Warning

 

Close

Confirm Action

Are you sure you wish to do this?

Confirm Cancel
Member Login
Posted: 12/7/2002 11:20:28 AM EDT
Ok, I am having a complete and total loss of brain function last night and today. I just swapped in a 75 Surburban 454 (only 80,000 original miles!!! ) into my 1 ton. Well I thought it to be a great idea to swap out the intake and distributor... Long story short, I thought I put everything back the way it was supposed to be, however, when I crank the engine, it pops and backfires through the carb (newly rebuily Q-jet). Please help. Thanks Joshua
Link Posted: 12/7/2002 11:24:28 AM EDT
[Last Edit: 12/7/2002 11:25:50 AM EDT by SKSBoy]
sounds like a timing problem, did you mess with the camshaft at all? try a timing light and rotate the distrbutor. edited to add, i'm a goof, i just saw you swapped the distrubitor, my monyes on the distrubitor alignment.
Link Posted: 12/7/2002 11:26:43 AM EDT
Make sure the distributor is timed to the camshaft correctly. Meplat-
Link Posted: 12/7/2002 11:36:41 AM EDT
Originally Posted By Meplat: Make sure the distributor is timed to the camshaft correctly. Meplat-
View Quote
Ok, but how? There was once a time that I knew how to do these things, however that knowledge has long passed. Again thank you all!
Link Posted: 12/7/2002 11:44:58 AM EDT
shadetree way of timing your camshaft........CAUTION!!!! a distrubitor delivers about 10,000 volts, so be EXTREMELY careful i.e. DO NOT touch any other part of the vehicle or you could be the human sparkplug wire (happened to my friend) so anyways with that said, loosen the camshaft retainer clip so that you can rotate it, then have somone crank the engine continuisly while you slowly turn the distrubitor, you should eventually find a spot where the engine will run, then use a timing light to adjust it perfection.
Link Posted: 12/7/2002 11:49:35 AM EDT
Pull #1 spark plug. Rotate engine to compression stroke, feeling for compression from cyl. where spak plug removed. pull distributor cap and line rotor with #1 spark plug tower. Check all plug wires for fireing order,1-8-4-3-6-5-7-2, start up and set timing.... fullclip
Link Posted: 12/7/2002 11:51:46 AM EDT
Originally Posted By fullclip: Pull #1 spark plug. Rotate engine to compression stroke, feeling for compression from cyl. where spak plug removed. pull distributor cap and line rotor with #1 spark plug tower. Check all plug wires for fireing order,1-8-4-3-6-5-7-2, start up and set timing.... fullclip
View Quote
How do I know which one is the compression stroke and the exhaust stroke?
Link Posted: 12/7/2002 11:52:01 AM EDT
[Last Edit: 12/7/2002 11:53:57 AM EDT by Striker]
Link Posted: 12/7/2002 1:32:35 PM EDT
You guys are awesome... I posted this in a 4x4 forum and I have had no responses.
Link Posted: 12/7/2002 2:00:06 PM EDT
Originally Posted By SKSBoy: shadetree way of timing your camshaft........CAUTION!!!! a distrubitor delivers about 10,000 volts, so be EXTREMELY careful i.e. DO NOT touch any other part of the vehicle or you could be the human sparkplug wire (happened to my friend) so anyways with that said, loosen the camshaft retainer clip so that you can rotate it, then have somone crank the engine continuisly while you slowly turn the distrubitor, you should eventually find a spot where the engine will run, then use a timing light to adjust it perfection.
View Quote
This is a dangerously ambiguous post if you're in a confused state already. He is NOT talking about the camshaft that operates the valves - don't EVEN mess with that if you didn't touch it before. SKS boy is talking about the distributor shaft and the cam for the points. I'm embarassingly not familiar with that engine, but I'm pretty sure that's what he meant. Also be aware that many distributors have a way engineered to help you so that you don't have it 180 degrees off and firing at the end of the exhaust stroke. Look for off-center, assymetric machining (if it's not a gear but a half shaft mating up with another piece), or some kind of mark on the gear. But the basic thing you need to do has already been covered by SKSboy, fullclip, and Striker: With the ignition key OFF: Get the cylinder 1 to TDC (eyeball & flashlight into the plug hole, careful turning of crankshaft with socket) after getting it on the compression stroke (air pressure on your thumb, again in the #1 hole). Then get the distributor in so that the rotor is close to the wire for cylinder #1 at the distributor cap. After that it should be a matter of adjusting the timing to specs. You can often do this alone, but sometimes a helper is really nice. It may help to see which way the rotor is turning as it approaches the #1 tower in the distributor cap. Also if you can't see in the plughole while turning the crankshaft, and it's a stickshift, it can be "bumped" with the [u]ignition key removed[/u] and the vehicle in 3rd or 4th. That's a little less precise and more trouble, but do-able. And make SURE you have adequate Pilsner Flow!![;)]
Link Posted: 12/7/2002 2:13:38 PM EDT
BlackDog, In addition be aware that on v-8 chevs the distributor also drives the oil pump. So if you get in a situation where everything else is aligned but the dist. wont go all the way down, you may need to pull it back out and using a looong screwdriver align the slot in the oil pump shaft so that the tang in the bottom of the dist. will mate with it. Remember the dist shaft is going to spin slightly as it engages the drive gear on the cam. Flaco
Link Posted: 12/7/2002 2:52:48 PM EDT
Originally Posted By Striker: You have to bring the #1 cylinder up to TDC ensuring it is on the compression stroke (both valves closed). Then re-align the distributor so the rotor button is pointing at the terminal on the cap for the #1 cylinder. If you marked the direction the rotor button was pointing in before you removed it and put the new distributor in the same way you are probably only off by a tooth or two. Take the plug out of the #1 cylinder,take the cap off the distributor and bump the engine over on the key. (unhook the wire to the coil so it won't start) Place your thumb or a finger over the spark plug hole. When you feel the compression against your thumb stop cranking the engine and check the rotor button. If it is pointing at or near the terminal for the #1 cylinder stop. If it isn't continue bumping until you feel the compression again. this should be the compression stroke. Check the timing marks and line them up using a ratchet and socket on the crank. Now pull the distributor up enough to clear the gear on the camshaft and put it back in with the rotor button pointing at the #1 terminal. I mark on the distributor housing where the #1 terminal is on the cap. It might take some cursing and swearing to get the distributor shaft in the right place. this is the shade tree/back yard way I do it. YMMV![;)]
View Quote
Pay attention to this post, and the one by flaco. Thanks guys, saved me some typing!! [:D]
Link Posted: 12/7/2002 3:09:48 PM EDT
It's out of time but not by much if it backfires through the carb. Don't do anything eles to it,DO NOT MESS WITH THE CAM! DO NOT TAKE ANY THING OFF OF ANYTHING! Set the distributor hold down so that you can spin the distributor and pull it up just so that it's clear of the cam. Take out the plug on Cyl. #1 in the firing order then hold you finger over the hole until you can feel the piston head,this puts the engine at "top dead center". Set the distributor down and run your plug wires the order in on the intake. In order for your motor to run it has to have the air,gas and spark come together at just the right time,the backfire from the Q jet is the spark firing the air and gas on the down stroke thats all it will stop after your set the time.
Link Posted: 12/7/2002 3:14:59 PM EDT
You can get to TDC on the #1 cylinder by inserting a thin wooden dowel and watching it come out until it peaks. You could also wrap up a screwdriver with tape. Be careful not to drop anything else in there.
Link Posted: 12/7/2002 9:50:41 PM EDT
It'll be easiest with two people... 1) Pull #1 sparkplug (drivers side front) 2) stick your finger in the hole (only enough to plug it) 3) have friend bump engine over slowly 4) when the compression(air) pushes past your finger, STOP. 5) lift out the distributor just enough to turn the rotor to realign. 6) align the rotor with the post that feeds the #1 plug wire 7) with your fingers clear of the rotor, have your friend bump the motor over slowly while you push down on the distributor housing. This will let it "drop-in" to the oil pump driveshaft while still being engaged with the cam gear and keeping you "in time"... 8) snug the distributor hold-down clamp...(you'll still need to turn the dist to set timing with a light) 9) install dist cap, and #1 sparkplug 10) start motor and set timing... *NOTE* When the #1 cylinder pushes air past your finger, you are nearing #1 TDC. Look at the balancer, and you will see the the timing mark on the balancer near the timing tab... Some of the responses in this thread are right on the money... Some are not... Don't stick ANYTHING "IN" the sparkplug hole.. ie: fingers or dowels...Don't forget there are still two valves in there moving around too... "Feeling" the piston at the top of the cylinder tells you nothing... It could be the top of the compression stroke OR the top of the exhaust stroke.... The only way to tell is to let it push compression out the plug hole... No need to worry about your fingers, I haven't seen anyone over the age of 5 that could get thier fingers all the way in a sparkplug hole... If your worried about your fingers, just loosen the plug till it barely hangs on the last thread... You'll hear it "hiss" when the piston approaches TDC... Just my $.02
Link Posted: 12/8/2002 7:25:05 AM EDT
Link Posted: 12/8/2002 7:56:31 AM EDT
[Last Edit: 12/8/2002 8:02:49 AM EDT by BlackDog714]
Thanks to all guys... I'll be trying to get it running tonight. The damn thing has me in a fit of rage right now![:(!] I think I was up too late to be doing this as I was very tired and only got 4 hours of sleep. Again thank you all for the suggestions. I was wondering how to check for TDC on the compression stroke w/o looking at the valves, and once again you guys solved it for me! Oh yeah, I am not a newbie when it comes to Chev motors, I just haven't had to work on a gas motor in 10 years! The 6.2 Turbo diesel that was in the truck blew the oil cooler line on the freeway and seized in seconds! By the time the pressure dropped, I couldn't have turned it off fast enough. Sometimes I hate being able to work on my own vehicles!
Link Posted: 12/8/2002 8:17:24 AM EDT
I am shocked no one suggested check the firing order for the plug wires. [shock]I cant tell you how many engine repairs people have done and gotten the wires crossed on the reinstall and had it towed in to the shop
Link Posted: 12/8/2002 8:18:42 AM EDT
As usual dragracer-Art is right on. Follow his advice. One way to check TDC if you don't have any help is to put a small piece of paper towel in the #1 hole. Not down in the cylinder, but just in the sparkplug hole. Slowly turn the engine over and when the paper shoots out you are on the compression stroke.
Top Top