1972 Chevy engine problems

[72chevylwbmo]

Hey everybody. I bought my son a 72 c-10 back in the summer and have been working on it ever since, not having much luck with it. The other day he told me that it was making a knocking noise. So I drive it around, I don't hear a knocking noise. It sounds more like a really bad octane ping. I can stop the truck and put it in park, rev it up and it sounds fine. Put it back in gear and take off and the noise is back. Pulled one of the valve covers off and the oil smelled burnt, really bad. Going to run some kerosene or something thru it to clean it out, then change the oil and see if it clears up any. The motor is a 350, th400 trans. Already had trans rebuilt. Any ideas as to what the problem could be. I'm not a real good mechanic or at least the diagnostic part. Any help is appreciated.

[jlsanborn]

How well does it crank over on the starter? Sounds like you may have too much timing in there.

Is there a PCV connected? It's function is to circulate fresh air throught the crank case and keep it smelling fresh in there! Are you sure kerosene is really necassary - that bad?

[72chevylwbmo]

The timing may be way off also. I need to bring it up to TDC and check the dizzy out and see where it is sitting at. The timing mark is setting at about 30 degrees before right now. If it set it at 8-10 degrees then it pops back through the carb real bad. I may also have to pull the timing cover off to see if it has jumped a tooth or somebody has put an aftermarket cam in it. As far as the smell of the oil. My son ran it almost completely out of coolant and was driving it. It got way to hot and was causing the knocking noise. I ran some Sea Foam through it to just flush it. Put a new radiator in it, everything is fine there now. The truck hasn't been taken care of so we have a lot of maintenance issues to take care of first off and then we want to do a resto. Not a complete frame off, just fix rust, paint, drive train. Make it a fun project that we can beat on every weekend around town.

[jlsanborn]

Sounds like you're right on track. If that 30 is your initial timing, then you've got too much. If that's the only way it'll run worth a darn then you've got something else going on.

You should pop a few photos and start a build thread!

[72chevylwbmo]

I plan on starting one but I have to get through a rental house rebuild first and get some funds saved up to do the truck. I hate working on 100yr old houses.

[72chevylwbmo]

Well here we are again. I worked all day on the truck yesterday. Replaced the timing chain, exhaust manifold gaskets, and spark plug wires. I think I need to move the dizzy one tooth to get it to run correctly now. One question I have is, would the worn out timing chain cause it to get like 5 mpg? This is what I am trying to solve at this point.

[jlsanborn]

A streched chain is going to retard your cam timing but only by a very small amount. Sounds like you need to address ignition timing first. At TDC (compression) that rotor should be pointing towards the #1 cylinder. When you get it timed the cap should be oriented so the electrical connectors are pointed straight towards the driver's side, probably turned slightly clockwise from there. Initial timing is going to be somewhere around 10 BTDC, plus or minus a couple. I usually keep advancing it a little at a time until I feel that it's getting hard to crank over on the starter (wha-wha-wha instead of wawawawa) then back it off a little.

Have you done a compression test? All the cam lobes still there?

[72chevylwbmo]

First let me explain what I did on the timing chain. I have heard so many stories I don't know what is correct anymore. I took off the chain cover and rotated the crank until the marks on the existing chain were lined up. Took that set off and replaced with the new set. I also noticed that the when the dots were lined up the dizzy was pointed 180 degrees out. I thought that was my problem. Buttoned everything back up and rotated the crank around til the timing mark was lined up at 0, now the dizzy is pointing in the correct direction (might be a tooth off) but still in the correct direction. Why or better how is this possible. I appoligize I am not that great of a mechanic, can someone explain this to me, please. I am planning on digging into the TDC timing tonight. Bring the crank up to TDC on the compression tonight and check out the dizzy location. I haven't done a compression test yet and I have no idea about the cam at this point.

[imjeff]

The crank turns twice for every revolution of the distributor. When the timing mark lines up you are either on 1 or 6. I would do more frequent oil changes versus kerosene. You don't have to move the distributor a tooth, you can move plug wires if that's easier.

Jeff

[72chevylwbmo]

I know it would be easier to just move the plug wires but I would prefer to do it the correct way. I bought the truck very used and am trying to get it running correctly. Who knows how often the PO changed the oil. Thanks for the input.

[imjeff]

Originally Posted by 72chevylwbmo

I know it would be easier to just move the plug wires but I would prefer to do it the correct way.

"The correct way" is getting the timing correct. Since this involves the relationship between the rotor and correct terminal I fail to see what's incorrect. Perhaps you could enlighten me?

[72chevylwbmo]

I was not trying to insult you with that comment. I have just read that the #1 pin on the cap is supposed to be the 2nd pin from the electrical connection. I was just implying that I would like to keep it that way. Wasn't trying to step on any toes, I appoligize.

[D.PASSMORE]

A piston stop or a finger over the #1 plug hole will get there for testing purposes. Take the Dizzy out, set the piston / valve to TDC on compression stroke. Set the distributor with rotor attached back in hole. You will have too probably turn oil pump shaft with large/long screwdriver to get lined up with bottom of distributor slot. Ensure that the tip of the rotor is pointing to #2 cylinder area. Snug distributor down, put distributor cap, mark which tower the tip of the rotor is pointing too. Place your #1 ignition wire in that tower and work your way around the cap in the proper sequence of wires for SBC. ENSURE that your wires are on the correct plugs - check at least twice. The #5 and #7 is notorious for getting backwards. Set your timing light up and fire it up. Ensure all vacuum are plugged and after warm up, try and idle the carb down to 750 rpm. You might have to play with the idle mixture screws on the carb or advance timing a little - (CCW) to smooth it out. Try and get the timing up to 12 deg BTC at idle. Test drive it then- you might to keep playing with it until you find the right tune. Hope this helps.

[72chevylwbmo]

D.Passmore, not trying to question what you are saying, but, everything that I have been told is that the rotor bug should be pointing towards the #1 cylinder. I am just trying to get this done correctly this time. I have heard that both methods are correct depending on what year motor you are working on. Can you tell me if this is true or not?

[imjeff]

It doesn't matter where the rotor points as long as wherever it points at TDC is where you put the #1 plug wire. Give yourself enough swing with the rotor to dial the timing in with a light. All the effort expended trying to get the rotor to point in an arbitrary direction will not change the end result at all. It's really a matter of 1-8-4-3-6-5-7-2 regardless of where you start.

[72chevylwbmo]

Ok imjeff, thanks for the info. Headed home to see if I can get her going.

[D.PASSMORE]

The issue that I found with a rotor point to #1 cylinder is that the timing advance canister will hit the intake manifold, you can run out of adjustment. In reality, the rotor has to fire on the #1 plug no matter what tower is the #1 plug wire is on. As long as you set TDC, set the distributor and point the rotor to that tower, that is #1. One of the reasons why they point the rotor to #1 is that plug wire sets were pre -made to fit that scheme. With a custom wire sets (cut to fit), again- you can make any tower #1 as long as the the engine is set to TDC and the rotor is pointing to that tower with the #1 cylinder / plug wire inserted into that tower. I use custom fit wire sets a use the below SBC sequence.

[jlsanborn]

All true, you can install the distributor in any orientation then correct it with the plug wires. I prefer to put it in the "correct" way so that the electrical connections are where they should be. I've always found that the vac can has plenty of swing in that orientation too. I suppose there's different intake manifolds out there where a tooth or two might work better.

Previous poster gave good advice too.... DOUBLE CHECK your wires vs. firing order.

Did your new timing set have three different keyways in the crank gear? My Boy hosed that up and had his cam out by 45 degrees and it actually ran that way (very very poorly however)!

[imjeff]

I agree on the orientation of the distributor...the vacuum pot and wire work well there. That has nothing to do with the rotor position within the cap...it only orients to plug towers.

Jeff

[jlsanborn]

That's right. You can jump the wires around to orient the housing however you like. I didn't say that very well before. What matters is that the rotor and #1 wire jive - don't matter where the rotor is pointed as long as you got the #1 wire there, then of course your firing order from that point.

[72chevylwbmo]

Thanks for that info guys. That is where my problem came from. I couldn't rotate the dizzy around far enough because the vac pot hit on the carb. I pulled the dizzy out and rotated it one tooth advanced and dropped it back in and all is well. Ran pretty good. I did a compression check on all cylinders and they ranged from 145 to 165 except for the #3 cylinder and it was at 190. When I pulled the gauge off milky antifreeze ran out of my hose. Looks like I will be tearing down the top end now to find the problem. If I have a cracked head, what would be good replacement heads?

[D.PASSMORE]

If you need more information or assistance working on your engine, post your question in this section (below), alot gear heads lurk over there too.

http://67-72chevytrucks.com/vboard/f...splay.php?f=24

[jlsanborn]

882 castings are pretty good (76cc, 1.94/1.60) but make sure you have those checked for cracks too. We just found three out of four that were cracked. The machine shop that we've been going to does it for free.