lifter valley vents
Thread Starter
Pro
Joined: May 1999
Posts: 749
Likes: 2
From: Gabriola BC
lifter valley vents
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
Thanks-bob
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: lifter valley vents (gkull)
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
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: lifter valley vents (clem zahrobsky)
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.
Instructor
Joined: Sep 2001
Posts: 171
Likes: 0
Re: lifter valley vents (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.
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: lifter valley vents (arnold)
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
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
5 MOST and 5 LEAST Popular Corvette Model Years in History!
Joe Kucinski
2027 Corvette Buyer's Guide: Everything You Need to Know!
Joe Kucinski
10 Things C8 Corvette Owners Hate (But Won't Tell You)
Joe Kucinski
10 Best Corvettes Coming to Barrett-Jackson Palm Beach 2026!
Brett Foote
Every Corvette Grand Sport Explained! (C2, C4, C6, C7, & C8)
Joe Kucinski
Pro
Joined: Dec 2002
Posts: 746
Likes: 1
From: salem or
Re: lifter valley vents (bob)
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
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
Instructor
Joined: Sep 2001
Posts: 171
Likes: 0
Re: lifter valley vents (speedjohnson)
Ask me how I know...sj
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: lifter valley vents (speedjohnson)
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
Instructor
Joined: Sep 2001
Posts: 171
Likes: 0
Re: lifter valley vents (clem zahrobsky)
that happens from improperly vented rocker covers and also the "G" forces in the corners hold the oil in the covers.
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: lifter valley vents (arnold)
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
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: lifter valley vents (speedjohnson)
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.
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.
Le Mans Master
Joined: Mar 1999
Posts: 6,744
Likes: 1
From: delmont pa
Cruise-In I Veteran
Cruise-In II Veteran
Re: lifter valley vents (gkull)
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]
[Modified by clem zahrobsky, 3:30 PM 12/28/2003]
[Modified by clem zahrobsky, 3:32 PM 12/28/2003]
Thread Starter
Pro
Joined: May 1999
Posts: 749
Likes: 2
From: Gabriola BC
Re: lifter valley vents (clem zahrobsky)
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
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
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,444
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: lifter valley vents (clem zahrobsky)
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!
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!