New Cylinder Head Question

[tekfire07]

I had my #7 cylinder spark plug leave the head. So I am replacing the head. I tried to helicoil it and no go. So I purchased a newly rebuild head. Decked, with new springs and valves.

Is there any break in procedures, that I need to follow? Or do I bolt it on and good to go?
Thanks in advance for any help.
Erik

 

[West 1]

Just drive normally, for the first 100 miles keep the RPM under 3500 if you can just to help all the valve keepers and parts work in a little before they see high RPM. Before installing your valve cover squirt some oil on the valve tips and valve springs just so something is there on your first start up. Not much to worry about. Good luck with your job.

 

[strutaeng]

Do you know why was the spark plug blown out? That's not a common issue on these engines AFAIK.

Did the piston make any contact with it?

 

[West 1]

I would suspect it was put in loose and just worked around till the threads were ruined. It happens.

You are correct the GM LS heads are robust. The 4.2L straight 6 GM had did blow spark plugs out but not the 4.8, 5.3, 6.0 and 6.2. At least I never saw it.

 

[LsHart]

So u replaced just one head ? It's going to have both banks running way off from each other. Do to one bank as u do to the other.

 

[07burban88]

I agree with the above statement in doing both banks when doing heads that way you have equal compression and less chance of misfires. also be aware the exhaust manifold bolts love to leave the chat and brake. I'll have a set of 12 in my inventory before I try head jobs on my 07 burb, but that's just me

 

[West 1]

Doing 1 head only has been done for many years at all repair shops. It does not cause any issues at all.

I had a neighbor install one GM 305 head, 58cc small chamber small valves on a Chevy 350 engine that came with the large 76cc chambers and larger valves, he had the 305 head and did not want to buy the proper head. That engine ran fine? Big difference in compression side to side caused no issues at all.
Not recommended by any means but pretty funny that it ran well for the guy. Who would have guessed and it was in a truck with a flat bed, he worked it regularly. I would imagine he had to run premium gas but I never asked.

If this was my truck and I was that deep into the engine for repairs I would be thinking about replacing the lifters on both banks and the trays that hold them, it is just too much labor to go back in later when one fails. If this is a very low mile engine lifters would not be a concern.

 

[hagar]

Its not doing one head that is the problem, it is that you decked one head only. Be prepared for a cyclinder imbalance and possible percieved misfire codes because of it.

 

[hagar]

Well.. depending on how much was taken off of course. Under a couple thou just to true it should be ok.

 

[LsHart]

The whole point is to have a balanced engine. Seals wear different from one side to the other and mileage also is a factor. The least amount of adjustments by the computer is what everyone wants. So unless ur trying to sell a truck, always do in pairs.

 

[West 1]

In actual experience the one head replacement works. As mentioned shops do this all the time. Even if the new head was surfaced they take off maybe .002 as a check to see how straight your head is then if needed they may take off a little more. The .002 usually cleans up the surface and the head is good to go.

Even if they took off .010 it is not enough to cause issues.

Many on. here rebuild engines all the time. Do you know that your brand new pistons are de stroked .020 from the factory to allow shops to surface blocks and heads while not causing issues? Other than Performance Pistons, ALL aftermarket pistons are destroked .020 just for this purpose. Sometimes one piston is purchased to replace one bad pistons. The new piston will be destroked .020. No one throws away that engine or says it is bad due to this .020 destroked piston. They install it and run it. No negative effects are ever noticed.

In a serious race engine this would never be done but in the aftermarket for passenger cars and trucks it is done every day. I would not hesitate to run the new head on one side only if I had one bad head.

You are not changing the compression from 10:1 to 8.1. The difference will be something like 10:1 one side and 9.9:1 on the other bank. Probably much closer than this example.

Do you know that even at Mother GM if a block comes in that has one slight variation in cylinders they might put a .010 over piston in one cylinder while the other 7 cyllinders were standard bore. They don't scrap a block because of a minor issue that can be fixed with one oversized piston. Does not happen often but it does happen.

In my working carreer we had the contract with GM for many of the pistons they used. In my last few working years GM would only buy your piston if you could supply what they called the power cylinder. The Power Cylinder was composed of the Piston loaded with RIngs, the connecting rod with the Rod Bearings installed so the entire Piston Rod, rings and bearings were ready to drop directly into the engine. Sealed Power and Mahle were competing for that business at the time.

I am not blowing smoke at you because I have rebuild a couple engines in my life I am sharing information from the Automotive aftermarket and the Production Engine Rebuilders association.

The original poster here will have zero issues because he is replacing one head only.

 

[hagar]

In actual experience the one head replacement works. As mentioned shops do this all the time. Even if the new head was surfaced they take off maybe .002 as a check to see how straight your head is then if needed they may take off a little more. The .002 usually cleans up the surface and the head is good to go.

Even if they took off .010 it is not enough to cause issues.

Many on. here rebuild engines all the time. Do you know that your brand new pistons are de stroked .020 from the factory to allow shops to surface blocks and heads while not causing issues? Other than Performance Pistons, ALL aftermarket pistons are destroked .020 just for this purpose. Sometimes one piston is purchased to replace one bad pistons. The new piston will be destroked .020. No one throws away that engine or says it is bad due to this .020 destroked piston. They install it and run it. No negative effects are ever noticed.

In a serious race engine this would never be done but in the aftermarket for passenger cars and trucks it is done every day. I would not hesitate to run the new head on one side only if I had one bad head.

You are not changing the compression from 10:1 to 8.1. The difference will be something like 10:1 one side and 9.9:1 on the other bank. Probably much closer than this example.

Do you know that even at Mother GM if a block comes in that has one slight variation in cylinders they might put a .010 over piston in one cylinder while the other 7 cyllinders were standard bore. They don't scrap a block because of a minor issue that can be fixed with one oversized piston. Does not happen often but it does happen.

In my working carreer we had the contract with GM for many of the pistons they used. In my last few working years GM would only buy your piston if you could supply what they called the power cylinder. The Power Cylinder was composed of the Piston loaded with RIngs, the connecting rod with the Rod Bearings installed so the entire Piston Rod, rings and bearings were ready to drop directly into the engine. Sealed Power and Mahle were competing for that business at the time.

I am not blowing smoke at you because I have rebuild a couple engines in my life I am sharing information from the Automotive aftermarket and the Production Engine Rebuilders association.

The original poster here will have zero issues because he is replacing one head only.

Replacment pistons do not have a .020 reduced compression height. GM does not build engines with one cylinder 10 thou larger than the rest.

 

[West 1]

Open any piston book and verify what you stated. Sealed Power, Mahle, Silvolite. The number manufacturers here in the USA is smaller every year but these 3 still exist. All aftermarket pistons are destroked and have been for the 50 years I know of. Performance Pistons are not destroked.

If you want to see what is done at the factory visit companies like Jasper engines, AER in Texas these production engine rebuilders see 30,000 engines torn down each year. They can share what is seen every day in the tear down shop.

I have been out of the industry since 2019 so my information is becoming obsolete for sure but some of this is common knowledge.