Show full size 924Board.org
Discussion Forum of 924.org
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
 Technical FAQ924 FAQ (Technical)   Technical924 Technical Section   Jump to 924.org924.org   Jump to PCA 924 Registry924 Registry

How to correctly assess 924 cam followers

 
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions
View previous topic :: View next topic  
Author Message
jasespace  



Joined: 24 Sep 2017
Posts: 1
Location: Olinda, Victoria, Australia.

PostPosted: Sun Jun 17, 2018 11:42 pm    Post subject: How to correctly assess 924 cam followers Reply with quote

I am rebuilding my NA '77 924. I have a collection of cam followers which are all second hand. Some seem better than others. I have had my cam reground to its original profile. I have read that you should not use second hand lifters with a new cam. But replacing all new lifters is not within my budget. How do I assess which lifters are useable? What is the trick to maintaining this part of the engine in good condition? I know I should make sure the oil feed tube is clean and working with a new plastic elbow. I imagine using good oil and upper cylinder head lubricant will help.
Also, are there any tricks to setting the clearance? Turning those screws while the cam is bolted down seems harsh to me. Doesn't that damage the valve caps? I was thinking it would be better to measure all clearances, unbolt the cam, make adjustments, bolt it down again and recheck.
Thanks in advance, Jase
Back to top
View user's profile Send private message Send e-mail
safe  



Joined: 18 Mar 2017
Posts: 4
Location: Sweden

PostPosted: Tue Jun 19, 2018 2:02 am    Post subject: Reply with quote

If you see wear on them, they need replacing.
If you can feel wear with you fingertips, you might need replacing, your fingers can feel very small imperfections.
If you have worn followers, I can't afford to replace them just chuck in an old camshaft and not your new.
Back to top
View user's profile Send private message
daniel  



Joined: 18 Jun 2009
Posts: 612
Location: Sydney, Australia

PostPosted: Tue Jun 19, 2018 11:33 am    Post subject: Reply with quote

Technically yes you should always use new cam followers, however as you have mentioned this is not always practical. Have a look at the follower and try to determine how it has worn. If there is any evidence that the hardening has been worn through, toss it away. Next is to see if the follower is concave or convex. If the follower is concave you 'shouldn't' use it, although it is possible to use - ill explain later. If the surface is flat or better still convex and the surface is free from damage, go for it. Most cam grinding shops will take followers like this and re polish them so they are 100% but you MAY get away with using how they are.

Back to convex followers, everyone will tell you no good but I have experience to suggest otherwise. Back when I was building FVee motors we had a control cam and had a maximum valve lift. I built several motors with badly worn convex lifters and never had an issue. The idea is that as the cam lobe hits the lifter and drops away into the followers 'dip', provided you could still achieve the max valve lift through rocker geometry, you could increase the effective duration, i.e. from when the valve opens you can lift the valve list curve up so the valve opens more rapidly and stays at peak lift for longer.
_________________
Over the top of skyline, total brake failure.... hit the wall at over 200 kp/h at the dipper, so anyone who has to brake for the esses is a pussy.
1977.5 Race Car, CAMS Group S Spec
1989 944 Cabriolet
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    924Board.org Forum Index -> General Discussions All times are GMT + 11 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group