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GM Rocket block oiling problem

General engine tech -- Drag Racing to Circle Track

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rewguy
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GM Rocket block oiling problem

Post by rewguy » Wed Jul 31, 2019 5:14 pm

4.170 bore, 4.125 stroke, 452 c.i. Engine is draining the oil pan about 900 feet into a 1320 pass. Pressure drops to zero. Let off throttle, eventually comes back....but takes 15 or so seconds which seems like forever. 50mm cam tunnel, roller bearings, .0035 cl mains, .0031 cl rods, 50mm roller cam bearings, morel lifters, Titan pro pump with bypass set to 85 lbs., Jeff Johnson kicked out rear sump pan / 6 1/2 qt capacity, although the pan looks visually bigger to me....but that's what it seems to measure and that's what he claims as well. 60lbs pressure cold idle, 53 lbs W.O.T. oil pressure......never comes close to the bypass preset. Pumps it ALL upstairs. 7 (1/2") oil drain back holes in bottom of valley with 4 vent stacks as well. Vac. pump pulls 12" at W.O.T.. Any way to restrict oil to the top on this block? I don't believe oil restricting pushrods will be enough. This problem is extreme. I've ran the system a quart and a half over full, and it still runs it dry. Mid nine sec. car roughly. Any ideas? I'm at a loss.

p.s. When the engine first fired it would not oil the rockers.......I added small grooves to the pushrod feed hole to help. About .020 deep, and .025 across. PLENTY of oil then. But I have a very hard time believing that the grooves are the issue with running the pan dry this quickly.
Last edited by rewguy on Wed Jul 31, 2019 5:31 pm, edited 1 time in total.

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Re: GM Rocket block oiling problem

Post by rewguy » Wed Jul 31, 2019 5:21 pm

20190731_155754.jpg
20190731_155628.jpg
Lifter to bore clearance is .0019
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Last edited by rewguy on Wed Jul 31, 2019 5:24 pm, edited 1 time in total.

rewguy
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Re: GM Rocket block oiling problem

Post by rewguy » Wed Jul 31, 2019 5:22 pm

It has been suggested that there has to be a fairly large leak internally to cause this..... But I can't seem to find it with any certainty. Oil is Valvoline VR-1 20W-50.

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Re: GM Rocket block oiling problem

Post by af2 » Wed Jul 31, 2019 5:46 pm

Are the plugs in the cam oil ports in the back of the block in?
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Re: GM Rocket block oiling problem

Post by rewguy » Wed Jul 31, 2019 5:54 pm

af2 wrote:
Wed Jul 31, 2019 5:46 pm
Are the plugs in the cam oil ports in the back of the block in?
yes. Every plug is in. The two in the lifter valley, and the 3 on either end.

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Re: GM Rocket block oiling problem

Post by rewguy » Wed Jul 31, 2019 5:59 pm

https://sciencing.com/convert-psi-gpm-w ... 74602.html

I even got the weight of a cubic foot of engine oil and did the flow math for a .060 pushrod hole moving 100 psi (MUCH more than my psi) with atmospheric pressure on the other end...(i.e. NO restriction, like a rocker arm), and at 100 psi w NO restriction, all 16 pushrods WIDE OPEN should flow no more than about 2.08 qts over a 10 second period. With my 53 psi wide open pressure, and rocker arms as a restriction, and the fact that my problem is evident on the gauge at about 7 seconds in.....possibly less......I seriously doubt that the "more than adequate" top end oiling due to the small lifter grooves could be more than a quart or so in 10 seconds.

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Re: GM Rocket block oiling problem

Post by Zmechanic » Wed Jul 31, 2019 6:01 pm

Where does the vac pump pull from? Valve cover(s)? What do the drain backs in the heads look like?

If you pull from the valve cover (or anywhere else really) you have to make sure it doesn't FLOW at lot to the vacuum pump. It can pull a lot of vacuum, but that doesn't tell you how much volume of gas its FLOWING to make that vacuum. (Like the stupid shark vacuum commercials where they would hold a bowling ball. All depression, no flow). If it's flowing a bunch of air out of the vacuum pump, it could be sucking oil up to the top end and holding it. Now as to where it's getting that volume, could be blow by, could be bad sealing somewhere. Something to think about. Air going the wrong way through your drainbacks could be your issue. Another way of thinking about it.

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Re: GM Rocket block oiling problem

Post by rewguy » Wed Jul 31, 2019 6:38 pm

Zmechanic wrote:
Wed Jul 31, 2019 6:01 pm
Where does the vac pump pull from? Valve cover(s)? What do the drain backs in the heads look like?

If you pull from the valve cover (or anywhere else really) you have to make sure it doesn't FLOW at lot to the vacuum pump. It can pull a lot of vacuum, but that doesn't tell you how much volume of gas its FLOWING to make that vacuum. (Like the stupid shark vacuum commercials where they would hold a bowling ball. All depression, no flow). If it's flowing a bunch of air out of the vacuum pump, it could be sucking oil up to the top end and holding it. Now as to where it's getting that volume, could be blow by, could be bad sealing somewhere. Something to think about. Air going the wrong way through your drainbacks could be your issue. Another way of thinking about it.
It is pulling from the front of the drivers side valve cover. The drainbacks at front and rear are somewhat small.....but the drain backs around the pushrod area are huge......each of the (4 per side) are about 1" x 2 1/2". Not just individual holes like some. I have used the identical heads on other engines w vac. pumps as well and never had one issue.

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Re: GM Rocket block oiling problem

Post by stealth » Wed Jul 31, 2019 7:40 pm

Lifter valley drilled for wet sump use?
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Re: GM Rocket block oiling problem

Post by af2 » Wed Jul 31, 2019 7:45 pm

stealth wrote:
Wed Jul 31, 2019 7:40 pm
Lifter valley drilled for wet sump use?
HMM?
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Re: GM Rocket block oiling problem

Post by rewguy » Wed Jul 31, 2019 8:05 pm

stealth wrote:
Wed Jul 31, 2019 7:40 pm
Lifter valley drilled for wet sump use?
I have 7 - 1/2" holes, and 4 lifter valley standpipes in the valley.

we had a similar 14 degree engine, rocket block or iron eagle.....Only had 4 - 1/2 inch holes and it did have a small cavitation issue for about a half a second near the finish line.. Same application, and similar everything. That's why I decided to add three more drainback holes AND the vent pipes on this latest one.

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Re: GM Rocket block oiling problem

Post by tenxal » Thu Aug 01, 2019 8:19 am

Have you tried it w/o the vacuum pump?

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Re: GM Rocket block oiling problem

Post by Warp Speed » Thu Aug 01, 2019 10:03 am

That is a bunch of bearing clearance!

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Re: GM Rocket block oiling problem

Post by exhaustgases » Thu Aug 01, 2019 1:27 pm

Warp Speed wrote:
Thu Aug 01, 2019 10:03 am
That is a bunch of bearing clearance!
Yeah for 0W-20 it would be.

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Re: GM Rocket block oiling problem

Post by BILL-C » Thu Aug 01, 2019 2:05 pm

We ran into similar problem, just not quite as bad. A -12 hose from fuel pump block off plate to valve cover helped with drain back a little. Opening up vent holes in timing cover area and lifter valley fixed problem. You can't have oil drain down through the same holes that blow by vapors are trying to come up through at the same time.
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