Watch what you buy - Cracked Head
04-12-2004, 03:48 PM
#12
I asked only because I was looking into buying a 2nd hand head.... If it was a one time sele then I will let it rest as is....
Just want to make sure it does not happen twice....
Beroz
Just want to make sure it does not happen twice....
Beroz
04-12-2004, 04:07 PM
#13
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Take note that it wasn't a total loss. I did get the cams, rocker arms, gears, sprockets and a bunch of other stuff that I'll need with a value well over the $400 i spent.
04-13-2004, 05:42 PM
#15
Understand the problem of not getting what you expected after paying a reasonable price for the head. All is not lost though.
Most of the cracks pictured are not in a structual part of the head. The only suspect one is near the hex headed plug.
If it was one of my heads I would just drill the end of the cracks (stop then growing) and TIG weld the cracks to keep the oil in. I would make up a spigot to put in the hole where the cam intermediate idler shaft sits to make sure that it doesnt move with the heat. If the head is heated to 200C before welding the likelyhood of warping will be reduced, esp if it is cooled down in the same oven.
0.010" off the head is not a major problem. If you dont want the extra approx 0.2 point increase in compression get a head porter to remove approx 1.5cc material from each combustion chamber. You would remove about this by deburring and polishing the chamber anyway.
Other S2K forum heads, please dont flame with with lots of "high and mighty" attitudes about repairs like this. I know many people will not consider this sound engineering practice, wont be the same as original, shouldnt have to do it in the first place etc etc. My background is in race engines and sometimes you get a head that is rare or hard to replace and you have to embark on repairs of this nature. The worst I've seen was a Cosworth historic motor that had no combustion chamber left ( owner claimed he shut the engine down as soon as he heard any noise). That head needed a new combustion chamber built up by welding, new inlet/exhaust ports made, new valve seats, cam journal line bore, new spark plug thread and lot of hours. This F20C head repair is relatively simple, and may resurect a head destined for scrap metal. It doesnt hurt to have it repaired and ready on the shelf as a saturday night special in the event of someone having a blow up and needing a head in a hurry.
Speedracer.
Most of the cracks pictured are not in a structual part of the head. The only suspect one is near the hex headed plug.
If it was one of my heads I would just drill the end of the cracks (stop then growing) and TIG weld the cracks to keep the oil in. I would make up a spigot to put in the hole where the cam intermediate idler shaft sits to make sure that it doesnt move with the heat. If the head is heated to 200C before welding the likelyhood of warping will be reduced, esp if it is cooled down in the same oven.
0.010" off the head is not a major problem. If you dont want the extra approx 0.2 point increase in compression get a head porter to remove approx 1.5cc material from each combustion chamber. You would remove about this by deburring and polishing the chamber anyway.
Other S2K forum heads, please dont flame with with lots of "high and mighty" attitudes about repairs like this. I know many people will not consider this sound engineering practice, wont be the same as original, shouldnt have to do it in the first place etc etc. My background is in race engines and sometimes you get a head that is rare or hard to replace and you have to embark on repairs of this nature. The worst I've seen was a Cosworth historic motor that had no combustion chamber left ( owner claimed he shut the engine down as soon as he heard any noise). That head needed a new combustion chamber built up by welding, new inlet/exhaust ports made, new valve seats, cam journal line bore, new spark plug thread and lot of hours. This F20C head repair is relatively simple, and may resurect a head destined for scrap metal. It doesnt hurt to have it repaired and ready on the shelf as a saturday night special in the event of someone having a blow up and needing a head in a hurry.
Speedracer.
04-13-2004, 05:49 PM
#16
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Joe Alaniz offered to have it sent out to a welder to see if it could be repaired, but I said no, because it had already been milled by .010. With the turbo, I want the compression ratio to go down, not up.
04-13-2004, 06:39 PM
#17
Fperra,
Understand if you already have another head. It could be worth resurrecting the other one for a rainy day. Saves time for you or someone else if there is a head ready to drop on a motor with fresh valve seats and the correct chamber CC's. Of course you would have to be up front about the repairs if you on sold it.
If you are going to turbo the engine you will want to deburr and polish the combustion chamber to reduce the possibility of hot spots and sharp edges. You can remove more material and lower the compression below that of an unmilled head without having to remove too much material.
I would also suggest that any used head is milled/resurfaced before installation, especially with a turbo to ensure that the metal head gasket has a good sealing surface. Normally you loose at least 2-3 thou in the process.
Another use for the head could be as a sacrificial lamb to test different porting designs, eg, larger port volumes, shapes or valve seat profiles.
Good luck with your project.
Speedracer.
Understand if you already have another head. It could be worth resurrecting the other one for a rainy day. Saves time for you or someone else if there is a head ready to drop on a motor with fresh valve seats and the correct chamber CC's. Of course you would have to be up front about the repairs if you on sold it.
If you are going to turbo the engine you will want to deburr and polish the combustion chamber to reduce the possibility of hot spots and sharp edges. You can remove more material and lower the compression below that of an unmilled head without having to remove too much material.
I would also suggest that any used head is milled/resurfaced before installation, especially with a turbo to ensure that the metal head gasket has a good sealing surface. Normally you loose at least 2-3 thou in the process.
Another use for the head could be as a sacrificial lamb to test different porting designs, eg, larger port volumes, shapes or valve seat profiles.
Good luck with your project.
Speedracer.
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