burninator Posted March 7, 2011 Share Posted March 7, 2011 A little background... So, last fall while autocrossing I broke my radiator, dumped my coolant, and overheated my car. This all happened within 15 seconds, so it wasn't running long that way, but it did have to sit with no coolant in it after having been brought up to running temp. After repairing the radiator, refilling the coolant, and running it for a minute or 2 I found oil in the water. Determined it was a blown head gasket and let it sit until now. Now, I pulled my head and found that it is warped. Took it to the machine shop for inspection and it is about 14 thousandths warped. He also pressure checked the valves with water and determined that the valves are leaking a bit. He indicated I could use it like that but it might be down a bit on power. The exhaust was white/gray before this incident happened and I don't know what the compression ratio was, it ran and that's about all I cared about at the time. I say this because maybe it was leaking and/or warped a bit the whole time, although it never had oil in the water until the incident. Its an L28 block with an N47 head. I have an older head that's still on my L24 that's in pretty unknown condition, but ran before the swap. So, what should I do? I can't afford to do a valve job on it (like $250), but having it surfaced flat would be cheap ($65). I though about trying to lap the valves myself but I don't know if that would help the seal much. Or I could have the old head from the L24 checked out and use it if it's good. If the old head needs any work would it be worth it? Quote Link to comment Share on other sites More sharing options...
CamH Posted March 7, 2011 Share Posted March 7, 2011 What are you running? Carbs or EFI? If EFI, you'll need to drill the top of the intake ports for the fuel injectors on the older head. If you're running carbs the older head will work with no modification. Keep in mind that most of these older heads will probably have leaky valves. It's all old stuff and these things wear with age. Use this tool to see if compression with the different head will be acceptable: http://www.ozdat.com/ozdatonline/enginedesign/ Quote Link to comment Share on other sites More sharing options...
burninator Posted March 7, 2011 Author Share Posted March 7, 2011 What are you running? Carbs or EFI? If EFI, you'll need to drill the top of the intake ports for the fuel injectors on the older head. If you're running carbs the older head will work with no modification. Keep in mind that most of these older heads will probably have leaky valves. It's all old stuff and these things wear with age. Use this tool to see if compression with the different head will be acceptable: http://www.ozdat.com/ozdatonline/enginedesign/ I'm running carbs, and the compression ratio is almost the same with either. 8.38:1 with the E88 head vs 8.4:1 with the N47. Though if I have the head surfaced to take out 14 thousandths of warp it would be a bit higher. Quote Link to comment Share on other sites More sharing options...
CamH Posted March 7, 2011 Share Posted March 7, 2011 I think you'll be good either way. The valves probably leak on the E88 as well if I had to guess. Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 7, 2011 Share Posted March 7, 2011 A little background... So, last fall while autocrossing I broke my radiator, dumped my coolant, and overheated my car. This all happened within 15 seconds, so it wasn't running long that way, but it did have to sit with no coolant in it after having been brought up to running temp. After repairing the radiator, refilling the coolant, and running it for a minute or 2 I found oil in the water. Determined it was a blown head gasket and let it sit until now. Now, I pulled my head and found that it is warped. Took it to the machine shop for inspection and it is about 14 thousandths warped. He also pressure checked the valves with water and determined that the valves are leaking a bit. He indicated I could use it like that but it might be down a bit on power. The exhaust was white/gray before this incident happened and I don't know what the compression ratio was, it ran and that's about all I cared about at the time. I say this because maybe it was leaking and/or warped a bit the whole time, although it never had oil in the water until the incident. Its an L28 block with an N47 head. I have an older head that's still on my L24 that's in pretty unknown condition, but ran before the swap. So, what should I do? I can't afford to do a valve job on it (like $250), but having it surfaced flat would be cheap ($65). I though about trying to lap the valves myself but I don't know if that would help the seal much. Or I could have the old head from the L24 checked out and use it if it's good. If the old head needs any work would it be worth it? Usually pressure testing a head means testing the water jacket for leaks. If you were blowing white smoke before this happened, then the leak your machinist is talking about is between the water jacket and the intake or exhaust port. So this means that your head is junk. You could use the head from the L24, but it has smaller valves. You could still use it though. Pete Quote Link to comment Share on other sites More sharing options...
burninator Posted March 7, 2011 Author Share Posted March 7, 2011 Usually pressure testing a head means testing the water jacket for leaks. If you were blowing white smoke before this happened, then the leak your machinist is talking about is between the water jacket and the intake or exhaust port. So this means that your head is junk. You could use the head from the L24, but it has smaller valves. You could still use it though. Pete I'm positive that he was talking about the valves leaking. I don't know if his method is common practice, but we had a lengthy discussion about it and I'm sure that is the case. Also, his diagnosis of leaking valves and recommendation of a valve job doesn't make sense for a cracked water jacket. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted March 7, 2011 Share Posted March 7, 2011 You can lap the valves yourself if your seats look good. You can buy valve compound at most auto parts stores. After you lap the first valve, check that the seating mark on the valve is in the middle of the valve surface. Not a big deal. You may need to shim the cam towers after getting the head resurfaced. Quote Link to comment Share on other sites More sharing options...
z-ya Posted March 8, 2011 Share Posted March 8, 2011 (edited) I'm positive that he was talking about the valves leaking. I don't know if his method is common practice, but we had a lengthy discussion about it and I'm sure that is the case. Also, his diagnosis of leaking valves and recommendation of a valve job doesn't make sense for a cracked water jacket. My concern is the white smoke before you blew the head gasket. So either the head gasket was already leaking, or you do have a leak in the water jacket. Edited March 8, 2011 by z-ya Quote Link to comment Share on other sites More sharing options...
burninator Posted March 8, 2011 Author Share Posted March 8, 2011 My concern is the white smoke before you blew the head gasket. So either the head gasket was already leaking, or you do have a leak in the water jacket. I see what you mean. Point taken. I'm fairly confident that this is not the case, but I'll double check with him. I was figuring the head gasket may have had a small leak or something. Quote Link to comment Share on other sites More sharing options...
burninator Posted March 9, 2011 Author Share Posted March 9, 2011 Okay, the water jacket is not cracked, it's just the valves that are leaking. Quote Link to comment Share on other sites More sharing options...
kiwi303 Posted March 9, 2011 Share Posted March 9, 2011 How much of that leakage is soot, gunk and carbon buildup stopping them closing? A good clean and a lapping should solve MOST of the leakage problems if it's only minor leakage. Quote Link to comment Share on other sites More sharing options...
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