OK, so Im a little confused here, I have been looking at this picture of a 3x2 intake for the 421 Poncho and have a question. Now I know there is a water cross over in the front of the intake and the intake ports are siamesed at each end. This leaves the question, is there another water cross over in the center? Is that what we see in the center of this intake? If so, why one in the middle of the heads? I noticed that it is deleted on the 421SD 'bath' type tunnel ram, was this a different head or were they just blocked off? Thanks guys, Doc.
No, it's an exhaust crossover for carb heat. If your running your car as a daily driver, the heat to the carbs makes your life a little simpler, but for race only applications, it's not really nessecary.
Now that makes a lot more sense!! Had I thought about it for a few moments it should have been obvious. Thanks mate! Doc.
That is not a 421 intake. It looks like a '59 model. bolt pattern interchange is 1955-1960, then 1961-1964. The 421 came out as a race engine over the counter in late 1961. then first installed n cars in 1962 but, only as a race engine. street versions first came out in 1963. Only race engines deleted the heat crossover in the middle. hope this helps. Steve www.pontiacheaven.org <DIR>Hosting 11th annual Pontiac Heaven, show, swap, drags, party and all around good time. Saturday April 4, 2009 at Speedworld near Phoenix, Az Also hosting- 7th annual Nostalgic Show and Go! and swap coming Sunday April 5, 2009 to Speedworld. Phoenix, Az </DIR>
yes, you have to be careful about what year intake you have. 1955-1960 is one group, 1961-1964 is another, and 1965-1966 tripower intakes are another group. They are not interchangeable. But, any Pontiac block from that group will fit any other Pontiac block from that group, for instance a tripower from a 1962 389 will fit a 1963 421. Of all of them, the 1966 tripower is the most desirable. It used a larger center carb. (Notice on the pictured manifold, the center ports are a bit smaller than the front and rear). Plus, the 1965+ manifolds will fit on all 1965+ heads, except for the very late 301 and 265 engines ( which basically have no hotrod potential anyway, so we'll ignore them). So you can grab a 1972 455 block, throw on a set of 1969 heads (although you'd have a very high C/R) and a 1965 tripower setup.
It has been over 40 years and I'm no Pontiac expert but I put a 421 in my 63 Catalina in early 68. I found a set of real Super duty heads to go on it. My 63 4 bbl intake would not work. I had to buy an aftermarket intake to fit the special SD heads. It bolted up but it did match the SD heads. The rocker arms are different also. SDs are 1.65 to 1 389s are 1.5 to 1. It would bend push rods with the 389 rockers. I went to the Pontiac dealer in 1968 and they wanted 100 1968 bucks for the factory SD stamped steel rockers, balls and nuts. Crane had just started making SD aluminum roller rockers for 110. I bought the Crane. I think people throw around the super duty tag too much. I could be wrong but I don't think they made 3-2s for the SD. Weren't they all dual quad? Super duty stuff was never intended for the street. I believe you could get a 421 tri power but I'm pretty sure it was not a SD. That is why real SD parts demand so much money. The Pontiac guy that bought my car in 1969 bought the car just to get that engine.
This Intake is a 61-64 Super duty dual 4 barrel . The carbs are not correct and will be up For Sale soon .
Manifold APPEARS to be the factory aluminum 1961 SD 3x2 manifold that fits the 306 cylinder heads. This manifold would have the casting number 540510 which is what appears in the picture, but my eyes are not as good as they once were. Jon.
You're right, that's just what it is. The '61 SD engine used 1960 style cylinder heads, intake manifold, and timing chain cover.
P/N 540510 is the '61 389 SD intake. This is a one-year only number. Easy ID feature is : all '61-63 SD intakes are aluminum (exception is '60, where 2 of the 3 are iron, the 3rd aluminum). RPO intakes are iron. SD 3x2s were only used on the 389SD ('60-61-62). '61 421 SDs were all 2x4s.
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