BBC Timing
 

Curious if you guys cranked up the timing (on a dyno) until the engine didn't make any more power and left it there or dialed it back a bit because it's in a boat? Mine are set at 33 degrees btdc. Is that in the realm of a pretty standard setting? The thought is to keep it concervative because in a boat you can't hear them knock etc. I am running REC fuel which I believe is 90 octane? Not sure if there is more hp to be had safely or even if that amount of hp (small amount?) would make any difference in a boat. As is they are 500 hp @ 5300 tq is 517 @ 4400. Only 9:1 compression. Thanks for your thoughts.

I should have said that total advance is 33 degrees and it's all in at 3000 rpm.

Lots of guys on here with way more experience than me, but that sounds about right.

might get more replies in teh tech forums not general boating.

Most will probably say 32-34 total.

Had my motor 540 freshened last year. Got it back and had some issues, so during my troubleshooting I checked timing. Was supposed to be 34* but the mechanical advance wasn’t working correctly and it was running up to 44* all in around 3000 - not good. At any rate, boat ran the same mph at 34 as it did at 44. At that low of comp probably wouldn’t hurt anything to try 34 and see if it runs and better.

Moved and merged with his other thread:kiss:

32-36* is the norm for most BBC builds.

On your typical modded big block with 9ish:1 compression. 34 for pump gas, 36 for race gas. There are a MILLION other factors, but with the info you've given here its a safe bet.

Thanks everyone for your input. I'll leave it at 33 .

I don’t know where your initial is but msd largest bushing is 18 degrees which makes going into gear a bit challenging as your base will be 16. I recently put in a 14 degree bushing and have my base at 20 and it’s a lot happier. I did buy a Daytona control box but may not install it now. Just some food for thought. Not sure what ignition you are running.

I bought the ready to run MSD distributor for marine use. My dyno guy installed the "black bushing" and I believe he used the lightest and the medium springs for the advance. He knew it was for a boat and I did mention that I need / want it to behave around the docks.

Heads and cam play a big part with timing. Mine were set to 42 degs when I bought the boat. Ran it like that for 2 seasons before I put a timing light on them. Pulled plugs and no detonation was found. Dug into the distributors (MSD) and found springs rusted/missing and mech adv stuck at full advance. Freed them up and replaced springs. Set to 36 degs total. Starters are much happier. Lost a couple of MPH on the top end. Normally, I agree 36 degs total should be max but there are exceptions.

yeah , that’s the 18 degree bushing. Like I mentioned, if it needs a little more initial there are larger diameter bushings available

Yup, I think they came with a couple different bushings and springs. The dyno guy says that this is always the first thing he does is swap out what ever bushing for the black bushing. If you look at my posts, you know that I'm no mechanic. So I say this as a question: I don't know if it matters or not but the dyno guy said it has a ton of vacuum at idle. Does that mean it should handle the load of in and out of gear better? He knew these were going in a boat and I told him that I needed them to be good around the docks etc. These are not crazy builds and the cam I understand is pretty mild and on a 112 degree lobe separation. I'm hoping it works as is. If it gives me trouble, this will be the first thing I look at. Thanks for your help.

You should be good. Lower vacuum big cam motors not so much.

I played around with big timing on the upper end with VP110 as a safety net so to speak. No extra performance measured. 32-36 seems to be the best all around number. Where I did experience very noticeable gains in regards to timing was coming up on plane in the 2200-3200 rpm band. If set too low (about 22-24 in my case) boat felt sluggish getting on plane. Just a few more degrees and it really woke up and was almost like a new motor when coming on plane. So I would put as much timing as the motor allowed in that rpm band that didn't cause detonation.