Where Should the Timing Be Set on a 383 Stroker
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Join Date: May 2008
Location: hells training ground (aka Ariz)
Posts: 3,113
Re: Timing and Carburetor setup for 383 stroker
Backing up just a little, and not to diminish or degrade ANYTHING that has been said. That is ALL great and sound advice. Storm and longhair have a lot of experience and smarts to share.
I just am seeing something here that is a flip side of this coin. You need to be 100% sincerely honest with yourself in decising which road you go down here. If I am wrong in the USE of this vehicle, then you need to ignore everything I'm about to say and heed the sound advice you have already received.
It looks to me.....
like you are running this motor much like it IS a race motor right??? I say do away with the 'street' stuff and build it , drive it, tune it, and RACE it like what you built it for. Am I reading wrong what your doing with this thing???? It is a off road, fly through the desert as fast as you can go weekend warrior???? I have a couple friends that run trophy trucks and that's just an INSAINE way to spend your weekend but hey,,, everyone has their addictions ( me included LOL)
If so, I suspect you are running around 3000-4000,, and 4500 most of the time, on and off the throttle like a circle tracker. THAT is a very different animal than a normal 4500 pound street driven truck.
You need to tune it like it's a 3000-4500rpm+ driven machine, not a street machine,, (Again be HONEST with your self,, if the desert is a once a month thing and you drive this on the street the other 27 days a month,, the below comments are NULL AND VOID!
The long rod, flat top, tight quench, 383, with the AFR aluminum chamber is a very VERY efficient combustion chamber. Most of the guys are finding the normal 34-36 total timing is WAY more than is needed for the efficient chamber. I ran a 383 similar to yours with 6" rods, AFR 210's angle milled buttloads to 54cc for 12:1 compression. On the dyno we proved 31-32� was all it wanted, even running C-12 fuel (108 motor octane). Lots of the SBC small efficient chamber motors are more succaptable to too much timing. Sneek up on it cautiously. Detonantion is a ugly thing.
Go make a couple of hard runs and pull 2 or 3 plugs. Then...
Here is one of the BEST plug reading pages I've ever found.
http://cochise.uia.net/pkelley2/sparkplugreading.html
If your not going to run a Wideband O2 and monitor what is going on (which I can not stress enough,m that is the best $ you will ever spend on tuning the thing), then cutting the motor clean after a hard run and let things cool, and read the plugs is your best answer. You have an advantage over us drag racers,, you can just STOP,, any-darn-where you want and let it cool and read the plugs. Take advantage of that.
You have a LOT of motor there. I looked up the specs on that roller cam and I can't say I'm sure why you picked a straight pattern (230/230 @ 0.050") cam with those heads. Talk to AFR and Tony will adamantly advise you to run a split patern, with AT LEAST 7-10� more exhaust duration. Your under .6 lift so it should be really durable, but the straight pattern,,,, Are you running some wildly HUGE exhaust primary???
OK,,, All that aside, TWO things I see that should stand out from 'normal' tuning.
Your running 2500-5000,, you don't need a timing curve. Your above it at 2500-3000 rpm anyways! Again being honest with yourself,, how much time is the motor really running between idle and 2500???
Down side of no curve is you need a ignition system with a start retard (most all MSD and Mallory have automatic start retard under 500rpm) Without a start retard you will be knocking the nose-cone off the started regularly (or buying pinions for the mini starters) and seriously fighting hot starts. In the desert you know battery survival is dismal at best,, internally broken battery posts are part of the game. A hard starting motor is foolishness in the desert,, but a timing curve when running above 3000 all the time is also. (Pick you headaches carefully) The motor will be easier to tune with a locked out timing.
Your on and off the throttle , running above 2500-3000 all the time,, you need a good carb set up for OFF ROAD. Talk to Patrick James at Prosystems and tell him EXACTLY what your doing. A vacuum secondary carb seems useless for flying through the desert at 60mph, bouncing off ruts, ditches, rock and cacti.. on and off the throttle like a dirt track racer! I know Patrick builds off road carbs that can take the slosh of the desert, but you KNOW EFI is the 'right' answer to what your doing here,, right? Look around and there is starting to be a of the Holley Commander (precursor to the Atomic EFI) MPFI systems out there pretty reasonable. It's a good, tunable, reliable ol system. And the prices are getting right. I saw one go through RacingJunk not long ago with 32# injectors, unmolested harness and a Walbro pump sell for $1800. That's getting reasonable for what benifits you will see in the offroad.
Just my 2� for you
be SURE where your going before you spend them.
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Last edited by Marv D; 06-01-2013 at 11:03 AM.
Where Should the Timing Be Set on a 383 Stroker
Source: http://67-72chevytrucks.com/vboard/showthread.php?t=582625
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