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Old 12-13-2010, 06:03 PM
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Oil restrictors/ Lifter valley riser tubes

I have a couple of question concerning me on my 350 chevy build.

1. Is it good or bad to use oil restricktors on a mechanical flat tappet cam build?

2. After break in, is it ok to use lifter valley riser tubes on a mechanical flat tappet cam?

This is strictly a racing engine.

Thanks

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Old 12-13-2010, 06:31 PM
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It really depends where the oil holes in the lifter are located if they are in the oil band you could restricted the oil to the valve train but I wouldn't and never have except a dry sump engine with sprayers in the valve covers. If the oil holes are on the side the side of the lifters not in the oil band its all ready restricted.

You can just plug the holes between the lifters, The vent tubes are for engine where the lower end and the top end are sealed off from each other as it equalizes the pressures.

Lets face it you have 2 big oil returns in the rear of the blokc and 2 in back of the timing chain and if you need more ventilatoin then that you have got some serious problems with blowby.
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Old 12-13-2010, 06:34 PM
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Bad idea to restrict the oil feed passage with a flat tappet cam, I would never do it, especially with the hard time flats have been having with oil quality. I've done it and not done it on the same engine in the past and couldn't tell the difference, it sure didn't show up on a time slip in the 1/4 mile. Same with valley vents, there isn't enough advantage in windage control for it to be worth the risk.

It looks trick on the engine stand to have vally plugs or valley vents, but once the intake is on...who cares. Only place I can see it would be any real advantage is a very high rpm drag engine in class racing, where even 2hp could be the difference in winning or losing and the thing gets tore down evey so often. Otherwise it just has the possibility of hurting durability more than it helps power lost to windage.
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Old 12-13-2010, 06:46 PM
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Quote:
Originally Posted by Backwoods
I have a couple of question concerning me on my 350 chevy build.

1. Is it good or bad to use oil restricktors on a mechanical flat tappet cam build?

2. After break in, is it ok to use lifter valley riser tubes on a mechanical flat tappet cam?

This is strictly a racing engine.

Thanks
In my experience restrictors have no useful effect. The oil losses around the lifters and there bores is minimal. For a high RPM race motor the stiff valve springs are working real hard and get real hot, unless you provide oiling of the top end from an external source, the spring life and failure rate is 100% dependent upon the oil coming up the push rod. There isn't any sense in reducing this.

The stand offs have the advantage of allowing breathing between the upper valley and the crankcase without forcing all those gases through the same holes on the block ends you're trying to get drain-back oil through. They also help keep small parts from getting to the pan if a rocker trunnion breaks. Yes these trunnions don't need much oil, but those damn wound tighter than a drum valve springs do, as I already said.

Many guys restrict the rear oil returns which drain onto the crank. This is a good idea but an engine that typically sets tail low will fill the back side of the valley. I screen these returns and paste their upper parts closed with epoxy leaving a small number of slats open on the bottom, this slows the drain back onto the crank but allows the valley to empty when the engine is shut down. I open up the forward drains and also screen them to keep garbaged parts from getting to the pan. So the vast majority of oil collecting in the valley flows back to the pan by way of the timing case.

Assuming this is a wet sump engine, you need a deep pan unless there just isn't ground clearance then you have to go with a hammer head pan to get the volume. Volume is your friend as some of that oil will be in the valley, figure a quart and a half ain't coming right back to the pan. The other thing is to give the oil a moment to relax and dump entrained air before it dives back into the pump. For a wet or dry sump system you want a good windage tray to peel the oil away from the crank and put it where the pump (pump's) can get it. A crank scraper is very valuable to catch the oil centrifugal force is slinging against the passenger side of the pan and crankcase. There is so much oil slinging off the crank that I don't think the loss of drain back because of the valley vents will have any effect on cam and tappet life. This is a lot different from a street engine not only from the amount of flying oil, but actually the higher RPMs are a lot easier on the cam and tappets than the comparatively slower loading seen at street RPMs. There have been all sorts of fixes for accelerated cam and lifter wear over the years from electron beam drilling the lifter foot to bleed oil on the lobe, gun drilling the cam with intersecting holes from the lobes to provide oil on the interface, to casting the cam tunnel closed or attaching sheet metal trays under the cam, either of these to keep a flood of oil around the cam and lifters. This latter baffling thing is mostly the purview of distance racers where heat from the tappet and lobe interface from running at high RPMs for long periods can wipe these parts out.

For windage trays I way more prefer those with many smaller louvers with the louver facing up and open into the direction of rotation. Thusly configured the louvers act like a crank scraper, using the natural motions of the thrashing parts to collect the oil and get it to the pan. For a wet sump, the pan needs to have baffles and trap doors to keep the vital essence at the pump pick up and out of the crankshaft if this is a drag engine. This is a big problem with hammer head pans as there isn't great deal of depth above the pickup and plenty of space where the oil can go and the pick up can't follow, so you've got to keep what you can contained by the pick up.



Bogie
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Old 12-13-2010, 06:54 PM
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I was told that with the shaft rockers I didn't need the extra oil to the rockers and with a dry sump oil system the valley vents were needed.

Your answers matched my feelings. Why restrict oil from the rockers and why not let the oil run back down onto the cam through the valley holes.

Thanks.
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Old 12-13-2010, 07:17 PM
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Thanks for the replies.

I bought a canton oil pan with a windage tray. Would a crank scrapper be needed as well? The motor will be launching at about 5800 rpms and shifting at 7500.
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Old 12-13-2010, 07:47 PM
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Oiling system on the SBC is pretty much bullet proof, why mess with it?

Vince
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Old 12-13-2010, 09:23 PM
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When I got asked about this before I would reply
"Guys act like gallons of oil fall out of the lifter valley onto the crank when in reality it`s not enough to cause any power loss. And if does create a power loss it`s so small you don`t even notice"
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Old 12-14-2010, 12:22 AM
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oil restrictors and valley tubes

im with vince on this one,the sbc is as close to perfect as you can get in the oiling department.i use the vent tubes in our purpose built quarter mile engines.the piston to wall clearances are set up loose compared to street rods where oil control needs are different.so are the rod and main clearances.in a case like drag racing you can lose a hp or two from windage of returnind oil but this isnt the reason we do it.with a loose drag engine the resulting fog from drainback overwhelms the rings sometimes.never restrict upper end lube in the lifter gallery feed.always galls lifters and bores.a 5 qt pan will empty quick with drag race clearances at 8000 rpm.i restrict upper lube using a slightly smaller orificed pushrod which doesnt starve the lifter bores.so my opinion for what its worth.main concern is getting the picup no more than a 1/4'' from the pan bottom using clay.then braze it there.stock oiling and drainback.and evacuators.good luck with it.---billy
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Old 12-14-2010, 02:37 PM
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Quote:
Originally Posted by Backwoods
Thanks for the replies.

I bought a canton oil pan with a windage tray. Would a crank scrapper be needed as well? The motor will be launching at about 5800 rpms and shifting at 7500.

I was told that with the shaft rockers I didn't need the extra oil to the rockers and with a dry sump oil system the valley vents were needed.

Your answers matched my feelings. Why restrict oil from the rockers and why not let the oil run back down onto the cam through the valley holes.

Thanks.
Depending on model, the Canton has a scraper built in. The simple length of straight steel bending from the pan wall is plenty good to capture the oil slung of off the crank.

Right about shaft rockers with roller bearings, these don't need much oil, however, oil is needed to cool the valve springs, which is why I don't recommend cutting the supply to the lifters which feed the push rods on the Chevy unless you're using modified rocker covers with spray bars to put cooling oil on the springs. I've tried external top end oil returns a couple times but not sure the result was worth the effort, complication, and reliability issues

Over all there are a lot of problems around the need to use oil to cool engine internals and the need to get it off the crank where it's absorbing power. A world where both needs have to be fulfilled. Underside of the piston being an example where oil is used to cool the topside of the piston from below, yet the extra oil becomes a control problem for the rings and a windage problem for the crank. You'll aways be stuck trying to find the right edge for all these competing requirements and there isn't an ipso-facto solution this will flow back and forth in your own mind and with what's considered the current solution. Certainly as time passes different materials and processes will affect the answer as well.

Bogie
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