Go Back  Offshoreonly.com > Technical > Do It Yourself, Boating on a Budget
Dialing my setup 383 carb Alpha >

Dialing my setup 383 carb Alpha

Like Tree1Likes

Dialing my setup 383 carb Alpha

Reply

Old 09-22-2019, 07:39 PM
  #1
Registered
Thread Starter
 
Join Date: Sep 2009
Location: Lake Winnipesaukee, NH
My Boat: 87 Formula F 223LS, 383 Stroker
Posts: 325
Default Dialing my setup 383 carb Alpha

I have things working pretty well on the engine. You may recall that I had been fighting some head gasket issues which now seem corrected. I bought a new DUI ignition as well, it's been working as it should, It's basically the same style GM did through the eighties until fuel injection came on, but with some modern electronics and windings that give a supposed 50,000 volt spark.

My engine is a 10:1 383 Chev with Dart Iron Eagle 76 cc chambers and 75 cc runners with some porting to open the intake runners. Theres a Quick Fuel M750 on an Edelbrock Dual Plane Airgap for fueling. The cam is a Comp Cams OE roller style CS 268XFI HR13, Valve Lift .570 Intake .565 Exhaust, Duration at .050, 218 Intake 224 Exhaust, 113 Degree Lobe Separation Angle, Intake Centerline 109 Degrees.

I admit that I borrowed the cam idea from SB's 355.

It runs well now but I have an issue with idle. To get a decent idle in gear around 750 rpm, the engine runs about 1050 in neutral. I don't think that's too good for the drive gears. I want to be able to lower the neutral idle without stumbling the engine in gear. My old boat had a 350 in it and I got hardly any rpm drop in gear with that one, but it was a far less aggressive cam. .

Am I right to think that I want more base timing? I already have my distributor set up for 34 degrees all in, I'm leery to go much past that without a dynamometer session.
So with my 22 degree distributor the base timing is 12 degrees. I just can't hear if the engine is breaking up so I haven't dared to run any more advance.

I can tell you I get 155 or 150 degrees showing on the dash temp gauge, and I run quality 93 octane fuel, usually Shell. i have an air fuel ratio sensor set up too. so I can manage my fuel with jetting and feed adjustments.

I emailed the distributor company, they will recurve it for me if I return it over the winter.

I was thinking I should test the idle with more timing til it's happy, then go for an advance curve that stops where I need.

What do you all say?

BTW sorry about the bold cam details, it's a copied section of their description that I could not see a way to un-bolden.

Last edited by NHGuy; 09-22-2019 at 07:52 PM.
NHGuy is offline  
Reply With Quote
Old 09-22-2019, 08:26 PM
  #2
Registered
iTrader: (1)
 
Join Date: Mar 2012
Location: Cape coral, FL
My Boat: 35 Fountain
Posts: 4,008
Default

This is where modern ignitions help. I had the same issue and swapped over to Daytona sensors ignitions boxes. They have an idle stabilization feature that basically throws timing at if it tries to drop below a certain rpm. Best thing I did with an aggressive cam
Crude Intentions is offline  
Reply With Quote
Old 09-23-2019, 12:58 AM
  #3
Charter Member # 55
Charter Member
 
Griff's Avatar
 
Join Date: Oct 2000
Location: Omaha
My Boat: .......32............. ............Active Thunder....
Posts: 17,048
Default

For testing idle only, Advance the base timing to about 22* and play with the idle and see if the additional helps.

Of course, don't run the boat much above idle with that much timing.
Griff is offline  
Reply With Quote
Old 09-23-2019, 07:59 AM
  #4
SB
Registered
iTrader: (1)
 
Join Date: Nov 2004
Location: On A Dirt Floor
Posts: 10,000
Default

I have the exact same cam installed in a regular 5.7 with Brodix heads and Weiand Air Strike Manifold. This is just like Eddy AirGap but has fully divided plenum. Not sure how much this (fully divided vs slight cut out in AirGapRPM) effects idle on small cam motors. Also has BG650 SeaDemon that has 4 corner idle mixture screws.

Not promoting one part over the next, just stating what this engine has.

Anyway. With 10-12 initial timing this motor will and has idled "all day long"..no issues. TBIV distributor. 22* Module.
.035" spark plug gaps. Projected nose spark plugs.

Difference in 1/4 turn on the idle mixture screws can and does (in my app) make a ton of difference for great, or not so great, idling. Cold especially since choke is removed from carb.

800rpm neutral idle. 600-650 in gear idle. Lightweight boat. 21"-23" props. Cleaver/round ear/etc all perform same when in gear idle.

Last edited by SB; 09-23-2019 at 08:02 AM.
SB is offline  
Reply With Quote
Old 09-23-2019, 11:05 AM
  #5
Registered
Thread Starter
 
Join Date: Sep 2009
Location: Lake Winnipesaukee, NH
My Boat: 87 Formula F 223LS, 383 Stroker
Posts: 325
Default

Good to know. Maybe a fatter mix is all it will want.
SB likes this.
NHGuy is offline  
Reply With Quote
Old 09-23-2019, 11:15 AM
  #6
SB
Registered
iTrader: (1)
 
Join Date: Nov 2004
Location: On A Dirt Floor
Posts: 10,000
Default

Double post.

Last edited by SB; 09-23-2019 at 11:26 AM.
SB is offline  
Reply With Quote
Old 09-23-2019, 11:15 AM
  #7
SB
Registered
iTrader: (1)
 
Join Date: Nov 2004
Location: On A Dirt Floor
Posts: 10,000
Default

Could be. On the trailer I set the idle mixture screws for best idle, and then I turn them 1/8-1/4 turn richer as somewhere near here seems to best for putting into gear and less time to warm up at docks before idling off with no drama.

Like others have mentioned a few degrees extra of initial timing can do wonders sometimes too. I didn't need it though.

Last edited by SB; 09-24-2019 at 01:54 PM.
SB is offline  
Reply With Quote
Old 09-23-2019, 02:27 PM
  #8
Registered
 
Join Date: Oct 2010
Location: Cheboygan, MI
My Boat: 1998 Velocity 280
Posts: 1,008
Default

I'm running a bit more cam and before I went to Daytona Sensors, I had to lock my distributor to get it to idle decently. Looking at your specs, you are going to need a lot more initial timing with that cam. I too also highly recommend Daytona Sensors ignition with idle stabilization with a little tweak to the timing table. I set the timing below my idle set point to max timing set point. The built in idle stabilization will oscillate between base timing and all in timing to stabilize the idle which can make things better but not perfect. I added full timing at 500rpm or below dropping to 24* at 1000 and then backup again to 34* at 3000rpm. I don't have a choke and cold starting in northern Michigan in 60* temps, can be tough. With this new setup, I was absolutely shocked at how well it stayed running cold. Once warmed up in gear with steering to lock I couldn't stall it, before I could hardly keep it running.
ThisIsLivin is online now  
Reply With Quote
Old 09-23-2019, 04:14 PM
  #9
SB
Registered
iTrader: (1)
 
Join Date: Nov 2004
Location: On A Dirt Floor
Posts: 10,000
Default

Originally Posted by ThisIsLivin View Post
. Looking at your specs, you are going to need a lot more initial timing with that cam.
You may have missed my post just above yours. I do it all the time too. LOl.
SB is offline  
Reply With Quote
Old 09-24-2019, 12:01 PM
  #10
Registered
iTrader: (1)
 
articfriends's Avatar
 
Join Date: Jun 2004
Location: Frankenmuth
My Boat: EX 99 MPH 272 Baja owner, 1999 Scarab 33 AVS NOW
Posts: 6,317
Default

Make a limiter bushing, put it on pin in distributor so you can set base timing at 20 or 22 but still only get 32/34 total. 10-1, im going to say if you go higher on total you may be rattling it, Smitty
articfriends is offline  
Reply With Quote

OSO Sponsor
OSO Advertiser
OSO Advertiser
OSO Advertiser