Help with timing - Pontiac 455 - Hot Rod Forum : Hotrodders Bulletin Board
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Engine
User Name
Password
lost password?   |   register now

Reply
 
LinkBack Thread Tools
  #1 (permalink)  
Old 10-27-2011, 11:40 PM
Registered User
 
Join Date: Oct 2011
Location: United States
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Help with timing - Pontiac 455

I installed a Pontiac 455 in my 65 GTO, and I realized I have no idea with this combo what a good starting point for my timing would be. I am pretty sure the initial timing is going to want to be higher than stock (which was 12 degrees, IIRC), but it has been a while since I worked on anything and I just want a decent starting point. I will eventually have it dyno-tuned, but for now it is just me.

455 @ .060 OB
Heavily ported 6X heads, 2.11/1.77 valves
9.75:1 compression
Performer RPM
Holley Street Avenger 770 cfm
Cam Specs:
Int Duration @ .050 - 230
Exh Duration @.050 - 234
Int Lift - .505
Exh Lift - .510
Lobe Sep. 111.1

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 10-28-2011, 12:16 AM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
You may end up using more, but I would say to start at 16º-18º. Keep track of your total timing as you tune. Keep the vacuum advance at 10º or so. I had a very similar combo (9.25:1, Performer (not RPM) w/4777 650 cfm Holley, 108º LSA, couple more degrees intake duration on a single pattern cam, Rhodes on intakes only, 1.66 exh.valves, 6x-4 heads were only about 175cc intake ports after I was done porting them), it ran effortless 12.7's w/a 3.31 rear gear in a '81 all steel Camaro. Shifted at 5000 RPM. It was timed 18º initial and 34º total.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 10-28-2011, 07:54 AM
DENCOUCH's Avatar
Registered User
 
Last photo:
Join Date: Nov 2007
Location: Great Pacific Northwest
Age: 67
Posts: 409
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
Pardon me please

Quote:
Originally Posted by cobalt327
You may end up using more, but I would say to start at 16º-18º. Keep track of your total timing as you tune. Keep the vacuum advance at 10º or so. I had a very similar combo (9.25:1, Performer (not RPM) w/4777 650 cfm Holley, 108º LSA, couple more degrees intake duration on a single pattern cam, Rhodes on intakes only, 1.66 exh.valves, 6x-4 heads were only about 175cc intake ports after I was done porting them), it ran effortless 12.7's w/a 3.31 rear gear in a '81 all steel Camaro. Shifted at 5000 RPM. It was timed 18º initial and 34º total.
not meaning to hijack the thread, but I have a question about the headers used in the 455 swap. What worked for you cobalt327?
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 10-28-2011, 10:14 AM
Registered User
 
Join Date: Oct 2011
Location: United States
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Timing

Cobalt: What exhaust did you use with that combo? I have Doug's on mine, and they fit fantastically, but mine is obviously Pontiac/Pontiac.

After messing around with the engine this morning, it seems like it really likes a lot of initial timing to idle decently - around 20-22 btdc. At that point it manages to pull about 13 inches of vacuum as well.

In addition to having higher compression and 1.65 Roller rockers, and bigger valves, it also has a Hydraulic Roller, not a flat tappet, so the valve openings/closings are much more aggressive as well. I might even go more in the future but want to keep the power brakes without having to use a vacuum pump.

I am running a 200-4R with a Ford 9" 3.55 gears. With a fiberglass hood and other mods, as well as it being a convertible, it is actually a fairly light car at approximately 3300 pounds curb weight.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 10-28-2011, 01:00 PM
WDCreech's Avatar
Grumpy Old Goat Herder
 
Last photo:
Join Date: Apr 2006
Location: Anchorage, Alaska
Age: 70
Posts: 1,320
Wiki Edits: 0

Thanks: 3
Thanked 29 Times in 27 Posts
Quote:
Originally Posted by seattle_ice
After messing around with the engine this morning, it seems like it really likes a lot of initial timing to idle decently - around 20-22 btdc.
20-22 btdc with or without the vacuum advance conected? Initial timing is always w/o vacuum advance.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 10-28-2011, 01:00 PM
Registered User
 
Join Date: Oct 2011
Location: United States
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Without vacuum of course. And at ~800 rpm.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 10-28-2011, 02:17 PM
WDCreech's Avatar
Grumpy Old Goat Herder
 
Last photo:
Join Date: Apr 2006
Location: Anchorage, Alaska
Age: 70
Posts: 1,320
Wiki Edits: 0

Thanks: 3
Thanked 29 Times in 27 Posts
Are you sure that the outer ring on your balancer hasn't slipped?
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 10-28-2011, 02:18 PM
Registered User
 
Join Date: Oct 2011
Location: United States
Posts: 4
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Quote:
Originally Posted by WDCreech
Are you sure that the outer ring on your balancer hasn't slipped?

That has occurred to me. And no, I am not sure. I probably should check it.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 10-28-2011, 04:47 PM
cobalt327's Avatar
WFO
 
Last wiki edit: Intake manifold
Last journal entry: 1980 Malibu Wagon
Last photo:
Join Date: Mar 2009
Location: Atlanta
Age: 59
Posts: 5,037
Wiki Edits: 1616

Thanks: 128
Thanked 597 Times in 546 Posts
I used Hedman 4-tube headers from Summit, I just looked to get the part number, but none are like what I bought- mine were a standard bolt- on collector, not the ball and socket type they sell now. But they were the standard painted headers, nothing fancy, 1-5/8" primaries. If I had it to do over, I'd have used more carb, an RPM intake and 1-3/4" headers- although I really am on the fence regarding the header primary diameter, 1-5/8" seems small for a 455, but w/the low shift point...

The exhaust was 3" from the collector w/an "H" after the collector, before the Flowmaster mufflers. The muffs had a simple 3" turn-down about 10" long that exited just before the rear axle. In other words, the mufflers were as far rearward as the chassis would allow. Oddly it didn't have any interior drone, although it would set off car alarms any time I idled through a parking lot. One of my evil pleasures was to idle through the local mall in front of the theater.

My short time (60') was 1.7 seconds, matted it from an idle. Tires were L60 McCreary's (now made by American Racer Tires). I had a lot of fun using McCreary tires on the street. I could put 4 lengths on a guy, w/o breaking the freaking speed limit!

The McCreary's were made for dirt track or drag racing, but they do have a DOT number. In BIG lettering it reads "ROAD STAR".

This is also on the sidewall (check out the Treadwear rating):



These days there are plenty of good drag radials to use (these are bias), so traction shouldn't be that big of a problem.
Reply With Quote Quick reply to this message

Recent Engine posts with photos

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




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

Posting Rules
You may post new threads
You may 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
? Pontiac 400 Timing Set beertracker Engine 9 12-11-2010 08:41 PM
Timing a 75 Pontiac 455 badams_iyns Engine 3 11-29-2008 10:18 AM
pontiac timing Blob Engine 5 06-24-2006 05:54 AM
timing on a pontiac natas Engine 3 08-09-2004 06:38 PM
pontiac timing 67bird Engine 11 02-10-2004 09:11 AM


All times are GMT -6. The time now is 05:06 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.