XXO/BVGC '38 Chevy Coupe Build

[desotoman]

Buddy,

Have you given any thought to a mushroom lifter cam? Just curious.

Tom G.

[38flattie]

Yes Tom, I have.

The current cam setup uses Chrysler/Dodge adjustable mushrooms (left in pic), with the head cut down to 1.260".



Why?

[desotoman]

Sorry, I guess I missed that part of the build. Good choice for lifters.

It has been many years since I researched the cams for flatheads but I remember the larger the diameter lifter you can get into the motor, the faster the rate of valve lift. Except for possibly a inverse radius roller cam, but most people don't want to grind those because the grinding wheels have to be so small. Those were some of the things I found out 30 years ago.

Tom G.

[jl222]

Well, I had the wind taken out of my sails today!
 
Chris had made a prototype head chamber, so that Joe Abbin could do the initial flow test.
 
Garry Odbert has been porting and testing his Caddy flathead, and getting 185-187 CFM at .500 lift, with a stock head, with the valve pockets cut to allow .500 lift. Garry offered to flow our head, for comparison.
 
Here are the numbers-intake side at .100 lift 64cfms lift, @.200- 123cfm, .300-150cfm, 400-163cfm, .450-166cfm, and .500-166cfm.

Garry reported a good, smooth airflow, which was about the only positive news!

In addition to disappointing flow, Garry did a dye test, and it looks like fuel is all in one 2'' spot, centered over the exhaust valve, unlike some heads, we placed the spark plug over the intake valve! Garry is going to send a pic this evening.


So, I'm pretty confident that no matter what the engine does on the dyno, we've left some HP out of the engine. Garry's port are not identical to ours, but that is only part of the equation.

We'll get it on the dyno, but I'll still be feeling disappointed in not getting more testing done prior to getting parts made. Ideas are good, but I'm kicking myself for not doing more testing! I'm definitely going to look at other piston/head options, for a major redo this fall.

  More boost and a big intercooler with water injection will help out the flow numbers

              JL222

[panic]

I'm not sure how a KR translates into another engine.
The KR has both valves tilted in toward the bore as they approach the deck, but not as much as some automotive engines.
KR valves are also both inclined to the bore in the thrust axis by 4-1/2°, which sinks their seats in the wrong direction: against port flow. IMHO much of the development work was to cure this, especially the complex 3-dimensional shape between the valve reliefs near the bore.

[38flattie]

jl222, that's always an option!

I'm not sure how a KR translates into another engine.
The KR has both valves tilted in toward the bore as they approach the deck, but not as much as some automotive engines.
KR valves are also both inclined to the bore in the thrust axis by 4-1/2°, which sinks their seats in the wrong direction: against port flow. IMHO much of the development work was to cure this, especially the complex 3-dimensional shape between the valve reliefs near the bore.

Panic, you're exactly right about the KR's angled valves. Cadillac has the same thing, angled at 6 degrees-one of the reasons we felt the KR chamber design would work on this. This is also one of the reasons for the heavy relief in the block.

Garry is going to modify the head chamber, and try and improve the flow.

[38flattie]

Ok, The prototype roller lifter bock is finished!

As soon as we verify the fit and measurements, and decide on what changes we want, if any, I'll get a set of them.


We ran a cable clutch last year, and are switching to a hydraulic slave setup for the crashbox,this year. The new pedal assembly, and firewall mods should be done Monday, and I'll post pics.

[38flattie]

Last year, we struggled with the clutch pedal. It's location was fine for the shorter guys, but a real PITA for Dale and I. With the new tranny going in, we wanted to get rid of the cable operated clutch, and use a hydraulic one.

Pinkess added a firewall recess, and hung some Wilwoods for me, while I was at work. Sitting in the car, I like the setup much better!

[38flattie]

Nothing exciting, but progress none the less!

I spent yesterday, and this morning, fabbing up new front shock mounts .They're now inside of the sheet metal, and other than the bottoms, out of the airstream. A little black paint, and I'll be finished!

Then I decided to install the new hubs. It should have been an hour job, tops, but not with my luck. It turns out that the bearings and races I need, 1.375" ID, and 2.5" OD, are non-existent-as in no one makes them. I was able to find 1.375" by 2.5625 setups, so I bought those, and dropped the new hubs at the machine shop. I'll be able to pick them up in the morning, and finish the job.

[38flattie]

Well, after messing around with the new hubs all morning, I determined there is more machine work to do, to make these fit. The spindle will need machined back 1/2" for the back bearing, and the hub will need the front bearing set in another 5/8", to fit correctly. I've got too much to do to try and get ready for El Mirage, so these are going on the back burner for now.

Anyone see a reason that I couldn't just machine the rotors off my existing hub, for now? I need to get rid of all the weight in the front that I can!

[Stan Back]

Apparently there's no free in free parts.

[Stan Back]

Just lookin' at them in the picture above looks like that would work.  Plus it looks like you'd still have a mounting point for an inner wheel disc.  The rotating mass would be a lot less, and the steel remaining would be close to the center and wouldn't make that much difference anyway.

[38flattie]

Free parts? Never works that way! Lol!

I don't see any reason not to trim the rotors off, so I'm going to try it.

[GH]

Buddy, that's what I did on my Studebaker. The rotors were mid size GM, I had a machine shop turn the rotors off and just used the hub.

[38flattie]

Thanks Gary!

I just set the dyno appontment with John Beck, for March 12-13. So, I thought I'd do this:
 
http://www.jalopyjournal.com/forum/showthread.php?t=672239