Bigger valves?

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Bigger valves?

Post by blgitn » Thu Jun 06, 2019 10:11 pm

Has anyone put bigger valves in a Model T block? How big can you go? Are there any articles on it out there?

Tim Williams
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Re: Bigger valves?

Post by Tim Williams » Thu Jun 06, 2019 10:48 pm

I know of one T engine with 289 valves in it.

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Re: Bigger valves?

Post by gelfling » Fri Jun 07, 2019 12:57 am

I discovered that my '12 roadster has larger intake valves when I did a valve job. They are shortened Fordson tractor valves. Replaced the burned
stock T exhaust valves, but kept the intakes as they looked real good. Not sure if there is enough room for the same size exhaust valve.

Kevin Pharis
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Re: Bigger valves?

Post by Kevin Pharis » Fri Jun 07, 2019 1:51 am

I went 1.720 intake valves in my speedster, and 1.600 exhaust. Go in the block just fine... takes a bit of head and gasket clearance work to get it all to work tho. Chebby S/B aftermarket exhaust valves are almost a direct replacement, and come in a variety of sizes, finishes, and materials. Mine happened to be Manley brand, tulip polished, chrome stem, and stelite tipped.

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Re: Bigger valves?

Post by Kerry » Fri Jun 07, 2019 3:28 am

2 problems I've come across over the years with, 'for the big valve fit'
seats 011.JPG
seats 011.JPG (30.28 KiB) Viewed 1947 times
are hitting the gasket and this one a few times.
The block will or can warp away from the valve seat from heat on the exhaust.

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Re: Bigger valves?

Post by Wayne Sheldon » Fri Jun 07, 2019 4:50 am

Fun stuff. There were a couple of articles published "back in the day" that were reprinted in one or both (I forget?) of the two books ( "Model T Ford in Speed and Sport" and the old "Fast Ford Handbook" , since re-titled). In it, Murray Fahnestock tells how to adapt four cylinder Dodge valves into a Ford racing engine. Years ago, I had one such engine. It was an original era built modified block racing engine, and the remaining valves in it exactly matched the valves in the Fahnestock article. Eventually, I used the engine along with a bunch of other original era speedster parts I had collected, and put together a decent racing car (wish I still had it).
Those valves were about as large as could be used in a T block. The edge of the valve was right at the edge of the cylinder. The block still had a standard bore, and I don't think going even .020 oversize would still allow the valve to fully seat. The valve ports were ground out so large, the intake ovaled almost to square. The exhaust still round, but both intake and exhaust were up to thin on top, and taken down as much as they were taken up. The problem was, Whoever did the work, went a bit too far. One of the exhaust ports was too thin inside, and cracked into the water jacket. They did a hokey patch, and eventually used the engine as modified to an air compressor with the cracked area blocked completely off. It had been a new replacement engine, with a very late 1927 serial number. With virtually no miles on it, I figure they wanted to get some sort of use out of it. At least it was kept around long enough to reach me.
When it was acquired by some friends of friends, it was just an empty block with a bunch of lead in a couple exhaust ports and a few valves left in place. Nobody really wanted to try to run the thing, and eventually I bought it. I figured this thing NEEDED to be made to run again, even if only for a little while. Besides, I wanted to hear this thing RUN! So, I cleaned it up. Removed the lead, and studied the damage. I figured it was not a good candidate for welding. Too much thin area. However, a modern patch on the water jacket side would stay cool enough to probably hold up for some amount of time.
Since I have always needed to work on a tight budget, I fit a good crank, rods and cast iron pistons into the block. I had to peel open a copper/asbestos head gasket, carefully trim the asbestos and re-roll the copper back into place. This on two sides of each of the eight valves. I also had to grind space into the standard T cast iron head for the valves to clear. Onto this, I installed a '20s midsize Carter updraft carburetor.
So. How did this stock head cast iron piston big valve engine run? Just to see whether it could do it or not? I "spun a donut" on dry pavement in that car. It is the only time in my life I ever tried that, and it DID IT! I have never driven or ridden in any other car that handled mountain curves and climbs like that car did. I do know, a well sorted Rajo or Frontenac would be able to outrun or outperform it. However, I passed several OHV Ts going uphill on the several Endurance Runs I drove it on. I don't know if it was luck? Or, maybe my careful attention to the tasks of trimming the head gasket just worked out well. But I never needed to pull the head the whole time I ran that car. And the patch was still holding just fine. Eventually, the demands of a needy family forced the car to be sold. I did hear through the grapevine a few years later that it was still running well.

I think I found some modern Chevrolet V8 valves that fit well in place of the original Dodge valves. I still hope to modify a T block and try to run something similar again. Only, I think I won't grind it out quite as big as that one was done. I do have four old Fordson valves that the stems fit a standard T block. But the head is only slightly smaller than those Dodge valves were. I think those on the intake only should work quite fine!

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Re: Bigger valves?

Post by blgitn » Sun Jun 09, 2019 9:34 am

Thanks for the pointers! I have those books around here somewhere; I need to dig them out.

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Re: Bigger valves?

Post by Les Schubert » Sun Jun 09, 2019 2:28 pm

Following the logic of the era speed books, I have installed Fordson tractor valves as intakes and kept the stock size exhaust valves. One of the issues with the intakes is that the stock gasket is very close or interferes. I have used one of my “special “ copper shim head gaskets and a Prus head. The bottom end is a pressure oiled Crower crank and a 280 cam

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Re: Bigger valves?

Post by Erik Barrett » Sun Jun 09, 2019 5:12 pm

We use 351 Windsor Ford V8 exhaust valves, 1970 vintage with great success. They are large enough to put in without having to replace worn out valve seats but not so large they get into the head gasket. They have to be shortened a bit and you can ream out your worn out valve guides to 11/32”.

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