383 timing

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josh_2562
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383 timing

Postby josh_2562 » Thu Apr 17, 2014 10:52 pm

Hello everyone.
Bought my 1st carmotor boat off of my buddy last weekend. He had some problems with the distributor melting wires. I took the boat out for a ride and the engine would spin up to 5200rpms and start right up and ran good. got the boat home after stopping by the car wash and sparying it off. Cranked it up to make sure it still ran. Noticed the tach was not working so i messed with the wires going in to the distributor and the tach started working again. About 30 seconds later the engine shut off like some one shut the key off. Checked and had no spark.knowing my buddy had been having problems with the distributor i decided to put a new msd distributor in it.

I wasn't sure what the timing should be set at so I searched on here and found 32degs is a safe #. Set the total timing at 32 degs.the engine will only spin up to 4800rpms set at 32 degs. I set the timing at 3000 rpms is this right?
Could the timing being off make it lose 400rpms?

I took the cap off the old distributor and one of the advance weights and spring was loose in the distributor.
Thanks for any help

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skinny99
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Re: 383 timing

Postby skinny99 » Thu Apr 17, 2014 11:15 pm

K.I.S.S. Have you tried setting the timing to 34* or 36* and doing a SHORT Wot test to see if it gains the lost RPM's?
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josh_2562
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Re: 383 timing

Postby josh_2562 » Thu Apr 17, 2014 11:29 pm

No. I was going to try that but didnt want to try it with out asking here 1st.
Also the engine im told is a 383 with aluminium heads. I can't find any markings on the heads besides a W. The Intake is aluminium with a large chevy emblem on it. Thanks for any help

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skinny99
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Re: 383 timing

Postby skinny99 » Fri Apr 18, 2014 7:37 am

Post some close up pics of heads and intake. Someone here will have used them.

32* is a good starting point. It is safe and the engine will run well. All depends on cylinder head design. Older conventional combustion chambers generally like up to 36* of timing to run optimally while newer fast burn designs can run their best as low as 30*. We are fortunate that with that big Air Brake/Dyno we have on the back off our boat we can make changes and get instant feedback. If you make a change and it gains WOT RPM you "generally" have made a good change. Of course there is more to it than just WOT testing but that is a good start.
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flying fish
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Re: 383 timing

Postby flying fish » Fri Apr 18, 2014 8:04 am

Might want to think about setting your timing according to what your spark plugs look like. Timing is heat, so make the heat right in your cylinder.

Gaining 400 RPM may lean her out to the point of hurting engine.....

Adding or taking timing away is same as adding or taking away fuel when talking heat in the cylinder.

Chase correct burn, not some RPM? Adjust prop accordingly. JMO-
15' DB - 6.2 LSA - 4 blade 82" R - 2.52 CH-4

josh_2562
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Re: 383 timing

Postby josh_2562 » Fri Apr 18, 2014 9:35 am

flying fish wrote:Might want to think about setting your timing according to what your spark plugs look like. Timing is heat, so make the heat right in your cylinder.

Gaining 400 RPM may lean her out to the point of hurting engine.....

Adding or taking timing away is same as adding or taking away fuel when talking heat in the cylinder.

Chase correct burn, not some RPM? Adjust prop accordingly. JMO-


Fish the boat turned 5200rpms before I changed the distributor out. How do i check the plugs? I know what color to look for. But do i hold it wot and shut if off or just drive it normal for a while then check them? Thanks for any help

josh_2562
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Re: 383 timing

Postby josh_2562 » Fri Apr 18, 2014 9:39 am

skinny99 wrote:Post some close up pics of heads and intake. Someone here will have used them.

32* is a good starting point. It is safe and the engine will run well. All depends on cylinder head design. Older conventional combustion chambers generally like up to 36* of timing to run optimally while newer fast burn designs can run their best as low as 30*. We are fortunate that with that big Air Brake/Dyno we have on the back off our boat we can make changes and get instant feedback. If you make a change and it gains WOT RPM you "generally" have made a good change. Of course there is more to it than just WOT testing but that is a good start.


I found the heads online. There l98 corvette heads. Thanks for the help

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Re: 383 timing

Postby loudmouse » Fri Apr 18, 2014 9:57 am

You need to set timing after full advance is in. That may happen 4000 or 4500 or could be as early as 2400 depending on how the distr is set up.
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14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

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josh_2562
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Re: 383 timing

Postby josh_2562 » Fri Apr 18, 2014 12:44 pm

loudmouse wrote:You need to set timing after full advance is in. That may happen 4000 or 4500 or could be as early as 2400 depending on how the distr is set up.


Loudmouse I set it at 3000rpms. I then ran it up to 4000 rpms and the timing did not change any more. Im going to put a set of lite springs in the distributor. Thanks for the help.

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Re: 383 timing

Postby loudmouse » Fri Apr 18, 2014 2:00 pm

Yes . I like full advance In before my cruz rpm. I also like atleast 18° @ idle. If you know how to read plugs you can keep creeping up timing and adding fuel to keep cylinders cool. Much HP is gained by a really good tune and on the edge. Everything is in the details.
15' Alumitech deckover LSX TT Oxbox 84" JX 4-blade
Gas required Water optional :dontknow:
Built and Tuned by Me
14'X8' JW, Chevrolet 122CID LNF Turbo Engine, Ox box, 80" NGR 3 blade

Life is short, eat your dessert first! :downtown:

flying fish
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Re: 383 timing

Postby flying fish » Sat Apr 19, 2014 8:15 am

The ground strap wraps around your electrode on spark plug. Adjust burn until this burn mark is approx 5/8 way up ground strap. This is above spark plug threads and below corner.

Probably a good idea to invest in an air fuel ratio meter. Eliminates all guess work.


On a carburated (mechanical secondary) piece, you can adjust burn on idle circuitry, wide open on primary burn and wide open throttle burn. Wide open on primary burn is as important as WOT burn.

Be conservative. On an airboat, engines break fast. If your burn is into the threads, are you pushing 1500+ degrees EGT'S on an extended run? :)
15' DB - 6.2 LSA - 4 blade 82" R - 2.52 CH-4


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