Larger valves installed in the more common small valve heads.
NOTE: Guys, please be aware I did not invent this mod. The first I heard about this was in Bill Fishers book "How to Hotrod Corvair Engines" back in the mid 70's. I could not afford a set of 140 heads back then so I added the bigger valves Bill Thomas had installed in his performance heads in the 1960's. This idea faded with the release of the 140 heads. I'm just providing a performance mod for guys that don't want to mess with 4 carburators, dual exhaust, having to locate 140 sheetmetal, etc. This is an awesome upgrade for the person who needs to have their heads rebuilt. The great thing is the engine will retain a totally stock look but be much more enjoyable to drive.
Now you can have much better low and mid range power while using the more common small valve heads. High performance small valve heads include our welded (step removed) combustion chambers, bigger high press valve seats, new bronze guides, larger stainless exhaust and steel intake valves with hard chromed stems, new valve keepers. I also remove cooling fin flash.
The chambers are welded in the step area and fly cut back to the stock location there by keeping the pushrod geometry unchanged. Valve seats are installed with a .008" to .010" interference fit. The hard chromed valves are compatible with the bronze guides. Valve cover surface milled.
Heads can be built on 80hp, 95hp, 98hp, 102hp, 110hp and turbo heads. Turbo heads are not welded in the squish area. Contact me for info. Rebuildable cores needed.
Several options are available:
An extra carburetor mounting pad fit in the same location as on the 140 hp. heads, Install 140 exhaust tubes, Angle port exhaust, Intake manifolds removed and IR intakes welded (to adapt 3bbl Webers or EFI, etc.) Fly cut to fit big bore P&C sets such as 92mm or 94mm VW P&C's, Fly cut to increase compression, CC combustion chambers, Apply thermal barrier coatings
Typical horse power gains from the basic big valve heads is approx. 20 hp. I will be verifying this figure on a chassis dyno soon.
These heads will not make the same hp in the higher RPM's as the 140 heads but will make more torque in the lower RPM's (where most of us run our engines). They are exceptional on a stock street engine. Carb jetting may require a step or 2 size increase.
Pricing for these heads, ready to install is $1200.00 pr. plus shipping/handling.
10.03.2009
Flow Data:
Here is the data on a stock 110 head. I tested the flow on the center cylinder and had installed intake valves in the outer cylinders to prevent false air from being drawn in. All the air flowing through the port came through the carb mounting hole. Note the low CFM numbers compared to the race head above.
z 28.4 40.9 40.6 < MARK 0.10 21.3 71.3 70.8 < MARK 0.20 18.7 83.4 82.8 < MARK 0.30 17.4 90.1 89.4 < MARK 0.40 16.9 93.4 92.7 < MARK 0.50
Here is the data from my big valve conversion head. The numbers look wimpy. I still need to dyno this set-up. My Monza with the big valve heads feels a lot better than a 4 to 5 CFM flow increase can give. I think.
z 28.1 45.8 45.4 < MARK 0.10 20.6 74.7 74.1 < MARK 0.20 17.8 87.8 87.2 < MARK 0.30 16.8 93.9 93.2 < MARK 0.40 16.5 96.0 95.3 < MARK 0.50
I did not run the test past the 1/2" valve lift. Not many people run cams this radical on a 110 engine. Just interesting data.
