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**johnl** · 09-29-2014, 04:41 PM

It does sound like the HG is most probably leaking. I have no opinion to offer on the different gaskets, but make sure you check the head face for warpage. There will be a factory acceptable tolerance for head warp, but my experience (non Honda) is that this can be too optimistic. I've re-fitted heads that were within warpage spec, but still caused the gasket to leak (and no, there were no nicks or other damage on the head face). Machining the face fixed the problem in (both) these cases. These days if I can measure any but the most minute warp I have the head face machined. Be aware that (despite appearances) even fairly expensive metal ruler / straight edges (what most people use when checking for warp) are not really all that straight, but slightly bowed...

Make sure there are no sharp edges at the edge of any machining you might get done (i.e. at the edge of the combustion chamber where it meets the head face). It would be a good idea to have the head pressure checked for cracks.

While you have the valve springs off, check for excessive clearance between the valve stems and the valve guides. It's normal for there to be a very small amount of movement when you wiggle the valve head side to side, but any more than this then the guides need replacing (there is possibly a spec for acceptable 'wiggle'). The valve stems may be worn as well, so measure the diameter against specification (you can usually see any significant stem wear). New valve stem seals.

Check the valve lip and seats, do they have a nice three angle cut? If not then having this done helps gas flow (many engines have a three angle cut as stock, but not all). If altering the lip / seat angles in this way (adding an angle cut each side of the seating angle) never reduce the width of the lip / seat contact on the exhaust valves (the valve will run hotter as it won't be able to conduct as much heat away into the cylinder head because of the reduced contact area), but it can be a good thing for the inlets. If you find it seems to be taking a lot of paste grinding to get a good lip / seat contact, then the valves likely need refacing in a valve grinding machine (excessive paste grinding can result in convex and concave seating faces, which is a bad thing).

While the head is off you might want to clean up the casting roughness in the inlet / exhaust ports, and the combustion chamber. Unless you are attempting to enlarge the ports (which is probably not advisable unless you are building a high rpm race engine), just get rid of the worst lumps, dags and casting seams. Don't polish the ports, a slightly rough surface is a good thing, but it's good to polish the combustion chamber. If you're even keener you might 'port match' the junction between the manifolds and the head ports (though I have heard it argued that it is a good thing for the exhaust port to be somewhat smaller than the entrance into the header pipe). Of course nothing in this paragraph is actually necessary, but will help power slightly (maybe or maybe not enough to notice, but there is at least a feel good factor...).

**johnny_h** · 09-29-2014, 09:28 PM

Originally posted by CrimsoN View Post

Hiya guys, first post so please bash me if I get something wrong.

I'm about to replace the head gasket on my CB7 with Fel-Pro HS9851PT or Evergreen HS4012. The questions I have are:

Has anyone used and if so the results of using Fel-Pro or Evergreen gaskets and seals?
Is Fel-Pro or Evergreen a reputable manufacture around the community?
Any tips or tricks before undertaking the procedure?
What other procedures should I preform while having the head off?

The few things I have planned while replacing the head gasket are:

Valve adjustment
Valve lapping via grinding compound
Valve polishing
Valve cover paint job

The reason why I'm replacing the head gasket...
About three days ago I noticed my CB7 having a rough idle more than usual but cleared up after 30 seconds or so. Thought nothing of it since the weather is getting colder around here. But yesterday I had a large white cloud of smoke in gulp the car on start up coming from the exhaust. I let the car warm up to operating temperature to see if it's just condensation but the smoke persist and lingers in the air for ~10 seconds. I checked the coolant in the reservoir and it's down to half but the coolant in the radiator was missing a quart. After topping off both the reservoir and radiator and bleeding the cooling system I started the car and check to see if there were any bubbles in the radiator. There was a constant pulsating burst of bubbles and I also notice white steam coming from the exhaust side of the engine block. The CB7 has almost 300k miles with original motor and transmission. No history of burning noticeable oil/coolant or overheating.

Thank you guys in advance for taking the time to help me out with my dilemma. Her name is Epona and I love her!

Honestly I prefer Fel-Pro, I never had any issues with their products

**CrimsoN** · 09-30-2014, 10:18 AM

Originally posted by johnl View Post

It does sound like the HG is most probably leaking. I have no opinion to offer on the different gaskets, but make sure you check the head face for warpage. There will be a factory acceptable tolerance for head warp, but my experience (non Honda) is that this can be too optimistic. I've re-fitted heads that were within warpage spec, but still caused the gasket to leak (and no, there were no nicks or other damage on the head face). Machining the face fixed the problem in (both) these cases. These days if I can measure any but the most minute warp I have the head face machined. Be aware that (despite appearances) even fairly expensive metal ruler / straight edges (what most people use when checking for warp) are not really all that straight, but slightly bowed...

Make sure there are no sharp edges at the edge of any machining you might get done (i.e. at the edge of the combustion chamber where it meets the head face). It would be a good idea to have the head pressure checked for cracks.

While you have the valve springs off, check for excessive clearance between the valve stems and the valve guides. It's normal for there to be a very small amount of movement when you wiggle the valve head side to side, but any more than this then the guides need replacing (there is possibly a spec for acceptable 'wiggle'). The valve stems may be worn as well, so measure the diameter against specification (you can usually see any significant stem wear). New valve stem seals.

Check the valve lip and seats, do they have a nice three angle cut? If not then having this done helps gas flow (many engines have a three angle cut as stock, but not all). If altering the lip / seat angles in this way (adding an angle cut each side of the seating angle) never reduce the width of the lip / seat contact on the exhaust valves (the valve will run hotter as it won't be able to conduct as much heat away into the cylinder head because of the reduced contact area), but it can be a good thing for the inlets. If you find it seems to be taking a lot of paste grinding to get a good lip / seat contact, then the valves likely need refacing in a valve grinding machine (excessive paste grinding can result in convex and concave seating faces, which is a bad thing).

While the head is off you might want to clean up the casting roughness in the inlet / exhaust ports, and the combustion chamber. Unless you are attempting to enlarge the ports (which is probably not advisable unless you are building a high rpm race engine), just get rid of the worst lumps, dags and casting seams. Don't polish the ports, a slightly rough surface is a good thing, but it's good to polish the combustion chamber. If you're even keener you might 'port match' the junction between the manifolds and the head ports (though I have heard it argued that it is a good thing for the exhaust port to be somewhat smaller than the entrance into the header pipe). Of course nothing in this paragraph is actually necessary, but will help power slightly (maybe or maybe not enough to notice, but there is at least a feel good factor...).

Thank you very much for all of the information you provided! I didn't know about the valve guides possibly wearing out. I'll be sure to add that with the list. I now have a few other questions.

Is having the head machined, getting the having the angle cut, valve refacing pricey?
Do head gaskets fail without a overheating problem?

Honestly I prefer Fel-Pro, I never had any issues with their products

Content to hear about Fel-Pro's quality on your vehicle. I went with the Fel-Pro gasket set. Hoping I can get it in this Friday. Crosses fingers. I'll be sure to add pictures of the process if anyone is curious.

**johnl** · 09-30-2014, 01:17 PM

Originally posted by CrimsoN View Post

Thank you very much for all of the information you provided! I didn't know about the valve guides possibly wearing out. I'll be sure to add that with the list.

The guides and stems may well be OK, but it's wise to check while the springs are off and it's easy to check side to side play, and also take the valves out to measure the stem (or at least look to see if the stems appear worn). Always fit new stem seals at this point, they should be cheap enough.

Originally posted by CrimsoN View Post

Is having the head machined, getting the having the angle cut, valve refacing pricey?

Machining the head face is usually relatively cheap, maybe $50 to $80 or so(ish). Don't machine the head face unless it's needed (or there is any doubt that it might be needed). Every time the head is machined it causes the cam timing to become slightly retarded, and it's at least possible that the head might have previously at some time been machined once already.

I've never paid for a seat cut, so ask your local machine shop. I would expect it to be more than machining the head face (mostly because there are sixteen valves, so time would add up). It's not unlikely that there is already a three angle cut on the valve seat. It may be a bit more likely that the valves don't have a three angle cut. The machine shop should be able to tell you by looking at the components.

Valve refacing shouldn't be very expensive (but again I've never paid for it...), but if the valves need any more than a very slight refacing then it might be better to replace the valves. If you take too much metal from the lip then the valve will become recessed into the seat (i.e. become sunken relative to the surface of the combustion chamber), and this will adversely affect gas flow.

It's not all that likely that the valves will need refacing, modern valves are very hard compared to many old school (standard) valves, and don't wear the lip as badly. The same goes for hardened valve seat inserts (as in aluminium heads) compared to seats cut directly into cast iron. I only mentioned it because the valves should only require a light lapping with fine grinding paste, any more suggests a problem.

The valves and seats may not need lapping at all, check first using the afore mentioned 'engineers blue', or even grease will tell you much the same thing. If the seating surfaces appear to be giving a good seal (i.e. good contact around the entire valve and seat) then you may well do more harm than good by lapping them.

Another way to check for valve seal is to invert the head (with springs in position) and fill the combustion chambers with petrol, if any leaks out into the ports then a valve is leaking.

Originally posted by CrimsoN View Post

Do head gaskets fail without a overheating problem?

They can, but not if the failure involves the water jacket. If the failure does involve the water jacket then the engine may not overheat straight away, but it's only a matter of time, these things only get worse.

A failure that wouldn't involve the water jacket (and so wouldn't cause overheating) would be if the gasket failed between two cylinders where no water jacket exists, but you would then have a loss of compression in the two affected cylinders as compressing air in the cylinder on the compression stroke leaked through the failed gasket into the adjacent cylinder that is not on a compression stroke. The engine may still run reasonably if the leak is small, but soon there will be a misfire in both adjacent cylinders.

Note also that a failed head gasket does not always mean that coolant and oil will mix (either in the crankcase or in the cooling system, so you don't always get 'cream' in the oil and coolant when a HG leaks, but cylinder pressure can still over-pressurise the cooling system.

**Eleanor_cb7** · 10-04-2014, 10:14 PM

I had the felpro and it was good lasted 110xxx miles then i cjanged the head with the same gasket. Id say its good

**wildBill83** · 10-05-2014, 08:36 AM

While the head is off freshen up everything under your timing cover. I would replace the water pump and possibly the oil pump if you want to be safe. In my LX MRT I skim over the repair. I also posted photos of a head gasket job on a Toyota in another thread.

Don't forget a new radiator cap and thermostat.

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