is it a 348 or 389

[bigwin59]

With the new to us truck 1959 big window. The body is pretty straight nothing major. Still has 4 speed manual on the floor.

When I looked at the engine the valve covers say Pontiac M/T. The numbers on the block correspond to a early 60 Pontiac 389. Going through the specs on the truck GMC used Pontiac motors and possibly the 389 was downsized to a 348.
The motor has a freshly rebuilt appearance and sounds very healthy as if it has a healthy cam in it.

So how do i figure it out?

[AZ59apacheguy]

Definitely not a 348, they call thosw " W " engines. The valve covers are in the shape of a " W "

[dwcsr]

Its a Pontiac 336 based on the 370. part will interchange. GMC used Pontiac motors back then. some times Buick in the larger trucks

[OrrieG]

If you are really ambitious you can put timing tape on the balancer and use a dial indicator at the rockers to figure out the cam timing and lift, then start looking for ones that are close, or if you are tearing the engine down (does not sound like it) the end of the cam should have an manf grind #.

The valve covers are relatively rare so take care of them. Not a poncho guy so someone else will need to chime in on how to decode the casting or sn stamp on the block....

Every W block engine in a rod is a 409 unless you know how to tell the difference...

[capnduane]

http://www.pontiacsafari.com/MPC/Pages/page_0061.jpg Here's a chart that shows all the 389 engines they built in 1960. Several came with the AFB carb, which yours has. The hipo engines had hot cams, and higher compression. Of course a lot of years have gone by, and anything could have been changed.... Sounds like you have a good one, the Poncho in my '55 runs real strong, and has a hot lumpity cam, and I don't have a clue as to what it is! Enjoy!http://www.pontiacsafari.com/L1Early.../V8%20Engines/ More info on your '60 engine.

[Dan in Pasadena]

Originally Posted by OrrieG

...Every W block engine in a rod is a 409 unless you know how to tell the difference...

Now this is funny...and pretty much true.

[bigwin59]

Originally Posted by capnduane

http://www.pontiacsafari.com/MPC/Pages/page_0061.jpg Here's a chart that shows all the 389 engines they built in 1960. Several came with the AFB carb, which yours has. The hipo engines had hot cams, and higher compression. Of course a lot of years have gone by, and anything could have been changed.... Sounds like you have a good one, the Poncho in my '55 runs real strong, and has a hot lumpity cam, and I don't have a clue as to what it is! Enjoy!http://www.pontiacsafari.com/L1Early.../V8%20Engines/ More info on your '60 engine.

Thanks I will look at charts and compare the numbers. You are only a stones throw from me.

[bigwin59]

So here is the numbers.
536387 m-4
Found online a company called butler performance, I gave them the info. According to them it is a 1960 389.
Then looking at the charts looked like a 10.75:1 heavy duty. Just missing the tri-power. That said it also came with a 4 barrel carb also.
So part of the mystery solved.

Thanks for pointing me in the right direction.

[capnduane]

Cool.... Nice hi performance 389, should have loads of torque and bottom end. You scored! Just was over your way, had lunch in Cherry Valley at Flo's. What a beautiful day for a drive thru San Timeteo Cyn. Here's a pic of the Poncho in my '55.

[bigwin59]

Originally Posted by capnduane

Cool.... Nice hi performance 389, should have loads of torque and bottom end. You scored! Just was over your way, had lunch in Cherry Valley at Flo's. What a beautiful day for a drive thru San Timeteo Cyn. Here's a pic of the Poncho in my '55.

Not all. Flos is great. The guy who is helping with body work will be over Saturday so I can give him some $. He is going to get the body filler and stuff. Hope to start the work next weekend.

[chip46wis]

Definate poncho

[MARTINSR]

Originally Posted by Dan in Pasadena

Now this is funny...and pretty much true.

My brother joked one time years ago that somewhere is a field of many acres covered with Corvettes with the hoods off, front end up in the air from the lack of engine weight because all the "Corvette" 327's are in street rods.

Brian

[MARTINSR]

Just so everyone knows what a 348-409 looks like.





It's a very cool, distinctive motor. One interesting thing about them is the combustion chamber is in the cylinder and not the head.



Check out how the top of the cylinder isn't flat.



Brian

[OrrieG]

Originally Posted by MARTINSR

My brother joked one time years ago that somewhere is a field of many acres covered with Corvettes with the hoods off, front end up in the air from the lack of engine weight because all the "Corvette" 327's are in street rods.

Brian

I read somewhere that there are more 67-70 BB Corvettes on the road today than were produced, many "matching numbers". Very good records exist on the numbers produced, etc. and because of prices lots of incentive to build a fake. Same with Shelby Mustangs...

[Speedbumpauto]

"Just so everyone knows what a 348-409 looks like."

Horrible design kept around by simply being unique, especially in the looks department. I love the look but until you have had to do machine work on one or, much less, install pistons in a block that's been bored enough to take away that relief which lets the ring compressor fit, you haven't experienced the total joy of one of these engines.

[70gmcjimmy]

It might be possible he meant "347" a Pontiac V-8 introduced in 1957.

DAC