Pulled the head to fix a broken header bolt and was surprised.
Thread Starter
Joined: Nov 2001
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From: Doylestown PA
Pulled the head to fix a broken header bolt and was surprised. Well, since the power tour last June, I knew I had an exhaust leak on the #1 cylinder due to a broken header bolt that was stuck in the head. I finally got around to pulling the head to have the bolt hole drilled and tapped and noticed that two other bolt holes had stripped. As you can see, I had exhaust leaks pretty bad in all four cyclinders.
A quick question, take a look at the combustion chambers, everything look good?
Also, take a look at #1 piston, I have an eyebrow that occured when I had weak manley springs on the car that broke after 1000miles. I had the head off then to replace the springs and noticed the eyebrows then, so they haven't gotten any worse which is good.
I'm going to be pulling the passenger head in the next few days, and we'll see how that side looks. One thing I did notice is that I have a lot of carbon buildup in the exhaust ports which has me a little puzzled. The car was tuned well. I get very little knock at all, but may be running a little rich, as I don't have a wideband yet. I'd like to go down to a thinner head gasket, to try and bump up the static compression and decrease the quench thickness, but I'm thinking I should cut valve releifs to make sure it doesn't have valve to piston issues.
A quick question, take a look at the combustion chambers, everything look good?
Also, take a look at #1 piston, I have an eyebrow that occured when I had weak manley springs on the car that broke after 1000miles. I had the head off then to replace the springs and noticed the eyebrows then, so they haven't gotten any worse which is good.
I'm going to be pulling the passenger head in the next few days, and we'll see how that side looks. One thing I did notice is that I have a lot of carbon buildup in the exhaust ports which has me a little puzzled. The car was tuned well. I get very little knock at all, but may be running a little rich, as I don't have a wideband yet. I'd like to go down to a thinner head gasket, to try and bump up the static compression and decrease the quench thickness, but I'm thinking I should cut valve releifs to make sure it doesn't have valve to piston issues.
That's running pretty rich there. How's your intake look? Is there a lot of oil getting in there from the PCV? That could easily cause that buildup on the pistons. How do the plugs look?
Thread Starter
Joined: Nov 2001
Posts: 10,813
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From: Doylestown PA
Well, I do have a catchcan on the pcv system and it's pretty effective. There was very little oil in the manifold and the intake ports actually look pretty clean.
I was wondering if the exhaust leak had something to do with how dirty the exhaust ports were.
Fact is, I might just be looking for a problem that doesn't exist. The car ran well, mileage was between 16-17 mpg around town with a pretty heavy foot, and I know that I'm running rich, only because I was to be safe since I don't have a widband and don't want to go unsafely lean.
Once I get it back together, I'll start to lean out the tune gradually and monitor knock.
I was wondering if the exhaust leak had something to do with how dirty the exhaust ports were.
Fact is, I might just be looking for a problem that doesn't exist. The car ran well, mileage was between 16-17 mpg around town with a pretty heavy foot, and I know that I'm running rich, only because I was to be safe since I don't have a widband and don't want to go unsafely lean.
Once I get it back together, I'll start to lean out the tune gradually and monitor knock.
How much are the heads milled? Do you have a thin gasket? If you don't have a borderline setup (aftermarket valves, heavy mill...), then the valve float could be causing the eyelashes.
Thread Starter
Joined: Nov 2001
Posts: 10,813
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From: Doylestown PA
Well, it was the stock gm, non mls gasket. I'm not sure how much the heads were milled, but I think it was roughly 0.020", but I will measure to be sure. I definitely think that the eyebrows were from the old manley springs that were on it before. I knew I had valve float issues, and probably kissed the rev limiter one too many times which caused the eyebrows.
The valves are 2.05 and 1.60 I beleive, but will meaure them once I get the head back from the machine shop. I'm going to have them cc the combustion chambers as well so I have a better idea of my current compression ratio and it will give me a general idea of how much was milled off the head.
The valves are 2.05 and 1.60 I beleive, but will meaure them once I get the head back from the machine shop. I'm going to have them cc the combustion chambers as well so I have a better idea of my current compression ratio and it will give me a general idea of how much was milled off the head.
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Originally Posted by ArcticZ28
Exhaust leak prior to the 02's will cause the engine to dump fuel.
Thread Starter
Joined: Nov 2001
Posts: 10,813
Likes: 15
From: Doylestown PA
All the valves are perfectly intact and all four pistons look like that. I measured it and it's very shallow, less than 0.005" according to the digital caliper. My fingernail barely get hung on it, so that's why I beleive it's from an over rev / vavle float from the old springs. Supposedly they didn't have enough seat pressure to hold the lifter on the cam.
Looking at my hp tuner's log, I did notice that the driver's side was reading between +3 to +5 fuel trims at almost every cell, so that's most likely due to the exhaust leak.
Looking at my hp tuner's log, I did notice that the driver's side was reading between +3 to +5 fuel trims at almost every cell, so that's most likely due to the exhaust leak.
Thread Starter
Joined: Nov 2001
Posts: 10,813
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From: Doylestown PA
Originally Posted by hammertime
Thats what I thought too. I wouldn't try leaning it out without a wideband, and I would check PTV clearance with your current setup before milling the heads, or plan on cutting clearance for the valves.
Thread Starter
Joined: Nov 2001
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From: Doylestown PA
Originally Posted by SSwanner
you shouldn't have any P-V clearance problems with the tr224 cam in your sig. even with some good milling and thinner gasket.
Originally Posted by The Alchemist
Well, I do have a catchcan on the pcv system and it's pretty effective. There was very little oil in the manifold and the intake ports actually look pretty clean.
I was wondering if the exhaust leak had something to do with how dirty the exhaust ports were.
Fact is, I might just be looking for a problem that doesn't exist. The car ran well, mileage was between 16-17 mpg around town with a pretty heavy foot, and I know that I'm running rich, only because I was to be safe since I don't have a widband and don't want to go unsafely lean.
Once I get it back together, I'll start to lean out the tune gradually and monitor knock.
I was wondering if the exhaust leak had something to do with how dirty the exhaust ports were.
Fact is, I might just be looking for a problem that doesn't exist. The car ran well, mileage was between 16-17 mpg around town with a pretty heavy foot, and I know that I'm running rich, only because I was to be safe since I don't have a widband and don't want to go unsafely lean.
Once I get it back together, I'll start to lean out the tune gradually and monitor knock.
Thread Starter
Joined: Nov 2001
Posts: 10,813
Likes: 15
From: Doylestown PA
Originally Posted by V6 Bird
Your tune is way off with that exhaust leak at the head. Here's why....Air mixes into the stream of flow and flows down to the 02 sensors....02 sensors see more air than usual and add more fueling. Fix the leaks and the car should run a little better and possibly need a retune as well.
On another note, my father-in-law had a friend who builds / restores cars look at the head, and he said that the first bolt hole needs to be welded, but since the head is an aluminum alloy, it's going to be pricey.
Originally Posted by The Alchemist
Exactly, no doubt in my mind at all that I'm running too rich and fully expect to see the same on the passenger side. This is part of the reason why I bought HP tuners myself.
On another note, my father-in-law had a friend who builds / restores cars look at the head, and he said that the first bolt hole needs to be welded, but since the head is an aluminum alloy, it's going to be pricey.
On another note, my father-in-law had a friend who builds / restores cars look at the head, and he said that the first bolt hole needs to be welded, but since the head is an aluminum alloy, it's going to be pricey.
Thread Starter
Joined: Nov 2001
Posts: 10,813
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From: Doylestown PA
Originally Posted by Beaflag VonRathburg
Or just call Gunnar at Patriot and get a set of $300-400 new LS6 heads. They'll mill them for no extra cost. Then just switch over your valve train and call it a day.
Originally Posted by SSwanner
you shouldn't have any P-V clearance problems with the tr224 cam in your sig. even with some good milling and thinner gasket.
As information, my setup consists of a .045 gasket, 243's milled .010, 2.02 and 1.57 valves, and a TR 224 114. I'm right within spec. I measured almost exactly .080 clearance on the intake. Apparently I can add about .015 since I measured with a checking spring, but that's still close.
A 2.05 valve will eat up clearance with not only the diameter, but the margin too. The margin for those that don't know is the part that hangs down into the combustion chamber below where the valves hit the seat. Here's a good example between a stock valve and an aftermarket one with a big margin. The stock valve is on the right by the way.
Last edited by Xtnct00WS6; Mar 14, 2007 at 11:52 AM.
Thread Starter
Joined: Nov 2001
Posts: 10,813
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From: Doylestown PA
Hmmm, good point Xtnct00WS6. Like I said, I've got some measurements and calculations to do before I can make a decision. Are those measurements in your picture accurate? The aftermarket 2.05 vavle sticks into the combustion chamber 40 thousandths more than stock valves? Maybe I need to rethink using the aftermarket valves and go back to the stock vavles. But wouldn't a valve job specific to the valve negate that difference?
I'm just thinking out loud and creating more confusion for myself.
I'm just thinking out loud and creating more confusion for myself.