Another "Will this work in an LN3 Question" - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


1987-1991 Parley with regards to your 1987 to 1991 Bonneville, Olds 88 or Buick Le Sabre Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

Reply
 
 
 
Thread Tools Search this Thread
Old 09-27-2005, 04:05 PM   #11
Senior Member
True Car Nut
 
Join Date: Apr 2004
Location: Three Oaks, Michigan
Posts: 4,879
Thanks: 0
Thanked 0 Times in 0 Posts
opensourceguy is on a distinguished road
Default

unfortunately you can't do that. it'd be the same effect as overtorquing the rocker bolts..

also, he said upgrading to stock roller rockers, not full rollers.. so idk.

also our pushrods are pretty light to begin with.. probably not going to make a noticable difference, and no matter what, you shouldn't be revving your engine that high if you are getting valve float... LN3s don't like upper rpm runs.
opensourceguy is offline   Reply With Quote
Old 09-27-2005, 05:00 PM   #12
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Feb 2005
Location: Walled Lake, MI
Posts: 95
Thanks: 0
Thanked 0 Times in 0 Posts
maybe2fast is on a distinguished road
Default

what is the stock duration of the LN3 and roller stock rockers?
maybe2fast is offline   Reply With Quote
Old 09-27-2005, 11:26 PM   #13
Senior Member
Posts like a 4 Banger
 
Join Date: Mar 2005
Location: Appleton, WI
Posts: 124
Thanks: 0
Thanked 0 Times in 0 Posts
2seater is on a distinguished road
Default

These are the figures I derived when I degreed the stock cam during my engine build. I couldn't find any stock specs so I checked when I installed the stock 1990 roller cam. All figures @ .050" lobe lift. The figures should be very close, although absolute accuracy is not guaranteed.
Intake opens @ 20.5* ATDC, closes @ 27.5* ABDC, 187* duration and .250 total lobe lift.
Exhaust opens 30* BBDC, closes 26* BTDC, 184* duration and .255 total lobe lift.

I have a cam from an '88 also and I did not install it so I do not have the opening and closing points, but I did install it in a jig I made to check the lobe lift and duration. The cam appears to be square, 180* duration on both lobes and a little more lift @ .260 on both lobes.

Interesting that both engines have the same ratings and I have heard several comments that the cars feel different between the two years even with the same gearing and tire size? With the very mild specs, it is no wonder they run out of wind at about 4500 rpm.

From Smokey Yunicks engine experimenting, little is gained from lighter lifters, pushrods and even rockers to increase the rpm potential. It does seem contrary to logic, one would think all would make a difference, but the springs, keepers and valves are where lightness has the greatest gain. At the rpm'* we are working with, it should make little if any difference. We are running 1/2-2/3 the rpm'* he was working with and smaller valves as well.
2seater is offline   Reply With Quote
Old 09-27-2005, 11:32 PM   #14
Senior Member
Certified Car Nut
 
Join Date: Mar 2003
Posts: 12,432
Thanks: 0
Thanked 0 Times in 0 Posts
J Wikoff is on a distinguished road
Default

Wait, the exhaust closes before top dead center and there is no overlap with the intake valve? Or was that a typo?
J Wikoff is offline   Reply With Quote
Old 09-27-2005, 11:51 PM   #15
Senior Member
Posts like a 4 Banger
 
Join Date: Mar 2005
Location: Appleton, WI
Posts: 124
Thanks: 0
Thanked 0 Times in 0 Posts
2seater is on a distinguished road
Default

No, it is not a typo. The figures are @ .050" lobe lift, the valve isn't actually closed, so it is likely open slightly at TDC, the valve will be open even more with the stock 1.6 rocker ratio. With essentially no overlap, the engine should be emissions friendly and a good torque producer too, but lacks top end breathing. I did not check the actual total seat to seat duration. I know it sounds wrong, but as the piston has done almost all of it'* upward travel as the crank gets nearTDC, it is primarily swinging over center at that point. We have a relatively long rod with a pretty high rod ratio, so the piston actually dwells a longer time at the bottom and top of the stroke. If I remember right it is close to what a Chebbie 350 has if 6" rods are fitted.
2seater is offline   Reply With Quote
Old 09-28-2005, 11:40 AM   #16
Member
Posts like a V-Tak
Thread Starter
 
Join Date: Feb 2005
Location: Walled Lake, MI
Posts: 95
Thanks: 0
Thanked 0 Times in 0 Posts
maybe2fast is on a distinguished road
Default

I am just going to do the roller rockers from the series 1 for the purpose of wear after the mileage on my solid rockers. and the rollers will help the motor run alittle nicer

Plus its fun to work on your car
maybe2fast is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
L27 rockers on LN3 question about guide plate. mAsalicio Performance, Brainstorming & Tuning 4 05-28-2007 01:41 PM
Yet another "which ScanTool to get" question... agrazela General GM Chat 13 01-20-2007 11:05 PM
Where is the "chime" / "dinger"? PPrash 1992-1999 6 11-21-2005 09:11 AM
'91 L "snakes" intake on a "C" engine ? padgett 1987-1991 5 07-21-2003 08:12 PM
"D" or "OD" ? BusMaster007 1992-1999 23 01-09-2003 03:09 AM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not 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 Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 07:13 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.