Login    Forum    Search    FAQ

Board index » Racing Forum » Engine & Cylinder Head Tech




Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2
Author Message
 Post subject: Re: This year
 Post Posted: Sun Dec 23, 2012 4:36 pm 
Offline
Moderator
User avatar

Joined: Tue Apr 18, 2006 3:20 pm
Posts: 1457
Location: Missouri
Beretta wrote:
At 800 lift and running 8000rpm IMO 250 on the seat is not enough....I have had issues there before and now running just over 300 on the seat and 825 on the seat and everything looks just fine and valve adjustment never moves...

With a BBC valve that weighs ~20% more than a sbc valve and larger diameter springs and retainers, it will need a lot more spring than a sbc.

I ran some used Nextec springs on my 18º engine that had ~275# with .780" lift shifting at 9000rpm and never had a problem (titanium valves though). The 414 dragster engine had ss valves and 230# springs, .700"lift, turning 7200 at the shift. IMO a lot of people have gone to "too much spring is just right" valvetrains. A lot depends on the lobe you use. The slam the valve open lobes like a Comp TK lobe will need a lot more spring than a Comp Hi-Tech lobe.

The 383 engine I build and work on for a friend has a Herbert cam with net lift around .650" (shift ~7200-7400) and we thought his springs might be getting weak so we pulled them and tested them at 160# ... O:) I thought wow, not good. Put some 230# springs on it and back to the track with no noticeable change. [-(

I like the springs available today where they get weak long before they break normally, unlike the older K1000 types that would just break when they got bad. not good.

Rick


Top 
 Profile  
 
 Post subject: Re: This year
 Post Posted: Mon Dec 24, 2012 4:56 pm 
Offline

Joined: Tue Jun 10, 2008 1:27 pm
Posts: 213
Location: Letellier MB Canada
I was looking for ideas building headers and i found this pic. Last one on the page. The best use for a nextec spring =;
http://www.yellowbullet.com/forum/showt ... p?t=434080

_________________
Image


Top 
 Profile  
 
 Post subject: Re: This year
 Post Posted: Thu Jan 31, 2013 8:53 pm 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:44 pm
Posts: 1423
Location: Clawson, Mi.
PSI springs all the way for me... PAC and Nexteck can take a hike, but that's just my opinion... Get the biggest pushrods you can stuff in it, and your going to have reversion with that cam too:ie black carbon all the way up into your plenum of the intake!!!! been there already and just changed MY cam to help it out a bit. Running thru the pits at idle or low speed will do this too.
A 112 or 114 LSA would give you better power as a few cam grinders would say :-k seems like a lot of guys have a cam LSA like that, some more, some less.

Good luck with the tunnel ram, that should really be a fun ride \:D/

_________________
Image
Thanks To;
DART
Motor City Muscle
Induction-Solutions
Fuelab Fuel System
D & S Engines
My Wife & Family




R.i.p. Doug Cunningham, gone, not forgotten.


Top 
 Profile  
 
Display posts from previous:  Sort by  
 
Post new topic Reply to topic  [ 18 posts ]  Go to page Previous  1, 2

Board index » Racing Forum » Engine & Cylinder Head Tech


Who is online

Users browsing this forum: No registered users and 2 guests

 
 

 
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

Search for:
Jump to:  
cron