bob

Does anyone have a set handy for a sbc. I want to spin some up on the lathe and wonder what dia hole they have in production ones. I am not sure it makes a lot of difference but thought I would check.
Thanks-bob

clem zahrobsky

just cut to length and thread 1/4" pipe with NTP thread. :chevy

gkull

It's much easier to just install a cam valley pan. It accomplishes the same thing.

clem zahrobsky

the vents are installed to prevent the oil drain back over the rotating assy. thru the drilled holes but still let the pressure out of the crankcase. if you block the drilled holes then all the crankcase pressure comes up thru the drain back hole at the back of the block and prevents the oil from draining back down to thepan. the valley pan helps keep the hot oil from heating up the bottom of the intake manifold and causing fuel distribution problems :chevy

gkull

Clem years ago i tapped and installed plugs and screened the drain backs. Then i got to looking at a valley pan. It's like putting a roof on. All the lifter oil spash is kept from draining straight back down the center it has to run to the larger end drain back holes. Also hot oil being throw up never hits the bottom of the manifold like you said. I also drilled blind holes and pop rivited the pan in place.

arnold

You're stating the valley pan seals well enuf to prevent oil from draining into the center holes, and thus over the crank?

clem zahrobsky

the oil comes out of the lifters and lifter bore so you must either plug the holes or use the vent tubes to prevent the oil from running back down over the crank. :chevy

bob

I also like the vents so that the crankcase gases can escape without bubbling the draining oil. Thanks for the comments-bob

speedjohnson

Don't do it! Don't use them!

Sure they look cool. But, without a dry sump to scavange out the valley you'll collect all your oil up there and will run your sump low in hard cornering.

Ask me how I know...I've got a great video of my oil gauge at "zero" in the corners and with hard braking at PIR. This gave me a nice set of toasted rod bearings as a result. Yes, I had a roadracing pan. Yes, I had an accusump. Yes, the pan was full of oil and the accusump fully charged at startup...I had radiused and smoothed the fore and aft valley drainbacks and yes, I had valley oil stands. Duh. sj

arnold

By chance, are/were you using a HV oil pump at the time? Regardless, seems odd that the oil would not drain down (adequately) either from the front or rear. Sounds as though, forces prevented the oil from draining. Is/was there enuf pressure from below to cause the oil to back up, such as water backing up, attempting to go down a kitchen garbade disposal, or attempting to empty a gas can without a vent? No, draining oil does not have pressure to assist it's return to the pan, as oil leaving the oil pump, but something doesn't seem correct here? With a sublaxation in my neck, I gotta clean off my gas soaked, dishpan hands now.

clem zahrobsky

that happens from improperly vented rocker covers and also the "G" forces in the corners hold the oil in the covers. you need a properly designed oil extra capacity pan and any oil pan you need to run 1 or 2 quarts over full on road courses to make up for the oil that get trapped in the rocker covers in the corners. another problem i have found is if you install the road race oil pan on the engine stand upside down you can cause the trap doors in the pan to be locked in the open position causing the oil pressure loss problem because the oil is running away from the pickup. do not ask how i know this. :chevy

arnold

Clem, rather than a passive system, I prefer a more aggressive crankcase pressure evacuation vacuum pump setup.

clem zahrobsky

using a crankcase evactuation system requires rods with oil pressurize wrist pins ,valve spring oilers,special seals, rocker cover gaskets etc,because there is very little oil mist in the engine. the biggest advantage of negative crankcase pressure is that you can run run very low tension oil rings for less HP wasting drag. this also does not work very well unless you are running a dry sump system and some dry sump pumps have the capacity to evacuate the crankcase

arnold

Thanks for the input Clem, especially, concerning the trap door tip. Obviously, sucking the daylights out of the crankcase till pan distorts, is not the answer. :)

gkull

SJ - I also didn't understand how oil wasn't getting back down soon enough and you experienced oil starvation.

I actually installed plugs in the past. but i also radiused the front and rear holes before screening for better drain back. I also give my heads the same same treatment to promote drain back.

I have a larger road racing pan and I run oil restricted top end. I have a bright red light for loss of oil pressure and I have never had it come on even when running at (PIR) years ago.

You not the first to smoke a motor because of high "G" turns. I've seen some C-4's and C-5's pop.

The last 2 years i had .060 oil restrictors and I blame them as a partial cause of lifter failure while racing at Thunder Hill California.

This year i drilled the restrictors out to .125 to save the lifters and I still haven't sucked the pan dry. I only use blue printed and polished out standard Melling oil pumps with one shim to get my max oil pressure at 75-80 psi at anything over 3500 rpm.

clem zahrobsky

you need oil flow to cool the valve springs that is why valve covers with sprayers are used in race cars. years ago when chevy was testing V-8 stock block chevy powered indy cars at indy they kept losing valve spring pressure after a few laps. it turned out to be that the G forces in the turns at indy was preventeing the oil from getting to the valve springs. they ran a dyno test with see thru valve covers and at 6000/7000 RPM they cut off the oil flow to the heads and in less than 30 seconds the exhaust valve spring turned red hot. when you a start up a new engine that is why you need oil flow to the springs right away. comp cams sell a product called "spring spray" that when sprayed in the springs stays there till the oil starts to flow. on drag race engines i would put "stand tubes"in the oil return holes in the heads so there would be a layer of oil to cool the valve springs next the the head and exhaust ports. :chevy


[Modified by clem zahrobsky, 3:30 PM 12/28/2003]


[Modified by clem zahrobsky, 3:32 PM 12/28/2003]

bob

clem and gkull and anyone

Interesting thoughts--on one hand it seems ( with solid lifters and full roller rockers ) the norm is to restrict the oil to the top end to ensure more to the bottom bearings and I can't say I gave too much thought to spring cooling. What is opinions on restrictors? .060, gkulls .125, no restrictor, something in between?
bob

clem zahrobsky

i never ran anything smaller than .125

gkull

Clem is right about the oil spray. I also lost @20 pounds of spring pressure in two years with oil restrictors. I had nice Kmotion springs with as sold 225# seat and something like 540 open at my .640ish lift. I used +.050 height retainers to lower the closed P. to @195# but the high spring rate keeps the open about the same.

Well I threw them away and started over. Dart heads have a very tall valve cover lip which helps oil return. I would never consider stock heads again. I run springs made for .720 lift 1.56 dia. So cooling isn't as much of a problem. I increase the max lift with the retainers and never really stress them.

Years ago i over revved a motor on tranny failure and I had to cut the valve stems off to pound them through the guides. I had valve piston impacts on a few cylinders.

It's a learning courve to always build better!

clem zahrobsky

GM was the people who orignally came up with the spaybars in the covers for the indy car project. :chevy :chevy