SBC Iron Eagle Platinums combustion chambers

[modracer64]

The Iron Eagle Platinum editions come in 3 combustion chamber sizes - 49,64,72.

Is the difference between the 64cc and 49cc the shape or the depth of the combustion chambers?

Are they the same casting but machined differently to get the different combustion chamber sizes or are they completely different castings.

Thanks

D

[Awesome Bill]

Different casting, same valve placement and height, just a smaller combustion chamber. Works very well with large small blocks and flat tops or dish pistons.

[modracer64]

I ask because I just got my heads yesterday but when I pulled them out of the box to look at them the chambers look the same as the 64cc ones but I ordered 49cc ones. The box, as well as the numbers stamped on the ends of each head indicate they are the heads with 49cc chambers, but I was thinking they had a distinctly different shape than the 64cc chambers yet these look just like the 64's. I was thinking on the 49's that the intake valve side of the chamber on the side of the chamber next to the spark plug hole is noticably closed off and has noticably more material than the 64cc chambers. I also thought this difference in chamber shape was why an off the shelf domed piston can't be used with the 49cc versions.

I took them to my machinest and he said these new 49cc heads are basically the 64cc castings but factory milled to get the 49cc chamber. He also said thats why the 49cc versions start having issues with valve to piston clearance with big lift roller cams. He also said you can use an off the shelf domed piston if you wanted to just not a big domed piston.

Thanks

D

[want-a-be]

The pistons I posted a pic of in the tech section started off as .163 domes. Depending on your deck height and other compression dependent numbers. You can get up to about 16-1 pretty easy with that.

Without truely knowing myself. I'd say they are not getting the 49cc by decking. Looks like too much room between the deck and the valve seat. To me it looks like they filled in around the spark plug bridge some to lower the cc on the chambers. Might be wrong about that though.

There are alot of things that will effect piston to vlave clearence. Type of cam and how it's ground, and the quality of your pistons are the main things. Of course the lift of your cam has just a lil to do with it...lol. The cam I'm using on those pistons and the 49cc heads is a .680 lift roller. So I guess I'll be putting the "supposed" piston to valve problem with these heads to the test pretty soon.

LAter, Don :cool:

[modracer64]

Yeah the problem I'm having is I can't tell just by looking without another head to compare to if it actually is a 49cc chamber or a 64cc chamber. There are just no pictures I've seen of each one to tell the difference by looking at mine alone. I guess I will have to cc the chamber to verify it.....I'm not a professional engine builder so I wasn't planning on doing that step. However, in order to get the compression I want without having interference problems with the piston tops I'm going to have to check it so I get the right pistons.

[want-a-be]

Only way to truely know the CCs of the heads is ccing them. Even a beaker type will do.

Later, Don :cool:

[Awesome Bill]

the whole reason for 49 cc heads is to raise or keep the compression up and use flat top or dome pistons. We use no domed pistons with 49 cc heads with our 406 right up to 499" sbc engines. Most 434 engines with 60cc combustion chambers, .005 deck and 10cc gasket puts us over 15:1 with a 10cc Wiseco piston. So thats why we use the flat tops with NOS engines and we normally start with a lot less compression. The 49cc heads work very well with larger flat top engines and wanting to keep the compression over 12/1. Even with an old 350, the compression is a huge gain when not wanting to change out pistons and get more power. It will raise the compression with a flat top piston to about 11/1. A cheap engine for just putting heads on. Watch the tight lobe seps with the larger sbcs, this puts the piston to valve closer than anything. Of course, if your running enough duration to hit, your running the wrong camshaft to start with. That is of course, is your using a quality piston and they have placed the valve reliefs in the correct locations.

[modracer64]

Most 434 engines with 60cc combustion chambers, .005 deck and 10cc gasket puts us over 15:1 with a 10cc Wiseco piston.

So, if my calculations are correct you are running in the neighborhood of .050 piston to head clearance??

Do you ever run it tighter than that?

D

[want-a-be]

For steel rods you can go as low as .045" add at least .010" to that for the aluminum rods.

Later, Don :cool:

[Awesome Bill]

we run it usually @ .035 / .040 for steel rods and .050 / .060 for aluminum naturally aspirated only.

[want-a-be]

A tight quench area is pretty important imo.

Thanks, Don :cool:

[Awesome Bill]

But, usually that comes with shrouding of some type if the valve pockets are the same depth. These are not pro stock shallow chambers. Ofcourse, we can cut those pockets and open up the valve a little easier. I think everyone agrees a tight quench area promotes good power naturally aspirated only and its even better with the shallow 30-40 combustion chambers and a huge bore. Smaller bore and deep chambers, it does get the compression up and usually makes more power.