XXO/BVGC '38 Chevy Coupe Build

[desotoman]

Hell, it sounds more interesting than my project!

Sorry I did not mean to derail this thread. So back to your project build.

For your pistons did I understand that they will be a flat top pop up design? If so I will give you something to ponder. In my research years ago, I talked with Don Ferguson Sr. a lot about Flatheads. At one time he ran pistons as you are describing. He showed me a few that had holes in them and the holes were not where you would think. They blew through at the very top corner of the piston where it meets the chamber.

That is why I did not like the first Navarro heads made, and had a 240Z cut put on the pistons, which was a ramp style cut for about an inch across the transfer area. I did that so the piston could absorb the heat better. I don't know what ever happened to those heads or pistons as I sold them to someone in Oregon, after I was able to talk Barney into changing the head to a dome radius.

Just something to think about.

Tom G.

[38flattie]

Tom, I wasn't be sarcastic in the least- I really would like to hear more about your build! As there are not many flathead builds on the board, seems to me this thread is as good as any.

I'm going to run coated pistons, but even this may not help the damage you describe.

Do you know or have a theory as to the cause?

Was this hole always on the edge towards the valves, or in random placed?

I assume the domed pistons solved this problem, since there was no 'edge'?

How did the domed pistons and the flat top pistons compare flow wise?

[desotoman]

Tom, I wasn't be sarcastic in the least

I know you weren't, but this is your build and it's about a Caddy which I think is cool.

Back to the pistons, we did lose a little flow, and static compression, but not much and since the motor was supercharger I was not concerned about the flow, or compression, as much as the reliability.

The pistons I saw had the holes in the same spot, which was toward the valves or facing the transfer area. I don't remember if they were coated or not. The radius at the top was very small maybe 1/16 of an inch, if that.

As I said before just something to discuss with the other guys and get their view on the subject, as this was years ago and things are constantly changing so you might not have the same problem. 

Tom G.

[38flattie]

Tom, thanks for the stories, and info. I have passed your concerns along to Dale. seems Dales idea, at this point at least, is to "have it chamfered like the Baron Popup head has".

Hopefully, this will solve the problem!

Staring into the crystal ball, checking out the future . . .

I like the Phase 2 head, but I'm wondering why the big bend in the bowl.  Looks like about an 85 degree turn, right at the point where you need to smooth out the flow.  If you're starting from scratch, you could straighten out the ports by cutting the intake face at an angle, along with the exhaust, and raising where the port enters and exits from the both sides.  You'll increase the radius and smooth out the flow, yes?  It's not like you're trying to match it up to an existing manifold.

My 2 cents, and worth about half that . . .

Also curious about the bowls in the block - how much room you have to play with on those ports.  Any pics?

Ok, I found a better pic of the valve bowls. As you can see, there is planty of room to move the pushrods around some.

This is also a mockup pic, with a 1.75" exhaust, and a 2.05" intake. These Caddies have lots of room for valves!

[Milwaukee Midget]

Thanks for that.  Looks like plenty of metal for shaping.

So the firing order is 1-8-7-3-6-5-4-2, and you have shared 3-5 and 4-6 exhaust.  At least you don't have a cylinder robbing situation on the intake side, but have you thought about how to address the overlap on the 3-5 and 4-6 exhaust? 

I guess it's essentially the same as a flathead Ford (180 degrees), but it's a very different port shape and location.

This one just keeps getting more interesting. 

[38flattie]

Good question!

For the 3-5 and 4-6 exhaust, we're going to spilt the ports. I've asked for, and received permission to do this.

I have no artistic ability, bit I think I can muddle through this! Lol! The first pic shows the 4-6 port. The white lines are where cuts will be made to remove the heat riser. the red line indicated where the port divider will go.

The second pic shows the 1/2 plate that will span the intake and exhaust ports.It also shows the split port. Again, I asked for and received permission to install this plate, to keep from splitting the engine. The top center is not all that strong of design,as you can see in pic 3.

[Milwaukee Midget]

Fascinating.  I have a similar situation with the Midget (both intakes - shared ports - and exhaust - shared 2-3), which I can only remedy with different LCA's for the 1-4 and 2-3.  I'm required to keep stock port arrangements in GT, and I simply don't have enough material in the head to try something like this without restricting flow.

This block clearly gives you enough material to work with, and the extra port height that the modified heat riser gives you may actually help direct flow out of the port.  

Very crafty.  

[38flattie]

Thanks. I don't know about crafty, but I think it will work!

Ok, I read you were solving your shared port situation with a “scatter pattern” cam-I get that part.

But above, you mention the only remedy being different LCA's. What is LCA? Is that the same as LSA?

[Peter Jack]

Lobe Center Angles???

Pete

[Milwaukee Midget]

Lobe Center Angle.  Based on the cam degrees, not crank.  Lift and duration being equal, by tightening the outside pair LCA's in my application, and widening the inside pair, you effectively minimize the time that 1&2, and 3&4 intake valves are open at the same time, which minimizes cylinder robbing.

It's a sad compromise compared to individual ports.

Seeing as you are starting out with a blank cam, I was thinking that a similar compromise could be made on the exhaust side of your engine to minimize back pressure and pumping losses when the 5 and 6 open, but the solution you came up with makes a lot more sense.

Good article on LCA by David Vizard - the guy who co-designed my cam.

http://www.stockcarracing.com/techarticles/scrp_0612_lobe_centerline_angles/index.html

[38flattie]

Thanks for the link- That's a very informative piece!

Should have progress pics soon, but in the meantime, Mike and I have been discussing the OHV conversion.

This is just a rough draft, to get port design, and port paths. We're trying to get a path roughed in, that misses all the head bolts, and will flow good. The draft still needs a lot of 'polishing', but it's a decent draft.

[Rex Schimmer]

It looks like you are trying to miss the head bolts at secure the original head over the valve area, ever thought of just making a separate plate to cover this area and then making your new head with a notch to go over this plate or make the head narrower but this would allow you to use just the head bolts that are around the cylinder, which is what every other head does and not have to contend with the 8 bolts in the old valve area. Sure would make installation and removal of the heads easier.

Another thought would be to add a 1/2 to 3/4 plates over the entire top of the of each cylinder bank, secure this plate to the block with counter sunk or counter bored bolts that match the existing head bolt pattern then bore through the plate and install sleeves that include the plate thickness, then you can establish a new head bolt pattern into that plate which can be what ever you want. This would raise the deck height by what ever the plate thickness is but this looks like a "labor of love" project anyway so it is just a few more hours on the mill.

Again just "kibizing"!

Rex

Rex

[38flattie]

 
Rex, why do you always have to rain on my parade? Lol!
 
That's a great idea. I guess I was so blinded, thinking that we had to make this work with the existing bolt pattern, that I didn't consider anything else. I really like the second idea, of plating over the entire cylinder bank.
 
This would allow us to design the head for optimum performance, not optimum for what we have to work with. I passed this idea on to Mike, and we will discuss it further tonight or tomorrow.
 
In the mean time, please keep "kibizing"! It helps me immensely!
 

[Peter Jack]

It also allows for a longer rod which many feel is an advantage. (I agree.)

Pete

[desotoman]

Another thought would be to add a 1/2 to 3/4 plates over the entire top of the of each cylinder bank, secure this plate to the block with counter sunk or counter bored bolts that match the existing head bolt pattern then bore through the plate and install sleeves that include the plate thickness, then you can establish a new head bolt pattern into that plate which can be what ever you want. This would raise the deck height by what ever the plate thickness is but this looks like a "labor of love" project anyway so it is just a few more hours on the mill.

Again just "kibizing"!

Rex

Isn't there a rule against doing this type of thing? Something to the effect of deck height has to be within .150 of original deck height and original material. I could be wrong but I remember something to that effect in the rule book. Might want to check the intent of this rule.

Tom G.