348/409 Motor

[Verne_Frantz]

John,
Be wary of truck blocks unless you're planning on building a blower motor. They have 2 fly-cut wedges removed from the combustion chamber to lower compression to about 7.5. You can't make that up with different pistons.
There are some ways to recognize a truck motor externally (if it's mostly complete). The intake will be a very low-rise with extra threaded bosses near the front to mount an air brake pump. The dist. is one with a govenor and has a wide metal band around the base. The water pump is huge and the valve covers will have the 4-wire loom tacked at the middle, rather than the rear.
Good luck.

Verne

[PeteLeathersac]

Verne,

Unlike the later MK1V passenger and truck engines being different from each other, w/ the W motors can't you mount external passenger car parts like intakes, waterpumps etc to the truck engines even though they're lower in performance internally?.


~ Pete

[Verne_Frantz]

[ QUOTE ]
Verne,

Unlike the later MK1V passenger and truck engines being different from each other, w/ the W motors can't you mount external passenger car parts like intakes, waterpumps etc to the truck engines even though they're lower in performance internally?.


~ Pete

[/ QUOTE ]

Yep! You can bolt any passenger car stuff (including Z-11 if you wanted to) onto a truck block. You're still dealing with low compression and there's NO way around it unless you weld up the fly-cut wedges.
Remember, W motors have flat head surfaces, ie: no combustion chambers in the heads (except for 13cc around the valves). The combustion chamber is in the block above the cylinder bore. IT's a 16deg wedge between the top of the piston and the head.

Verne





Sorry, I forgot to resize the pictures.....

[Kim_Howie]

Type in Gasser on e-bay there is a 55 chevy with a 348 in it cheap.

[PeteLeathersac]

Quote;

Verne,

Unlike the later MK1V passenger and truck engines being different from each other, w/ the W motors can't you mount external passenger car parts like intakes, waterpumps etc to the truck engines even though they're lower in performance internally?.

~ Pete

--------------------------------------------------------------------------------

Yep! You can bolt any passenger car stuff (including Z-11 if you wanted to) onto a truck block. You're still dealing with low compression and there's NO way around it unless you weld up the fly-cut wedges.
Remember, W motors have flat head surfaces, ie: no combustion chambers in the heads (except for 13cc around the valves). The combustion chamber is in the block above the cylinder bore. IT's a 16deg wedge between the top of the piston and the head.

Verne

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Thanks Verne!.

I yanked a good running '65 XX suffix W-motor out of a dumptruck a few years ago for my '49 Stude pickup project and like I think Hep may be too, am not as concerned about high performance as I am for simply running a W-motor under the hood!.


~ Pete

[John Brown]

[ QUOTE ]
Be wary of truck blocks unless you're planning on building a blower motor. They have 2 fly-cut wedges removed from the combustion chamber to lower compression to about 7.5. You can't make that up with different pistons.
Verne

[/ QUOTE ]

Won't most of those fly cuts go away when the block is bored?? A picture would be nice. It would help i.d. a truck block if I were to see one apart. Are those eyebrows in the last picture what you are talking about?

[Verne_Frantz]

John,
Sorry, but I don't have any pics of the truck block notches. (or externally) Maybe you might find one on the 348-409 site? The notches are very deep, maybe 1/4", so overboring won't do much to reclaim compression. You'd have to bore it almost .090" just to begin to cut into the combustion area where the notches are. That area is rough machined and a larger diameter than the finished machined cylinder wall.
The pic I posted is of a '62 409hp block (.057" over). IT was only to illustrate the swept part of the cylinder vs the wedge chamber above it.

Verne

[PeteLeathersac]

Is this the truck block notch Verne?.

http://www.superchevy.com/features/p.../photo_04.html

And they're on all truck blocks whether 348 or 409's?.

What's the whole story on the two notches in earlier blocks and one notch on the later blocks thing...two is worse?.

Do 409's always have the counterbalanced crank and the 348's the round one where the flywheel bolts on?.

And are the distributors and waterpumps W-motor only or do SB or BB ones fit?.

Thanks!.

~ Pete

[Verne_Frantz]

Pete,
Not to cast any disparaging remarks toward Super Chevy, but that picture is NOT of a machined wedge in a truck block. That’s a severely damaged block from a failure. It’s a mess. Note that the cylinder next to it doesn’t have any such “notch”.

As to the other questions, I’ll respond later as accurately as I can after I recheck some references on the “notch” issue.


Verne

[Verne_Frantz]

"And they're on all truck blocks whether 348 or 409's?."

All truck blocks, whether 348 or 409 have 2 notches. Both engines were rated at 7.75:1 CR.

"What's the whole story on the two notches in earlier blocks and one notch on the later blocks thing...two is worse?."

I don't believe that's accurate. Because of the 348's smaller bore, one notch was milled to provide exhaust valve clearance. With the standard piston (low perf), that produced 9.5:1 CR. For the hi-perf 348s with compression higher than 10:1 the piston dome was modified (raised) in the wedge area which made the combustion chamber smaller. Two notches are obviously worse, because you're starting with a base 7.75 CR. Even with hi-perf pistons, I doubt you could get to 9.0:1 CR.

"Do 409's always have the counterbalanced crank and the 348's the round one where the flywheel bolts on?."

As far as I know, all 348s have a round flywheel flange on the crank and all 409s have one that's asymmetrical.

"And are the distributors and waterpumps W-motor only or do SB or BB ones fit?."

Yep, they're W-motor only, along with the oil pump drive shaft due to the shorter distributor. The water pump bearing & shaft are the same as SB though, so there's no problem having them rebuilt.

Verne