Pocket V8

[Sixtysixdeuce]

So, although I have a fair amount of experience in manufacturing, I'm still very new to the world of model engine building. As such, this is not going to be a runner, but just something fun to put together that offers proof of concept, machining experience and an opportunity to learn what works and what doesn't for when I begin my build on an actual working engine.

Anywho, it started with me merely trying to see how well I could machine a miniature crankshaft. It began life as the smooth shank of a 1/2" grade 8 bolt, but after about 9 hours, became a decent little loose copy of a SB Chrysler crank.

Well, I fondled it for a few days, then decided it needed a home. After about 8 hours, I had the block. Unfortunately, this was where I learned of one of my tooling shortfalls; the bit I was using to bore the cam tunnel walked significantly as it went in, nearly coming out at the #7 tappet holes. Oh well, like I said, not a runner.

Today's projects were the cam and bed plate/pan. Copied a BB Chrysler cam I had lying around, since it has basically the same profile as the SB cam, save for the distributor/oil pump drive being at the front. Cam is machined from a piece of 3/16 mild steel, the lobes are hand filed.

On the bed plate, the reason I decided to go this route was simply a matter of practicality; the main journals are so thin, there is barely enough room for a 00-90 screw, and I have not had good luck with 00-90 taps in the past.

Here's one for perspective:

All the head and pan screws are 0-80 socket heads. The block and bed plate are, as will all other aluminum parts be, 7075-T6. I do not like working with 6061.

So, that's it for now. I'll hammer out the heads next, I think. Rods are gonna be tricky, haven't quite worked out how I'll do them yet. They're also going to be cylinder specific, as this entire build so far has been nothing more than scratch paper for "plans"; no actual drawings, really just wingin' it. As such, there is some slight variation in journal width and distances between each.

And I apologize for the crappy pics. Can't find the camera battery charger, so having to use my phone for everything right now.

 

[bigrigbri]

Considering the scale and the time spent machining this is a very good start indeed. For the rods I would make em from either ally or brass so it gives some good bearing action.

 

[stevehuckss396]

Same thing happened to me. If it is going to be a static model it will be cool but maybe think about running
it on compressed air. It would take a little design work but you already have the hard parts done. Would be
worth the extra effort.

 

[Sixtysixdeuce]

Steve-Yours is definitely prettier! And I'm sure you're holding better tolerances.

Like I said, there's a great deal that is off on this, as I'm not working from plans at all, making it up as I go, and doing a fair amount of eyeballing. This is for fun, and for me to gain experience in machining these very tiny and intricate parts, learning what I can and can't get away with, as well as things like stop working when your eyes are so tired your vision is blurring, or you'll be remaking a part for sure.

Anyway, got a head done today, along with valves. No rockers yet, as I need to order up some 000-120 screws and a tap to make that work. Might try with 00-90, though.

The valves are .120" and .140" respectively, with 0.038" stems. I machined them from 3/16 music wire (hard on cutters!), they still need to be cut and grooved for retainers. I haven't figured out springs yet. The ports are drilled, then hand profiled with an 0.062 ball end 2-flute mill in a Dremel. The guides are machined into the head for now; due to my lack of tooling, I had to get them close with a 3/64" end mill, then chuck up a 1/8" OD roll pin to give them a rounded profile. One of them got mangled a bit when the roll pin broke, but it actually worked out fairly well once I heat treated the pin a la mapp gas torch and water. Would be a no-go on steel, but strong enough to make a jagged semi-round aluminum boss much closer to really round.

I have really got to get some better micro drills, though. Lost another tiny one tonight, a #64 that broke off on the intake side of the head when drilling the holes for the manifold bolts. Anybody got suggestions on a good set of wire gauge drills, #61-80?