I just rebuilt my engine and have a couple of questions.
Engine is a 454 bored .030, Mild cam, heads are stock (no valve work)
Approx. 9-9.5:1 cr
Running a tunnel ram with dual 660's.
All new MSD ignition (Billet distributor, Digital 6 box, and coil)
Basically to give some history on the engine, I recently blew a head gasket which opened a can of worms. Turned out I had a cracked head and blown piston rings. I've heard MANY reasons as to why this happened. The main reason was detonation. (This is why the ignition is all new). When the boat blew, it had dual 600dp's. I was told I had a leaning problem also so I picked up the 2 660 setup.
The boat idles, but loads up after a bit. I have good response and runs well up to about 3000 rpms. After the 3000 mark, the secondaries begin to open and all I hear out of the headers is popping as if it is missing.
My questions are:
1.) What should my initial timing be and what should the total be and at what rpms should I read my total timing?
2.) Do you think the carbs are too big for this particular setup?
Any ideas will be VERY helpful because I'm completely lost at this point!
~Paul
Another thing I forgot to mention is the distributor has adjustable springs and stop bushings for the curve.
I can have 18, 21, 25, or 28 degrees of total curve and basically can have the curve total out at anywhere from 2400-5400rpms.
Any idea what how many degrees of curve I should have and what rpms I should set it at?
Most will set the timing to be all in by 3000 rpm. Total timing is usually 36*.
My dist. lol (83606 (marine)) Set the mosty aggressive you can to keep the timing OUT untill you come off idle and it should be fine. Try 8 or 10* base timing, 25* advance stop in the dist, that's a 33* to 35* final advance. I THINK the curve took the blue and the silver (light) spring, but look in your instruction manual. Timing will all be in by about 2800RPM. An aggressive advance curve works well in jets since they don't really spend any time in the partial advance area.
I just put that dist in my 454 over the winter, it is base timed 10 deg, test-run on my storage stand, and ready to tear the lake a new one.
You'd do better performance-wise (and gas mileage-wise) with a single 700-750CFM 4-barrell on a Performer RPM Air Gap intake tho. No bling-speed there tho.
You'd do better performance-wise (and gas mileage-wise) with a single 700-750CFM 4-barrell on a Performer RPM Air Gap intake tho. No bling-speed there tho.
yea, what he said...
When an engine bangs and pops on the upper end it is usually a sign of too much fuel, more than you can burn. Dual anythings on that engine is way too much fuel. As mentioned, try a single 4 of some nature, maybe one of those 650 DPers and you'll be alot happier using the boat instead of working on the boat.......MP
Ok so my timing was WAY off then. I had the stock springs in the distributor which doesn't fully advance until over 5000 rpms!! And for some reason I thought my base timing should have been down in the 5-7* range. Looks like my engine was running WAY TOO retarded! I'm going to try the new distributor springs this weekend. Hopefully I don't have to change out my carbs. I just spent money on those damn things! Thanks for the replies guys!
Ok so my timing was WAY off then. I had the stock springs in the distributor which doesn't fully advance until over 5000 rpms!! And for some reason I thought my base timing should have been down in the 5-7* range. Looks like my engine was running WAY TOO retarded! I'm going to try the new distributor springs this weekend. Hopefully I don't have to change out my carbs. I just spent money on those damn things! Thanks for the replies guys!
Don't worry too much about different advance curves. or timing at idle. Most jet boats don't plane or operate below 3000 rpms.
2800 - 3000 rpms is typically when most, if not all distributors are at full advance. The most important thing to look at is your total advance.
I would set it for anything between 32* - 36*total advance @ 3000rpms and above. Anything less you lose power and anything more you'll just be beating up the bottom end. I've heard some run successfully above 36* but I think most would agree there is really no point.
BTW disconnect the vacumm advance and plug it.
I have seen popping both on the dyno and on a boat due to retarded timing but the popping only occured while cruising or at lower rpm's. As soon as we started the pull on the dyno the popping went away. It could also be too much carb. We are running a single 850 DP on the 460 Ford with good results. I also timed the initial at 20 deg with total in at 3000 rpm at 36 deg.
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