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Going to do a winter rebuild on my 235 and wondering about valve sizes and where to get them from. Want to build a strong street motor. Any other "Bolter" tips appreciated. Already have two carbs and Fentons installed.

I think you're the first person to ask about different valve sizes for the 235! This isn't a common upgrade for these engines - for most questions asked about how to get a high performance out of a 235, the answer is: replace with a 250 or 292.

That doesn't mean it's not impossible. I would say your best bet would be to find a competent local machine shop and take the head and valves in and ask what they can do, and how much it would cost. You should be able to find stock parts, but it will cost some extra in labor.

It's possible the shop will be able to find a larger valve with the same length and stem, and machine a larger seat into the head. Maybe the 250 valves are a good match, I really don't know. They can flip through their books and find a match.

The most limiting factor will probably be the distance between the intake and exhaust seats. For my Austin-Healey they make special "figure 8" valve seats to help prevent the seats falling out when they're too close. [You never know, the Healey engine is pretty close in size and displacement to a 250, that actually might be a source of parts. ]

You might want to consider just enlarging the exhaust for best perf increase. They probably need new seats anyway. Can probably do that without worrying about the seats falling out.

How large of valves will probably depend on the head, so it might be interesting to find an old "dead" 235 head, saw it in pieces, and see how much room you really have to work with before you breach the water jacket.

There shouldn't be a problem with piston-to-valve clearance, should be no different than a stock valve due to the vertical operation so have them grind up a custom cam to your specs depending on what you want. More torque, more HP, etc. Maybe they have an off the shelf 235 cam that meets your needs == less money.

Don't forget to port and polish to really take advantage of those new larger valves.

Do this BEFORE the new seats are installed, but after the seat machining. Or have the shop do this. Really easy to get carried away and nick the seat surface. Not fun to pay for the valve job twice...

-Boyo

I've built a few hot 235s, and here are my obervations from doing it:

The main problem with 235 port flow is the fact that the ports are siamesed. The adjacent cylinders share intake ports, and the #1 and #6 cylinders have their own exhaust ports. 2-5 use siamesed exhaust ports. Bigger valves aren't needed on a 235, cuz the bottom end will redline before it runs out of breath. 235 valves are only slightly smaller than some OHV V8 valves I've seen. Porting, polishing and bowl blending on the head ports shows some marginal improvements. Cutting the head about .040" and using the victor/reinz gasket will bump up the CR too. Have the block zero-decked and the rotating assy balanced. Cutting the main journals .030" and radius-ing the journal fillets will reduce bearing speed and help prolong main bearing life. But the crank is prone to flexing at high RPM due to only 4 main bearings. The later 230-292 engines had 7 mains for better crank support.

Clifford made a 260M mechanical cam thats pretty radical, pulls hard from 1,800 to 5,000 RPM with a rumpy idle. Use with dual-wound valvesprings and comp retainers and locks. Make sure to install new guides and umbrella seals. But you don't wanna twist a 235 past 4 grand anyway or you're risking a failure. Use recon connecting rods with new bolts.

Badger cast pistons and plasma-moly or iron rings are good for a street motor. The total-seal plasma rings seal off great, but WILL pull oil thru valve guides if everything isn't new.

The best performance induction setup is a single 390 CFM holley 4160 4bbl with 58 primary jets on a clifford single-plane intake. Dual-carbs work well too, but you'll be tuning some strange idle and part-throttle probs due to lower vacuum readings. Fenton headers with 2" duals and smittys sounds really good.

Ign is best done with a petronix conversion kit in a stock distributor. Use one light and one medium spring from a moroso advance curve kit. Put a piece of 14 gauge wire in the vac advance mechanim to limit total vac advance. Set base timing for 12 to 15 degrees BTDC.

Total cost is around 3 grand for a whopping 160 HP. Low-end torque for days... WHOOO!

chip

In addition to what Chip said, the 235 types use an exhaust valve identical to the 1.50 valve used on lower performance Chevy small block V-8's, a bigger 1.60 valve is available. The intakes have a longer stem, untique to the 235/261, perhaps a valve from another engine can be machined to match ?Larger valves will certainly help upper rpm power if the engine can use the extra breathing, but will generally reduce low speed power where a street engine operates 95% of the time. Like said above, this is an antique design never intended for high performance work, limited by poor breathing.But it is fun to build them anyway,just keep the limitations in mind and they will blow off Flattie Fomoco V-8's, so all is not doom and gloom.

Yeah, so if you ever reach 88 MPH and go back in time, you'll rule the street in 1953.

*sings* Go, go, go greased lightning.....

I have bought 1.5 Manley race-flo valves for a 235 thru Northern Autoparts 1.800.831.0884.