The Stovebolt Site Forums The Shop Area The HiPo Shop Oversize stovebolt intake valves- - - - -

Back in the "days of old when knights were bold"- - - - -Chevy spray-oiler 235 engines used with Powerglide transmissions had bigger than standard intake valves- - - -1.94" in diameter. Those valves can be fitted to other stovebolt heads with a little creative machining, assuming one can find a source for them. They're getting pretty hard to find, and E$$$PENSIVE, since the last engines to use them were produced in 1953.

However- - - - -there's a work-around available. There's a high performance exhaust valve made for Chevy big block V8s that has almost identical dimensions- - - -head diameter, stem diameter, and stem length. Using an exhaust valve in an intake application isn't a problem- - - - -just don't try to use intakes for exhaust valves- - - -they'll burn out quickly. The only big difference is the location of the keeper groove, and it's a very simple lathe operation to add a groove at the right place. The part is a Manley brand #11583-1, and Summit racing has them, priced at about $38.00 apiece. Not everybody's cup of tea, I'm sure, but this is just another example of being able to use a non-standard part to duplicate something that's getting hard to find!
Jerry

I had one those 235’s with the Powerglide. Mine was a 1950 that came out of a car. The transmission I sold about 4 years ago and the complete 235 was purchased along with other parts just last year.

John

It's interesting to note that the bigger valves only had a limited run of about 3-4 years. Maybe the engineers figured out that the convoluted gas flow of the stovebolt head just couldn't benefit from a slightly larger valve size, or possibly the parts department logistics of supporting two different valve sizes was just not practical? Other modifications such as reshaping ports and increasing the efficiency of the exhaust side of the equation will probably be needed to fully realize the supposed improvement. It's also possible that the only measurable power gain happened at RPM ranges the average street driven engine rarely, if ever ran.
Jerry

I have purchased 2 sets of NOS 1.94" intake valves off Ebay in the past few months. I paid $98.00 for one set and $112.00 for the second, both were free shipping. The NOS stuff is still out there, you just have to find it.
Jerry, that's a good tip on using the BBC exhaust valve. Would it be possible to share a picture of a modified valve?

I have one on order. I'll do a photo shoot of the lathe setup and the groove-cutting procedure soon. The valve I listed is not a standard BBC exhaust valve, and it has a 45 degree face angle instead of the 30 degree angle used on the stovebolt valve. It would probably be simpler to change the seat angle of the stovebolt head instead of trying to modify the valve face. That 30 degree angle was another one of those "over-engineered" features of stovebolts- - - -not really necessary for practical use.
Jerry

The single valve I ordered arrived yesterday. I don't have the holding fixture for my lathe made yet, but the only difference I can measure (other than the head diameter) is the position of the keeper groove. The big block valve has a groove 1/4" from the top of the stem, while the stovebolt valve has a groove that's 3/4" from the top. A simple plunge cut the right depth with the proper shape and width of tool bit will duplicate the stovebolt valve. I'll be using these valves, along with the 1.6" diameter stainless small block V8 exhaust valves, on the 300+ cubic inch "261" that's on the drawing board. That's the one with the three side draft Harley Davidson carburetors.
Jerry

Pardon the simplistic question, but couldn't you also just use taller springs to match the new valve's higher lock? Or maybe shims below the regular ones? Either way, great way to work around ancient, no longer available parts!

I'd need to make spacers 1/2" tall to make up for the different keeper groove position. That would look pretty oddball, even if I'm the only one who knows it's there under the valve cover. Making another keeper groove is "Machining 101" once the holding fixture for the lathe chuck is made, and the process will be exactly the same for all the valves. For reference- - - -the Chevy OEM valve with the 1.94" diameter and a 30 degree seat angle part number is 3835519.
Jerry

Right on. Spoken like a gentleman with easy access to a lathe :-D I'd have to do the spacers because I can make those, but lack the machine tools to do the valves.

The same process could be done with a drill press and a needle file, or even a hand drill motor clamped into a vise, and some very careful measuring and sneaking up on the final dimensions. Do a little research on what custom gunsmiths in the 18th Century could do with nothing but a forge and some hand tools, and maybe an apprentice or two to turn a hand-cranked drill press!
Jerry

Oh, I've done some interesting things with just a hand drill. I've had to make missing and unavailable mountain bike hub parts. Thankfully some of the dimensions are such that you can start with a taken apart cartridge bearing or two, then do a bit of creative welding and grinding.

My neighbor has a lathe, though I think it was meant mostly for wood. I've used it to turn larger items like oddball bottom bracket axles that you can't get, or eBay seller thinks it's made out of platinum. It's a hundred years old, so it won't me machining new pistons or anything, but it's adequate for bicycle parts and can chuck up larger pieces, probably a 2" chuck at least (I never measured it).

I have used a Brake lathe for some "creative" machining, I believe I could do a valve stem on it.

I have a PM 12" X 36" lathe with DRO. It's the best tool I have ever owned. I live in the "one off" world and it has paid for itself many times over. If I need an oddball bolt I just grab a piece of hex rod and whip it out. I have a medium sized mill. I'm not fast or trained but I can get some stuff made.