NAXJA Forums -::- North American XJ Association  

Go Back   NAXJA Forums -::- North American XJ Association > NAXJA Unibody Jeep Technical Forums > Jeep Cherokee XJ (1984 - 2001) > OEM Tech Discussion
HOME Member FAQ Sponsor Info Rules Bylaws E-Mail

OEM Tech Discussion Forum for OEM (Original Equipment) or stock XJs and MJs.

Reply
 
Thread Tools Display Modes
  #16  
Old April 11th, 2019, 13:18
old_man's Avatar
old_man old_man is offline
NAXJA Member
 
Join Date: May 2003
Location: Loveland, Colorado
Posts: 15,628
Re: Octane and power

I adjusted the quench height when I built my stroker almost 20 years ago. I run 10.4 on regular with no ping.
__________________
Tom Houston - Former Colorado Chapter President , Terminal Adrenaline Junkie, and Rocket Scientist
Loveland, Colorado My teardrop build
You're just jealous because the voices don't talk to you.
Reply With Quote
  #17  
Old April 11th, 2019, 15:24
Cummins90 Cummins90 is offline
NAXJA Forum User
 
Join Date: May 2016
Location: northern CT
Posts: 95
Re: Octane and power

I dont mean to thread jack but what is stock quench in the high OP engines?
Reply With Quote
  #18  
Old April 11th, 2019, 16:19
RCP Phx RCP Phx is offline
NAXJA Forum User
 
Join Date: Mar 2003
Location: Phoenix,Az
Posts: 12,236
Re: Octane and power

IIRC it's .030-040", I set mine at .035".
Reply With Quote
  #19  
Old April 11th, 2019, 18:51
cal's Avatar
cal cal is offline
NAXJA Warranty Voider
 
Join Date: Nov 2004
Location: Hammertown, USA
Posts: 17,379
Re: Octane and power

.088".

Mine is .022.
__________________
I'm not a complete idiot - there are parts missing.
Reply With Quote
  #20  
Old April 12th, 2019, 06:00
old_man's Avatar
old_man old_man is offline
NAXJA Member
 
Join Date: May 2003
Location: Loveland, Colorado
Posts: 15,628
Re: Octane and power

Quote:
Originally Posted by RCP Phx View Post
IIRC it's .030-040", I set mine at .035".
You might want to check your numbers again. IIRC (its been 20 years) the stock quench height was some where around .085" with the gasket. I decked the block (not the head) .030" and went with the Mopar thin performance gasket and ended up with .050-.053" IIRC. That coupled with HC803CP pistons has been great for me. I have 200k+ on it and it is still running strong.

Having said all of this, the cam you run has a lot to do with this.
__________________
Tom Houston - Former Colorado Chapter President , Terminal Adrenaline Junkie, and Rocket Scientist
Loveland, Colorado My teardrop build
You're just jealous because the voices don't talk to you.
Reply With Quote
  #21  
Old April 12th, 2019, 15:22
tech1001 tech1001 is offline
NAXJA Forum User
 
Join Date: Oct 2016
Location: Los Angeles
Posts: 104
Re: Octane and power

Yup you live in California like me the gas here is shit they mix all kinds of additives to gas and we lose power and mileage . my 2001 likes the mid grade best , and then there are the winter and summer blends . plus we are paying almost $4.00 a gal.
Reply With Quote
  #22  
Old April 14th, 2019, 10:35
CJR CJR is offline
NAXJA Forum User
 
Join Date: May 2005
Location: PA
Posts: 186
Re: Octane and power

When I rebuilt/modified my 88XJ 4.0L, @ about 384,000 miles, it was set-up as follows:
1. Static CR: 11.25:1 (measured)
2. A Comp.Cams regrind that gave a Dynamic CR of 8.8:1 to enable using 87 Octane gas.
3. Venolia flat-head forged pistons w/slip-fit Tru-Arc'd removal pins (i.e. no pressed-in pins).
4. Quenched Height about 0.040 inch.
5. SS Manley valves and ported heads.
6.Cloyes roller timing chain drive
7. Balanced engine.

My engine runs great and my 88XJ is now at about
500,000 miles.

Best regards,

CJR
Reply With Quote
Reply


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

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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
9.2:1 CR can I run 89 octane? mjdriver Jeep Street and Performance 20 July 27th, 2007 09:08
CR vs Octane. DirtyMJ Jeep Street and Performance 30 July 8th, 2007 00:12
what CR do you have to run 91 octane mjdriver Jeep Street and Performance 13 April 17th, 2007 11:35
I have to run on 89+ octane! How come?? IdeaMan OEM Tech Discussion 7 June 29th, 2006 17:57
89 octane 10% ethanol gas versus plain 87 octane?? csr_011 OEM Tech Discussion 9 May 23rd, 2005 22:19


All times are GMT -7. The time now is 01:29.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
NAXJA and NAXJA logo's Copyright NAXJA. All content/images Copyright NAXJA 1999-2014