'73 Vega GT All Aluminum Wildcat 355 Project

Contents:
Page 1: Engine Block prep
Page 2: Head mods
Page 3: Induction
Page 4: Engine Assembly
Page 5: Front Suspension Mods
Page 6: Rear Suspension/Weight Transfer Mods
Page 7: Rust Repair and Undercarriage prep
Page 8: Frame Rail fabrication/Unibody support
Page 9: Body Mods
Page 10: Transmission Mods
Page 11: BMW Radiator Swap

Buick 300 head modification for larger valves
Here's some pix of the exhaust valves I'm using. They are exhaust valves for the VW1600 Type IV.

You can see the refined tulip shape. This shape is condusive to better flow in the exhaust side.
Here's the pix of the intake valves.
They are from the "Iron Duke" Pontiac 2.5L 4. You can see that the tulip shape is not used here. Later valve developement discovered that reducing the profile actually increases the flow characteristics of an intake valve. This is because the direction of flow over the valve head is not straight down. It actually flows laterally accross the backside so reducing the profile makes sure there is less obstruction for incoming gases.

This is shots of the finished installed valves:

You can see the difference in height of the valve collets makes the spring retainers sit at different heights. I had my machine shop double check for spring height based on my cam specs. They had to shim up the exhaust side a little to make up the difference in retainer height. The valve guides also needed to be sleeved for the smaller diameter valve stems (7mm).

Here's a couple of quick pix of the mild porting job I had done.

The next thing I'm in the middle of researching is how to adapt stock Volvo B16 rocker arms to the 300 heads. We have all heard that racing teams in the 80's often did this modification so they could still comply to the racing rules and still have adjustable valve trains.

I ended up with a nice set of roller rockers from Harland Sharp They aren't listed on their website but they will make them. You just need to call and ask for them. I got them for $400. Pretty good deal for my engine choice. They do require new pushrods though. These take ball lifter ends and cupped rocker ends. You can order them from a custom pushrod maker. I have a contact and I'll post it when I have the info in front of me.

This is an excerpt from an online article written by Dan LaGrou, owner of D&D fabrications, where I got the idea:

HEADS
When Buick introduced the 300 cubic inch V-8 in 1964,
aluminum heads helped keep the weight of the new cast-iron
block engine down. But because of the higher cost of aluminum
casting vs. cast-iron, these heads were only offered on the '64
engine. The 1965 - 67 300 sported conventional iron heads. The
aluminum heads weigh only 18.5 lbs. each, complete with
valves, springs and retainers (vs. Rover's 20.0 lb.) and hold
somewhat small valves at 1.625" intake and 1.313" exhaust.
The advantages of the 300 heads for the stroker motor
are numerous. First is obviously the light weight. Secondly, the
combustion chambers are dimensioned for the 300's 3.750" bore
which works nicely to that of the Rover, particularly after the
Rover bore is taken out to 3.710". The 54cc combustion
chamber, using a .050" thick composite Rover head gasket, will
yield a 10.4:1 compression ratio. Because aluminum heads
dissipate heat quickly, they can tolerate higher compression
ratioswithout detonation.

The stock 300 heads will not breath sufficient air and
fuel to keep up with the demands of the stroker engine. Dan's
recipe calls for larger valves, mild porting and a few other tweaks
to bring the heads up to the performance levels we are seeking.
The intake valve is replaced with a 1.720" diameter piece from
the 1988 - 92 Pontiac "Iron Duke" 151ci 4-cylinder engine
(Federal Mogul p/n V2530). The 300 head's exhaust is opened up
using Manley P/N11659-4 Volkswagen 38mm (1.496) (updated part #) stainless
steel intake valves.The larger valves will require new seats, such
as Precision PC1500-31 (exhaust) and PC1750-39 (intake),
which any competent machine shop can easily install, and the
new valves and seats get a three-angle grind. The machine shop
will also grind the valve lengths to match the Buick 300 stock
length.
The guides on the 300 heads are undoubtedly worn and
the new valves stem diameters differ from the stock 300's, so the
guides must be sleeved. One guide liner option is Ohio P/N
6896H. At the same time, have the machinist cut the tops of the
valve guides and install a Perfect Circle style valve stem seal on
the intakes only.
Pockets should be opened up to match the valve seat diameters.
The face of the boss supporting the valve guide is smoothed and
shaped to minimize airflow restriction and the length of the
guide cut down. Shave the gasket side of the head to insure a
flat surface for sealing with the block.

VALVETRAIN
Use stock Buick 215 or Rover pushrods and rockers,
along with Crane 99849 small block Chevy springs. Hold the
valves in place with stock VW(Sealed Power P/NVK204) and
Pontiac (Sealed Power P/N216) keepers meshed with '87-'91
GM P/N 10040230 2.5L retainers. Either Buick 215 or Rover
lifters willwork.

More to come

I forgot to add my CAM specs. On the advice from D&D I went with their favorite cam profile from Bruce Crower:

Cam is a Crower 50232 with an intake lift of 0.488", an exhaust lift of 0.490", Duration 276º, Duration at 0.05": intake 214 degrees, exhaust 218 degrees. Lobe separation angle: 112 degrees.

I'll add a pic when I get it.