Hi there

Me and a couple of pals "fixed" a tired old LG4 in my IROC-Z -86 this autumn, and the result is less than stellar.

First off, I want to say that yes - we're a bunch of imbeciles. Although two of my pals have some education in fixing cars they are kind of unexperienced. Me, I'm a mechanical engineer, but I just do CAD all days. This is my first attempt at doing somehting serious with a car.

We swapped the heads for a pair of WP S/R Torquer, the intake manifold for a dual-plane Edelbrock, and build a new exhaust using a pair of cheap-*** headers. The AC went out together with the A.I.R system which is supposedly not needed on such old cars here in Sweden. There were no catalysator. I had first intended to replace the CC Q-Jet with an Edelbrock Performer, but it turned out to get complicated so I kept the Q-Jet.

Now my engine runs, albeit not that well. It starts nicely if I pump the gas pedal and floor it while the engine cranks. It vibrates quite a lot beneath 2000-2500 rpm, it misfires occasionally, it drinks coolant, the ventilation settings are b0rked (the engine dies on some settings, the engine fan stops working on others, etc), and more.

So in my foray to find the errors and address them, I need to get a few things straight first.

First thing to find out: is vibrations and rough running something that a dorky-made "performance" exhaust may cause?

I mean, when I rev it to 5000, it sounds all right and doesn't vibrate that much and the engine sound happy enough. It makes me wonder if the headers might be such that in order to enhance flow at high revs, it has a flow pattern between cylinders that might bite the low-end in the ***?

If that is not a possibility, I have to move on and look for other causes, like the ignition timing and such.

 

I'm thinking that problem has to do with the distributor. Did you install it correctly? Pointing at #1 at TDC? Or it could be something as simple as you have a couple wires reversed.

 

That is entirely possible, but I have looked well at the cables and they do look correct. I should probably examine the sparkplugs.

To tell the truth - we didn't even adjust the ignition very scientific either. Just turned the distributor until the idle sounded well. Then did a test run and turned it back a wee bit... That would be the thing I will check next, when I figure out how it is done properly.

 

I second ignition but the loss of coolant(?) would have me concerned.

If it's dying at certain HVAC settings you may have a vaccuum leak somewhere in the dash. All the vents are vaccuum controlled. You can rule this out by temporarily plugging the ports at the carb. This leak may not have been very noticeable when the engine was running correctly.

With the new headers, you've retained the O2 sensor, right? The ecm needs it to properly set mixture for the ccc-qjet. Without it you'll run rich or lean with idle and throttle transition issues.

 

> If it's dying at certain HVAC settings you may have a vaccuum leak
> somewhere in the dash. All the vents are vaccuum controlled.

Say what? o_0 That would explain why the engine dies abruptly on certain ventilation settings...

I plugged a halfdozen pipes on the carburetor, but what with the snakepit of EGR/A.I.R/cold start etc. tubes that were there, I have probably put stuff back wrong. God knows what the EGR valve is doing now.

> With the new headers, you've retained the O2 sensor, right?

Yes, we drilled up the stud and put it there, but when I got the car it was in an even worse state than now so it was never connected back then. I plugged the cable I think is the right one to it, and can't really tell whether it is working.

The coolant is leaking from the radiator, as far as I can tell. No smoke, no steam, oil looks fine.

Another problem that bugs me is that after our "fix", the oil pressure gauge maxed out the moment I turned on the ignition (not the engine) and has stayed there since. Someone says it is probably a grounding error but I fail to find the error. Something that sounds like a warning buzzer beeps intermittently when I drive it. I doubt the oil pressure is really at fault though, since it ought to have failed catastrophically by now it it were.

I just went out and advanced (retarded?) the ignition a bit by pulling the distributor half an inch clockwise. I think the engine runs a tad smoother now, but it still vibrates more than it used to before our "improvements". It feels as if not all cylinders are working. Good idle, sounds clean when I rev it up - albeit not as strong as I would expect (stronger than before the component swaps though) - but when I put it in high gear and rev something like 1700-2000 it rocks the cradle and coughs quite a bit. Exhausts smell like gasoline on warm idle, which is odd as it didn't do that before.

Oh well, once I find my Heynes handbook again, I will start looking at what color the cables to the O2 and oil pressure sensor should be. And I will try removing EGR hoses and plug the connectors to see what happens.

(I told you we're a bunch of imbeciles... =)

 

The vaccuum line for the vents comes off the manifold behind the carb, try plugging it to see if there's a difference.

Proper procedures after the swaps would be to set timing to 4 degrees with a timing light then adjust the carburetor settings for proper dwell at idle. With your mods you've likely gotten the factory carb settings (idle mixture and Idle Air Bleed) outside of the range in which the ecm can control mixture. When the O2 sensor doesn't see a reading within it's "narrow band" it won't go into full feedback mode. Assuming all the sensors, etc. work properly, of course.

If your oil pressure guage is pegged high you may have inadvertently grounded the sensor wire that connects to the sender behind the distributor (bronze can looking thing screwed into the block with a single wire connected to it). Sometimes it will ground temporarily then the needle gets stuck up behind the bezel edge.

The O2 wire should have a dedicated plug that connnects to the sensor. It will not connect to anything else.

 

Only four degrees? I have to check that.

I guess I will need to tear the carburetor apart and rebuild it over the winter. As it looks now, I fear that it might break if I touch it. Stuff wiggle.

The O2 sensor wire connector was splinters. Most of the plastic connectors are. Several weren't even connected. I looked at where the wires came from and where they reached and plugged them in. I might have gotten stuff wrong.

I'm no guru but it is clear to me that the former owner was an utter retard. I swapped this car for a motorbike, and he said it was a TBI 350 that was a transplant from a van because the old engine had cracked one winter due to lack of antifreeze in the coolant. It turned out it was a carbureted 305 with the original engine... I wonder what he was smoking. I hope the bike explodes.

Thank you for your kind help!

 

if its eating coolant and runs like hell, the intake manifold could be leaking(losing coolat into the oil/cylinders) as well as possibly causing a vaccume leak, which could cause things to run poorly. if you havent changed the oil lately this would be a good time and when you do see if the oil is milky

 

On the timing keep in mind that it's four degrees with EST wire disconnected. When idling with EST wire reconnected to dist, you'll see +20 degrees.

 

VICTORY! TRIUMPH!

It turned out that we had set the valve lash too hard.

I removed a few sparkplugs and found that #2 was sooty. That triggered me to remove the valve covers and unscrew every rocker nut half a turn. Then I put the covers back, turned the ignition key and GRAWL the engine started instantly, happy as can be.

A lap around the countryside confirmed that the vibrations are gone and the engine runs strong and smooth!

Well, at least as strong and smooth as one can expect from a 20 year old 'Roo with a moribund LG4 that got a few new performance components assembled by a bunch of nerds... It does still blubber a bit in high gear at half gas, and the performance feels like slightly more than 200 BHP or so.

I took it to a DIY station and changed the oil and filter. The oil was pitch black and smooth, no sign of water or foam or anything. So I figure the coolant leak comes from outside the engine block, thank goodness.

Remains to be fixed: oil pressure gauge, trip meter, parking light, interior lights, hatch button doesn't work, rust, tires are 225/50-15, paint is ugly, convert from gas to E85, change camshaft, 454 Motown, Lysholm blower, dragbars and parachute. ^_^

 

You just backed off all the rocker nuts a half turn....?

I wonder how well it would run if you had adjusted all the valves properly?

 

Yeah, well - to make a long story longer:

When we changed the cylinder heads and reassembled the valve rockers, I had read that the proper way to set the lash is to tighten until you can't turn the pushrods with your fingertips, then add half a turn.

I have heard everything from no extra turn to one full extra turn, including 1/4, 3/4, from all kinds of sources. I figured it is not that essential when you have hydraulic lifters.

Anyway - what I failed to understand first was that if I check half a minute later, the adjusted pushrod will "come loose" as its oil was put under pressure. So we were cussing and tightening and scratching our heads and tightening more.

When the day came where we tried to start the engine, it wouldn't work. After a lot of troubleshooting - including finding other sources of failure - we also loosened the rocker nuts a bit.

The engine ran, albeit badly. It did not occur to me until today that I might have to loosen the rocker nuts even more.

Now that I have run the engine for a while - and changed to new and thicker oil (old oils degrade and I am quite certain that the old one was a 5-50 since I put it there, this time I put 20-50) - I will set the lash one more time tomorrow. But I think it is okay since I can hear no clatter or suspect noise from the heads.

I can't begin to describe the relief I feel. We have been poking and bending and humming and hemming and flipped through manuals and searched the web like morons around this car for three months. I was beginning to think I would have to write it off as a failure, especially after I accidentally drove it ten miles without coolant. =/ It seems to have survived that without damage though. God bless cast iron!

 

You tighten the nut until zero lash then an additional 1/2 turn. Zero lash is when there is no up/down slack between the tip of the pushrod and the rocker arm/lifter seat. You can also tighten the rocker nut down until you start to feel slight resistance while rolling the pushrod then adjust 1/2 turn. This has to be done on the back side of the lobe.

 

I think the most important thing is what mike1986fyrbird just said, you need to set the valve lash at the correct point of the cam rotation (backside of the lobe). So when you set valve lash properly you will need to be rotating the crank by hand and adjusting the different rockers at different points. You can't just go across the board and set lash on everything with the engine at the same point in rotation, some of the valves will be off. Don't worry I also made this same mistake the first time I installed heads.