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ENGINE TIMING?

D

DAVE

Well-known member
HELLO ALL. I WAS WONDERING ABOUT ENGINE TIMING ON A 400 SBC WHAT SHOULD IT BE AT 3000 RPM AND HOW SOON SHOULD IT ALL BE THERE I WAS THINKING 38 DEGREES TOTAL AT 3000 RPM AND HAVE IT ALL THERE AT 2000 OR 2500 RPM ANY HELP WOULD BE GREATLY APPRECIATED 400SBC EDELBROCK CARB AND HEI NO VACUM ADVANCE HOOKED UP
 
I have been told anymore than 38 and your eatin metal up. I was runnin 36 with a lockout distributor by msd and it was great no advance at all just 36 degrees timing. you may need to put a seperate toggle to turn on the fire after you spin it over and get oil up to the engine. I had a malfunction in there and blew it to peices and couldn't get another one right away so went with mechanical advance which kicks all 36 in at about 1800 it works ok also. my engine builder says no more than 36 but lots of my friends run 38 I dont know anyone runnin more but maybe some do. are you running a multi spark box on it , i would they make a kit to switch it over. but I carry a spare hei just in csae all the fancy stuff dies again changin a distributor and settin the timing beats gettin pulled in or walkin out thats my 2 cents worth
 
36 to 38 degrees of total timing is way too much for a 4.125 bore 400. It's pushing the edge on a 4.00 bore 350. The best way to get the throttle response everybody wants. Is by running an aggressive timing curve. Put the weakest springs in the distributor you can. I actually leave out one spring and only run one. Even better if you are willing to fine tune your motor. Lock down your distributors mechanical advance. To make this work properly you need to play with your carburetors discharge nozzles (squirters). I never run over 34 degrees on a 350 and 32 on a 400. You will not make any more power by adding timing. Believe it or not pulling out ignition timing at higher RPM increases max power. But air boaters want snap and low end torque so the best thing to do is adjust your timing curve. When you have the curve kit right it will snap the same as running 38 degrees but be more forgiving when you run your boat hard and dry. I can assure you if somebody is running 38 deg in a 400 and hasn’t hurt it yet one of three thing is happening. They don’t run it hard for long periods of time or their timing light or timing marks are off. 400’s run better with less timing because the have such a big bore and when you run over 32 degrees of timing they go into detonation very easily when you hammer them. I can’t begin to tell you how many times I have tested all different settings of timing. So once again beware of someone who gives you a magic number because each motor likes something different. I hate too see people hurt the motors because of mis information.
 
Just a quick note regarding detonation. It is a bad thing.

After making a late night run, pushing through some detonation, I had to replace my engine. Not just rebuild it because it warped the block. I ended up coming into the landing at 11:00 at night on four cylinders (with a V8). Don't run if you are getting detonation. At least stop and adjust the timing a bit.

My two cents.
 
That's exactly what I mean if you had just a few degrees less of timming you wouldn't notice the diferance and you wouldn't have burned it up. Was it a 350 or a 400? Also I filled in the blanks on my last post incase somebody didn't read between my lines. 36 to 38 degrees of total timing is way too much for a 4.125 bore 400. It's pushing the edge on a 4.00 bore 350. The best way to get the throttle response everybody wants. Is by running an aggressive timing curve. Put the weakest springs in the distributor you can. I actually leave out one spring and only run one. Even better if you are willing to fine tune your motor. Lock down your distributors mechanical advance. To make this work properly you need to play with your carburetors discharge nozzles (squirters). I never run over 34 degrees on a 350 and 32 on a 400. You will not make any more power (with a 400) by adding timing over (32 deg) . Believe it or not pulling out ignition timing at higher RPM increases max power. But air boaters want snap and low end torque so the best thing to do is adjust your timing curve. When you have the curve kit right it will snap the same as running 38 degrees but be more forgiving when you run your boat hard and dry. I can assure you if somebody is running 38 deg in a 400 and hasn’t hurt it yet one of three thing is happening. They don’t run it hard for long periods of time or their timing light or timing marks are off. 400’s run better with less timing (than a 350) because the have such a big bore and when you run over 32 degrees of timing they go into detonation very easily when you hammer them. I can’t begin to tell you how many times I have tested all different settings of timing. So once again beware of someone who gives you a magic number because each motor likes something different. I hate too see people hurt the motors because of mis information.
 
Are you running this 400 direct drive or reducted?If your running dd I would like to know how the boat performs,will it run dry,what type of hull,and what kind of prop.I am considering buying a 12' fiberglass boat with a dd sb400 on it and would like to have some idea of what to expect before I drive four hours to look at it and run it.I need a boat that will run dry well on flat ground at least.
 
Yep water thunder I checked again with some folks and they suggested 32 to 34 on a 400 and a little more on a 350. I would assume everyone would know to turn it back a little if they are detonating. Every engine is different every fuel is different and if your at the edge then you better pay attention to small changes as they can have big impacts in ways that are not pleasant especially to the wallet. It seems the feller who told me 36 to 38 on a 400 was confused with a 350 and they didnt call me and let me know when he melted it down, funny how that works huh sorry for the bad info it was with best intentions next time I will check em out a little better
 
The biggest problem I found with timing a 400SBC has been the stock harmonic balancers. Their usually 20 or so years old and the rubber ring in the balancer has slipped. So your timing tab reads 10 or so degrees off. They always seam to move in the direction that shows less than the actual timing. I learned years ago after blowing up a lot of nitrous motors. Too check your marks at TDC and degree every single balancer to the timing marks. On a big nitrous motor being off 3 degrees is the difference between winning or making 8 new ashtrays for the shop. And your right if your not 100% concerned about racing just back the timing off a couple of degrees
 
HEY GUYS THANKS FOR THE INFO ON THE TIMING THIS IS ON A BUDDYS BOAT WE SET THE TIMING TO 32 AT 3000RPM AND DISCONNECTED THE VACUM ADVANCE WAS THAT A GOOD IDEA AND ALSO SHOULD I REPLACE THE WEIGHTS AND SPRINGS IN THE DIST. IT SEEMS TO IDLE AT ABOUT 22 OR SO DEGREES INFO ON THAT WOULD HELP GREATLY
 
Here is a great all around combination that I have found for stock to mild 350 SBC in airboats. Install a curve kit, some people call them spring kits. Run the weakest springs and disconnect your vacuum advance (which you have already done). If you show no mercy and beat your boat to death set your total timing at 32deg. If you operate your boat in a sanely manner and don’t run the hill too hard set your total timing at 34deg. Do not be concerned about the initial timing the trick is to set your total at 32 to 34deg and then adjust your curve kit to get it there as quickly as possible.
 
Hey Waterthunder

I have a ZZ4 in my Boat and so far I am very pleased with it.What do you think of this engine and do you have any tips for this engine.
It has a mecanical marine distributor in it.
 
FYI, you big block owners should keep that total advance down around 28 to 30 degrees also. To much advance will cause bad things to happen.
 
(Sniper) The marine, MSD, old GM and HEI’s distributors all utilize the same mechanical advance weight and spring system. I would just install the springs from a curve kit and set the timing as I mentioned above. She will have more snap and throttle response I guarantee ya. (Guest) it’s nice to see somebody who understands each application is different just like you mentioned big block Chevy’s are a whole different ball of wax. I would bet you have a large boat from the timing you told me ya run.
 
You are pretty correct Waterthunder, the hull is not really that big but I use it for duck hunting on the Texas coast and it is usually loaded. I run a 16' Mark Robicheaux hull with a 450hp/502 with 2/1 and a 80" 3/blade PowerPlus. As I mentioned a person needs to pay close attention to timing and also fuel/O2 ratio, (don't error to the lean side). I use a O2 analyzer that displays rich/lean with indicator lights for tuning my engine. I have never wrecked an engine but have come close. I have had the exhaust cherry red all the way to the transom and this is not a good condition.
 
I ran a 350 driect drive for 2 1/2 years set it at 10 deg with the vacum advance hooked up turning a 72-34 at 3000 rpm all day.found out if you put to small of air filter on it will not rev up fast enough and won't turn max rpm.
 
Most people don’t want to hear this but the best crate motor to buy from GM is their iron head vortec 350 330HP. The ZZ4 has a serious down fall it’s their aluminum heads. They are a thin weak casting and blow head gaskets whenever you get them hot or run them hard. All G.M. aluminum head castings are thin and weak not enough meat in the deck surface where it counts the most. They warp after you blow a head gasket so you must deck them usually around .020 thousand. After you deck the heads they blow a gasket even quicker. I have seen it time after time. The heads will work for 6 or so months then they pop a gasket and have to be decked then they last 3 months get warped and must be decked again then they only last a month each time ya deck them they get weaker. If you want an assembled crate motor get the iron head 330 HP vortec. It’s a great motor and you can beat them like an anvil. If you are capable of doing the work yourself buy a vortec 330HP short block and put a set of after market aluminum heads on them. There are 4 or 5 different manufactures of good aluminum heads that I use on my customers airboat motors. If YOU GO THAT ROUTE STAY AWAY FROM ANYTHING TRICK FLOW, AFR or TWISTED WEDGE. Just about everything else is a good head and comes with a ¾ inch thick deck surface. If you get the short block and you bolt on the right heads, intake and rockers it’s easy make 375HP.
 
Waterthunder

I have been runnig the heck out of my boat for about a year now and so far I have had no problems yet out of it,the Engine temp never gets over 175 and the way I have it set up the max rpm is 4900.
when and if the head gasket blow can I just put a different set of heads on the ZZ4 block to cure having another problem?
 
I'm sure you will be alright only turning 4900RPM she will be trouble free for a long time.
 
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