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Old 07-28-2007, 05:55 PM
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Chevy 292 Timing Question

I've built a serious Chevy 292 inline 6 with forged 10.0:1 pistons, Clifford Lump Port Head, Hot Cam, Triple Weber Side Draughts, etc., etc. I've got a Mallory Unilite distributor that has had the mechanical advance locked to "0", an MSD 7AL-2 and an MSD Timing Computer. I'm wondering what I should set my initial timing at, where I should begin to bring in more timing, how much to bring in and when to have it all in. Any help will be appreciated.
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Old 07-28-2007, 06:03 PM
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Quote:
Originally Posted by BIG292
I've built a serious Chevy 292 inline 6 with forged 10.0:1 pistons, Clifford Lump Port Head, Hot Cam, Triple Weber Side Draughts, etc., etc. I've got a Mallory Unilite distributor that has had the mechanical advance locked to "0", an MSD 7AL-2 and an MSD Timing Computer. I'm wondering what I should set my initial timing at, where I should begin to bring in more timing, how much to bring in and when to have it all in. Any help will be appreciated.
If the mechanical advance is locked, there won't be any more timing to "bring in" except vacuum advance. Maybe I'm misunderstanding what you're saying.
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Old 07-28-2007, 06:05 PM
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What are the specs on the cam? Not that up on 292 inlines. Tell me about the head. And what intake manifold you're using.
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Old 07-28-2007, 06:20 PM
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Timing Computer

The MSD Timing Computer allows me to start to advance the timing at whatever RPM I choose, then it allows me to tell it how much timing to add and at what RPM to have it all in. So, if I have 10 degrees initial and I decided I wanted to add another 20 degrees of advance smoothly from 1200 rPM to 3200 RPM, I could program the MSD Timing Computer to do just that. My questions is...jsut how much timing do I want? I know each engine combo will be different, but I'm looking for guidelines.

thanks
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Old 07-28-2007, 06:26 PM
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I'm thinking you will want a total of about 34-40 deg. Start low and keep going up till the car slows then back off a couple degrees. I think you would need more than 10 deg inital.
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Old 07-28-2007, 08:34 PM
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Start with 10* inital, and at 1k start your curve. Add another 26* for a total of 36* by 3k RPM. For street driving, it will like full manifold vacuum to the can.

A long time ago, I ran a 292 with Oliver rods, and a set of forged slipper skirt pistons... Used a 194 head that had a set of Sissell bolt in lumps. Didn't run bad.....Thought I could do better......Cut up a set of 461X heads and did a hybrid conversion. Couldn't keep the welds from cracking. Couldn't keep the oil pump drive shafts in it. And, I also figured out that slipper skirt pistons don't belong in a Chevy 6.......

I sure hope you have better luck than I did. Dan
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Old 07-28-2007, 10:17 PM
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Thanks Dan

That's exactly the info I was looking for on the timing. The only problem now is that my distributor has no vacuum advance. I may just have to bite the bullet and get a new distributor....I think mine is set up too much for strip and will not work well on the street.

My head is a Clifford Lump Port (brass welded in lumps) that seems to run very well with the triple webers, for the short time that I had it running before I decided the motor made too much internal noise. My new engine builder has decided the original engine builder left a little too much clearance for the forged pistons in the cylinder and the noises I am hearing are the piston skirts slapping the cylinder.....now I have to decide if I want to live with it or re-bore and put in new pistons.
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Old 07-28-2007, 10:22 PM
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Oops, never heard of an MSD timing computer. Didn't know there was such a thing.
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Old 07-29-2007, 08:35 PM
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Cylinder wall flex is an issue the Chevy six has, and a slipper skirt style piston will cause more flex than an original full skirted style.

Side loading, and surface area of the piston must be taken into consideration.....

Are your cylinders now egg shaped from a poor piston choice. And this is causing your extra clearance, and piston slap? Just an idea...... Dan




================================================== ========

For every one reading this post, and not quite following some of the terms being used.........



The 292 Chevy Six was a tall deck truck motor. The bore was 3.875", and the stroke was 4.125".

These motors are a nine port motor.......6 on the exhaust and only 3 for the intake...

The Siamese intake ports had a flat floor, and a boss cast right in the middle of it to allow a head bolt to pass threw. In stock trim, 150cfm in the 500" lift range was about all they where good for.

Typical mods for the head included removing the boss, and adding a contoured lump to the port floor. The lump reduced port volume raising velocity, and gave the air and fuel a better approach angle on the valve. 240cfm could be had pretty easy.....(If you really want to get serious, Sissell makes a head that flows over 300cfm)

My hybrid head setup used a set of standard small block heads that have one cylinder cut off each one, and then the two 3 cyl pieces where welded back together. Drill and tap the deck for the new bolt pattern, and you now have a 12 port motor......

Typically, a sheet metal intake is used mounting 3 carbs. Mine ran 3 Holly one barrels from a Chrysler slant six. 3 carbs would give equal fuel distribution where a single 4 bbl would run the two center cylinders rich and the outside holes lean...
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Old 07-29-2007, 09:58 PM
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Pistons

the engine only has about 8 hours of time on it, so, no, the cylinders are not egg shaped. I think the original builder was a little too sloppy in his tolerances. I'm going to try and get over to my new builder at lunch Monday and see what his recommendations are.
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