Timing for 350 Chevy SB
- Thread starter Robert
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Keeper
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oh one more thing. When trying to find TDC with the engine together, make a "piston stop"
Take an old spark plug, smash the insulator out. Thread it for a bolt, screw the bolt into the spark plug, until is sticks out about 1/2 inch from the end of the spark plug, (you will need to cut off the little piece at the end of the plug)
DO NOT DO THIS WITH THE STARTER. Sorry had to post the warning.
Using a wrench!
Rotate the engine until the piston hits the stop, do not try to force anything. Mark the balancer where the timing mark is 0.
Rotate the engine in the other direction until it hits the stop again. Mark the balancer where the timing mark is 0.
The middle of those two marks is TDC of your engine.
Take an old spark plug, smash the insulator out. Thread it for a bolt, screw the bolt into the spark plug, until is sticks out about 1/2 inch from the end of the spark plug, (you will need to cut off the little piece at the end of the plug)
DO NOT DO THIS WITH THE STARTER. Sorry had to post the warning.
Using a wrench!
Rotate the engine until the piston hits the stop, do not try to force anything. Mark the balancer where the timing mark is 0.
Rotate the engine in the other direction until it hits the stop again. Mark the balancer where the timing mark is 0.
The middle of those two marks is TDC of your engine.
Screaming Metal
Active Member
Hahaha....that IndyCars is slick!
Now, I realize that you made your tape....your tdc is evidently off from the tape or the tape isn't laid out in degrees. IF IT IS 63 DEGREES
.....They've got the cam in wrong or something really funky in going on....
I'm strapping a skillet to my head now!
TDC ought to set at zero, -0-, >0<, (0.00), {0}, ZERO.
When you screw in your piston stop in #1, make sure your neg. battery cable is off. With a socket and a Long 1/2" breaker bar, roll the motor over till you hit the stop. Make a mark on your Tape there where the pointer is. And also, write that number down. don't care if its 275 or 1, write it down.
Now, roll the motor over in the other direction till you hit the stop. Make your mark and write down that number. Pull your shoes off if you need 2 count outloud, but TDC is exactly 1/2 way between those numbers. WHEREEVER that is....That is ZERO! Make that Mark RED so you won't loose it.
Put everything as it need to be, and adjust your timing so your 12 degrees BTDC, with your Vac. line pinched off or plugged. Hook up your Vacc. line and your motor ought to idle up some. Take it for a spin and see if its still running hot.
At least you got the distributor all straightened, and seated correctly. 63....damn....
Now, I realize that you made your tape....your tdc is evidently off from the tape or the tape isn't laid out in degrees. IF IT IS 63 DEGREES
.....They've got the cam in wrong or something really funky in going on.... I'm strapping a skillet to my head now
!TDC ought to set at zero, -0-, >0<, (0.00), {0}, ZERO.
When you screw in your piston stop in #1, make sure your neg. battery cable is off. With a socket and a Long 1/2" breaker bar, roll the motor over till you hit the stop. Make a mark on your Tape there where the pointer is. And also, write that number down. don't care if its 275 or 1, write it down.
Now, roll the motor over in the other direction till you hit the stop. Make your mark and write down that number. Pull your shoes off if you need 2 count outloud, but TDC is exactly 1/2 way between those numbers. WHEREEVER that is....That is ZERO! Make that Mark RED so you won't loose it.
Put everything as it need to be, and adjust your timing so your 12 degrees BTDC, with your Vac. line pinched off or plugged. Hook up your Vacc. line and your motor ought to idle up some. Take it for a spin and see if its still running hot.
At least you got the distributor all straightened, and seated correctly. 63....damn....
Screaming Metal
Active Member
Keeper and IndyCars are right! Take Your Time! A pistonstop will establish your TDC. DISCONNECT that neg. batt. cable....if you accidently hit the key, you could poke a hole thru the top of your piston, not to mention other motor damage!
I hope your math is off on the homemade timing tape. If your balancer is marked up to 16* BTDC, take a caliper or compass and measure the distance between TDC as marked and 5 or 10* on the balancer. Transfer this same distance from a marked timing mark, ie from 15* plus a 10* length and put a dab of white out. The quality of your work will result in the accuracy of your readings. You only need to mark to 35* max. 10 or 12 degrees base timing, plus mech adv total should be close to your marks. With the vacuum adv plugged, hopefully your total will be less than 40* High total advance is an indication of what kind of burn rate you have in your combustion chamber.
If you end up in the 34 to 36* total adv, I would consider that normal. Rather than get into all the particulars of ign timing, lets just concentrate on confirming yours is ball park and eliminating any high temps.
If your adv moved up 30* in 100 rpm increase, your marks are way way off or the advance springs and stops are bad off.
Here is a link that might be of help to you. I hope this does not violate site rules, if so, adjust as necessary, with my apologies.
http://www.jegs.com/InstallationInstructions/100/121/121-8360.pdf
If you end up in the 34 to 36* total adv, I would consider that normal. Rather than get into all the particulars of ign timing, lets just concentrate on confirming yours is ball park and eliminating any high temps.
If your adv moved up 30* in 100 rpm increase, your marks are way way off or the advance springs and stops are bad off.
Here is a link that might be of help to you. I hope this does not violate site rules, if so, adjust as necessary, with my apologies.
http://www.jegs.com/InstallationInstructions/100/121/121-8360.pdf
Man. I tried to make one of those, but I couldn't get the insulator material out from inside no matter what I did! Not many things beat me, but that one did! LOL
TriodeLuvr
Member
Not to insult your intelligence, but did you remember to calibrate the tape for *twice* the circumference of the balancer? It revolves twice for 360 degrees.
About the copper wire... it could only get stuck under a valve if you were 180 degrees off the compression stroke (or way off TDC when the wire went in). Sorry, I probably should have mentioned that the distrib should be pointing to #1 for this test.
Jack
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Screaming Metal
Active Member
Robert,
for the picking up the distr. and turning it a little....if the distributor doesn't sit all the way down, that is ok. Just keep bumping the motor over while you gently push down on the distributor, then when the tong on the bottom of the shaft lines up, it'll drop in. I usually use a remote starter button for installing the distributor....
for the picking up the distr. and turning it a little....if the distributor doesn't sit all the way down, that is ok. Just keep bumping the motor over while you gently push down on the distributor, then when the tong on the bottom of the shaft lines up, it'll drop in. I usually use a remote starter button for installing the distributor....
Screaming Metal
Active Member
Robert,
for the picking up the distr. and turning it a little....if the distributor doesn't sit all the way down, that is ok. Just keep bumping the motor over while you gently push down on the distributor, then when the tong on the bottom of the shaft lines up, it'll drop in. I usually use a remote starter button for installing the distributor....
When the distr. drops into place, I normally put the hold-down on and start the hold-down bolt.
And if anyone has trouble getting the porcelain out of the center of the plug to make a piston stop, get a glass of cold water out of the fridge, pour it into a old can of some kind. Heat that plug up in your vise with a propane torch, most everyone has one, get a pr. of pliers, take the plug outta the vise, drop the plug into that cold water....that shatters the porcelain. Then get a hammer or your handy air chisel, put your punch in it, it'll come out easily.
Then tap the spark plug shell for the bolt. I normally leave the hex head of the bolt to the outside of the plug, with a jam nut, that way I can adjust it. The part that goes into the combustion chamber, I round it off really smooth.
When I am fishing for TDC, I turn the motor very carefully, that crank and lever has alot of torque....feel the piston stop.
Finding TDC on #1, both your valves will be closed....should be on the heel of the cam.
(I didn't think I typed that slow....)
for the picking up the distr. and turning it a little....if the distributor doesn't sit all the way down, that is ok. Just keep bumping the motor over while you gently push down on the distributor, then when the tong on the bottom of the shaft lines up, it'll drop in. I usually use a remote starter button for installing the distributor....
When the distr. drops into place, I normally put the hold-down on and start the hold-down bolt.
And if anyone has trouble getting the porcelain out of the center of the plug to make a piston stop, get a glass of cold water out of the fridge, pour it into a old can of some kind. Heat that plug up in your vise with a propane torch, most everyone has one, get a pr. of pliers, take the plug outta the vise, drop the plug into that cold water....that shatters the porcelain. Then get a hammer or your handy air chisel, put your punch in it, it'll come out easily.
Then tap the spark plug shell for the bolt. I normally leave the hex head of the bolt to the outside of the plug, with a jam nut, that way I can adjust it. The part that goes into the combustion chamber, I round it off really smooth.
When I am fishing for TDC, I turn the motor very carefully, that crank and lever has alot of torque....feel the piston stop.
Finding TDC on #1, both your valves will be closed....should be on the heel of the cam.
(I didn't think I typed that slow....)
TriodeLuvr
Member
Have I got this wrong? I was thinking degrees of timing referred to the total cycle, say from one compression stroke to the next. Now I seem to remember that it means the actual crank travel (one revolution). I just looked at my own HB and it appears to agree with the latter. Eight degrees on the 6.5" balancer looks like approximately 1/2". Sorry, I've been away from all this too long...
Jack
choppedtop
Well-Known Member
I haven't thought about that in years myself. Intake/compression/power/exhaust. Yep, that is 2 revolutions. Funny how that stuff slips away.
Lee
Lee
Screaming Metal
Active Member
Jack, just dealing with the 'Before' section of the compression cycle, Just before top dead center, ie, BTDC. That piston just went flying up the bore at close to 1500 to 1800 feet per second. Now its slowing down and all that compressed fuel in the cylinder is waiting to be ignited. Static igition event SHOULD happen at between 8 and 14 degrees of rotation Before Top Dead Center, BTDC.
After installing a piston stop, what I do is just pull all the other plugs.
I do that to avoid fighting any undue forces (compression from other cylinders), so I can feel the piston stop.
Plus I'm old, I need my strength for other things....
After installing a piston stop, what I do is just pull all the other plugs.
I do that to avoid fighting any undue forces (compression from other cylinders), so I can feel the piston stop.
Plus I'm old, I need my strength for other things....
TriodeLuvr
Member
I think it's absolutely necessary to pull all the plugs. That piston stop scares me though. I used a dial gauge for this right after I bought my car. That confirmed the index plate on the timing cover was within ± 0.5° at TDC, which was more than accurate enough for my purposes.
Robert, I think your tape calibrations must be incorrect. Not only is the measurement out of the ballpark with vacuum advance disabled (63°), you recorded an increase of more than 30° (90-100° total) when it was reconnected. I don't think it's possible for the vacuum advance mechanism to move that far.
Jack
Indycars
Well-Known Member
I understand, that would be bad. But with it threaded and tightened against the bottom of the hole, that didn't cross my mind. Thread locker would add some insurance. This way gives a slightly larger surface to impinge on the piston top.
Indycars
Well-Known Member
Maybe it was the Champion plug, but I don't remember having any trouble with the insulator. Seems the center conductor was flexible, so I had to keep bending it until it broke.
Here's a different approach to finding TDC: http://www.summitracing.com/parts/ipa-7880/overview/
Anyone tried one?
Anyone tried one?
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