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Discussion Starter #1
Hi,
I have a Chevrolet Performance SP383 Stroker which has been timed per their recommended Specs as detailed below:

"Install Distributor as follows: (1) Locate cylinder #1 top dead center (TDC). (2) Rotate engine to 12 degrees before top dead center (BTDC). (3)
Align Rotor with the cylinder #1 terminal on the Distributor.
After the engine has been installed in the vehicle, recheck the oil level and add oil as required. It is also good practice to
always recheck the ignition timing after removal and reinstallation of the distributor. See step 4 or engine specifications for the
proper timing information.
3. Safety first. If the vehicle is on the ground, be sure the emergency brake is set, the wheels are chocked and the car cannot
fall into gear. Verify everything is installed properly and nothing was missed.
4. Start the engine and adjust the initial timing. If using an HEI distributor, set spark timing at 32 degrees before top dead center
(BTDC) at 4,000 RPM with the vacuum advance line to the distributor disconnected and plugged. The vacuum advance
canister should remain disconnected. This engine is designed to operate using only the internal centrifugal advance to
achieve the correct timing curve. Rotate the distributor counterclockwise to advance the timing. Rotate the distributor
clockwise to retard the timing".

Engine runs hotter than what I would like. Was thinking of hooking up the available Vacuum Advance. From the above Specs that were solely based on using Mechanical Advance, what would you recommend that I should use for timing Specs when adding vacuum advance to the mix?

Distributor is a Mallory 8360.

Took the car out yesterday. Air Temp was around 90 degrees. Temp was fine for a while and then started increasing to about 220 degrees when heading home to the garage. There were no long traffic stops. Radiator and Water Pump are new. Cold Case Radiator and Edelbrock Water Pump. Engine has a little over 600 miles on it. Car has a Vintage Air AC System. AC Condenser and a Transmission Oil Cooler are both mounted in front of the radiator.

Carb is a Holley 770 CFM with electric Choke and Vacuum secondaries.
 

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I don't know that vacuum advance would affect engine temp unless you're timing is already pretty retarded. What is your initial timing at idle, 700-800 rpm, without vacuum advance?
 

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Discussion Starter #3
It was suppose to be set at 12 degrees BTDC and then a total of 32 Degrees BTDC at 4000 RPM using mechanical advance only.
 

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"The vacuum advance canister should remain disconnected"

That would be absolutely hilarious, if it weren't all the way criminal.

Send an email to [email protected] and you will get the FREE package, instructions and pictures on how to PROPERLY set the vacuum advance up correctly (WHICH IS TO USE IT ON FULL MANIFOLD VACUUM).

And, YES, correct full manifold vacuum advance WILL help keep engine temps to the right levels.
 

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Mike
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I agree with Dave Ray. You should connect the distributor's vacuum advance (VA). Dave's instructions for connecting and setting/limiting the VA will provide a lot of useful information.

In a sense, running your engine in a mostly street driven car without VA during high vacuum situations (light throttle, cruising & idle) would be similar to having retarded timing. During high vacuum situations, the engine air/fuel ratio is leaner... and a leaner mixture takes more time to burn... so it needs more spark advance to to fire the mixture sooner. So without the additional advance provided by the VA, the engine is working harder than it has to during high vacuum operation.

Question... is the Mallory 8360 distributor similar to a MSD 8360 distributor?
If so, there are mechanical advance bushing and spring changes that could be made to optimize your advance curve for your 383.
 

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I would also agree with Dave BUT . . . . . if you have a GM Warranty I would run it the way they say at least for the warranty period.

That being said, I doubt that the timing has anything to do with the engine coolant temperature. You did not mention your fan setup in your comments. Is there a shroud on the radiator ?

Also, where do you have the temp gauge sender ? If you have a temperature gun check the temperature at the thermostat housing and see if it agrees with the gauge. That should be the hottest spot on the engine as far as coolant goes.
 

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Discussion Starter #7
RifRaf
I believe it is similar to the MSD version. It came from someone else off of another Engine, so I don't have any accessories that may have come with it or the manual.
 

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Discussion Starter #8
BillK,
Warranty is probably expired as it has been over 2 years even though the engine only has a little over 600 miles on it. Temp sender is in block on the drivers side.It is an aluminum Radiator with an aluminum shroud. I don't currently have a temp gun.
 

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Mike
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I believe it is similar to the MSD version. It came from someone else off of another Engine, so I don't have any accessories that may have come with it or the manual.
If it is similar to the MSD, you could always get the MSD Bushing & Spring Kit (part 8464) to gain some adjust ability in your distributor's advance curve.
If this kit did work in the Mallory 8360 distributor (... and it was my engine), I would probably install the blue bushing and the 2 medium weight/tension springs to control the mechanical advance. I would then set the initial timing to 14°- 15° BTDC (VA disconnected). This set-up would would provide about 35°- 36° of total mechanical advance at about 3000 rpm. I would then follow Dave's instructions for connecting and setting the VA.
  • Note: If the Mallory 8360 is similar the MSD 8360, you will need to make a vacuum advance limiter plate (if needed)... since the Crane VA limiter plate will not fit into this distributor. Below is a photo of the "home made" limiter plate I made for my MSD 8360 (red arrow).
265102
 

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Don't want to hijack this thread but how much Vac is available? Is there a Vac canister that will be all in at 8 hg?
 

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"That being said, I doubt that the timing has anything to do with the engine coolant temperature" Sorry to use 40 plus years of my own personal engine design and ignition development to give all that info that GMPP erroneously disagrees with, but, correct ignition timing, not retarded, has proven, over and over again, to give more efficiency, better fuel economy, better drive ability, and cooler running engines, many, many, many times I have given it to people, FREELY.

As far as the Mallory and MSD, please remember that about 6 years ago, MSD purchased Mallory (not far from me here, in Cartoon City), and then, 2 years or so ago, Holley purchased MSD, so they could have a distributor manufacturing facility for their EFI and other setups. So, for stuff like the old FiTech EFI, now the revised units called Sniper, Holley/MSD distributors are only a pittance of cost, $445.00 or so. A suitable unit can be built for half that, even to a stock points type distributor.

As far as the vadcuum advance goes, Crane adjustable has all enyone needs, adjustable canister, 3 sets of mechanical advance springs, and the correct adjustable degrees stop plate outlined in my info package, gives all 20 stock vacuum advance settings, and everything in between them.

Ask for the vacuum advance package, you will then understand. IT IS FREE, NO ADS.
 

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Mike
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So this is off some other engine,and you know what the timing curve is, and it is correct for this engine as chevy performance requires ?
If you are asking me... these are the same timing and advance specs I use for my Dart SHP small block 400 and they seem to work pretty well (at least for me). From the posts and articles I've read, a lot of other sbc 383 (mostly street driven) seem to have positive results with a similar timing and advance curve set-ups when using a longer duration camshaft.

As far as "... it is correct for this engine as chevy performance requires?" I was just responding to the question asked by Kendogz57 (shown below).
what would you recommend that I should use for timing Specs when adding vacuum advance to the mix?
Based on the OP's post #1, Chevy specs recommended 32° of total mechanical timing at 4000 rpm AND to leave the vacuum advance disconnected and only use centrifugal advance. I can only speak for myself, but I wouldn't want to run these settings on a chevy 383 small block stroker built to the specs shown for the GM sp383.
And I still don't understand the logic of leaving the vacuum advance disconnected for a street driven performance engine (unless I was running an EFI that had an engine management system that controlled the entire advance curve).
 

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Is there a Vac canister that will be all in at 8 hg?
I believe there are 2 options for VA canisters that would be all in (full pull) at 8 hg.

The first option is to use an adjustable VA canister and adjust the spring tension within the cansiter on the low side so it would be at full pull at 8 hg (or lower). The main issue with adjustable VA canisters is that they provide a lot of additional advance (20+ degrees at the crank)... so you usally need to add some kind of limiter plate the the VA arm if you plan to connect the VA canister to full time manifold vacuum.

The second option is to purchase the 4V1053 VA canister from Rockauto.
From what I have read, this VA canister from Rockauto is supposed to operate in a similar fashion to the B28 and the DV1810 VA canisters. The 4V1053 VA canister is supposed to provide 15°- 16° of advance (at the crank) with a full pull at 8 hg.
 

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Discussion Starter #15
Looks like I will need to get a timing light to validate what the timing is currently set to and a Vacuum Gauge to see how much vacuum I have at idle. Then hook up the vacuum line from the Carb to the Distributor to see how much timing is added and go from there. Thanks for the replies.
 

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Info on just why I devised the vacuum advance stop, extensive.

I lived in Whittier, Ca., for decades, and did work for a company named Limeworks Street Rods, bring them a fenbder, they build a complete car around it, good blokes. Their engine of choice, ZZ4. They have built over 250 cars with ZZ4 engines in them. Problems: poor performance, rotten fuel mileage, and NOTING they did would cool the engine down from 220 deg/F, NOTHING.

Along comes Dave, looks at the specs for the engine, and finds GMPP "tuned" the engine on a dyno, and never drove one around the block, dyno insisted no vacuum advance, as the engines were sold in an "California EMISSIONS" specification for replacement engines for truck.

So, Dave looks one over, and finds:
Vacuum advance will work with the engine vacuum, but has NO way to stop down the degrees offered, offers way too many degrees, and would want to be on ported vacuum, EMISSIONS.
To compensate for the added second acceleration curve, should the vacuum advance be connected to ported vacuum, mechanical curve is slowed by garage door springs, curve starts 1,300 rpm's, limits way past 5,500 rpm's, way too slow
Mechanical advance stat, limit and curve is good, just painfully slow to compensate for emissions and if the vacuum advance is connected to ported vacuum in a very useless attemot to get the engine to run better.

Modifications:
Build a stop (first were set distance, after them, Crane 99619-1 adjustable) mounted to the correct side of the pull pin, to stop the pin at maximum degrees wanted, unlike what Crane outlines, push the pin into the diaphragm spring to stop the degrees down. Doing it the Crame method increases the vacuum needed to get the advance to operate. Stopping the pin travel/degrees down renders the advance useless, above the vacuum level of the engine. leaving the pin in its original static position, then stopping the pin travel as it advanced fixes so many things, separates vacuum and degrees settings, so both can be set independently.
When the degrees stop is set th the degrees wanted, the vacuum advance can then be connected to the correct full manifold vacuum, to help with efficiency and cooling when engine load is low to none, as in idle timing, no load cruise, Adding the 10 degrees with a stop on the vacuum advance, set to an initial 12 degrees, gets easy starting, IDLE timing of 22 degrees, just where the engine likes it, and better operational efficiency. MOST ZZ carburetted distributors use a 69120 vacuum advance stock, works on a stock engine when modified with the degrees stop
Then, because the mechanical advance springs were so hard, and the curve slowed so much, the performance was just plain bad, ONE spring that is considerably lighter is used to bring the start point down to 150 rpms above idle speed, about 800/850 rpm's, and limit the curve at a more reasonable 2,800 to 3,000 rpms, NOT at a set rpm specification such as a way too high 4,000 rpm's. One factor, 12 initial, 32/34 total is just fine, and those parts should be weights marked 41, center scroll plate of 375 (20 to 22 degrees crankshaft timing)

Now, before everybody chimes in with stupidity like "Tune it by ear", "Tune it on a Dyno", "All those modifications don't work", "Tune it with a vacuum gauge", please remember, I was part of the team that designed and developed the coil in cap large HEI, and worked on the previous stuff, the "Unitized", and have distributed the instructions package over 4K times, and I have not heard one response where they did not work. Specificatons, sure, they can change, but the basics, add vacuum advance degrees to the idle with full manifold vacuum, set the mechanical advance by set parameters, have proven so many times to work well on street operated engines with reasonable camshaft timing. Now, Top Fuel/Funny Car cams in street engines kill all this, but most sensible people use good common sense and don't use
"To the moon radical" cams.

All this stuff works just as well on engines that are NOT ZZ series carbureted units, PROVEN FACT.

And, NOBODY, NOT EVEN ME, is ever forcing anyone to do it right, EVERYBODY is totally free to do it all as you care to do it.
 

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Mike
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Looks like I will need to get a timing light to validate what the timing is currently set to and a Vacuum Gauge to see how much vacuum I have at idle. Then hook up the vacuum line from the Carb to the Distributor to see how much timing is added and go from there. Thanks for the replies.
Sounds like a good plan (y)
Do you know if your harmonic balancer has degree reference marks around the circumference of the balancer?
If not, use a tape measure... or ruler to measure the diameter of the balancer... and also get the appropriate balancer degree tape (example shown in the link below) that can be attached around the circumference of the balancer. This will make plotting and adjusting your advance curve much easier.
Please keep us posted on your results.
 

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If you are asking me... these are the same timing and advance specs I use for my Dart SHP small block 400 and they seem to work pretty well (at least for me). From the posts and articles I've read, a lot of other sbc 383 (mostly street driven) seem to have positive results with a similar timing and advance curve set-ups when using a longer duration camshaft.

As far as "... it is correct for this engine as chevy performance requires?" I was just responding to the question asked by Kendogz57 (shown below).

Based on the OP's post #1, Chevy specs recommended 32° of total mechanical timing at 4000 rpm AND to leave the vacuum advance disconnected and only use centrifugal advance. I can only speak for myself, but I wouldn't want to run these settings on a chevy 383 small block stroker built to the specs shown for the GM sp383.
And I still don't understand the logic of leaving the vacuum advance disconnected for a street driven performance engine (unless I was running an EFI that had an engine management system that controlled the entire advance curve).
I was referring to the OP,
he stated the distributor is off another engine, so I'm thinking do we even know what timing curve is in it now ? and from the o later post, it doesn't look like it.

Of course I would also run the vacuum can.
OP looks like you have a plan getting a timing light to see what you even have going on with your curve.
I would definitely set it up to work with the vac can.
 

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I was referring to the OP,
he stated the distributor is off another engine, so I'm thinking do we even know what timing curve is in it now ? and from the o later post, it doesn't look like it.
Got it... Thank you for the clarification!
 

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Discussion Starter #20
I ended up installing a Volvo 2 speed fan only hooking up the high speed side and took the car out for a ride this afternoon. Outside air Temp was 90 degrees. During the drive the temp never got above 186 degrees. When I got home and the car was idling while I opened the garage door it reached a max of 189 Degrees.

Still plan on hooking up the vacuum advance and adjusting the timing and Carb.
 
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