crank vs. cam timing (kinda long) - Team Camaro Tech
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post #1 of 13 (permalink) Old Mar 23rd, 03, 10:52 AM Thread Starter
 
Join Date: Dec 2002
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Unhappy

Hey all,
I'm hoping someone can shed some light on my confusion. I recently built my engine, and instlled the cam advanced (mistake #1). After finding that it did nothing for my bottom end power and made tuning impossibly hard (low vacuum), i decided i should reset the cam to 0* (straight up). I set the timing mark to 0*, with the rotor pointing to #1 cyl and began the rip and tear. Here is my problem; since my out-of-time cam is connecected to the crank, having the distributor pointing to #1, and both valves closed is irrelevant to TDC isn't it? Also, once i got the timing cover off, None of the marks seem to be oriented in any particular way. If got the triangle keyway on the crank sprocket up and off to the drivers' side. The circle pointing basically down. and the Dot on the cam sprocket pointing up toward the top. What have i done? Did i also install my distributor off? (it was pointing at #1). Can i just find TDC on the crank with the timing set unbolted and reinstall the cam and distributor? How is the crank keyway related to TDC? When i originally built the bugger, i used a piston stop to find TDC on my balancer (went left, marked. Went right, marked. Split the difference --> TDC). Also, i can't remember which mark on the crank sprocket is 0* (triangle, rectangle or circle) . I'm so confused!! Please help!! [img]graemlins/clonk.gif[/img]
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post #2 of 13 (permalink) Old Mar 23rd, 03, 11:44 AM
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Bill
 
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App, (God I wish you guys would include your real names !!)
This is a situation probably best shown to you , rather than in writing but I will give it a shot. You need to start from scratch and make sure you have the crank gear and timing chain installed correctly. Forget about ignition timing for now. Make sure that the crank gear is installed in the correct (rounded) slot, and that you have the dot on the crank gear at 12 oclock, and the dot on the cam gear at 6 oclock (dot to dot as they call it). Once you get that right, turn the crankshaft exactly one turn so that both dots are straight up at 12 oclock. Now... make sure both valves for #1 cylinder are closed. At this point you should be at TDC on the compression stroke for #1. Now... install your distributor so that the rotor is pointing at #1 and you should be pretty close.
Hope this helps,

Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner


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post #3 of 13 (permalink) Old Mar 23rd, 03, 12:05 PM
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John
 
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Your engine is now at TDC, number 1 firing. Remove the timing gears and reinstall the crank gear with the O at the top of the gear. This will (theoretically) put your cam neither advanced, nor retarded. If you align the gears with the marks at the TOP of both gears, the engine will be firing on #1. If you rotate the cam gear 180*, and align the marks top (crank gear), and bottom (cam gear), the engine will be firing on #6.

You will actually have to degree the cam to verify weather it is advanced, retarded or straight up.

John
'67 SS/RS (RR)
'68 RS conv. (J2)
'68 Z/28 (VV)
'68 Drag Car(ZZ) 11.30 @ 118
'73 Corvette Drag Car 12.64 @ 106

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post #4 of 13 (permalink) Old Mar 23rd, 03, 02:15 PM Thread Starter
 
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Thanks guys,
Those were both detailed and expediant responses!! I don't think i put both marks at 12 '0 clock last time. Is it possible it could have run that way? Could i have done any damage? How should i go about lashing the valves and making sure that they are closed on #1? Last assembly, i lashed the valves in firing order, while turning the crank 90* between each cyl. Could this give me a false impression as to weither or not the valves are closed?

p.s. - The original owner of a '71 chevelle and the owner of several muscle machines?!?! [img]graemlins/thumbsup.gif[/img] I'm so jealous! (that's me, green with envy, but happy for you both.) And to BillK, my real name is....AArgh..I just can't do it!! [img]tongue.gif[/img]
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post #5 of 13 (permalink) Old Mar 23rd, 03, 07:21 PM
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Tom
 
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Bill K, I have always skipped the first part of your explanation. I just put both marks at 12 o'clock. Is it just easier with dot to dot or what ?

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #6 of 13 (permalink) Old Mar 24th, 03, 07:06 AM
 
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Gee, I always thought the crank gear went at 12:00 and the cam sprocket went at 6:00 without any advance or retard keys like when using a stock set.

Am I missing something here? pdq67



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post #7 of 13 (permalink) Old Mar 24th, 03, 08:29 AM
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is this right? yeah, it's right [img]graemlins/thumbsup.gif[/img]

[ 03-24-2003, 11:09 AM: Message edited by: JIM68 ]

1968 Coupe, 327ci basketcase project
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post #8 of 13 (permalink) Old Mar 24th, 03, 09:34 AM
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Tom
 
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Cool

Jim68, neat graphics. Am I correct that your distributor should be firing # 1 at TDC (combustion). (Both dots at 12 o'clock)
P.S. That's how I've always done it.

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #9 of 13 (permalink) Old Mar 24th, 03, 05:57 PM
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Jim
 
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Correct [img]graemlins/thumbsup.gif[/img] , and the reason you wanna start out with cam @6 and crank @12, is just to ensure that the gears are in sync, if you put the chain on while both are at 12, you might not be able to see if you skipped a gear tooth. after installing D2D all you do is rotate the timing set so both are at 12 noon and drop the distributor in with the rotor pointing to #1 wire. And of course we are talking about installing the crank gear with the 0 keyway. Because is you install it 4 retarded the Dot to Dot will not be right in-line, it'll look like this: click here (328k)

1968 Coupe, 327ci basketcase project
1986 Chevy Stepside, 305ci/300hp
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post #10 of 13 (permalink) Old Mar 24th, 03, 08:03 PM Thread Starter
 
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OKAY,
so.....Dot to dot (cam at 6, crank at 12)is firing on #6, Intake on #1. Cam at 12, crank at 12 (having been rotated 360*) is firing on #1. Right? So if i have it dot to dot, i should rotate the crank two revolutions to check the sync. This will bring me back to dot to dot. Then i should rotate that crank 360* so that the crank and cam (which has moved 180*) are both at 12, then install the distributor. Right?
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post #11 of 13 (permalink) Old Mar 25th, 03, 07:48 AM
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Jim
 
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You don't have to rotate the crank 720s to check synchronization, just make sure you install it Dot to Dot.
If the #1 piston is set at TDC and then you install the cam gear and chain at Dot to Dot, the cam will now be firing #6 and beginning the intake on #1. You can either install the distibutor now pointing to #6 or rotate the crank 360 and install it pointing to #1.

1968 Coupe, 327ci basketcase project
1986 Chevy Stepside, 305ci/300hp
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post #12 of 13 (permalink) Old Mar 25th, 03, 01:45 PM
 
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Whew, thanks, I thought I mighta been screwing up all these years.

I forget, but I think I mighta done my first one 12 and 12???

And great display!!! pdq67



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post #13 of 13 (permalink) Old Mar 25th, 03, 06:00 PM Thread Starter
 
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Ahhhhhhh,
i see. it never occured to me that i might install the dist. pointing to #6. Y'know what's funny. I was using a Haynes Chev. overhaul manual while building my engine and it didn't mention the 12-12 thing!! In the second picture, it actually shows the marks both at 12, but it has an arrow on the cam gear at 6, as if the dot were still there. I thought that was weird . THANKS HAYNES [img]graemlins/thumbsup.gif[/img] (we need a gremlin for other fingers..) Anyway guys, thanks for the help. I think i'll fire it up tomorrow night after work. It seems like a few guys learned something here!!
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