minimum idle rpms - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans Advertise
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Hotrodding Basics
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 05-23-2019, 07:55 AM
Registered User
 
Join Date: Aug 2014
Location: Sherkston Ont
Posts: 207
Wiki Edits: 0

Thanks: 64
Thanked 17 Times in 16 Posts
minimum idle rpms

i was tuning my sbc engine and after checking timing,float level and adjusting carb i set my idle rpm to 750 in neutral since it is a stick car, being that the flat tappet cams lobes are only oil splash lubricated i got to wondering if a cam with stronger springs need more idle rpm to ensure adequate oiling, i know the older cars had about 600 rpm in gear but the cams and springs were somewhat lighter
and lower lifts were used than we use now, any thoughts ?
scotty

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 05-23-2019, 10:08 AM
chasracer's Avatar
True Hotrodder
 
Join Date: Oct 2018
Posts: 576
Wiki Edits: 0

Thanks: 40
Thanked 132 Times in 118 Posts
No. There's plenty of oil raining down on the cam from the valley area.
Reply With Quote Quick reply to this message
The Following User Says Thank You to chasracer For This Useful Post:
scotty57406 (05-23-2019)
  #3 (permalink)  
Old 05-23-2019, 12:55 PM
techinspector1's Avatar
Member
 
Last wiki edit: DynoSim combinations
Join Date: Oct 2005
Location: Zephyrhills, Florida, USA
Age: 77
Posts: 16,912
Wiki Edits: 326

Thanks: 1,890
Thanked 2,801 Times in 2,098 Posts
Scotty, the main difference between "older" motors and today's motors is the motor oil. Back before catalytic converters, the oil manufacturers added zinc and other minerals to the oil to serve as "extreme pressure" lubricants to protect that little pencil point of contact between the cam lobe and the lifter face (roughly 250,000 lbs per square inch, depending on springs used). Later, when catalytic converters were introduced, the auto makers found themselves with an excess of warranty claims from the extreme lubricants finding their way into the converters and rendering them useless for cleaning up the exhaust. So, the auto makers put pressure on the oil makers to cease and desist adding the extreme pressure lubes to engine oils. Realizing that the flat tappet camshaft design being used at the time would not survive without extreme pressure lubes, the auto makers converted their manufacturing process to use roller tappet hydraulic cams instead of flat tappet hydraulic cams and all was right with the world. But wait, what about the hot rodders who wanted to continue to use flat tappet cams? Well, one fix was to add the extreme pressure lubricants to off-the-shelf motor oils and that's pretty much how it's done today. Adding enough chemicals to the oil to make a 1200 parts per million mix will generally protect the lobes and lifter faces on a flat tappet cam. MORE IS NOT BETTER. 1200 works fine. This tutorial may help you and others reading this post to understand.........
https://www.crankshaftcoalition.com/...ips_and_tricks
Reply With Quote Quick reply to this message
The Following User Says Thank You to techinspector1 For This Useful Post:
scotty57406 (05-23-2019)
 
  #4 (permalink)  
Old 05-23-2019, 09:06 PM
55_327's Avatar
Registered User
 
Join Date: Jun 2011
Location: North Texas
Posts: 558
Wiki Edits: 0

Thanks: 7
Thanked 108 Times in 93 Posts
Just use some good oil with high zinc & phosphorus levels such as Driven Hot Rod oil, or even Valvoline VR1 Racing oil in the silver jar. Don't use the jar (blue, I think) that's labelled "Not Street Legal". It has fewer, if any, detergent additives, and must be changed frequently. https://www.jegs.com/p/Valvoline-Rac...gin|0||P_SKU|0
Reply With Quote Quick reply to this message
The Following User Says Thank You to 55_327 For This Useful Post:
scotty57406 (05-24-2019)
  #5 (permalink)  
Old 05-23-2019, 09:15 PM
Registered User
 
Join Date: Apr 2007
Posts: 12,409
Wiki Edits: 0

Thanks: 182
Thanked 1,143 Times in 913 Posts
Quote:
Originally Posted by scotty57406 View Post
i was tuning my sbc engine and after checking timing,float level and adjusting carb i set my idle rpm to 750 in neutral since it is a stick car, being that the flat tappet cams lobes are only oil splash lubricated i got to wondering if a cam with stronger springs need more idle rpm to ensure adequate oiling, i know the older cars had about 600 rpm in gear but the cams and springs were somewhat lighter
and lower lifts were used than we use now, any thoughts ?
scotty
Its a good idea to keep the idle up especially if this is a modern cam with short ramps and high rates of lift, the latter includes using higher than stock 1.5 rocker ratios as these magnify the force between lifter and lobe.

The SBC has a mostly closed valley floor, most drain back is on the ends and that mostly at the rear since most installations tip the engine and trans slighly down at the rear. So the cam and lifters are almost completly dependent on crank throwoff for lubrication. The short solution is to use EDM solids, these are drilled in the base to supply pressure oil on the contact point with the lobe.

By inspection with the engine running it's a good idea to verify the flat tappet lifters rotate in their bore. Sliding on the lobe without rotation is an invitation to sudden death for these parts.

Bogie

Last edited by BogiesAnnex1; 05-23-2019 at 09:26 PM.
Reply With Quote Quick reply to this message
The Following User Says Thank You to BogiesAnnex1 For This Useful Post:
scotty57406 (05-24-2019)
  #6 (permalink)  
Old 05-24-2019, 05:03 AM
75gmck25's Avatar
Registered User
 

Last journal entry: Engine replacement
Join Date: Aug 2006
Location: Alexandria, VA
Posts: 2,444
Wiki Edits: 0

Thanks: 4
Thanked 210 Times in 193 Posts
Many contributors to the board have their favorite choice for high zinc and phosphorus motor oils; however, some are racing oils or special purpose blends that are harder to find and sometimes more expensive.

For several years I've been using Mobil 1 15w50 synthetic, since it has 1200 phosphorus and 1300 zinc, and I can get it at Walmart and most auto parts stores. It also goes on sale frequently as part of store promotions. YMMV.

Another weird option for oil purchase is to buy it on Amazon. I was looking online for an oil filter for my BMW and Amazon popped up with an option to buy oil also. They had no issue with free shipping of a five quart bottle of oil.

Bruce
Reply With Quote Quick reply to this message
The Following User Says Thank You to 75gmck25 For This Useful Post:
scotty57406 (05-24-2019)
  #7 (permalink)  
Old 05-24-2019, 07:17 AM
55_327's Avatar
Registered User
 
Join Date: Jun 2011
Location: North Texas
Posts: 558
Wiki Edits: 0

Thanks: 7
Thanked 108 Times in 93 Posts
And if you want a thinner oil for better protection on cold starts, and less power-robbing:

Mobil 1 Formula M
5w-40
Phosphorus: 1000 ppm
Zinc: 1100 ppm

That's 25%-30% more than most modern oils.

https://mobiloil.com/~/media/amer/us...pecs-guide.pdf
Reply With Quote Quick reply to this message
The Following User Says Thank You to 55_327 For This Useful Post:
scotty57406 (05-25-2019)

Recent Hotrodding Basics posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Insurance
Please select your insurance company (Optional)

Log-in



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
65 psi low compression 388 chev stroker stanjr41 Engine 22 05-24-2017 05:58 PM
Engine Idle Too Fast With New Carb Canadian Charlie Engine 15 11-17-2010 09:21 PM
DARK brown--BLACK plugs SBC Joshua Lee Engine 128 02-03-2008 09:12 AM
Cam lope question joeford Engine 4 08-10-2006 08:14 AM
I'm going to make a bonfire out of my car blown69stang Engine 36 08-22-2005 03:36 PM


All times are GMT -6. The time now is 09:24 AM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.