Interesting Post on Hotrodders.com Originally Posted by BBCMudbogger how do you get the cut at the correct angle to the piston? Quote: The cutter I'm describing is made from an old valve (make sure it is valid and not bent or the head warped) and a cutting tool (like you would use on a lathe post) sharpened on the edge for clockwise rotation in your drill motor along the edge of the bit from the tip to the center of the valve head. You'll want the bit at a length equal to the valve diameter plus 0.100" (0.050" on the radius). In other words, if you were cutting for a 1.940" valve, the radius of the valve would be 0.970", so you would want the radius of the cutting bit to be 1.020" (center of the valve head to the end of the bit). Leave a radius of maybe 1/16th of an inch on the tip of the bit so that you don't create a sharp corner in your cut that could act as a stress riser in the piston crown, then silver- solder or braze the bit to the valve head. The cutting edge of the tool will be to your left as you look at the valve head with the tool part up and should be relieved as it goes to the other edge of the tool bit (to your right as you look at the valve head). If the valve sizes in the head are fairly close to the same diameter, you may get by with making only one cutter. If they are very dissimilar, like 2.020" and 1.600", you may want to make two cutters, one for intake and one for exhaust. You would have determined if both valve pockets need to be cut when you checked the piston to valve clearance in the first place. You do the cutting with the short block mock-assembled (piston at TDC and masking tape around the piston to stabilize it in the bore). Use an old head gasket of the type you will be using on final assembly or you can use the new gasket you're going to use on final assembly because we're not going to torque it down, just snug it. Oil the shaft of your cutter/valve and place it in the valve guide. Slip a drill-stop collar onto the valve stem and snug down the allen screw to hold the cutter in place while you put the head on the block. You can usually find these collars at the local hardware in various shaft diameters. If not, here's a link to a low-buck kit with several sizes. A SBC valve stem is 11/32" (0.34375"), so a 3/8" collar would be used. If you want to get technical, drill the 5/16" collar out to 11/32" for a snug fit. http://www.jackstoolshed.zoovy.com/...=&utm_campaign= With the head SNUGGED DOWN to the block with a couple of bolts to maybe 25 ft./lbs. (not torqued to final spec), loosen the collar and let the valve/cutter head drop down onto the piston crown. Move the collar down against the valve guide/boss and snug the set screw. Rotate the cutter counter-clockwise in the guide. If you encounter resistance, loosen the collar, then re-tighten. Keep doing this until you can rotate the cutter 360 degrees and find a little resistance at one point. That will be the high spot on the crown and the point from which you want to start your cut. With the cutter positioned at that point, use a stack of your feeler gauges between the guide/boss and the collar that equals the depth of cut you have determined to make to get sufficient clearance. For instance, if this is an intake valve pocket and you want the minimum 0.080" clearance, but your clearance was only 0.047" when you checked it, you would stack 0.033" of feeler gauge blades between the guide/boss and the collar to limit your cut to 0.033" in depth. Make absolutely certain that the collar is TIGHT. Not to the point of stripping the threads on the set screw, but TIGHT. Now, you're ready to cut. I will caution you here...GO SLOWLY AND EASILY. If you use just a very slight downward pressure on the drill motor, the tool won't chatter and your stop collar won't slide up on the tool and you'll be ok. This takes a lot of concentration and control, so turn off the radio and tell everyone who might be there to shut up. Although I've done this with the piston at TDC and it worked out well, actual valve to piston contact will probably occur at some point either before or after TDC during the overlap period. I think the next time I do it, I will cut at TDC, then move the piston to 30* BTDC, re-arrange the collar as above and see if the cutter will engage a little more material from a slightly different angle. Same for 30* ATDC. After you've made the cut, pull the head and intall the valve you will be using, retaining it with the collar and the set screw snugged lightly to prevent scarring the valve stem. With the head back on, set your feeler gauge blades to the theoretical valve lift plus clearance needed. For instance, intake valve theoretical lift 0.480" plus 0.080" clearance = 0.560". Pull the valve up tight against the seat. Stack your feeler gauges for 0.560" and place them between the collar and the guide/boss. Move the collar down and lightly snug it on the valve stem. Slide the valve down into the bore. It there is no space left between the collar and the guide/boss, you're good to go. For those of you who think this sounds like a lot of work and time, it is. Maybe it will give you a clue as to why racing motors are so expensive. Can you imagine paying someone $100 per hour or more to do this for you, cutting 16 reliefs?
Ok, lock the doors! Nobody leaves here until we find out who pi$$ed in Blown's Wheaties! The Isky tool works good. I've even seen guys make their own notching tools by by glueing abrasive sanding belt material onto an old set of valves. And I'm not an expert, I'm just old and have been doing this for awhile. In the future if you have a problem with me take it to a PM instead of wasting space in a thread.
I like that! Just happen to have a bunch of sanding belts and a set of valves from the '86 heads. I'll get an accurate measurement for the clearances. But, just thinking out loud here. If clearances are marginal, maybe I could go ahead and finish assembling it as is and give it a try. I've heard valves sing a little with no apparent damage. Worst case, if I get any valve/piston interference, I'd pull the heads back off and notch the pistons. Best case, no problems. More thinking out loud: Rather than using clay to check clearances I could put the heads on with valves but no springs. Think the new seals would hold the valves up so I could turn the crank without valve/piston collisions. Then rotate the crank and find the spot where each valve gets the least travel due to contact with the piston. With a dial indicator, measure the minimum travel for each valve. Subtract the valve lift and I'd have the minimum clearance for each valve and know how much I needed to notch to obtain the .080" and .100" clearances.
When I measure valve clearance I use light weight checking springs on the valves, available from just about any speed shop for around $5/pair and lifters that won't compress. I then put a dial indicator on the valve retainer at the same angle as the valve stem. Turn the engine over until the valves of the cylinder you're checking are at overlap, in other words the piston is approaching TDC on the exhaust stroke. Before TDC the exhaust valve is open, intake is closed and after TDC the intake valve opens and the exhaust is closed. Using a degree wheel on the crank I check the vertical valve clearances at 5* increments from 20* BTDC to 20* ATDC by pushing down on the valves and reading the indicator. This will give very accurrate vertical measurements but won't measure radial valve clearance in the piston's valve pocket. Clay (or silly putty or even a Tootsie Roll still in the wrapper ) works best for that. Often the actual clearance you have with the real valve springs as opposed to the light checking springs will have about .010"-.015" more clearance. This is because the heavier springs do a better job of seating the valve, engaging the retainer, etc.
OK, I miced the putty. Sorry, I should have done that first off. I was thinking clearance in excess of .046 would be OK. Still learning after all these years ... I have about .101" on the exhaust and .065 on the intake. (First time I've ever had a reason to use my late father's pointy mics.) So, I think I'll give it a try as is. If I get any valve/piston noise I'll have to pull the engine and cut some refiefs. I'm betting it will be OK or, if its not, I'll know it before any damage is done. If I lose that bet, I might not tell you guys. Thanks for all the advice and patience.
You are asking for trouble with that .065 Exhaust clearance issue.You should have at least .100.When that piston is chasing that valve up the bore, if valve timeing events arent spot on or you float those valves... It aint gonna be pretty.Forged pistons like to crack when hit with a valve,or snap the head off the valve. 100 bucks to notch em versus 3 to 5 hundred to replace the pistons??? Good luck man...
I edited my post to fix it. Got it backwards. Exhaust was .101 and intake was .065. Still not what it should be but its too close by .015, not by .035. I'm not going to float the valves. Risk of over-reving seems minimal with a stock C4. Again, I appreciate all the advice. Thanks for helping me understand the risks.:Handshake
Thanks, but I hope I have it all buttoned up way before a few weeks. I interpreted the rental charge as $40 for each valve size. So I was estimating $80 for two plus shipping both ways to get to ~$100. Anyway, I think Barry's suggestion to glue cut pieces of sanding belt to an old valve would do the job. I'll try that IF I HAVE TO. Just happen to have some belts and old valves. Like I said, I'm betting I'm in the 50% that works with this combo. We shall see ...
Look Here: http://www.fordmuscle.com/forums/engine-articles/484906-another-technique-piston-notching.html
Perhaps you need to update/correct your profile. It says you were born in '68. Let's see, I started racing in 1970 when you would have been, what, 2 years old? I rebuilt my first engine in 1973 when you would have been 5 years old. I didn't "jump all over what you said". You provided information that, according to my experience, was not accurrate. I related what I have witnessed firsthand on my own builds. Unfortunately posting on the internet often doesn't convey mannerisms or emotions. Statements can seem harsh even when it's not intended. I'll just assume that's how you misinterpreted what I posted.
Think you get to keep the house. According to this -- http://www.fordcobraengines.com/engineid.asp -- E7 block and E6 heads combo was not uncommon.
