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n00by check my timing logic please

2K views 50 replies 7 participants last post by  bms231 
#1 ·
SBC 350CI ~1979 apparently

On the timing tab, there is a white mark at the 8 degree "before" spot.

I am using an Innova 5568 timing light.

I pulled/plugged the vacuum advance port on the carb.

I reved the engine to 3000.

I pressed up on the innova digital gauge until the display read 36 degrees.

I adjusted the distributor counter clockwise until the white line on the harmonic damper matched the white line on the tab (remember there was a mark at 8 degrees).


Does that mean my timing is set to 36 degrees, or 28 degrees? Should I be subtracting the 8 on the tab?
 
#2 · (Edited)
The 8 degree mark is referring to timing at idle. Ignore it.

The light is supposed to do the work for you so simply align the 0 mark on the tab to the line on the damper.

If you want 8 degree's timing at idle, set the light at 8 and read the 0 mark on the tab to the line on the damper.

If you want 36 at 3000 then raise engine RPM to 3000 and set the light to 36 and read the 0 mark on the tab to the line on the damper.
 
#7 ·
This is spot on. You NEED to verify that the timing is no longer advancing past 3000 rpm's. I refer to this as the 'all in rpm' - meaning the rpm that the dizzy mechanical advance stops advancing. If you have a stock dizzy, then it might not stop advancing until 3500-3800 rpm's. If this is the case and you set it to 36 degrees at 3000, then it is possible to have a bunch more than 36 degrees.

Short story, I made this mistake once and it cost me a set of pistons as the dizzy that I installed wasn't all in until 3800 rpm's. In hindsight I figured the 44-45 degrees of all in timing detonated my hyper pistons to death in about 5 WOT runs to 7000 rpm's - sadness (2 broken ring lands). Dumb, young and full of ......arrogance on my part :)

This process is referred to as 'curving' your distributor.
 
#11 · (Edited)
Nope, we are saying to
1. Verify your TDC mark on your balancer using a physical piston stop (careful not to munch a piston - turn engine carefully)
2. Recurve your centrifugal advance so max happens at 3000 and limit centrifugal advance to no more than 20° advance (you may find that the pins for your centrifugal advance in your stock distributor are worn beyond use). Many kits are available and they are pretty cheap.
3. Then rev to 3000 with vac advance unplugged and set your total timing to 34°-36°. 34° for small cams - 36° for large cams.
4. Plug your vacuum advance into manifold vacuum and readjust idle speed and idle mix. if you get pinging, then get different vacuum can with less advance or get an adjustable one and try setting it to 12° additional advance from the vacuum can for a total timing at 3000 rpm steady cruise of 46°-48°.


#1 and #2 needs to be done before #3 is valid. Initial timing will be somewhere around 14° - 16°. Again, use the lower timing for small cams and higher for large cams. Adjust up/down in 1 degree increments and use lowest timing that gives equivalent best performance. Is this a stock engine?
 
#15 ·
I am in Raleigh, North Carolina

Maybe we should approach it this way...... What are you trying to accomplish on this engine? Fix a problem? Do routine maintenance? Try to make more power? Get better gas mileage, etc, what ???????? Then we can help advise the best path to accomplish your goals!
I kinda got dicked over buying blind on this one. So many issues with it. Right now I put in a new carb, new water pump, and new radiator. She runs now minus the huge rear main leak. I just want to get the car to be driven. She is going to be stock. I have no performance aspirations. Just ensuring the last great monkey didn't mess anything up. Since I already incorrectly set timing to 36 degrees off the -8 mark, I have to set it back to something that will run/drive.

Btw, this car has hooker headers and flowmaster exhaust
 
#17 ·
Look up at the top of the page at the header and hover over the word WIKI and then move down and click on engine. Then you want to click on ignition. You can read about "Determining top dead center"or click on "Hot rodding the HEI distributor" and scroll down to #4 in the contents. There is all the information you need to help you do anything here but you have to read.
 
#19 ·
half asleep so....

I have a Delco Remy HEI distributor. That kinda changes the points game.




^^ thanks for this. showed me about the HEI dist and how to check it and basically I don't have to worry about points. i know one more person pointed to this article so props.

Those videos are correct. They are leaving out that you want the distriutor to stop advancing at 3000ish rpm's as well.

http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor

All of this is a good read, but scroll down to the 'Ignition Advance' section - it should set you straight.

Good luck - Jim
double thanks. i am going to spin her up to the point where she stops advancing and set my timing off of that RPM.

Before you worry about replacing a rear main seal, lets talk about a few things first. It's a pretty big job that will almost certainly need the engine out to do correctly. Excessive pressure in the crankcase is a typical cause for rear main seal leaks. Does the vehicle have a working PCV valve? Is there excessive blow-by (is there smoke coming out of the hole in the passenger side valve cover when the engine is running, or does the PCV system handle it all?). If there is still a rubber tube from the right valve cover to the air cleaner, is the air cleaner full of oil? What kind of new carb did you put on it?
i am having a shop do the rear main. i have done it before on other vehicles and it is not worth doing in the driveway. shop owner is familiar w/ the sbc platform. it's still drivable...just pisses oil.

PCV..... yet another disaster of the previous owner. he put PCV valves in BOTH crank cases. Drew vaccum from the driver's side to the front of the quadrajet. so what happens? no fresh air cause the two valves are fighting each other. that right there could be the reason for the blown main?

when i pulled the quadrajet off it was pretty clean inside. now i run a 1406. i also run a breather on my passenger side valve cover! ugh # stupid people.







continuing with stupid...... guy cut the pig tail off the tach on the plug into the dist. so only one wire... battery. i have to buy a new plug to check dwell w/ my timing light (has it as a feature and requires metal to metal connection). i don't want to just shove a pin up a hole and hope for the best. i already do that with my GF. i mean .... i need sleep.
 
#20 ·
PCV system - need the pcv valve hose hooked up to a full manifold source on one valve cover and the crankcase breather line from the opposite side valve cover hooked into either the carb or air cleaner ABOVE the throttle plates. Also highly recommended to use the corret PCV valve for the application as long as the car has close to a stock cam (vacuum). Your description of how PCV works is erroneous - the idea of the system is that no matter what the engine operation state, i.e. idle, cruising, WOT or normal acceleration, that there is always a vacuum being applied to the crankcase. It's relatively important to understand the implementation of this system, otherwise, you have a good chance of having alot of seals leak.


Your description of what you are going to do to the timing will work to set the 'all in' timing degree and identify the 'all in' rpm, but the idea is to tune your dizzy to have the all in timing at the rpm and degree that you want - hence the reason for the articles camarodriver and myself attached.

And the tach wire issue you're describing is no issue at all. Most cars weren't built with a plug for the tachometer if the car wasn't built/ordered with one. But the solution is a short piece of wire with a spade connector crimped on that can be plugged into the tach spade connecter on the HEI dizzy cap.
======

Good luck - send me a PM to describe better.
 
#22 ·
PCV system - need the pcv valve hose hooked up to a full manifold source on one valve cover and the crankcase breather line from the opposite side valve cover hooked into either the carb or air cleaner ABOVE the throttle plates. Also highly recommended to use the corret PCV valve for the application as long as the car has close to a stock cam (vacuum). Your description of how PCV works is erroneous - the idea of the system is that no matter what the engine operation state, i.e. idle, cruising, WOT or normal acceleration, that there is always a vacuum being applied to the crankcase. It's relatively important to understand the implementation of this system, otherwise, you have a good chance of having alot of seals leak.
I think you meant BELOW b/c anything above is ported/timed vacuum. I have the PCV system sorted correctly at this time. valve in drivers side cover. hose to pcv port on front of carb (the big one in the center the manual says to use) and a breather on my passenger side valve cover.

Your description of what you are going to do to the timing will work to set the 'all in' timing degree and identify the 'all in' rpm, but the idea is to tune your dizzy to have the all in timing at the rpm and degree that you want - hence the reason for the articles camarodriver and myself attached.
so now this is even more confusing b/c people here are saying set timing off the rpm where the vehicle stops advancing timing. in my case probably 3200-3500 rpm. I haven't tested it yet, but I know at 3K it was still moving (vacuum disconnected). i read all the articles posted and then some over the past week and lots and lots of vids. it just gets confusing b/c everyone has a different idea of what it should be set at. all videos say sbc 2500-3000rpm. no mention of maxing mechanical advance. then people here say set it at max mechanical advance. ugh.
 
#21 ·
#25 ·
Where should I set the timing on my performance engine?


nest article I have read to date


I have a spark plug piston stop tool coming in today. I am going to find tdc, mark my balancer, and then set timing off tdc.
GREAT article hitting all of the nails on the head. Take note of the 1st three sentences in the last paragragh. Those sentences explain what I was describing in my last post which is this is considerered to be common knowledge amoungst hotrodders.

Best of luck and thanks for not getting crazy on me about me being too arrogant or condescending sounding.:thumbup::thumbup::thumbup:
 
#26 ·
Something else to note for intructional purposes only.

The amount of advance needed is largely a function of chamber shape. SBC being mostly a wedge shape they typically like about 36@3000. Fords are a little less and I think Mopar even less than these two.
The only way to know exactly is timed runs or an engine dyno however Hotrodders and engine builders have been all over this long enough that 36@3000 is key.

PM and Ill send you my number. Over the phone might be easier to explain.
 
#27 ·
Something else to note for intructional purposes only.

The amount of advance needed is largely a function of chamber shape. SBC being mostly a wedge shape they typically like about 36@3000. Fords are a little less and I think Mopar even less than these two.
The only way to know exactly is timed runs or an engine dyno however Hotrodders and engine builders have been all over this long enough that 36@3000 is key.
X2^2

An LS won't even begin to take this amount of timing due to chamber efficiency and head intake port efficiency. On a SBC it depends greatly on the head, chamber size, quench distance, and efficiency of the intake port. EVERY engine is different and it's the reason why everyone is giving you varying info. And if they don't acknowledge this, then you probably ought to take what they tell with a grain of salt.

FYI - timing advance - why do you need it? This another one of those items that implies that you have some basic, common knowledge. If you think about it, why does any engine ever need to ignite the fuel before top dead center(TDC)? That entire concept is contradictory to when you need power, but when the factors of chamber efficiency, flame travel and combustion chamber size come into play, then it becomes obvious as to why the spark has to BEGIN to ignite the charge prior to TDC.
 
#28 · (Edited)
bms231, we are saying to tune the "advance curve, Not setting the timing off the rpm. (Example) I purchase a new MSD distributor and I want to know what the advance curve is. 1. I set the initial timing at 14* 2. I rev the engine to 3000 rpm to see if my line on the balancer is aligned with zero on the scale with the advance knob is set at 36*on my timing light. 3. I rev the engine over 3000 rpm to see if it still adds timing. If it don't fine. 4. If it does then I have to change to a lighter combination of springs on top of the weights of the distributor. I have to recheck until no timing is being added after 2800-3000 rpm then I will have completed setting my "timing curve". This is why I showed you how to use the WIKI articles. Under hot rodding the HEI Distributor it explains all of this. I might forget to tell you something or tell you wrong. Look at the contents and scroll down to #15 and click on it. The ignition advance is made up of the initial timing, mechanical timing,or (Centrifugal timing) and vacuum advance. The initial timing and mechanical timing equals the total timing. The total timing is what you are setting to be all in at 2800-3000 rpm. Every distributor is set different so you you need to go through this process to set the ignition advance.
 
#29 ·
lots to reply to.... i def read hotrodding the HEI once last night and again this morning. i totally understand the concepts now... as well as a street distributor who often have mechanical advance stop at 3800+ and even read some MSD's stop advancing at 4500. crazy. 3000 to stop advancing + 36degree @ 3000 is key and i get that now. to achieve it there are various ways as adjusting springs/weights as well as checking the vacuum can. check.



as far as my PCV setup, a picture may speak a thousand words. a breather is in the back left buried below the ignition wires. ignore the throttle return spring. it wasnt done in this pic.
NOTE: This looks like crap. Step 1... get it running. Step 2.... pretty it up.






new issue.......

I decided to abandon that TDC mark at 8 BTDC on the timing tab. I have no clue if the guy marked it that way as an initial timing mark or TDC was so far off he re-marked them and 8 is actually TDC.

so i made myself a spark plug piston stop tool by taking an old spark plug, breaking out the ceramic, tapping it at 3/8x16 then putting a 3/8 bolt in there. assuming it doesnt have to be super long.




my problem now.....

after reading the WIKI above section "Procedure without removing valve cover" .... I can't turn over the engine by the crank pullet bolt. so i am going to buy one of these:



I am following this guy b/c I am best w/ video instruction and I think it does better than the wiki and says the same thing.




do i have to pull out all the spark plugs to make the engine turn over easier so i am not fighting compression? i tried w/ the crank bolt and it turned it an extra 1/2 turn in and don't want to snap the thing.
 
#33 ·
Pulling the spark plugs definitley makes spinning the engine over by hand much easier, but sometimes it's a pain to get all of the plugs out. The tool you linked makes the process A TON easier and doesn't require removal of the plugs.

I've made several of the engine turning tools with an old crank pulley and a low budget, throw away chinesium 1/2" drive socket. If you want I can attach a picture. The tool will make adjusting the valves about 10 times easier and quicker. But turning the engine over by the balancer bolt is a real no no on a SBC. You should pull yours and verify that you havenot stretched it. If the threads are stretched, then grab a new one - they are dirt cheap (even an ARP bolt and washer is not that expensive) and need to be installed correctly at the proper torque. FYI, getting a broken and stretched balancer bolt from the crank can be a giant PITA without damaging the threads in the crank.
 
#34 ·
I DID IT I DID IT I DID IT.... half way but I found the true TDC w/ that tool above to rotate the crank in both directions and the little piston stop tool I made.

This is what I came up with on the balancer. you can see the current mark is just a bit off. is it worth re-groving and moving the spot or is it close enough not to worry about? You can see my markings below. ignore the timing tab. i just put those on there so it's easier to see. i marked TDC 0 w/ sharpie so i can go back and paint it white. no clue why the guy painted it at 8, but what I did last week was WAAAAY wrong assuming 8 was TDC. that means my 36 degree is really 28 @ ~ 2900rpm


 
#42 ·
GOOD NEWS.... SET THE TIMING TONIGHT.

Mechanical advance stops at 3000 on the nose. Set it to 36 degrees. Runs great.


Idle mixture however............ that is my next hurtle. I understand the instructions. i think i just got them so far out of synch i had one screw all the way in and didn't change idle. backed them both out. screwed in. followed procedure. idles ok.

my only issue is I set the RPM to 850 initially then went to D and the car almost died at 490 RPM. so I upped the idle to 950 RPM and now in D it goes down to about 550. i know it has to do something with my idle mixture b/c timing is right.

this thread has been fun.
 
#45 ·
First thing to do is read this and then verify the recommended settings and adjustment's so you know where you are and you can decide where to go from there. These carbs are easy to work on so there's that but they are intolerant to dirt and debris and excessive fuel pressure's. Do you have a vacuum guage?

http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf
 
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