Bbc timing question

« **on:** September 08, 2014, 08:47:19 AM »

Hi guys. Im running a 454 .030 over and about 10.5 to 1 CR with MSD dizzy and 6A box. Edelbrock Air Gap. 750 vac sec holley carb. 049 heads Mercruiser aluminum exhaust manifolds. Spark plugs are set at .035 using R44 plugs. At 2500 RPMs timing is set at 25 adv, at 3000 RPMs I'm all in at 36 deg. Is my gap set correctly? Too small? Hows my timing? I just turned on my engine for the first time last night (breaking it in). So ALL parts are new except for dizzy and box. I'm getting a slight miss. When using my timing light on number one I see it jump to retard side about 10 degress. Also, one exhaust feels warmer than the other and it seems like more steamthan water. Any help would be nice. Thanks!

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« **Reply #1 on:** September 08, 2014, 09:10:05 AM »

Quote from: el mojado on September 08, 2014, 08:47:19 AM

Hi guys. Im running a 454 .030 over and about 10.5 to 1 CR with MSD dizzy and 6A box. Edelbrock Air Gap. 750 vac sec holley carb. 049 heads Mercruiser aluminum exhaust manifolds. Spark plugs are set at .035 using R44 plugs. At 2500 RPMs timing is set at 25 adv, at 3000 RPMs I'm all in at 36 deg. Is my gap set correctly? Too small? Hows my timing? I just turned on my engine for the first time last night (breaking it in). So ALL parts are new except for dizzy and box. I'm getting a slight miss. When using my timing light on number one I see it jump to retard side about 10 degress. Also, one exhaust feels warmer than the other and it seems like more steamthan water. Any help would be nice. Thanks!

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First and it's not a big deal. Your timing can come in sooner if you feel like it.

Second, is the miss really faint? Any popping?

In all honesty it sounds like a cross talking secondary in the distributor cap.

I would check a couple things out before I take it to the water. Check the condition of the mechanical advance. You should also investigate to see if the distributor bushings themselves have excessive slop.

As for the manifold temps. Water is very good at taking the path of least resistance.

As a side note. If the firing order is incorrect it will do both things you describe.

Good hunting.

GT

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« **Reply #2 on:** September 08, 2014, 09:18:47 AM »

It is a faint mis. About every 10-20 seconds. If I retard it then it becomes more of a pop. I adjusted the valves by tightening the rocket until there was a slight drag in the push rod then 1/4 turn of the nut. Stock stamped rockers. Thanks GT

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« **Reply #3 on:** September 08, 2014, 09:34:23 AM »

Quote from: el mojado on September 08, 2014, 09:18:47 AM

It is a faint mis. About every 10-20 seconds. If I retard it then it becomes more of a pop. I adjusted the valves by tightening the rocket until there was a slight drag in the push rod then 1/4 turn of the nut. Stock stamped rockers. Thanks GT

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Sounds like you may have the valves too tight.

I normally run hydraulic valves with a manual oil pump and go zero slop (different than drag) and 3/4 of a turn. You may have bottomed out a few lifters.

The spring in the lifters are extremely light. Too light to be able to feel any real drag. It will burn a valve in a heartbeat if left too tight.

You may have a couple things going on it seems.

GT

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« **Reply #4 on:** September 08, 2014, 09:40:01 AM »

Hmmm. Maybe this is a vetter explanation...I turned the rocker nut while spinning the pushrod with my fingertips VERY lightly

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« **Reply #5 on:** September 08, 2014, 09:41:25 AM »

As soon as my finger tips slipped on the pushrods I stopped. Then turned the nut 1/4 turn

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« **Reply #6 on:** September 08, 2014, 09:43:13 AM »

And by very lightl I mean about as tightcas you woud hold a pencil right before it slips through your finger tips.

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« **Reply #7 on:** September 08, 2014, 09:43:33 AM »

Quote from: el mojado on September 08, 2014, 09:41:25 AM

As soon as my finger tips slipped on the pushrods I stopped. Then turned the nut 1/4 turn

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Anybody else?

I have never done it that way..

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« **Reply #8 on:** September 08, 2014, 10:11:18 AM »

Quote from: GT Jets on September 08, 2014, 09:43:33 AM

Anybody else?

I have never done it that way..

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What GT said- they're too tight.
I take any vertical 'slop' out of the pushrod, jiggle method if you will, to find zero lash, then 180* (1/2) turn (roughly .060" prelaod, yes I measured .060', per G.M.)

sbc, bbc, and sbf, all the same

Dan'l

« **Reply #9 on:** September 08, 2014, 11:28:22 AM »

A quarter turn past zero lash would not be too tight. For all my years of adjusting hydraulic lifters I also preload the lifter half turn past zero lash on the base circle of the cam. Adjust the intake when the exhaust valve begins to open and adjust the exhaust valve when you see the intake valve half way closed, this way you are on the heel of the cam of the valve you are adjusting.

« **Reply #10 on:** September 08, 2014, 12:06:43 PM »

Quote from: 86caribbean on September 08, 2014, 11:28:22 AM

A quarter turn past zero lash would not be too tight. For all my years of adjusting hydraulic lifters I also preload the lifter half turn past zero lash on the base circle of the cam. Adjust the intake when the exhaust valve begins to open and adjust the exhaust valve when you see the intake valve half way closed, this way you are on the heel of the cam of the valve you are adjusting.

I don't thinkhe is at zero lash. I think the lifter is bottomed out.

It only takes 8 pounds of pressure to bottom an empty lifter. ...

Just a guess though.

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« **Reply #11 on:** September 08, 2014, 12:52:49 PM »

I have used this method before with no issues . Slowly turned the nut until I felt a very light drag on the push rod. Then quarter turn of nut. How is this different than turning until rod stops moving up and down? Did I mention that I was holding the push rop with the slightest pressure. Like trying to hold a snowflake between your finger tips

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« **Reply #12 on:** September 08, 2014, 12:58:40 PM »

Install the pushrods and rocker arms. Be sure the pushrods are seated correctly in the lifter and rocker arm. Turn the engine over in the direction of rotation until the EXHAUST pushrod just begins to move upward, opening the valve. Now adjust the INTAKE rocker of that cylinder. Carefully tighten the nut on the intake rocker while spinning the pushrod with your fingertips. You will feel a slight resistance in the pushrod when you have taken up all of the clearance. This is “zero lash.” Turn the adjusting nut to the specified pre-load – typically 1/4-3/4 of a turn, but this will vary based on the lifter number.
From Comp Cams website.

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« **Reply #13 on:** September 08, 2014, 01:12:29 PM »

Quote from: el mojado on September 08, 2014, 12:58:40 PM

Install the pushrods and rocker arms. Be sure the pushrods are seated correctly in the lifter and rocker arm. Turn the engine over in the direction of rotation until the EXHAUST pushrod just begins to move upward, opening the valve. Now adjust the INTAKE rocker of that cylinder. Carefully tighten the nut on the intake rocker while spinning the pushrod with your fingertips. You will feel a slight resistance in the pushrod when you have taken up all of the clearance. This is “zero lash.” Turn the adjusting nut to the specified pre-load – typically 1/4-3/4 of a turn, but this will vary based on the lifter number.
From Comp Cams website.

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Never said it was wrong. Just that is not the way I do it.

I always used an oil pump primer. Not saying that's right or wrong either.

Check your distributor.

GT

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« **Reply #14 on:** September 08, 2014, 01:25:02 PM »

Ah. I see.... I am leaning towards it being an ignition issue. I took all of the of the weights out and made sure they were clean and free moving with no excessive play or worn out bushings. Looked good to me. I alsobinstalled MSDs lock out for vac adv. If I remember correctly I used the light blue springs and red advance stop bushing in it. But I havent inspected the cap or rotor since running the engine. Priorvto break in it looked ok. It was used but the cap and rotor looked ok. The thing sticking in my mind is that when I noticed the mis, the timing mark jumped while I had the timing light on it.

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el mojado

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