Timing on Pontiac 400 - Pontiac GTO Forum
Pontiac GTO Pontiac GTO Forum

» Auto Insurance
Wheel & Tire Center

Go Back   Pontiac GTO Forum > The 1964-1974 Pontiac GTO > 1964-1974 Tempest, LeMans & GTO Technical Discussions
Register Home Forum Active Topics Photo Gallery Garage Search Today's Posts Mark Forums Read Auto EscrowInsurance

GtoForum.com is the premier Pontiac GTO Forum on the internet. Registered Users do not see the above ads.
Reply
 
LinkBack Thread Tools Display Modes
Old 02-24-2011, 10:20 PM   #1 (permalink)
 
Join Date: Feb 2011
Posts: 2
My Photos: (0)
Timing on Pontiac 400

Ok i have looked everywhere and cannot find a correct solution or question to this so here goes. I have a Pontiac 400 bored .60 over ported and polished 6x-4 heads, edelbrock performer rpm intake and cam, 1.65 roller rockers, edelbrock 800 cfm carb, and hei distributor. The only way to get it to start is if I set the timing at roughly 35 degrees what I believe is before top dead center timing mark on crank is under timing marks on engine. it idles around 700 or so with a little bit of a lope. I have heard that a 400 running 6x-4 heads is going to have higher compression and the cc's in the heads are around 90 or so, and the only way to get the engine to compesate for the higher amounts is to have the timing off by quite a bit. Do this seem right? Is there any ill affect to having it set this way if it is running good?
72luxlemans is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 02-24-2011, 10:31 PM   #2 (permalink)
 
Instg8ter's Avatar
 
Join Date: Sep 2010
Location: Near Detroit
Posts: 3,763
My Photos: (0)
you will need to run high octane in it to ward off detonation....96+ if you can get it.
Instg8ter is offline   Reply With Quote
Old 02-25-2011, 07:24 AM   #3 (permalink)
 
Join Date: Feb 2011
Posts: 2
My Photos: (0)
I know of a station about 20 miles away that sells 102 or 103 octane is that all I should worry about with the timing being where its at
72luxlemans is offline   Reply With Quote
Old 02-25-2011, 07:39 AM   #4 (permalink)
 
Join Date: Jan 2011
Posts: 172
My Photos: (0)
"Higher compression" is a relative term. Yes, -4s yield a little higher than -8s.

At 90 CCs, a 400 .060 over at "zero" deck (here that means .005 in the hole) will yield right at 8.8:1. No need for any "compensation" for 93 octane, should actually run well on 89.

If you have an aftermarket cam and intake, timing is a "hunt and peck" kind of thing. That is, you ned to find "the happy spot". each engine is different. Set intial at 10 BTDC and "total" at 32. Drive the car. Bump it up 2 degrees. See if it responds "better" (it should, but maybe same).

We genearlly try to keep "total" timing under 35, as Pontiac chambers a bit "too efficient" (yes, that IS possible) and are "timing sensitive". Beyond 36, we see head gaskets deteriorate rapidly. 670 heads are the "exception to the rule", as they have a "closed" chamber.

Jim
Mr. P-Body is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac GTO > 1964-1974 Tempest, LeMans & GTO Technical Discussions


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
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
timing for 67 400 mshidner 1964-1974 GTO General Discussion 2 09-16-2010 09:52 PM
400 Pontiac with six pack nicken Engine Discussions 6 11-10-2009 04:58 PM
Timing Help on 455 Pontiac Goatman455 1964-1974 GTO General Discussion 4 06-22-2009 04:02 PM
Pontiac 400 rebuild in Seattle boatgoat 1964-1974 GTO General Discussion 2 06-15-2009 06:00 PM
400 motor timing matt68gto 1964-1974 GTO General Discussion 2 11-09-2006 09:48 AM

Powered by vBadvanced CMPS v3.2.2

All times are GMT -5. The time now is 11:24 PM.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
SEO by vBSEO 3.3.2
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.