Go Back   Tech Support Forum > Automotive Center > Automotive Support

Weird Chevy 350 timing problem - HELP!

This is a discussion on Weird Chevy 350 timing problem - HELP! within the Automotive Support forums, part of the Tech Support Forum category. My son bought a 1974 corvette with non matching numbers. Turns out the engine was from a 1975 full size


Reply
 
Thread Tools Search this Thread
Old 10-17-2011, 10:21 PM   #1
Registered Member
 
Join Date: Oct 2011
Posts: 1
OS: windows vista sp2



My son bought a 1974 corvette with non matching numbers. Turns out the engine was from a 1975 full size - the engine code is "CMJ". It ran fine until the other day when it apparently jumped time. I say that because I was able to get it running again using the timing light and rotating the dist but it had zero power. (the mark had moved significantly)

After it jumped time, I got the edelbrock timing set that allows for three installs - retarded, straight, and advanced. The jegs guys said install it straight up for a stock cam. I now don't think there is a stock cam in there.

We knew the setup was weird because when we first timed it months ago, the timing mark on the balancer did not line up with the marks on the cover, rather it pointed straight up. At first maybe I thought the outer ring on the balancer had slipped. But when I started to tear down the front of the engine the other day, I set the engine to tdc (as I knew it) with the timing mark straight up. After pulling the balancer, the crank key was straight up too.

When installing the new timing set, the key ended up pointing around 130 as viewed from the front of the engine.

Now the engine won't run at all. It tries but won't stay running. I have found TDC with a compression gauge in #1 and the timing mark now lines up with the plate on the timing cover and the rotor is pointing to number 1. We took great care to make sure the marks on the cam and crank gear were perfectly aligned. The only thing I can think of is the cam is not stock and the gear set should have been installed differently. But which way and why???

Any insight or ideas would be helpful. One thing I was thinking was to just get a cam from edelbrock so at least I knew precisely what was in there. However, I want to minimize the money we put into this engine because, well, it is a CMJm the heads suck, and the casting is most definitely a 2 bolt. The long term plan is to run this engine for another year or two and then get a decent stroker crate motor and drop it in.

If you have experience with 350sb cams and whatnot and you can help I would greatly appreciate it!

__________________
activ123 is offline   Reply With Quote
Old 10-18-2011, 08:04 AM   #2
Moderator Automotive Center
 
octaneman's Avatar
 
Join Date: May 2009
Posts: 2,723
OS: WINXP



Hi active123


If you plan on stripping the engine to replace the camshaft you might as well do a complete job by replacing the timing chain to bring it to original specs. You are correct in your assessment that the key on the balancer shouldn't be straight up but on a 130° angle, on the sprocket the timing marks on the cam gear should be pointing downward to align with the crankshaft. The timing chain has jumped significantly for it not to start, by turning the distributor 90° either way is not a good sign so far all signs are pointing that the timing gears are stripped. You have to be aware of two things; 1) When replacing the chain on a 75 corvette the cam gear has three 1/2 inch or 9/16 bolts to remove and it comes out fairly easy, but the crank gear is different, you will need a puller to remove it because it has two key-ways on the shaft these things are on super tight. 2) When replacing the timing sprockets with new parts, do not buy the nylon type sprocket set if you plan on constantly booting the engine get the steel version it will last allot longer.

__________________



" What were dealing with is the battle between the future and the past, between the powers that were and the powers that have yet to be. " --- John Perry Barlow
octaneman is offline   Reply With Quote
Old 10-20-2011, 08:22 AM   #3
Registered Member
 
Join Date: Feb 2007
Posts: 300
OS: win7-64



ignore the compression gauge and marks, just pull the number one plug and rotate engine with a straw sitting in it and resting on the top of the piston. The straw will rise, pause, then start to drop, when it starts to drop, stop and go back. TDC is midway between the rise and fall points.

When installing the chain and gears, use the marks on the cam gears ignore all others, and when you're done, make sure the rotor is pointing at the number one tower in the distributor.

If engine has been reworked, it isn't uncommon for a different timing cover to be used, often timing covers have the marks in a different location to enable viewing with different accessories installed, so if the cover's changed but balancer wasn't the marks won't always agree.
__________________
kendallt is offline   Reply With Quote
Old 10-20-2011, 09:53 AM   #4
Administrator
TSF Manager
 
SABL's Avatar
 
Join Date: Jul 2008
Location: Galena, Ohio
Posts: 11,924
OS: WinXP Pro SP3, Vista Home Premium SP2



Quote:
Originally Posted by kendallt View Post
ignore the compression gauge and marks, just pull the number one plug and rotate engine with a straw sitting in it and resting on the top of the piston. The straw will rise, pause, then start to drop, when it starts to drop, stop and go back. TDC is midway between the rise and fall points.
This is correct......but.......it could be TDC of the exhaust stroke. The best way to tell is to remove the valve cover on the bank where #1 is located and observe if the valves are even (both closed) when the piston is at TDC....if the valves are not even, the engine is on the exhaust stroke.


This pertains to older engines not controlled by computer!!
As for placing the distributor on #1.......I can make most mechanics scratch their heads on that one. You can place the rotor any place you want as long as you match #1 spark plug wire with the rotor position and follow the correct firing order and rotation.

Another thing to be aware of is that the dist must drop completely for correct installation.....especially the SB Chevy engines. Locating #1 and dropping the dist in place does not mean the oil pump drive has engaged the oil pump. (My son did that once....and only once. I got a frantic call one night and he said he had no oil pressure after reinstalling the dist on his 350. I asked him if the dist was fully seated......after a "what?", I told him I would be home soon and would show him what was wrong. He was just young and starting his mechanical "career"......)
__________________
It's a good thing I never had any sanity......I would have lost it by now.
SABL is offline   Reply With Quote
Old 10-20-2011, 11:17 PM   #5
TSF Enthusiast
 
Join Date: Jun 2010
Posts: 560
OS: xp pro



The jegs guys ... were meaning if you have a high lope cam you might want to set it at a couple deg adv on the timing chain gears ... they also sell off set dole pins for the cam gear to advance it ... this offsets the valves not the ing timing
So even if you went a couple degrees on the cam timing gear it really isnt going to have much effect on the reg timing marks .... offsetting the cam gear is not a big thing when its a every day driver dont worry about that and set it at standard valve timing NO off set

your probably going to have to pull the timing cover again BUT first i would check my timing ... remove #1 plug and plug the hole with your thumb then bump the engine till you feel and hear the compression then do like kendallt said and use a straw and turn the engine by hand forward or backwards till the piston is at the top of it stroke ... that is TDC compression and #1 plug will be firing ... now pull the dist cap and see if the rotor is pointing at #1 ... if its pointing 180 away from #1 remove the dist and reinstall it so its pointing at #1
Remember the crank turns 2 times to the camshafts once so having the timing mark up doesnt mean diddly cause the cam can still be off 180 deg

If the dist is lined up when you do the TDC pull the timing cover you got it wrong ... (off a tooth or so)...
before you reinstall the timing cover start it for a couple seconds to make sure all is right
__________________
kjms1 is offline   Reply With Quote
Old 10-21-2011, 04:24 PM   #6
Automotive Team
Moderator
 
wolfen1086's Avatar
 
Join Date: Oct 2007
Location: Rainey, Virginia Beach, Virginia
Posts: 10,337
OS: Ubuntu 14.04.1



Also remember the firing order is 1 8 4 3 6 5 7 2. So whichever cylinder rotor is pointing to at TDC , so make sure its pointing to cylinder #8 the wires t go on in a clockwise direction. And #1 cylinder is the front one on the drivers side.

You probably already know this, but its a VERY common mistake to make.

__________________


Hampton Roads Virginia, I've been around the rock three times and this place was NOT on my top ten list of places to live
wolfen1086 is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
89 chevy 350
i have an 89 chevy 350 1/2 ton it has fuel to the tbi but not sure if its spraying fuel (new fuel pump) when trying to start up how can i test this it also is not getting spark and im sure its the coil or dist. on that. would that effect it not spraying fuel. thanks for anyones help
89chevy Automotive Support 1 08-24-2011 04:03 AM
Really weird and random display problem
Hi, So I have an ASUS laptop that I have had for a few years now. It's had it's fair share of abuse, I've already replaced the hard drive once. I was using the computer (specifically I was using Cubase software to do some audio processing) and all of the sudden the screen went bezerk and froze....
Olejay13467 Laptop Support 3 01-17-2011 01:41 PM
Weird Internet Problem at Friend's House
So my friend has Cox and I visit his house often. Awhile back I never had problems with his internet; originally he had DSL through Verizon. The problem started when he added a phone line. When I came over I could access the internet, but it ran strangely slow. We attributed this to his DSL,...
SpikeRosered Modems/Cable/DSL/Satellite 1 01-14-2011 11:56 AM
Weird Problem - can only install certain types of .exe's
Hey everyone, so i have a very strange problem. any time i try to open an install .exe with THIS type of icon: http://img545.imageshack.us/img545/1864/badicon.jpg i get the error, "windows cannot access the specified device, path, or file." however, i can open install .exe's with THIS...
Adomsky Windows XP Support 2 01-10-2011 04:20 AM
Weird video card problem.
ok i'm having a really weird problem with my onboard video card, with i know i should be able to play gta:sa on low settings and i should be able to play track maina nations and a few other games like cod2. but when i try to play track maina nations the game starts but when loading the track a...
trainergames Video Card Support 0 01-04-2011 01:25 PM

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 Off
Pingbacks are Off
Refbacks are Off


Post a Question


» Site Navigation
 > FAQ
  > 10.0.0.2


All times are GMT -7. The time now is 11:27 AM.


Copyright 2001 - 2014, Tech Support Forum

Windows 7 - Windows XP - Windows Vista - Trojan Removal - Spyware Removal - Virus Removal - Networking - Security - Top Web Hosts