rob vanharten

Guys I am trying to figure out why my 99 28' daytona eliminator is down about 10-15 mph from were is should be on top end. I have gm 572 crate motors that dyno at about 645hp. These engines have about 75 hours on them and run excellent. They have the hei distributors with the vacuum advanced blocked off. I started another thread discussing drive ratio's, x dimension, props, and all the other possible explanation for my low top speed. It was suggested to verify my total timing. This afternoon I threw the timing light on each motor and could hardly believe my eye's when I saw about 22 degrees of initial timing, and about 50 degrees of total timing on each motor!!! This seems almost impossible, and I would have thought the motors would have detonated themselves right in half with this kind of timing. I have had zero pinging, popping, or detonating that I have noticed. Could this timing actually be hurting performance??? GM recommends 36 degrees ot total timing for these engine's, very puzzled right now.... Please fire away with comments, and suggestions.

billy boats

HEI with vac advance blocked off? What is giving the advance to ignition ? Are you using an after market ignition box which now controls advance? In any case you most likely are not getting a correct reading from your timing light . Some ignition systems require you to use a jumper wire to put ignition into a base timing mode.

donzi matt

iTrader: (1)

I would check to see if the balancer slipped to start with and verify TDC first and foremost.

Bawana

There is a point where too much advance at a given RPM will fight against piston rotation. To me I think 50* is way too much. 36* total sounds more realistic for your setup. So to answer your question, yes timing can & will affect engine output.

SB

iTrader: (1)

Not impossible. I've had some BBC's run best with up to 42* total...but that was light cars and I wouldn't do that in a boat.

That said, you having a light catamaran may have kept you for eating a motor or two. A big heavy old Cig, Apache, or what have you - wouldn't have been so lucky.

You won't hear much detonation in a boat...that's near impossible...exhaust and other noises are too loud.

Pull your plugs and do a compression test on all cylinders to make sure you haven't hurt anything.

Then, set the timing by total.

BTW: did you just get this boat ? Or did someone else tune it for you ? I wouldn't understand how the timing would move that much - it would hve to be done by mistake or with little/ no knowledge om how distributor timing works.

rob vanharten

Yes I have only had the boat about a month now, and am just working some bugs out of it. The boat was rigged with brand new crate motors two years ago, and has been running in "this" state ever since. This is obviously way to much timing, could this be result of my poor performance?

billy boats

What ignition system are you using??
You said HEI Dist with vac advance blocked, so what is controlling the advance ? Thunderbolt, MSD, Daytona sensors,accel , mefi....?????

14 apache

iTrader: (1)

check it with a different timing light.

14 apache

iTrader: (1)

Sounds like stock HEI with a centrifugal advance. No cdi box.

SB

iTrader: (1)

HEI's with vac advance, are automobile units that use weights for mecahnical advance and vacuum for adding more advance for high intake manifold vac situtations - ie; cruising with light throttle.

So, that said, maybe time for some marine units.