XXO/BVGC '38 Chevy Coupe Build

[Rex Schimmer]

Lets try it with the pictures!

[38flattie]

Rex, I read your post, then spent 3 hours Googling "NACA 66018 symmetrical ", and reading about air foils, and the principle and theory of such.

I'm not the brightest guy, so it should come as no surprise that I don't fully understand" It has 3 internal turning vanes that split the air for each of the 4 injectors."  Are these vanes simply lined upside to side, with a cental pivot point
?
Any chance you could expound on that a little?

[SPARKY]

Imagine your hand with your fingers forward with the fingers dividing the forward facing inlet space into 1/3s and the bottom or heel of your hand dividing the space over the ingectors into 1/3s and they stay above the injector or carb openings by ??

[38flattie]

Sparky, That makes since. I'm guessing then, since they turn, they must be attached by a verticle rods, allowing them to pivot?


Ok, guys, we have two different schools of thought going here. hopefully, you guys can weigh in with some experience/opinions.

One of us feels that .00175-.0002 rod clearance is sufficient, and prefers a light weight oil like Royal Purple XPR 5-30w.

The other of us thinks .0025-.00275 is necessary for the rods, and prefers a heavier oil-20-50 weight.

Same thing on the tranny and QC rear end. One of us feels the traditional 80/90w, or 90-140w is necessary, and the other thinks a good synthetic 20-50w engine oil is sufficient.

What do you guys use, and what are your opinions on this?

[RichFox]

I like the idea of the wider clearance on bearings, with the thought being if more oil passes over the bearing surface, it will carry away more heat. Oil pressure may not be as great, but will still be plenty and the actual oil film will be cooler. I think 20-50w is fine in the trans. I still run 90W in my QC

[SPARKY]

I run 5-30 synthetic in my rear axles

you attach and seal the vanes to the sides of the scoop  you are just attempting to equalize the pressures and minimize turbulence

[Freud]

Years ago Herda made several scoops. Rochlitzer, Markleys and possibly Donny Torgeson got one.

I've left someone out but I can't remember who. I think Herda used one also.

I never looked inside them but I know the dividers were curved and those scoops are still around today.

FREUD

[BoredAndStroked]

I like the idea of the wider clearance on bearings, with the thought being if more oil passes over the bearing surface, it will carry away more heat. Oil pressure may not be as great, but will still be plenty and the actual oil film will be cooler. I think 20-50w is fine in the trans. I still run 90W in my QC

I'm with yah Rich!  I keep trying to tell Buddy that "Bigger is Better" - you can always half shell a bearing to tighten it up, but yah can't take .0005 off a journal later on.  Nothing like a good debate on bearing clearances to make ones day, but a good discussion is always good.

[JamesJ]

Sparky, That makes since. I'm guessing then, since they turn, they must be attached by a verticle rods, allowing them to pivot?


Ok, guys, we have two different schools of thought going here. hopefully, you guys can weigh in with some experience/opinions.

One of us feels that .00175-.0002 rod clearance is sufficient, and prefers a light weight oil like Royal Purple XPR 5-30w.

The other of us thinks .0025-.00275 is necessary for the rods, and prefers a heavier oil-20-50 weight.

Same thing on the tranny and QC rear end. One of us feels the traditional 80/90w, or 90-140w is necessary, and the other thinks a good synthetic 20-50w engine oil is sufficient.

What do you guys use, and what are your opinions on this?

75W-140W gear oil is not the same viscosity as 75W motor oil it is actually much less maybe like a 30W motor oil, the real difference is that the gear oil can take more shock or maybe its called film strength, dont know but the RP XPR oil has the same strength as gear oil, you would not want to use it for most application but you can use it for Bonneville, We run the XPR 5-20 in our rear end and trans, as for how much difference it makes, most likely not much in the big picture.

[38flattie]

I like the idea of the wider clearance on bearings, with the thought being if more oil passes over the bearing surface, it will carry away more heat. Oil pressure may not be as great, but will still be plenty and the actual oil film will be cooler. I think 20-50w is fine in the trans. I still run 90W in my QC

I'm with yah Rich!  I keep trying to tell Buddy that "Bigger is Better"

Now Dale, you know there is no 'hard and fast' (pun intended) rule there- otherwise, Nascar would have to rethink everything, and a lot of guys wouldn't have girl friends!

I was at Dale's last night, and he has been bust. He made intake hold downs, and match ported the intake, undercutting it, to help direct flow.

[38flattie]

The crank is ready to install!

[Milwaukee Midget]

Oooooo . . .

Aaaaaa . . .

Don't you just love that new crank smell? 

As always, nice piece of work.

[38flattie]

Well, the engine prep and assembly continues. Dale got the timing cover adapter plate drilled and mounted, and fitted the Donovan gear drive.


Tonight he will clearance the bottom of the block bores to clear the rods.

[maguromic]

Looking good Buddy!  Tony

[38flattie]

Thanks Tony!



I received an email, stating the person loved the build, but wondered why I would even bother making a separate post just to show an adapter plate and Donovan drive being bolted to the engine.

Well, probably because it just doesn't bolt to the engine! I understand that it may seem that simple, but there is a LOT more involved than that.

There is no gear drive made, that has a crank to cam centerline measurement that will work on the engine.The BBC .400 raised deck gear drive comes the closest, but is still .027 shorter than the Flatcad.

So, the crank centerline had to be raised .027, and the rules allow for .150. To raise the crank, larger mains were needed to cover the 'gap' that was left. This is one of the reasons we used BBC mains (2.75"), instead of the stock 2.459" mains. A Chevy BBC snout was ground onto the new crank, to fit the gear drive, and so that we could get blower drive parts off of the shelf. The stock Caddy dizzy drives off of the rear of the cam, so the cam had to have the BBC snout, and gear.

As a side note, this is the only engine I've been into, that has larger rod journals (2.46"), even if marginally, than it has mains(2.459). These are stock measurements, per the U.S. Military repair manuel.

The BBC has a different timing cover bolt pattern than the Cadillac, so an adapter plate had to be made to bolt the Donovan onto the block.

Hope this clears thing up!