nm9stheham
Well-Known Member
I think I know the answer.... but thought I'd ask. Any aluminum heads out there with 1.92" intake valves? The reason is to to put a set on a slightly bored 273 block, and the 2.02" valves may require too much notching.
Small Valve AL Heads
- Thread starter nm9stheham
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2.02’s will not fit and according to the published MP books, a 1.88 needs a cylinder wall notch. Off hand, I do not know of an aluminum head that has a 1.92 capability but there is an iron head like that. But IIRC, in a Magnum style head.
You do need smaller valves but I think it's more a combustion chamber size issue. It would be better to modify 273 heads. The chambers match the bore. If I ever pull these heads I will have them flowed. Just curious.
![041600951718[01].jpg](https://www.forabodiesonly.com/mopar/attachments/041600951718-01-jpg.1715247500/ "041600951718[01].jpg")
![041600951719[00].jpg](https://www.forabodiesonly.com/mopar/attachments/041600951719-00-jpg.1715247501/ "041600951719[00].jpg")
nm9stheham
Well-Known Member
Hey, TMM, I don't think that is any big issue.... the 675 heads that came on this 2 BBL 273 are over 3.8" chamber diameter, and reach 3.9" at the little 'cove' beside the exhaust valve. Did you get a measurement across the chamber?
Now if those 920 heads have the valve center lines set a little closer together, that might be an advantage. Can you put 1.88" valves in the 920's?
Now if those 920 heads have the valve center lines set a little closer together, that might be an advantage. Can you put 1.88" valves in the 920's?
I have a pair of 920 is upstairs in the garage but I won't be able to get to him until after lunch should be no reason why you couldn't put a little bit bigger valve in the 273 heads. They come with 180s and 188 is only .008 bigger and that's not much. Didn't they used to use an old 392 Hemi valve in those heads?
I think you are correct about that.....it was something I read long ago and don't remember "where" it was that I read it.......kinda makes sense as hot rodders will use anything that is available and inexpensive
How about 2"? I don't know if these would work but just thinking. Stainless Steel 392 Hemi Intake Valves
nm9stheham
Well-Known Member
Many thanks. If you could check the valve centerline distance too, that would be very much appreciated.
Will do.
nm9stheham
Well-Known Member
I got 1.865" centerline distance between valves on the 675 heads. (Measured outside to outside across 4 valve pairs on one head, averaged, and subtracted .375" stem diameter.) With 1.78" and 1.6" valves, that works out to 3.535" outside edge to outside edge on the valve heads..... juuuuust will fit into a 273 bore LOL!
I am beginning to think this is just old 318-Poly design dimensions that were fudged onto the 273.
I am also starting to think that some like the Edelbrock Performer head will have no more than about 3.8" outside-to-outside edge on the valves. This is because it is advertised to go on a 318 block, plus studying detailed pix on their website.
I am beginning to think this is just old 318-Poly design dimensions that were fudged onto the 273.
I am also starting to think that some like the Edelbrock Performer head will have no more than about 3.8" outside-to-outside edge on the valves. This is because it is advertised to go on a 318 block, plus studying detailed pix on their website.
Here's a thought, runs contrary to most common thinking.......off set the guide and push the intake towards the exhaust............otherwise, notch the bores for valve clearance and push as much dome into the chamber that you can to compensate for the increase in volume due to the notches
Edelbrock w/2.08/1.60 valves. This is as close as I could get with what I had on hand.
Edited post for Accuracy, and I know the above picture looks wacked and ill measured. But that’s what I came up with. It is not a Guaranteed 100% accurate measurement but I tried.
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Here's the 920 heads. I will get some measurements later.
nm9stheham
Well-Known Member
Thanks Rob... that is actually not looking all that bad...boy, there ain't much gap between intake and exhaust with that larger valve! I am sure there will be some bore offset versus valve positions to deal with.... but the notching option is not looking awful. (Famous last words....)
And I appreciate the ideas JB. The block wall thicknesses came out pretty even all around for this particular 273 block, and after a .027" bore, the thinnest spot on the pin axis would be around .150"....so some offset might be possible.
I am not a machinist so don't know how easy/hard offsetting the valve guides would be. I assume the seats would follow the guide locations more easily. I have plenty of compression to afford 1-2 cc's in notching.
@nm9stheham , the 920 chambers are 3.836 at the widest point. The valve center was 1.869 or close to it. The 920's are slightly larger than the 273 3.63 bore and slightly smaller than the 318's 3.91 bore. It looks like a +.030 273 would be perfect. My 273 is right there.
skrews
Well-Known Member
I don't think the valve spacing is different on any LA head, just the valve diameters.
nm9stheham
Well-Known Member
Tnx very much TMM! I really appreciate it.
Looks like the valve centerlines are the same as I got on the 675's so no help there. Yes, there still looks to be some chamber overhang on a 273..... 3.655" (a .030" overbore) is around .180" smaller than the 920 chamber diameter.
nm9stheham
Well-Known Member
It's looking that way.
Well, I just did not have the parts on hand to do direct measurements to see what is what, particularly for something with a 2.02" valve. I could look at the Edelbrock detailed pix and estimate from that, but you know what kind of trouble that can bring. At this point, with the info presented, I am inclined to go with them, fit things up, and notch.
Some nicely ported 920's would make life easier.....
nm9stheham
Well-Known Member
Hey Rob, if you get a dull moment and don't mind another favor.... if you drew an imaginary line across the centers of the valve faces, over to the far edge of the intake (right under where your caliper tip is resting), how deep is that valve edge below the head surface? I am just trying to get an estimate on how deep a notch might be needed; gotta keep the notch in the 'meat' of the deck, and above the top ring.
I'll get you after Church and dinner tonight. I also thinkI have to do that measurement again via looking at my picture. It looks screwy.
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