weird timing problem??? - Team Camaro Tech
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post #1 of 13 (permalink) Old Apr 23rd, 01, 12:35 PM Thread Starter
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Billy
 
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Location: Pasadena ,Tx 77503
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Question

ok..i have a 68 with the listed item below. the car runs really good but there is something wrong with the timing. i have to run well over recommended timing numbers. right now the timing is set at 35 initial and 50 total. this is with the vacuum advance unplugged. i have checked tdc and the balancer is within 1 or 2. the cam was degreed in and it was within 1 of factory specs of 106. i am running an HEI ignition with accel cap,rotor, and super coil. it has a mr. gasket re-curve kit with the medium springs.
does anyone have any idea what could be the problem with this. the motor does not detonate or turn over slow. i figure it shouldnt even turn over with this much timing in it but it will hardly run with anything around 16 timing. any help would be GREATLY appreciated. i have already tried peformance and general tech and got some leads but no answers. thanks in advance.

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'68 with a 355 and dart pro1 heads, XE284 comp cam, air-gap intake, th350 w/3000 stall and 3.73 gears.
'69 SS with a 427 with edelbrock alum heads, comp cam, performer rpm intake, with a muncie 4-speed and 4.11 gears
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post #2 of 13 (permalink) Old Apr 23rd, 01, 12:46 PM
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Have you tried a different timing lite make sure the ground on the lite is good. I don't know what else could be going on.

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post #3 of 13 (permalink) Old Apr 23rd, 01, 01:36 PM Thread Starter
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Billy
 
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i've used my dial back and my friends standard light.

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'68 with a 355 and dart pro1 heads, XE284 comp cam, air-gap intake, th350 w/3000 stall and 3.73 gears.
'69 SS with a 427 with edelbrock alum heads, comp cam, performer rpm intake, with a muncie 4-speed and 4.11 gears
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post #4 of 13 (permalink) Old Apr 23rd, 01, 08:50 PM
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Joe
 
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My 396 has the same issue. I verified the timig marks were correct at TDC and never could figure out the "problem". It runs good so I'm leaving it alone for now.

Joe

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69 396 w/SS Trim
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post #5 of 13 (permalink) Old Apr 23rd, 01, 11:33 PM
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You are measuring the timing with the vac advance disconnected, right? If I remember correctly, your car was running high 12's around 105 or so, right? And you had around 135 pounds of cranking compression with a 275DEH cam? Have you changed from the 275DEH to the XE284 like your sig says? If so, your cranking compression should be well lower than before...like 110-115 pounds? Your timing requirements sound like that of a super low compression engine...I have seen people put HO455 heads on their mid 70's 400 pontiacs and they needed timing like that to even run...those huge chambers dropped their compression into the low 7's. I have also seen bone stock 8-1 350's snap starter noses right off running with over 20 degrees initial. Have you made any 1/4 mile runs with less total timing, and did the mph improve? Sorry for all the questions, but I have been thinking about this since your last posts on the same problem and it just doesnt make sense. Have you tried yanking the distributor and turning the oil pump drive shaft about 1/8 of a turn and re-installing the distributor in a different "phase"? I just find it real hard to believe that any engine could ever run right with those timing figures, which is why I think the distributor is out of phase. I have had engines do similar things...require way more timing than they needed and found the dist off a bit...the timing readings were bogus, yet the engines still ran great.

------------------
375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova
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post #6 of 13 (permalink) Old Apr 23rd, 01, 11:34 PM
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Oh...one more thing...what kind of idle vac are you pulling? With the 275DEH, it should have been around 14-15".

------------------
375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova
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post #7 of 13 (permalink) Old Apr 24th, 01, 08:04 AM
 
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Question

I'm having a very similar problem with my '68 El Camino. If I run any kind of normal timing the thing backfires like crazy and runs terrible. I need to run 35-40 degrees initial advance. I tried swapping the distributor and carburetor, but that did nothing. The engine is basically a stock 327 with a mild cam. It pulled around 155-170 on all cylinders on a compression check and looked good on a leak down test, so it appears that the bottom end is in good shape. I thought the cam might have been installed wrong, but that's not the case. I haven't degreed it but the timing marks line up right and everything appears ok. I was going to degree it, but I need to order the kit and after reading 68and69's post I suspect that it will come up fine.

This is really driving me nuts. I just can't get the thing to run properly at all. Any help anyone can give would be greatly appreciated.
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post #8 of 13 (permalink) Old Apr 24th, 01, 08:15 AM
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Guys there are two timing markers and two vibration dampeners out there for a small block (not sure about big blocks). If you have a 68 or prior marker and you're using a 69 or later dampener (or vice versa), your timing will read wrong! So what you think is 50* may really be only 36* - or what you think is 36* may only be 24* - they're several degrees off from each other.

I know you said you checked TDC, but are you sure? Sometimes over the years you wind up with a couple marks on the dampener. The other possibility is that the timing chain jumped a tooth. Or . . . the dampener's outer ring has slipped.

If your mark is off all you need to do is remark your dampener by scribing or painting a new line on the dampener in the right spot or switch the timing tabs.


[This message has been edited by Eric68 (edited 04-24-2001).]
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post #9 of 13 (permalink) Old Apr 24th, 01, 02:04 PM Thread Starter
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Billy
 
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ok...travis, you hit everything except the craking pressure, at first it was about 135 but then we advanced the cam 2 and it came up to around 160. Then the cam went flat and i pulled the motor apart to clean it and install the new cam. Now the cranking pressure is still around 155-160 and it pulls like 11" of vacuum at idle(1100rpm). I know the balancer has the right mark on it, we used a piston stop with the heads of the motor and found TDC. The compression is around 10-10.5 because i had the block decked .037" so its almost 0" deck. Its got flat tops and 64cc heads. If your saying to pull the dist. out and stab it a tooth of everything i read and everyone i've asked said that it doesnt matter on a small block chevy, it only allows you to have more advance or retard when its a tooth advance or retarded(before hitting the firewall).

oh yeah...im taking it to the track friday if the weather hold out, i will let you know travis how the combo runs....im thinking LOW 12's now.

------------------
'68 with a 355 and dart pro1 heads, XE284 comp cam, air-gap intake, th350 w/3000 stall and 3.73 gears.
'69 SS with a 427 with edelbrock alum heads, comp cam, performer rpm intake, with a muncie 4-speed and 4.11 gears
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post #10 of 13 (permalink) Old Apr 25th, 01, 02:45 PM
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Sounds like the plug wires are one tower out of correct sequence to match the rotor in the cap; one tower is 45 degrees, so if you're showing 35 degrees initial and it's running, that's the same as having the wires one tower off with an actual 10 degrees initial. Just a thought - set it on #1 TDC and see which tower the rotor is pointing at, and make sure that's the plug wire that goes to #1.

Same symptom will occur if the distributor is in a tooth off - with housing properly oriented so the can doesn't hit anything and the gear a tooth off, rotor will point at the wrong tower with the plug wires correctly installed in the cap.

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JohnZ
'69 Z28 Fathom Green

[This message has been edited by JohnZ (edited 04-25-2001).]
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post #11 of 13 (permalink) Old Apr 25th, 01, 05:13 PM
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It doesn't matter where number one is on the dist. if you can time it to number one it will work. That is not his problem. He has TDC.ed the motor so his timing maks are right.The only thing I can think of is that his degree marks on the dampner are wrong. Did you use one of those timing tapes to mark the dampner maybe you got the wrong one

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post #12 of 13 (permalink) Old Apr 26th, 01, 09:45 PM
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Was playing with the 77 nova today...havent messed with it much since I got it in january, and just havent had time to do anything to it yet. Checked the timing....the timing mark was about 2" off, yet it starts very easily and will lay 60 feet of rubber with both tires, so obviously the "real" timing has to be pretty close to right, yet I am getting the screwy reading. I am going to play with it some more and see if I can figure this out, and I'll let you know what I find.

------------------
375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova
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post #13 of 13 (permalink) Old Apr 28th, 01, 10:22 PM
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Well, I found out why mine was reading funny...the balancer has spun about 45 degrees...with the #1 piston at tdc the timing mark is almost straight up on the balancer...since the engines coming out later (and the balancer will be replaced) I left it alone for now...just marked the balancer for tdc and set the timing to 14 initial...it was about 20 before and while it ran very good, I was getting some detonation. Now it runs harder than ever...I made a pair of nice long stripes down the road from the house today. Its very strange though...I have never driven a car with 2.56's that would run like this thing. I havent had it to the track yet...I am guessing low 15's.

I know its not that impressive but for the gears and the few apparent mods, it does ok

------------------
375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova
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