1.73" intakes with a Burtz 6.5 head

[AL in NY]

Has anyone had to modify their Burtz 6.5 head when installing on an engine with 1.73" intake valves? I don't want to order a Burtz 6.5 head and find out it won't work on my engine(a factory Ford Model A block).

[Jim Brierley]

It should, with no problem?

[Dodge]

You have to flycut the valve pockets in the head. The Valves hit by about .080
Same thing with a Snyder or Brum
field head.

[AL in NY]

I have a Brumfield 5.9 head and the larger intake valves do not hit the combustion chamber roof.

[CHARLIE YAPP]

Generally, the 1.73" valves fit Ford manufactured Model A and B cylinder heads. They did not fit my earliest Lion Speed heads and those would require milling treatment for oversized valve heads.

The larger valve heads DO work for better intake breathing on a 200 to 213 ci Banger. The stock valve head of 1.5" at the exhaust is perfect for all uses. Using bigger exh. valves may not do any harm, but the normal exhaust forces do most of the work and a larger valve is over kill.

Stock A and B Ford heads should be OK. I have not had a Burtz head to play with so, for me, that is an unknown right now. Terry Burtz did change the 8 ports in his blocks to improve flow. Larger intake valves will improve on that.

The thing is this. . . . Not knowing for sure is the builder's problem. It doesn't take long to test fit any & all types of heads and spin the crank 4 times to check valve to wall clearances. Put 4 studs in place with a gasket and leave the head lose for a slow and careful spin. Look for metal to metal contact.

The best evidence is to add some lightly oiled clay or "Play-Doe" around the valve's suspect areas. Put your hand on top of the head to sense movement. Gently remove the head and measure.

This also a good time to die-grind a little concave curve into the vertical walls around the valve heads to improve flow (so called shrouding) . . . The Lion I, II, III, IV and the "Rocket 428" have plenty of room for machining and or an 1/8" deep curve. Other heads? Who knows? So don't go nuts.

[Gene F]

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Post #4 - ditto
AND I have the IB-330 cam

[Dodge]

The Brumfield head we had was a 7-1, thats probably why they hit.

But I did just mock up a Burtz Head and they do hit. Using the Burtz ca.

[SAJ]

Dave Mossman in my workshop found the same thing. He had half a dozen Burtz heads milled straight down at the interference point with a 2 inch milling cutter. Terry commented that the water jacket at the interference point is 1/4 inch thick. Dave had about 2 mm taken off but just told me 1.5 mm would be sufficient.
I think a scooped shape using a die grinder would work better by leaving a wider gasket surface, but I don't have a Burtz head in front of me, so maybe I am envisaging it incorrectly!
I am leaving my 2 Burtz block standard, since the port shape looks good for a road car and B carb etc, but some pf Dave's customers are petrol heads and speed merchants with more modified engines.
SAJ in NZ

[AL in NY]

Thanks for all the reply's, I don't want to have to modify the Burtz 6.5, so I'll stay with the Brumfield 5.9.............

[Johan Ottosen]

I have had to modify my new Burtz 6.5 head, on a freshly decked block with new 1,73" valves, IB 330 cam. The engine runs fantastic.
I placed modeling clay in the head, and - over several cycles - lowered the head, without the head gasket - with valves and studs in place, onto the engine. It left an imprint for me to know where I should dremmel the cast iron. At first I used pieces of cardboard in between the head and block, so the valves did not touch and bend. It took a couple of days to do, but man it runs good.