sbc 355 - 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 06-27-2009, 10:11 AM
Registered User
 
Last photo:
Join Date: Apr 2009
Location: kentucky
Posts: 29
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
sbc 355

ok i have a sbc 355 that i need some help with. i just dropped the engine back into the car after adding a 142 supercharger and nos. i need some help with the timing and sparkplugs.

im runing 8.5:1 and a blower cam. the supercharger is set up to produce 8lbs and the nitrous has 125 hp jets. i just need a general idea on what to set the timing at. and what spark plug you guys would recomend since im using the blower and nitrous at the track.

any help would be great. thanks

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 06-27-2009, 01:30 PM
automotive breath's Avatar
Registered User
 
Last photo:
Join Date: Mar 2006
Location: New Orleans
Posts: 891
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I would lock out the ignition advance a set the total advance to 30 degrees for
starters. With the NOs you may need to add a ignition retard to take more
advance out on the spray. This would be a starting point, give it what it wants
carefully inspect the plugs for signs of auto-ignition after every WOT run.

I'd go with a cold plug like a autolite AR3911 for starters.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 06-27-2009, 10:14 PM
Registered User
 
Last photo:
Join Date: Apr 2009
Location: kentucky
Posts: 29
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
thanks

yea im running a 6al ignition and a Boost timing master that will retard the timing 1 to 3 degrees per lb of boost. so hopefully with the btm retarding the timing in high rpms i will be fine with the nos. Holley said that running nos with a blower is just basically like running a good intercooler. with expected 60% gains. so hopefully it will stay together lol im running all forged internals and iron heads.

this is my first build so for reminders: the total advance is the timing with the engine reved to about 3000 right? thanks
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 06-28-2009, 01:57 PM
automotive breath's Avatar
Registered User
 
Last photo:
Join Date: Mar 2006
Location: New Orleans
Posts: 891
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Total advance is initial plus centrifugal.

The plugs I recomended will not fit iron heads; start with a
autolite 292 for early iron heads with a 1 3/16 hex head or
autolite 131 for late iron heads with a 5/8" hex head


These plug are cold and might foul easily if you spend much
time at idle.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 06-28-2009, 02:07 PM
Registered User
 
Join Date: Dec 2004
Location: San Jose Ca
Age: 62
Posts: 472
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
I run 35 with a timing curve 8/71 406 chevy,Lots of info on internet from blower companies about this.
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 06-28-2009, 04:35 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,570
Wiki Edits: 0

Thanks: 3
Thanked 336 Times in 333 Posts
Start your tuning experimentation with 110+ octane racing gas.

The nitous does have a intercooler effect but also greatly speeds up the combustion speed. This requires that you use less spark advance when injecting nitrous.
As a starting tuning point use the tuning recomendations of NOS (Nitrous Oxide Systems) and remove 2deg of advance per 50hp of total combined power adder (nitrous + supercharger.)
+2deg extra
The 8psi will be worth about a 40% gain in HP (140hp) so that requires about = timing reduction as a 150shot or 3-4deg. then if you add another 200hp shot of nitrous shot, take and additional 4 deg out for a total of 8 deg retard.
I would start at 26deg for this setup and try it. ON RACE GAS.

Consider a water/methanol injection system (gaseous intercooler) to keep detonation in check and allow more timing.

Again start with high octane race gas and easy timing. add in 2deg timing at a time watching for trouble on the plugs. If the extra 2deg doesn;t increase your 1/4 mile MPH you don't need it.

A low/moderate amount of nitrous shot used right from the starting launch and over the whole 1/4mile will reduce the ET much more than a bigger race shot that cannot be used until down track.
Start at 100hp shot jets and make it go fast and work up.
Get a WOT nitrous switch and a nitrous window switch to avoid early engadgement at low rpm. Set the nitrous window switch to come on at the converter launch flash stall rpm point or just above and set the switch off window point below the engine rev limit. That last few feet at the end of the track won't effect the et worth overreving the motor.
Do not allow the rev limiter to engage with nitrous injecting.
As said earlier, roots blower motors like a lot of inital timing, Lock out the distributor advance. For 1/4 mile testing purposes you can eliminate the boost retard and just run the required net timing with the required retard figured in required by the combined N2O and blower boost. EG: 24 deg at idle Fixed for a big shot and 8psi boost.
Again do not try to experiment on pump gas. Good high octane race gas is much cheaper than 8, 16 or 32 new pistons.
Reguardless of how much cooling effect the nitrous has, you will still need high octane gas and/or water/meth injection for all but the most modest combined boost/N20 shot. There is no free lunch. Big power creates big heat.

You will go much faster FOR LESS MONEY with a moderate amount of nitrous and boost used right at launch and over the whole quarter mile on 110octane race gas that does not require excessive retard (robs power) as compared to trying to kill it with a big shot and a ton of retard that the chassis/tires can't handle.

Once you've found what the engine wants for tune on good gas you can find that happy medium for impressive but safe nitrous/boost power on pump gas or a 50-50 mix (and/or with water injection).
The water really absorbs the excess combustion heat and tames the combustion speed increase of the big shot.

Last edited by F-BIRD'88; 06-28-2009 at 04:53 PM.
Reply With Quote Quick reply to this message
  #7 (permalink)  
Old 07-01-2009, 08:23 PM
Registered User
 
Last photo:
Join Date: Apr 2009
Location: kentucky
Posts: 29
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
thanks

yea i will only be running a 125 horse shot of nos. guess i will start with the 28 degrees and go from there. i do need some help how how to figure the timing out. this is my first build. i havnt started the car yet but have it set at TDC on number one so at this point im guessing it doestn have any advance or retard. once i start it how do i need to go about setting the initial timing? should i set this at a certain number? and then what should i set the centrifiicul at? my balancer has a timing scale on it ranging from 0 on up to 40 or 50. just looking for the easiest way to set the total at 28 to start.
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 07-01-2009, 11:08 PM
F-BIRD'88's Avatar
Yada Yada Yada
 
Last photo:
Join Date: Oct 2005
Location: Ontario, Canada
Posts: 9,570
Wiki Edits: 0

Thanks: 3
Thanked 336 Times in 333 Posts
If you have to ask how to set ignition timing, you need to hold off on the idea of combining nitrous with a supercharger.

Educate yourself on how to set up a supercharged motor than runs on pump gas. Then make the progression to nitrous when you have a better understanding of it all. You are a little in over your head.
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 07-02-2009, 08:26 PM
Registered User
 
Last photo:
Join Date: Apr 2009
Location: kentucky
Posts: 29
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
sorry

sorry i thought this was a place i could find good advice not critisisim. this is just a project ive been slowly working on. not a daily driver or a pro race car. i wanted nos and a supercharger so thats what i did. but anyway i guess ill seek the advice elsewere on the timing issue. thanks anyway.
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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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
Freshly Rebuilt sbc 355 cranks over hard awoodman Engine 8 02-09-2009 06:52 PM
355 SBC heads zildjian4life218 Engine 6 12-08-2008 11:54 PM
Why not a 350 sbc? bowtieorbust Engine 29 09-05-2008 09:43 AM
Late model 350 SBC Question Smoker113 Engine 3 02-19-2005 10:12 PM
What is a 355 SBC? frankenvette Engine 11 09-12-2004 07:59 AM


All times are GMT -6. The time now is 12:33 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.