This is a continuance of a couple other threads. Low power led to a compression check. This led to pulling the head and discovering an abnormal amount of carbon build up and two burned exhaust valves. Theories for the excess carbon were bad piston ring to groove clearance and bad valve stem to valve guide clearance. The valves were original two piece so they needed to be replaced anyway. I purchased new valves with oversized stems, a ream,new springs/caps/pins and a Neway valve seat cutter Kit to cut a 3 angle valve seat. I got the engine pulled out this week end and got the transmission out. I had a chip out of the reverse drum and I needed to replace that and I wanted to replace the pinion gear on the drive shaft, otherwise this would have been engine in the car work.
I got the engine disassembled and old valves removed. I used a wire brush in a pneumatic die grinder to clean the valve seats and ports as well as the rest of the deck.
I used a tap handle to manually ream the valve guides for the new valves. Take your time and use only slight downward force to maintain a square cut and get the right clearance. I used too much down force on the first one and had to make a second pass. Reams don't like taking a slight cut and can dull quickly doing this. The ream should be easy to rotate as it is cutting. I used just my thumbs to rotate the handle and apply down force. The clearance needs to be 2 thousands and there should be no perceptable drag when the valve is dropped n the guide dry. I used windex as a lubricant. This was recomended by the tech I spoke with at Neway for both the ream and the valve seat cutter.
I removed the magneto coil assembly because I could see some scuffing on the pole faces and I run a distributor so I don't need the mag. The clearance on the rear main bearing thrust positions was acceptable but I did notice there were no shims on the crank flange between the flywheel and crank flange. I couldn't determine the exact cause for the scuffing but I concluded it wasn't a main bearing thrust clearance issue so I made a spacer to properly locate the oil funnel for the timing gear and bolted/wired it in place.
Step next will be cutting the new 3 angle valve seats. I test fitted the solid pilots that came with the kit. I got two sizes. You can see that the one lower in the block is a better and correct fit than the one sticking out further. Solid pilots were recomended over adjustable because the reamed hole diameter was at the extreme range of the adjustable pilot and the tech was concerned about the adjustable guide being sturdy/stable enough to prevent flexing during seat cutting. The solid pilot is surprisingly stable and I couldn't detect any flex with slight side pressure.
Pictures of the pilots and oil funnel
Looking good, good photo's - watching with interest, good luck.
Hi: Im in he middle of a rebuild like yours. I also had low power and also overheating. The car started great and idled good. But at speed or under load it had no power and overheated fast. So I started a teardown to find out why. It seems my problem was loose cam bearings in the block. The bearings fit the cam perfect. But when you pulled up on the front of the cam when installed in the block it was loose. I installed a micrometer on it and it had .020 play in the block. My lifter to valve stem air gap was about .016. At operating temp that may close to aprox. .012. If the cam is bouncing around .020 at speed or under load it could in theory give me a air gap of negative .008 at some times. Have you checked your cam bearings in the block.?? I have never seen loose bearings in the block discussed in the books or anywhere else. It may be a problem that gets overlooked.
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If you have loose bearings in your block, its critical that you set your valve to lifter clearance with the springs in place. Remove one spring at a time and set the lash on that valve. Reason is you want the tension on the cam to press down on the bearings just as would occur when you're running the car.
I used to set clearances with all the springs removed because it was easier. I noticed that after the springs were replaced the clearance increased about 10 thou. OK, I suppose, for a stock cam but not for a Stipe cam.
It doesn't take much looseness to affect clearances. The center bearing is usually the culprit. Hard to detect the looseness with the cam installed so I set clearances with the springs in place in all situations.
So Richard, you are saying with the springs all on the valves that are being forced open are pressing down on the cam? Good point.
I had not considered that before, I usually adjust all valves without any springs.
I will have to change my ways.
Yes, since the cam is under spring load at all times when the car is running, the bearings do not bounce around in the block but are always in the down position. Its not just the springs on the open valves that force the cam down, its all of them, although there is more tension on those with the valves open, as you observe, Aaron.