While waiting for the manifold castings to be finished up I've been working on a couple of different variations of this intake, for certain manifold applications. I have one customer who has a race engine with the water lines coming out of the front of the cylinder head on each side. He contacted me about getting a version of the intake adapter with the thermostat housing machined off, to give him more room at the front of the manifold.
This was something I'd already been thinking about, in preparation for the dyno testing I'm planning on doing on the adapter over the winter. There are a whole bunch of 351C intakes that I could test, and I'm sure not going to be buying one of every type, so I'm hoping to be able to borrow the manifolds for testing from various people. I've already gotten some offers on that, which is great. The problem is, to make the 351C intakes work on my adapter, they have to be machined to fit. However, if I cut the water jacket off the front of the manifold, welded up the holes, and then ran some AN fittings out of the front of the intake adapter casting to get the water out of the engine, then the 351C manifolds would fit without interference, and I could test them on the dyno without modifying them at all.
I also have in my possession at the moment a CHI 3V intake for the 351C. This intake is designed for use with the CHI cylinder heads, which are known to be really good units; I believe they won an Engine Masters contest at least once a few years back. Dave McClain was kind enough to send me his intake so I could work on a porting program to match it up to my intake adapter, but of course with all the adapters I have here at the moment, the manifold couldn't really be fit in place because of the interference with the water jacket. I really wanted to get going on this manifold program, because I was running late on it based on how long I told Dave I needed it.
So, with all that stuff in mind I sat down on Saturday morning this week and started working on a program to machine the water jacket off one of the intake adapters. I had to take three or four stabs at it to really get it right, but in the end it came out pretty well. Here's a photo of the front of the intake adapter that I machined, with the water jacket cut completely away:
I'll fit a 1/4" thick aluminum plate into each one of the water jacket holes, weld it up, punch a hole in the front of the adapter on each side and thread it for 3/8" or 1/2" pipe, and I'll be good to go on the dyno by hooking up an AN line to each side, feeding into a remote thermostat housing.
After I got this done, I put the CHI intake in place; here's a photo:
That manifold sure LOOKS like it ought to make power LOL! The bolt holes in this intake line right up with the 351C intake bolt pattern already machined into the adapter, so there was no issue there. However, the CHI intake manifold ports are a lot smaller than normal 351C 4V ports. In order to see how they would line up, I cut a gasket to fit the manifold and then laid it on the adapter and traced the openings. Here's a photo of the openings outlined with a black Sharpie on the adapter:
This intake adapter has not had any porting work done to it; the ports are as cast. As you can see, there are going to be some parts of the cast openings which fall outside CHI manifold's port envelope. This isn't the end of the world; you could certainly run the manifold with those openings there, because as they approach the FE port in the head the openings will get smaller and smaller, and eventually disappear just before the port reaches the FE cylinder head. But if you were going all out with one of these intakes you'd probably want to fill those cast port openings with epoxy, or else weld them up, to make the transition to the FE port as smooth as possible. Just something to think about if you want to run one of these intakes.
I'll be working on the machining programs for this intake over the next few weeks; it will take a while to get this done. I'll also have to give the adapter a special part number for use with these intakes; using this adapter with a standard 351C 4V port would result in a very large port mismatch where the manifold bolted onto the adapter. But, it still might work OK like that; one thing I have learned with all this intake manifold testing is that sometimes the engine just doesn't care about stuff like this...
