Engine with low vacuum. - Team Camaro Tech
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post #1 of 7 (permalink) Old May 2nd, 15, 05:10 PM Thread Starter
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Robert
 
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Engine with low vacuum.

I have a 327-210 engine but it has 186 heads on it now, 2.02/1.60 valves. The problem is the engine has low vacuum and the vacuum gauge fluctuates indicating a blown head gasket or leaking valves or weak springs. I did a compression check as well and the readings are as follows:
1-150 2-150
3-150 4-140
5-140 6-0
7-155 8-0

Does this indicate blown head gasket or something else? Maybe I put the head gasket on wrong.

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post #2 of 7 (permalink) Old May 2nd, 15, 05:44 PM
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Garth
 
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Re: Engine with low vacuum.

You need to leak down 6 and 8. Take the spark plug out of each cyliner individually and used compressed air to see where it comes out. Run both rockers off so the valves are not open or put each cyliner on TDC. Absolute zero usually means you have valves hung open or you have a nice sized 'inspection hole' somewhere. Since its 6 and 8 I would probably guess at a head gasket issue or something between the cylinders. Compression elsewhere looks good.

If you just put this engine together make sure you don't have to much lash and have the valves hung open.

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post #3 of 7 (permalink) Old May 2nd, 15, 10:48 PM Thread Starter
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Robert
 
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Re: Engine with low vacuum.

Thanks for the quick reply; unfortunately I don't have a compressor, so I'll have to wait until I can have it towed to a mechanic. I guess I can check the valve lash, I adjusted them one full turn after the push rod did not spin. Maybe I can back it off a 1/2 a turn.

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post #4 of 7 (permalink) Old May 2nd, 15, 11:11 PM
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Re: Engine with low vacuum.

I've had the pushrods spin with zero lash or properly set hydraulic lifters. I would not do the old spin method it's not fool proof. Set your valves to zero lash (when your push tube dosent go up and down with your fingers) and then run the adjusting screw down 1/2 to 3/4 turn down. This might not fix your problem but since you can't do a leak down test this might save you some money. Might be able to rent a compressor from Home Depot.

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post #5 of 7 (permalink) Old May 3rd, 15, 05:48 AM
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Garth
 
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Re: Engine with low vacuum.

No spin and then a full turn is probably too tight, especially if the lifters were not pumped up when adjusted. Even though you have compression on the other cylinders it may be too tight on the others also once the lifters pump up.

The last post is what you want. No up and down motion in the pushrod, zero lash, then 1/2 turn. Adjust the opposite rocker when exhaust is opening and then intake closing.

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post #6 of 7 (permalink) Old May 3rd, 15, 01:58 PM Thread Starter
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Re: Engine with low vacuum.

Okay, I started over, readjusted all the valves and turn them only 3/4 turn after the push rod stop spinning by hand. Check the compression again and the readings were as follows:
1-150 2-150
3-150 4-145
5-150 6-145.5
7-155 8-145.5

The vacuum reads a steady 17. It appears #6 & #8 were too tight. Thanks to everyone.

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post #7 of 7 (permalink) Old May 3rd, 15, 02:23 PM
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Re: Engine with low vacuum.

Low vaccuum assuming lave lash correct.. correct and clean PCV valve and no carb / valley cover leaks
1/ If the idle speed and mixture screws are not 1/2 turns out +/- 1/2 a turn.. the secondary butterflies are too far open.
And/ or
2/ idle (not initial) timing to far retarded, espec have a after market cam

If u have a blown head casket,
1/ check the spark plugs u will have one that is 'brand new ' clean and inspection in that pot with piston TDC so can see the top.. that will be clean too.
2/ Have a hydrocarbon/ Cox gas check done on the radiator... using a free check in this country, like a free battery check.. and takes about as long.

If u are reading the vaccuum gauge, and not experienced as to what looking at or done prechecks on the engine Odds are it will be the the secondary butterflies to far open.. in effect a big vaccuum leak.

r something as simple as a couple HT leads around the wrong way or a dieing spark plug.. or if new one has been dropped on the ground while installing

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