Magnum ignition with 525SC
 

I have 1997 454 mag carbs, with Thunderbolt V ignition. I have bought the blowers and carbs from 525SC's. My motors are 8.5:1, a 525SC is 7.5:1. Can I safely use the stock ignition system? My modules have 24* advance totally in @3700rpms, 525 has 22* advance totally in @4500rpms. I was thinking of setting my base timing to 11* to come up with the right total advance of 35*. Will it idle decently, and will the advance coming in early, combined with higher compression cause pre-ignition or detonation problems? I want to run 93 octane. I really don't have the money to buy 2 complete ignitions systems, it woulld be good to run what I have.

I would strongly recomend the crane ignition box which has a direct connect to your distributor and programmable curves. Use the preset blower curve and set max timing at 30 degrees. Anything more and your asking for trouble. If you absolutely are out of money then run what you have and still limit your max to 30. You will have to get a degree tape if your balancer is unmarked. Do not trust a timing light with advance built in. If it wants to back fire off idle then advance it 2 more degrees and try it. Make sure you also use colder plugs like ngk 5673-8.

yes it will work fine merc set theirs up like that for warranty /(for sure it was no other reason ) you will have a great combo stay around 5 to 6 lbs of boost ..alot of times we lock or pin the dist to have 34 degrees at all times as it relly helps idle !!
I would have a total of 32 to 34 no more the dyno nor your boat would show little if any difference

IT WILL BE A BEAR !!!!:D :D :D

Thanks guys!

I wouldn't run any more than 30-32 degrees total timing. you won't notice the ndifference from 35 and you have some safety margin then. It doesn't take long to hurt a boat motor if it's detonating.

I would try to set it up with at least 10 initial and no more than 30 total to start using the cheapest gas you're likely to run. Check your plugs for detonation and adjust your timing to maximize the total. On the Tbolt IVs, you could use the V6 box, not sure about the Tbolt V thogh.
Less than 10 initial and you'll probably foul plugs at idle, over 30 with 8.5:1 and you risk detonation.
I would rather loose a couple hp by not running as much timing and have my engine survive a few extra years.
Gary

We run 8.5 and 9.0 all the time and 30 to 34 degree's locked or advancing 92 or 93 oct as I said theres little differance in performance from 30 to 34 :D :D :D :D

bobby daniels
You're probably right. Just playin' it safe.
Gary

Yep GARY and safe is always smart !!:D :D

I plan on running 93 octane all the time, I hope it will be happy with that.