January 2008 - an attempt to build a sheetmetal intake

For years, I've been contemplating a sheetmetal intake for my race 304. No one made a 304 4bbl (the Ismail's do now) so I thought I should build a sheetmetal tunnel ram for it.

Blair Howze kept encouraging me.. and then one day said "I'm coming up to help" to kick me in the tail to get going on it.

We started with some 3x1/4 or so flat bar.

Which then was drilled to mount to the intake side of the head.

I drug in a spare 304 block and put some heads on..

I had some firring strips handy which turned out to fit nicely into the intake ports - we thought we could use these to help hold the square tube intake runners in place during assembly.

I used my plasma cutter to rough out the holes for the intake - note that the exhaust crossover passage wasn't cut out - and that's on purpose to keep the intake cooler.

We spent the rest of the DAY with the die-grinder cleaning up the holes for both plates.

The plates were bolted to the heads and then some square tube cut..

Some 1x2 rectangle tube was mitre cut for the water crossover tubes and test fit.

Then my real problems began..

This doesn't look so bad, until you realize the front two runners need to be put in place, and by doing so, they go right over (barely) the top of the water crossover (which also needs a front-to-back (cut and laying on the valley pan) tube). Still not a big deal, except we need to get a thermostat housing in. The stock intake puts it "back" a bit, over the valley pan.. right where the front runners are.

There's also a bit of a problem with the plenum being rather long front to back, which would probably result in poor fuel distribution to the front/rear cylinders with the centers being rich.

I cut another batch of runners that are all angle cut, to bring them into a more central location, more ideal for a single carb setup, but I still had the same problem with the thermostat housing.

I wanted to build a mount that would take the stock (heavy, cast iron) thermostat housing, so I wouldn't have to redesign much of the IH cooling system, but the whole thing is just "so big". Blair lobbied for a 351W thermostat housing, but I don't have any of those lying around, and then there's hose sizing and fitment issues.

The result was.. I quit.

I might get back to this again, but we're building a bigger SV for the new racer, so the hot little race-304 probably won't see much development effort any more. ;)

What I have learned...

Draw up the intake gaskets in CAD and send them to some place like e-machineshop and have them made. Save yourself a full day of air compressor abuse and die-grinding.

Then I think I'd try for a full on tunnel ram - high rise. I ran out of thin-wall square tubing and didn't have enough left for "round 3" of this project, but if I did, I might've tried for the ~15" (IIRC) runner length I calculated I wanted/needed for a tuned-tunnel-ram for the RPM range I wanted, and just make it tall!

This would help with my thermostat housing problem by moving the entire intake plenum and runners up-up-and-away from the thermostat area.

I might also be inclined to weld bungs to the intake plates and just use braided stainless hose for the water jacket, instead of my angle-cut 1x2 rectangular tube. It was going to get ugly when I cut the two 1x2s for the front to back installation and then cut the front of the front one out to build the shallow/wide thermostat housing mount.

Photo Gallery

Discussion at the BinderPlanet about my Intake Project