Help!!! 4cyl Main block Journals

[nissan20det]

Hey guys,
Okay so this is my first engine build and i decided to make a scaled down 4" long SR20DET (Japan turbo 4cyl).;D

Now I'm working on the block, shaped, bored cylinders and cut out crank housing. I am now trying to cut my blocks main journals. Now i do not have a lathe or access to one. I'm using a Sieg x2 I only have 2 hand fulls of endmills a boring head and a 4" rotary table. now my first thought was to take 1/8 ball nose endmill find center cut a line .0625 deap and then mirror that on the girdle I have made. then when I mate them (there bolted together along with 2 dowel pins to stay true) there will be close to a 1/8in hole nice and center all the way down. then stand it up and jobber drill and ream it to .3760. now i think this would have worked fine although I spaced that the block is billet aluminum and the girdles some grade thats quite softer so as you can guess the bit walked into the girdle like crazy. so Damn!

Well the i thought ok lets give it a shot to take a 7/16 endmill plunge down(wile bock girdle still together) . k well this made it down 3 journals cool. then i figured ok well if i flip it no way ill get it centerd so popped in a 7/16 drill bit figured ok i have 3 journals to keep this bit from walking that should work.....NOO ughhh still walked

So then i tried .5 same way but higher drill speed slower feed and I got close but the bottom is still slightly off (not quite half and half circles) so. Then i tried making a boring bar. 3/8 cold rolled steel made an angled slot then put a HSS square bar in... Tried that and Just too much vibration really not cutting what so ever. AHH!! WTF:wall:

Soooooo, Im now at the point of these journals getting to big my bearings are gonna be big already. The next thing i try really needs to work to not have to scrap 15-20hrs on this block. Please feed me some ideas im open to any thing as long as its not use a lathe or go buy this $50-100 endmill/jobber bit

 

[barnesrickw]

I had a infinity G20 with the NA version of that engine. Stout little runner. Really like the old version it in the old 510. Don't have an answer to your question, but I like your engine. Someday I hope to make som Saab engines.


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[nissan20det]

sweet! ya datsun's are the S**t. I have a 90 240sx thats all races out 6 point D1 cage and have the sr20det fully build 497hp 576ft-tq sucker rips bro! check her out.

https://www.youtube.com/watch?v=Iq8ZVpPoZfQ

 

[Lakc]

If the girdle is that much softer then the block, your best bet is to scrap the girdle, as its probably not the right material for the job anyway. "Soft" aluminum has a poor record of longevity for engine parts, scrapping even more work.

If you dont have a lathe to do a proper "line bore" job then you have to build one around the part. A large U shaped bracket to bolt the block in the center and holes at the crank centerline to guide the boring bar.

 

[nissan20det]

thanks for the response. the girdle is 5052 t65 and the blocks 7075 t70. so the girdle is not necessarily soft just softer. but im not sure i follow you i understand line boring although when doing that the boring bar is held center on both sides. I cant really do that on a mill (that i know of) thats why i tried to make that boring bar.? can you explain in more detail on what you mean? thanks

 

[gbritnell]

Ok, here's what you do to fix the situation.
Set up your block vertically on the mill. Make sure it's set up true to whatever edge you're going to use as a reference. You say you have a boring head. Bore out the first 2 journals. Hopefully you have enough travel to do this. Now make up a brass bushing to fit into the first 2 journals. It should be a nice tight slip fit. The bore of the bushing should be made to a standard size so that you can make a drill rod cutter. Using a piece of drill rod you can file 4 flutes on the end, something similar to a 4 flute end mill. You will need to reduce the diameter where the flutes are by .001-.0015 because when you harden the cutter it will grow by this amount. To harden the cutter use a propane torch or oxy-cetelyne torch and bring the color up to a carrot orange color then quench by sticking it straight into a container of water, if you're using W-1 drill rod. Now polish the rod where it was hardened and mike it making sure it will go through your bushing. If it's too big you'll have to emery or stone it to fit. Clean up the flutes so they are nice and sharp at the cutting edge. I use diamond hone sticks. Now with your spindle on center, chuck up your cutter, insert your bushing, crank the spindle down until the cutter is just above the 3rd journal, start up the mill running at a slow speed (150-200 rpm) using lubricant peck down into the 3rd journal. You will have to keep pulling the cutter out because the small flutes will load up with chips. Eventually you will work your way through. Once through move the cutter down to the last journal and repeat the procedure. Apply some oil at the 3rd journal to keep it from galling. The 3rd journal will act as a guide to support the cutter. When you're finished you will have the first 2 journals cut to size and the next 2-3 undersize. Clean everything up, rotate the block, indicate true and re-clamp. Now indicate the end journal bore and using your boring bar finish boring to size.
Everything should now be in line and to size. If your block has 5 journals and you can't bore deep enough to get the center one then you can use a hand reamer to clean it up. (as long as it's a standard size)
It sounds like a lot of work but when trying to line bore an engine on a mill there is hardly any other way to do it. You just don't have the tool support to make everything concentric. On a lathe you're supporting the bar at both ends so all the bores should be true and concentric.
gbritnell

 

[nissan20det]

Awesome! Thanks okay well that's kinds what I was thinking I started that and got to the 3rd journal with the boring head. I'm just to scared to flip it and try the last two. And ideas on how to get it centered when I flip it I can't fit a dial Ind. Through the first two hole and measure the Finnished journals. I also cant make a piece of stock to fit cuzz the top two journals are smaller than the bottom 3???

 

[nissan20det]

Hey guys so this is what i came up with so far. this only took me an hour to make i have not tried this yet ill test on some scrap. I would like to get some input on my cutter IE angle,shape ex....

 

[nissan20det]

okay so there a pic of a broken carbide 1/8in endmill. Now i figured this should be a good cutter although I need some input on what shape i should make it? just like a lathe turning bit, just i nice squared off corner? and also shown in the pics is how should i position it, angled,straight? im figuring angled and then a set screw 90 degrees to that angle but what do you guys think? and do you think this will work...any mods?

 

[nissan20det]

oops forgot the pics....................

 

[gbritnell]

Now that's a setup I would never have thought of. Sir I applaud your ingenuity. As long as the fiit in the bearings is tight (fixture) I see no reason why it wouldn't work. Do you have enough travel to get through the entire block?
gbritnell

 

[stevehuckss396]

I would try grinding the tip to a ball and then grind the tip to the center of the shank or just a hair under.

 

[nissan20det]

sweet! thanks I'm not sure how i thought of that haha, so yes the bearings are a very snug fit. pressed in both fixtures and the oiled brass bearing on the sliding fixture is a butter fit. and yes ill have about an inch of access movement on both sides if i place the cutter in the correct spot.

Steve thanks that's exactly what i needed thank you. see the last two pics i posted, how should i orientate it in the 3/8 line bore rod.

 

[stevehuckss396]

how should i orientate it in the 3/8 line bore rod.

90 degrees and it will cut both directions but will be a pain in the ass to adjust. 45 degrees will allow for a longer tool bit.

 

[nissan20det]

okay cool ill try 45 degrees here in a bit i through more pics up tonight

 

[barnesrickw]

You making it the 16v DOHC like the real deal?


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[barnesrickw]

You should message me how you got 475 hp out of a 2.0 l engine. Pretty amazing.


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[nissan20det]

Yes I will be going for the o original 16v head however I will be sorting out all the bugs(timing, cams) with an 8 valve head at first.

Steve does this look appropriate?

 

[nissan20det]

Wish me luck im testing this out right now

 

[nissan20det]

damn!!! sooo..... the trust bearing i was using on the head had to much play... seemed great at first but i guess that was all grease that was keeping it tight. as i spun this and made the first cut it started very well nice constant spiral chip coming off but as soon as that bearing grease moved around enough it began to have slop that grew and grew. Now after 2 min of trying this it wiggles like a siv. So i have another bearing angular contact sealed ball bearing MUCH tighter with an OD to big. Big enough that i made a small collar that pressed into the bearing and press onto my line boring rod. I just have to bore out the heads fixture to hold the new bearing and give her another shot minyana!

Cutter design seems to work great Steve THANKS!
i went with 90 degrees felt 2 ways to cut probably will be more useful