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I like it, ORB is a better seal vs npt. Staying with 1/2 ID on all the passages?
While you have the block in the mill you should turn it over and slot The bearing saddle oil feed holes.
Already slotted the holes lol. That's actually why it was in the mill to start with. I drilled the passages out to .531 (17/32"). Gotta do a few more checks then I'm gonna try to take it to the machine shop next week to get decked. Then, I can order pistons/rods. Just checked the intake runners on the W7 heads...258cc on the nose.
Well give us a pic of that lol. We like pics! We like pics!
I think he is talking about the oil filter bolt hole. It has a chamfer where you could use an O ring, but that thread is not npt. You have to make up a custom length bolt to put in that hole when going external. The length and thread of that bolt and the entire mod is in the old engine book, you have to get the length of that bolt right or tightening it when too long bottoms out on the inside of the block.
Yes, I meant the old oil filter hole. It's a 3/4-16 thread which is nothing too exotic. But, that is the same size as 8AN, so an ORB fitting (plug) goes right in. The chamfer 'could' leak but I think it won't as it looks pretty consistent. Here are the cutting tools...a 23/32 end mill (or you can use a 23/32 drill) and two taps. The first tap is a Butterfield interrupted thread version....painfully expensive but the quality of the threads is excellent. The interrupted thread results in a tap that only takes about 1/2 the force to turn...nice. Then, a modified 'normal' TRW tap...the end is cut off by about 4-5 threads. This allows you to tap to the proper depth without the nose of the tap hitting the block first.
I did not have the luxury of a milling machine. I cut the threads in my block with a hand drill and hand tools. You need some serious leverage to turn a standard 1/2 inch pipe tap by hand. I agree you need a cut off tap to get the threads right in a shallow hole. You appear to have a machining background as do I. Glad to see you are handy. Nice work. I always say that to be in this hobby, sometimes you have to improvise and use what you have available to you. You have to Mcgiver it lol.
If you're doing them by hand, an NPT ream is a life changer. They're kind pricey for a one off, but they make all the difference. Gives you the taper, so you're just cutting threads in that, vs digging in deeper and deeper as you go. https://www.mscdirect.com/browse/tn...eamers-Sets/Taper-Pipe-Reamers?navid=12106203
Oh, I've drilled lots with a hand drill. I have a Dewalt drill that I affectionately call 'the wrist breaker'. With a big drill bit, it loves to grab, then twist your arm around much faster than you can let it go. I actually hardly ever use it for that reason. I ordered a 23/32" drill bit that is ground with a 17/32" pilot... I was gonna use it with my weaker cordless drill but they are gonna take another week to get it done so it tipped me in the direction of using the mill. But I've learned that my ability to hold a drill bit straight leaves something to be desired.....so it's either piloted bit or the mill for me. Yes, the reamers are nice. With the interrupted tap I didn't bother with one but they do produce a nice result.
Never heard of those types of reamers before. You taught me something. Thanks for the tip.
Here is the main saddle slot. I'll make the bearings slotted to match. The slot is 1/4" deep and a little bit over 1/4" wide. I didn't want to go much over 1/4" wide because I want the saddle to have enough meat to support the bearing. You can also see the 5/16" x 5/16" set screw in the cam feed hole. I installed these ahead of time so I can back them out and maintain the thread-ability of it. I'll center drill the set screws .125" before they go in for the final time.
Very nice. I am at a loss to explain why I see a counterbore similar to this on some factory blocks and not on others. I think this helps the rod oiling big time. May I ask how you determined which direction to elongate the slot. I went 1/4 inch by 1/2 long on my bearings as well for the same reason. Adequate bearing surface, although the load is lower on the top bearings.
He slotted it so the oil timing is retarded from where Chrysler has it, and is making it closer to small block Chevrolet timing. IOW’s, Chrylser has the oil timing too far advanced and gregcon has put it back where it should be by retarding it, or I guess you can say he also made the timing longer. I did that and it helped, but over 8000ish it would still grab a bearing.
Here's my reasoning....I slotted the area that is normally drilled by the main feed and cam feed...basically I turned the two round holes into a slot. Then, I kept slotting an additional 'hole size' in the direction of rotation...this was because of YR's timing posts and also because it made sense in that it followed what's going on at the #1 main due to the added left galley feed. Also, because it is a fairly symmetrical slot... XX degrees off center in either direction. All this would not mean much without the bearings being slotted because they only have a single 1/4" hole. I agree, the top half of the bearing is less loaded but my gut tells me to keep the bearing well supported. I've seen the small blocks that were made with the big hole so it has to be OK but it doesn't seem ideal. I dunno.
Maybe some rounding and blending in the slot to aid the turning of the oil.
Not saying this is right or wrong, but after reading that lengthy article about rod bearings being oiled by centrifugal force, oil timing should not be that critical. Making sure the feed passages in the crank throws stay full seems more important. Sanborns explanation for the slots was to allow more time for those passages to fill up. As long as there is oil in there, the rods should oil all the time. IMHO.
As I said, if you just look at a SBC and how it oils, with half groove bearings and literally nothing else, then the oil timing IS at least an issue. Getting the oil into the bearing at the right time is what allows the oil film to carry the load. That’s why full groove main bearings gets the rods oiled to higher RPM than half groove bearings. I personally never had an issue with the mains getting oil.
Yes, I will smooth these out with a carbide bur, this is just 'out of the mill'.
If you recall we read an article that claims that rod bearings are oiled by centrifugal force of the spinning crank. That is how the rods get there pressure and feed. According to the article and to Sanborn, who also never used full groove mains, the mains fill up the drilled crank feed passage and the centrifugal force pressurizes The rod bearings. I am saying that if that is true, that timing is less critical and fill time or dwell time would be more important. According to that article, the rods are not only pressurized when the oil holes line up. They are pressurized all the time.
I need to go back and read it again, but I understand that centrifugal force gets the oil put to the rod, but when the oil feed hole in crank isn’t lined up with the groove in the bearing, the only oil available is what’s in the oil passage in the crank at that time. And even when the oil hole in the crank gets to the groove, it takes time to initiate flow to fill the passage. The higher the RPM, the less time there is to get oil to the crank. Im not sure why Sanborn didn’t use FG bearings. Did he ever say why he didn’t use them? And I can’t find the link to that article! I should have printed that thing off.
Here is something I just found. It’s not specifically about the topic we are discussing, but the author touches on oil timing, and when the oil should be fed to the crank and rods. PROBLEMS IN HIGH-SPEED ENGINE DESIGN on JSTOR
Would you believe I was reading that the top rod bearing actually has more load than the lower...I think it was on the Bill Miller Engineering site...
Why not? I have a crankshaft in my living room and carb parts in my bedroom!
what size hole did you drill