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Buick 401 piston question


Guest ZenMaster
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Guest ZenMaster

Hello,

I am currently in the process of parting out a 1966 Riviera. Turns out it has a 1965 LT motor. The information on the top front of the block is LT followed by 448 and then 5H936540 which does not match the car VIN. It also had a Quadrajet intake manifold which I thought was 1966 only and pop up pistons. So my two questions are;

Did any of the 401's come with pop up pistons?

What year or years was the Quadrajet intake available for the 401/425 motors?

Thanks in advance for your time. It is very much appreciated.

Larry

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This info is off the top of my head. I'll look at some books tonight to check for sure.

The Quadrajet was introduced in 66. Earlier 401's used the Rochester GC or the Carter AFB carb. Sharing the same intake bolt pattern.

I don't believe the engine # would match the VIN. Earlier cars might, but not in 65 or 66 Buicks.

I take it that you mean 'domed' pistons. All high compression 401's (11:1 ?) would have domed pistons.

Bill

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For 1966, the last 8 digits of the cars VIN should match the engine serial number. 1957 was the first year that the car and engine serial numbers match for Buick. Your engines serial number indicates that it came from a 1965 Riviera or Wildcat built at Flint, MI. The Q-jet was available only on the 1966 425 (MW code) and a very few 1966 401's built for special applications (MS and MU codes). Sounds like someone took a 1965 engine and put the 1966 Q-jet intake on it. The 1966 Rivi you have came with the 425 so it could have been an easy swap if there was a problem with the block.

5H936540

5 = 1965

H = built at Flint, MI

936540 = sequential number, range for Flint built Riviera and Wildcats was 900001 to 955320

Edited by sean1997 (see edit history)
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In 1966, the Quadrajet carb appeared only on the 425 in the Riviera and was also a rare option on some '66 Skylarks with the 401. It appears that someone used a '65 short or long block and refitted the '66 intake to that block. You can tell if the heads are '66 heads or are the '65 heads. Easiest might be to see if the original paint on the heads is red, only the Riviera engine was red. The '66 heads were the only nailhead heads that have valve seals on them. Something else to look for is a lifting loop cast into the water cross over pipe - '66 only. Casting numbers were pretty much used for lots of engine over lots of years. You could have any mix of '65 and '66 parts.

Here's a link to decoding '65 VIN's http://www.teambuick.com/reference/years/65/65_vin.php

Ed

As for now, no one that I've heard of has figures out the three digits that appear with the Engine Production Code letters. LT = 1965 - 401; 448 ???????

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Guest ZenMaster

Thanks for all the helpful information. Looks like someone used parts from different years for this motor. There is no "lifting" hook on the water crossover and even though the engine was painted red, I think it was a quick job to make it look original as the back of the vibration dampener was blue green. The gentleman I bought the car from (not the original owner) said that to his knowledge, the car was originally a 425 with the 2 4 barrel intake option. I wonder where that beauty ended up? The other thing I found interesting was the 3.42 posi rear axle. (Yes, I am saving the posi unit as well as the ring and pinion.)I have the feeling it used to be quite a fast car. If the rest of the car had not been such a mess, I would have tried to save it. But, like my wife says, some have to die so others can live. Thanks again for all your help. This is an awesome site. Larry

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I suspect the 3.42 axle ratio was due to the suspected 2x4bbl induction system. OR somebody ordered it that way if the 3.42 was not standard for the engine/trans combination it came out with.

IF you can track the transmission code (on the tag or a stamping in the rh accumulator cover?), it might give a further clue . . . not to forget about the distributor number, possibly.

IF the car was an original 2x4bbl car, it might have been that it "drank gas", hence the more efficient Q-Jet items to replace them.

Just some thoughts,

NTX5467

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