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Discussion Starter · #1 ·
I'll try to make the story short:
396, HEI ignition w/vacuum advance, mild "crane" blue racer cam, unknown CR, Holley 750. Idles & runs great. No pings, no flat spots.

I had the car dyno tuned after a carb rebuild, and they were having a heck of a time. Timing was set to initial 14 deg of advance. So, they tried advancing the timing "by ear" - it worked great, they surmised that the balancer was not marked correctly, because it was WAY off. I picked up a TDC locator to remark the balancer whenever I could. It is a Summit 396-427 balancer replaced by a previous owner.

This past weekend, I set out to correctly mark the balancer - put the locator in the #1 hole, turned the engine until stop, marked the balancer at 0. Turned the engine the other direction until stop, marked the balancer at 0 again. The exact center of the two marks is where the balancer should be marked for it to be correct.

You guessed it, the mark on the balancer was in the right spot!!! I'm stumped - I have a timing light with an advance dial, and it's off the scale. What gives???

Is it possible I should have measured between the 2 marks in the other direction? I measured between the marks in the shortest distance, not the longest distance - the short distance between marks was about 1/4 of the way around the balancer.

Any assistance is greatly appreciated.
 

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Did you start at TDC of the compression stroke? If you started at the top of the intake stroke, it will not be correct.

Dave
 

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Discussion Starter · #3 ·
I did not - I didn't know it mattered, but now that you mention it that makes a lot of sense. In fact, it may explain how the balancer was initially installed, as it is on the mark if done the way I did it. I'll try it again tonight. Shouldn't it be a standard # of degrees off if done the other way?
 

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Since you have an advance light this shouldn't matter, but there are two different timing tabs for each diameter HB. All you need is to find TDC (of the compression stroke), THEN: score a line on the HB (if it is the pre-made groove, even better) next make a continueing line on the timing indicator. White out works best for me.

Then make sure your wires track around the distributor in the correct firing order.

Then crank it up and see where the mark is. If the two lines line up, and the gun knob is on 15, then your at 15*BTDC. You can also turn and track the light to get a good estimate of WHERE the hell is is versus whre it should be.

Shouldn't be off the scale. The gun trigger lead is on number 1 plug wire right? Front drivers side.


good luck.


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71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.2 @ 86.8mph
1/4: 12.7 @ 107.8mph (1.93 sixty foot)
--have pulled a 1.85 sixty foot (before street tires or course).
Picture of me roasting the tires and other guy stuff
Video of me staging (smoke of course)

[This message has been edited by BB_Mike (edited 09-25-2001).]
 

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I got to get me one of those lights!

That sounds like too much fun!
 

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It doesn't matter whether it's the top of the compression stroke when determining top dead center. The crankshaft (and balancer) goes around twice each time the plug fires.

Setting the timing "by ear" is generally not a good idea. It might run good at idle, but that's not where it is important.
 

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Good point Rich,

Sorry for the bad info Xtreme.

I'm going to punish myself by forcing beer down my throat until I have learned my lesson.
 
G

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Beware the high buck dial back timing light and MSD ignitions. Just went through this with BillK, mark was all over the place. Checked their web site and found you can't use one of these with the MSD. Got the 30 dollar light out and it worked just fine.
 
G

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Good question. If it's an MSD like unit it may suffer from the same problem. I never saw anything like it, that mark was rotating around, would not stay put.
 

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Do you have an "advance curve kit" installed in your HEI?

If so, the part that is held by "e"clips and sits between the weights needs to be flipped over. The kit can be used on both clockwise and counter-clockwise rotating distributers. If it is installed in the wrong direction your timing will be off the scale.......

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"I don't drive FAST, I just FLY low!"
 

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My first car had a 396 with a chevy solid lifter cam in it. Car wouldnt idle below 24 degrees advance. No matter how much you held the throttle open, below 24 it would die. Ran like a raped ape, especially up top. Dad almost made me sell it before I even got to drive it! He only had to try it once. Car took had 11.5:1 compression and took 2 cans of octane to every tank. Through a rod after a month of driving to school. (at 80mph on the way down from 120+). Took the motor apart later and found the timing gears were one tooth off. Put that same cam in a 402 straight up. Car ran like a dog. 327 was much faster, but the timing marks lined up correctly now.

Maybe your cam timing is off? Just a suggestion.


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Brandon Chamberlain

64 malibu ss 283 & glide
70 C10
87 Firebird Formula

previous chevys
68 SS396 chevelle
72 malibu w/cowl induction,sunroof, and a/c
68 chev impala
 

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My 427, 12.5:1 has a high timing also the balancer mark is not even close to the timing tab it is way at the top.More compression means more timing ?I'am going to put a timing tape on the balancer to see where it is set at.Someone said they were running with there mechanical advance locked out at 36.Does that mean you have 36 at base idle also.I did not think an engine would turn over with that much.Chevymad you said your had 24 so i guess thats not true.I'am not sure if thats my case or not since i just got this car recentley.The engine is fresh with about 1000 miles on it.Who ever has there timing locked out? Can you tell me what is done by this or how it is done its new to me.I have a MSD distributor no vacume advance can.The person that set my engine up must have gave it a lot of timing or locked it out one of the other.I guess the tape will tell me more.Maybe tonight i will get the tape on.
 

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14* of initial advance??? soooooo... what's wrong with that? was that with the vac. connected, or without, if with, that's fine, if without then that's fine too(just leave it) mine is set at 17-18 initial, with no vac. advance.. and 36 total.

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Brian L34
Some of the stock cars guys I used to race with would lock out the mechanical advance at 36 because idle quality wasn't important but erratic timing at continuous high rpm caused by movement of advance weights could be a big problem. You're right, it won't start with that much advance, so they put a toggle switch in the power feed to the distributor. Once the engine is cranking over fast, turn on the power to the distributor and it will start, even at large advance numbers.
If you ever put an MSD equipped car on the scope, you will see what looks like a double pattern. I assume that they use the fancy red box to fire the plug a second time a few milliseconds after the first and I think the double hit is supposed to be a more reliable fire starter. I think that is also what screws up the timing light pickups on the advance type lights.
Don
 

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Discussion Starter · #17 ·
Sorry guys, I wasn't able to check it out last night - worked too late.

junglejimmie, I don't know about that advance curve kit - the setup is as delivered from Summit, I will look into that also.

ChevyMad, cam timing could definitely be an issue, my next cam change will take care of that. I don't really know how to tell otherwise. I know I expected better than 251 hp at the rear wheels, but can't explain why it's not there - my guess is my CR is low.

Chev-hell, I set it at 14 w/o vacuum adv, then it got bumped WAY up from there at the dyno.

I don't have a multiple-spark MSD box yet. I'll keep you posted as I get more data during the week. Thanks!
 
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