Before starting the first machining operation on my production intake adapters, this morning I finished up "experimenting" with one of the adapters to make the Yates style intake manifolds work. I have not yet done any port programs for these intakes; I wanted to just cut the flanges of the adapter to see how they would fit, and get an idea of where the port location was. I had to take about .500" off the intake flange surface of my intake adapter to make the 2991 Edelbrock manifold fit. Here's a couple of photos of the manifold sitting on the adapter:
One issue that presents itself with these manifolds is that with the reduced thickness of the adapter, counterboring for the bolts in the adapter that bolt into the FE heads has to be increased, and the adapter can get a little thin in this area. I think I will have to supply special bolts, with reduced thickness heads, for intakes that are machined for these manifolds. With those bolts I can counterbore less. Also, the angle of the 1, 4, 5, and 8 ports in the adapter have to increase somewhat with the reduced thickness. FE cylinders are on a 4.63" center, and 351C cylinders are on a 4.40" center, so the outboard ports in the adapter have to be angled to match the FE head port up with the 351C head port. This is especially pronounced on ports 1 and 8. When you reduce the thickness of the adapter, the angles of the ports in the adapter get bigger. I'm going to be able to compensate for that somewhat, by reducing the width of the pushrod holes and sneaking the port a little closer to the pushrods, but there will still be more of an angle there than there is with the standard 351C intakes. Hopefully that will be more than compensated for by the improved performance of the Yates style manifolds; we will see at dyno time.
After the Edelbrock 2991 intake I worked to fit up the 2865 intake. This one was more of a challenge. Just plunking it on top of one of the standard intake adapter, it was way, way too high. I ended up machining my test adapter another .250" on the manifold surfaces to improve the fit of the 2865 intake. That was as far as I wanted to go with machining the adapter surfaces, but the manifold still didn't fit correctly. However, this intake has a very, very thick flange, just over .800" thick. The 2991 intake, like most others, has a 0.500" thick flange. After machining the adapter and test fitting the 2865 intake, it turned out that I can machine .300" off the 2865 intake's flange, and it will fit just about right on the adapter. So, if someone wants to run the 2865 intake, there will be some custom machining to the intake required, but I can certainly handle that if necessary. Here are a couple of shots of the 2865 intake sitting on the adapter; the flange of the intake has not yet been machined:
Developing the port programs for these two intakes will take some time, but I have a few weeks here before I have to worry about that, while all the castings get run through the first machining operation. Lots still to do...
