350 mild cam? - 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 12-18-2012, 07:58 PM
1979chevy's Avatar
Registered User
 
Join Date: Dec 2012
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
350 mild cam?

Hi im new to this site, i have a 1979 chevy big ten silverado with a factory manual 4speed ive been trying to fix up, I have a question on the 350, its not original i was told it was outta mid 80s halfton but its a 4 bolt main, eldebrock intake with new 600cfm carb, but the question is with vacuum advanced unhooked i run 18 degrees. this truck runs great, sometimes takes a few cranks in the cold to get it going but i think thats just a old carb motor, i know that a stock 350 runs around 10ish i believe, so does this mean i have a mild cam?? i dont know a whole lot about internals of motors but i have a pretty good idea as i rebuild small engines and do alot of maintance and minor mods to my 3 trucks, any help will be nice thanks!!

    Advertisement
Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
  #2 (permalink)  
Old 12-18-2012, 08:29 PM
Registered User
 
Last photo:
Join Date: Jan 2011
Location: Hopewell, Va
Age: 62
Posts: 1,191
Wiki Edits: 0

Thanks: 0
Thanked 117 Times in 113 Posts
350 mild cam?

I would say someone changed cams inthat engine. Most aftermarket cams require more initial timing somewhere 16-20 degrees. If you have a timing light with an advance knob on the back have someone hold the rpms at 3000-3500. Point the light at the scale and turn the knob until the line on the balancer aligns to zero. How many degrees is the scale on the back of the timing light reading? Should be 36 degrees. When your done run a vacuum hose from the right port on the carburetor to the distributor. Now check the timing with the vacuum hooked up. Set the advance knob to zero then point at the scale and turn the advance knob until the balancer line aligns to zero. The scale on the timing light should be on 50 degrees.

Last edited by cdminter59; 12-18-2012 at 08:46 PM.
Reply With Quote Quick reply to this message
  #3 (permalink)  
Old 12-19-2012, 08:37 PM
1979chevy's Avatar
Registered User
 
Join Date: Dec 2012
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
cool ill try this tommarrow, i ask someone that knows there fair share about small blocks and they said it probably has...ugh i cant quite remember what he said but its a factory height on the nobs just alot longer durantion is what he said...this truck has some crazy torque let me tell you, so im going with what this guy told me. thanks for you info really appreciate it!!!
Reply With Quote Quick reply to this message
  #4 (permalink)  
Old 12-22-2012, 04:19 AM
American Muscle's Avatar
305 Turbo-Fire 240hp
 
Last photo:
Join Date: Dec 2008
Location: under the hood
Age: 31
Posts: 625
Wiki Edits: 0

Thanks: 0
Thanked 1 Time in 1 Post
With a manual four speed i bet it does have monster torque. Even with 3;08 gears that baby should burn rubber real good

Last edited by 68NovaSS; 12-22-2012 at 04:50 PM.
Reply With Quote Quick reply to this message
  #5 (permalink)  
Old 12-22-2012, 05:02 AM
Registered User
 
Join Date: Aug 2006
Location: Alexandria, VA
Posts: 1,756
Wiki Edits: 0

Thanks: 4
Thanked 65 Times in 63 Posts
I am running a mild cam in my '75 GMC K25 (350 engine, Summit 1101 cam, Edelbrock performer manifold and quadrajet) and use about 16 degrees of initial timing and 18 degrees mechanical (vacuum advance also adds about another 18). It starts and runs very smoothly with that combo, which is good for hauling with a work truck. I have about 18-19 degrees of vacuum at idle.

I have not tried going for max initial timing, but most articles I've read over the last few years don't recommend going over about 18 degrees initial with a stock engine if your mechanical advance still works correctly (and adds 18-20). The stock GM setting for base timing is usually about 6-8 degrees, and that's much too low.

I also have 4.10 gears and stock height tires, so low end pull is excellent.

Bruce
Reply With Quote Quick reply to this message
  #6 (permalink)  
Old 12-22-2012, 02:45 PM
Cars, Trucks, Boats
 
Last photo:
Join Date: Dec 2012
Location: Toledo, N.W.Ohio, USA
Posts: 1,395
Wiki Edits: 0

Thanks: 0
Thanked 149 Times in 144 Posts
.. Most 1970's engines and some 1980's engines had horrible very low compression ratio with dished pistons and large chambers in the heads... this big combustion space requires early cam timing to get the fire burning fast enough to fill all that space before the pstons go down in order to get what little power was available out of them... BTW, the Summit 1101 cam is almost identical to a stock 327/350/400 cam... However, I wouldn't go any bigger cam without increasing the compression ratio from the stock ' 8.5:1 ' (actually about 7.6:1).... to at least 9.0 - 9.5:1... otherwise, a bigger cam acts like a vacuum leak...

.. Newer engines with higher compression ratio and especially true Vortec engines with fast burn chambers as well may only need 32-34 degrees total timing at WOT above 2500 to make max power... even with a mild performance cam...

.. If you think your engine has power now, drive one with a properly built 350 with good quench...!
Reply With Quote Quick reply to this message
The Following User Says Thank You to BuzzLOL For This Useful Post:
1Gary (12-23-2012)
  #7 (permalink)  
Old 12-23-2012, 05:34 AM
Member
 
Last photo:
Join Date: Dec 2004
Location: San Antonio, Texas
Age: 50
Posts: 4,021
Wiki Edits: 0

Thanks: 0
Thanked 23 Times in 23 Posts
20 at idle and 38 total works well on old school 350's.

However, you need to use an adjustable vacuum advance canister and set it to add only 10 degree of timing instead of the factory 20. As 48 to 50 degrees should be the max timing (mechanical + vacuum).

I would also use manifold vacuum with the vacuum advance. so timing would be 30 degrees at idle (20 mechanical and 10 vacuum).
Reply With Quote Quick reply to this message
  #8 (permalink)  
Old 12-23-2012, 01:47 PM
1979chevy's Avatar
Registered User
 
Join Date: Dec 2012
Posts: 3
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
i beleive it has 3:07 gears, i did do a compression test on it and i was surprised on how low it was! idle at 600rpms it was about 75lbs, although it was about 5 degrees outside and i just started it, but when i revved it up to about 1500-2000 it only built up to maybe 125ish....is that bad? i know it has the normal small block valve seat problem when u first start it smokes blue for a few seconds but clears out quickly, do you guys know how rare a silverado 4speed is? it is factory! but i was told it was pretty rare and havnt seen any other trucks with the 4 speed and if they do there the cheyenne or scottdales not silverado
Reply With Quote Quick reply to this message
  #9 (permalink)  
Old 12-23-2012, 04:45 PM
Registered User
 
Last photo:
Join Date: Jan 2007
Location: canada
Posts: 564
Wiki Edits: 0

Thanks: 0
Thanked 3 Times in 3 Posts
you dont do a compression test with the engine running
Reply With Quote Quick reply to this message
  #10 (permalink)  
Old 12-24-2012, 04:29 PM
Cars, Trucks, Boats
 
Last photo:
Join Date: Dec 2012
Location: Toledo, N.W.Ohio, USA
Posts: 1,395
Wiki Edits: 0

Thanks: 0
Thanked 149 Times in 144 Posts
.. Yes, compression test is done with engine off and throttle wide open (or removed)... check all 8 cylinders, you're especially interested in any cylinder way lower than the others... checking it at idle or with throttle closed lets little or no air in and gives a low reading... vacuum can be checked with engine running...
Reply With Quote Quick reply to this message
  #11 (permalink)  
Old 12-24-2012, 05:23 PM
techinspector1's Avatar
Senior Curmudgeon
 
Last wiki edit: DynoSim combinations Last photo:
Join Date: Oct 2005
Location: Hemet, California, USA
Age: 72
Posts: 12,875
Wiki Edits: 326

Thanks: 751
Thanked 979 Times in 826 Posts
Quote:
Originally Posted by BuzzLOL View Post
.. Yes, compression test is done with engine off and throttle wide open (or removed)... check all 8 cylinders, you're especially interested in any cylinder way lower than the others... checking it at idle or with throttle closed lets little or no air in and gives a low reading... vacuum can be checked with engine running...
Warm the motor up. Turn the motor off. Wire the throttle blades wide open so the motor can breathe. Remove the 12v feed wire to the coil so the spark plug wires will not fire and light the mixture that will be blown out of the spark plug holes when you turn the motor over with the starter. Mark the spark plug wires for the cylinder they belong to. Remove all the spark plugs. Insert the gauge tip into the first spark plug hole and turn the motor over with the key. Let the motor turn over until the gauge needle will rise no farther (usually 4 or 5 "chuffs" from the cylinder). Write down the results and go to the next cylinder.
Reply With Quote Quick reply to this message
  #12 (permalink)  
Old 12-24-2012, 05:30 PM
Cars, Trucks, Boats
 
Last photo:
Join Date: Dec 2012
Location: Toledo, N.W.Ohio, USA
Posts: 1,395
Wiki Edits: 0

Thanks: 0
Thanked 149 Times in 144 Posts
.. Awww... you take all the excitement out of it if you disconnect the ignition... becomes another boring job... LOL!
Reply With Quote Quick reply to this message
  #13 (permalink)  
Old 12-24-2012, 05:48 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
Quote:
Originally Posted by 1979chevy View Post
Hi im new to this site, i have a 1979 chevy big ten silverado with a factory manual 4speed ive been trying to fix up, I have a question on the 350, its not original i was told it was outta mid 80s halfton but its a 4 bolt main, eldebrock intake with new 600cfm carb, but the question is with vacuum advanced unhooked i run 18 degrees. this truck runs great, sometimes takes a few cranks in the cold to get it going but i think thats just a old carb motor, i know that a stock 350 runs around 10ish i believe, so does this mean i have a mild cam?? i dont know a whole lot about internals of motors but i have a pretty good idea as i rebuild small engines and do alot of maintance and minor mods to my 3 trucks, any help will be nice thanks!!
On a deal like this you need to know that TDC is being accurately shown by the damper line and timing tab. There were several different damper/tab combos used through the years and if they're mixed up you can get a false reading. If the outer ring of the damper has slipped you will get a false reading as well.

Setting up a performance advance curve is always needed w/a stock distributor. This alone can make a big difference in how well the engine runs.
Reply With Quote Quick reply to this message
  #14 (permalink)  
Old 12-24-2012, 07:17 PM
Cars, Trucks, Boats
 
Last photo:
Join Date: Dec 2012
Location: Toledo, N.W.Ohio, USA
Posts: 1,395
Wiki Edits: 0

Thanks: 0
Thanked 149 Times in 144 Posts
.. X 2... I forgot to mention that. A piston stop tool (~$5) can be used to verify that your timing tab is the correct one and/or the outer ring of your engine damper hasn't slipped around on the rubber putting its mark in the wrong spot...
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
chevy 350 w/ mild cam.. idle/gear probs foodstamp Engine 17 09-26-2012 05:46 AM
sbc 350 choosing cam mild build quickchevy95 Engine 12 11-07-2008 06:28 PM
mild cam for a 454 boss350 Engine 4 11-23-2006 06:19 PM
cam recommendation for mild turbocharged 350. turbo78z Engine 1 11-15-2006 04:32 PM
mild 327 or mild 350 adam15425 Engine 3 10-20-2004 04:17 PM


All times are GMT -6. The time now is 05:09 AM.


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.