Good catch CDM! I watched that every time- glad you got it. Herb is right, that shroud is super rare/hard to find! I have a couple examples of the top part of the shroud, but not the shroud itself. If/when you tear it down, would you share some detail pics of of the lower shroud? And come to think of it, you might have the original thermostat in the housing!
Thanks for the input re the fan shroud. I had no idea. It will be restored with great care. Should look good on a roadster. Are the two louvered pieces above the shroud a part of the original shroud or possibly added by somebody later?
That's a stock piece and also harder to find (that's the one that I have a couple of). Like herb said earlier, Chevrolet decided to hold off on the straight 6 until '29, but they had already stretched the chassis. It was MUCH easier to design a couple stamped pieces of tin to make up the distance than lengthen the torque tube/shaft for one year!
Mac; sorry to ignore your question. Yes, when I get into it I will document the teardown and post pics. Always fun to see these old guys come back to life.
CDM, no worries and thanks for sharing your find! JUST got these rocker pics from Stevie G- I picked up a set of slightly used rockers off of espay a while back to scavenge the working parts (8 of them for about $20) and gave them to Steve for a student needing a senior project . Here's what his student came up with-they are 1.7 to 1 and the stand is just to hold them, but things are progressing :
Any input on what material to make a new shaft from would be great. We are looking to put them together in groups of two or four(most likely four). Obviously steel, but what alloy, and what heat treat?
How about Thompson shafting? It's case hardened pretty deep, ground to VERY close tolerance. AND CHEAP, that should make that school teacher happy. It's available from Mc Master-Carr. There are actually differant size shafts tolerancewise, plus and minus, depending on the bearings you use. It can be drilled easily through the center for oil, and through the side with carbide on a drill press for mount screws or oil.
Thompson shafting? That's a new one on me. Thanks, I'll look into it. On the plus side, this isn't an 8K rpm engine.
Just looked it up, it's under hardened and ground shafting or linear shafting. Says hardness is 60-65C, which is pretty darned hard. There's a stainless version and a chromed version too. Says tolerance for shafts up to 1 1/4 is -.0005 to .001., but I know they make close tolerance stuff too. I have a catelog from the Co. too. There's a type O? and maybe N?, haven't looked at that for a long time. One has plus tolerance other negative. Think the close stuff is within .0002. Metric too. For example 3/4 is $6.29 for 6 inches in my book. I have drilled through the side already. Use a SPADE carbide drill to get through the case with LOTS of down pressure in a drill press or milling machine{prefered}, then a regular drill through the soft center.
Thompson shafting is the ticket for the shaft. I am a little concerned with the 1.7-1 ratio, however. First, as pointed out, this isn't a 5K motor, so there isn't any need for that much lift. Second-- the camshaft and lobes are anemic by even 1928 standards, and there is the load at the lifter/lobe interface that wants to be considered. Herb
For non-racing engines valve lift doesn't need to be more than 25% of valve diameter. I used NOS Dodge 6 cyl. lifters that required reaming the tappet guides to .625 & slightly reducing the lifter foot diameter to clear the block next to the cam bearing boss. Then getting the cam reground with a newer profile of your choice would be deluxe. Pat
Good information. So now we need to figure out what grind for the cam, and what size valves. Thanks guys! Fortunately editing the ratio is pretty easy.
Sizing the valves is easy because you're limited by what will clear the cylinder, unless it's going to be a race engine I would limit cam duration to no more than 225 deg. @ .050 cam lift with 215 deg. better for street driving. Pat
Herb, Thanks for chiming in! The cam will wind up being a new grind, so except for the limited overall diameter, we can design the lobes as we want! What ratio would you recommend for the rockers?
For anyone who might mis it; there is a pretty good looking '28 engine freshly listed on eBay. It's in eBay motors; vintage; parts& accessories, chevy engine.
Since I'm not racing anybody, I don't mind telling you what's in my engine. First off Mac--while the contour of the lobes definitely influences how well the lifter follows the cam, you are still working with a shaft that has a small diameter, and only 3 (probably by this time) loose bearings. The more lift that you give the valves, be it from the cam and/or the rocker ratio, the more violent the valve acceleration at any given RPM--and also the more spring pressure you need to ensure that the lifter will follow the cam on the closing side-which is important. I would not go over 1 1/2-1 on the rockers, and even then keep all the reciprocating parts as light as possible. My pushrods are aluminum, my lifters weigh 72.25 grams (vs 91.5 grams stock--and remember that I am using a '27 block which has smaller diameter lifters stock) My rockers weigh .6 oz more than '28 rockers, but could be lighter, and my valve spring caps are aluminum. Camshaft--at.050" lift--IO 5º BTDC-- IC 43º ABDC EO 47º BBDC--EC 3º ATDC For some reason I didn't write down the lobe lift in my notebook--but the duration is 228º, with a 110.5º lobe spread Valves---this is with 3 port head---but '28 head could be the same Intake Sealed Power V1932--69-78 Ford 302, 351 Winsor. Head turned to 1.72", cut seat area to 30º, face head to .060" land. shorten stem .230" This as large as you can go with 3.75" bore Exhaust Sealed Power V1823--Pontiac '68 350 w/4bbl carb, '69 428, '70 400 w/ 4bbl carb. Head 1.660" (stock) remove .260 from stem. Springs-"55-'57 265 Chevy--installed height 1.700"=74# seat pressure, 165# full open. Later I made up an adjustable cam gear, and made intake opening and exhaust closing equal, but no noticeable difference Car weighs 1800#, front 860#, rear 940# wet That's about it. I did no porting, but did port match with manifold. If there were hill climbs like they have in California, I would have liked to see how well it would have done. Comments Pat? Anyone? Herb
Herb, Thanks again for your info/wisdom! Like I said before, I desperately need to read my copy of Automotive Math . In my (severly) limited knowledge, I figured that upping the ratio would help with breathing, but I understand what you're saying about having to up the spring pressure, etc. Bottom line- I owe you some more Jimmy Johns Talk to you soon, Bill PS- I'm still looking for the info for the 455 heads and will try to take pics this weekend!
From experience you'll have to go thru all the cams you have or can borrow & find the one with the least wear by measuring from the nose of the lobe to the bottom of the heel. This will determine how much lift you can regrind the cam to. Welding on the lobe will seriously warp the cam, I've had an A cam shatter in the hyd press trying to straighten it. The Chev4 cam is not heat treated the same as an A but you'll still have a lot of hrs into it. You may have to be content with .27/.296 lift. As far as lobe separation angle & duration it depends on the weight and intended use of the car. I think Herb's cam would be real exciting in a light car but maybe not in a conservative touring car. Generally I try to stay with 225 deg. @ .050 with 112 separation angle for performance street. Closer separation is better for upper end performance. All of this is also dependent on what you have for an intake & exhaust system and your compression ratio. More duration you can have more compression. No compression occurs till the intake valve closes, so for pump gas you would try to limit cranking compression to 155 lbs. with an iron head & 180 with aluminum head. Hope this isn't more answer than you wanted, Pat
This'll be going in a light speedster body, so weight won't be an issue ('cept for my donut cravings as of late ).
This just popped up on Espay... if only I were a rich man!!! Mercury mainly built bodies for the Ford T chassis, but they did make them for Chevrolet (and Dodge, Rich and Doug) as well: http://cgi.ebay.com/ebaymotors/Chev...7008076?pt=US_Cars_Trucks&hash=item20c36324cc
Was at the Portland swap meet today and bought an oil pump set up for a Ford A/B and was set up for a mag drive. And it looks like....... Norm
Very cool, Norm! Sorry that I haven't posted on here lately, but things are slow right now. Stevie G still has his students fussing with rocker arm designs and a thermostat houskng for the Olds 3 port head, but nothing past that.
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