop bushing so my setup will be a bit different than the MSD kit but you can change the stop bushing to say a 10 or so degree stop bushing and set your initial to 25 or so. basically setup your stop bushing first than set your initial, afterwards adjust the carb, that 650 might be a tad small for your engine.

[wd69ss]

ok well in that case my initial timing is way to low and I bet im not stopping the advance till way late. I have the msd charts and a few springs. Ill see what i can do
Thanks

[H2Ogbodies]

A 650DP isn't too small-after verifying base timing, if it still has a hesitation/miss @ part throttle/cruise I would look at a few carb mods. DP series Holleys are not your everyday driver carbs-they require some babysitting. First, an off idle stumble indicates a lean condition....either a vacuum leak or lean fuel mixture. Let's rule out a vacuum leak for now-instead swap out the stock 30cc front accelerator pump for a 50cc one. Front jets are most likely 72's and the rears are 78's I'm willing to bet so maybe step up to 77's in the front and leave the rears alone for now. Do one change at a time and take the car for a spin-verify if it gets a little better.

Next, swap out the progressive secondary slip link for a 1:1 link IF there's still a small but less noticeable off idle hesitation. This way, the fuel enrichment circuit will provide fuel at the same rate as the primary circuit. At the same time I would suggest swapping to a rear 50cc pump kit to match the front kit anytime you run a 1:1 slip link. Take the car out again and see if there's any difference. I guarantee you'll notice a difference with the 1:1 slip link change but I would still do things one step at a time. And, open up your plug gap a bit....I'd say after all these changes, take your plugs to .052

[H2Ogbodies]

If you have a hard time finding tune up Holley performance parts, PM me-I stock a complete Holley line and I do a lot of carb tuning-not trying to give ya a sales pitch but I know my parts and I actually build with what I sell also....a lot of people can sell parts but have no clue how everything comes together sometimes.....lol