409 heads on a 348

[348'sforever]

I finally found some 63 340 horse 409 heads. I have a friend who did this years ago, but I think his were the 425 horse heads. He found 2 cooling ports in the heads that the 348 didn't have and plugged them. I checked my heads and they look the same as the 348 head gasket. Am I safe in thinking that the 340 horse heads are the same as the 348's? Will my 348 tri power manifold fit these heads? Thanks for any help. I really appreciate it, as it seems that Murphy's Law has been running wild in my efforts.

 

[oldskydog]

The 340 hp 817 heads are basically the same as the 1147, 586, and 333 heads as far as ports and runners. Obviously the 333 heads have machined combustion chambers and rotator pads but otherwise the same.

 

[409gang]

It all depends on what year you 348 block is, I believe if it's a late 58 and on 409 heads fit as the later 348 blocks have the cooling holes for the spark plug cooling in the 409 heads. As far as the tri-power yes if you have 340hp heads (small port) the tri-power should fit. I just put a set of 425hp heads on a 348 with a 2 x 4 intake (Edelbrock) for the high horse heads. What is the casting # and date code of your block? Those heads you found should be 817's as that is the last 3 digits of the casting # for 63 340hp heads and they should be small port.

 

[348'sforever]

Thanks again for the help. My engine is a 61. My friends was a 58 Impala. The 409 heads I bought are 817's. I'm grateful that I found this club. It's nice to ask for help from people who know what they are talking about. Fred 348's forever

 

[409gang]

Your good if you have 817's with that tri-power and that 61 block should be fine with those heads.

 

[Gofish]

Just saw a 409 with small-port heads and a tri-power over on the Jalopy Journal H.A.M.B. site. Cool.

John

 

[neilswheels]

Interesting info, I wasn't aware that any other head fitted a late 58. Will 817's make much difference? I'm runnng tri power, I looked at ally heads, but they dont fit, if memory serves me thats because the inlets dont match up?

 

[scott hall]

As long as it’s a late 58 with cooling holes or the pads there and not drilled. Then use head gasket as a guide and drill them. All small port heads use the same gasket and match small port intakes such as the tripower.

 

[neilswheels]

Is there an advantage in running later small port heads, apart from possible cooling benefits?

 

[scott hall]

I believe the later heads (817 333 1147) do flow better than (791 379) but don’t have my own proof.

 

[Greg Reimer]

The small port heads on the W motor look to be ample, and for street use and cruise nights they work fine.The main reason that the 690 and the 583 head make much more power has not so much to do with the port size, but the fact that the roof of the port has been raised a lot. The floor of the port is curved upward on both series heads, it is pretty dead on air flow, leaving the top 2/3 of the port left to accomplish all the air flow. The reason the Z-11 cranked it on pretty well is that the entire intake side of the head was raised and straightened, and so were the intake ports. The intake on the Z-ll was a dual plane, not good, but the entry angles and the air flow was straightened out considerably. The port entry angle on the small port W motors was so low that the roof of the ports was right about on the center line of where the center of the port should have been. Raising the roof of the port and filling in the floor to effectively straighten it out and reduce the changes in angles between the plenum of the intake and the bowl around the intake valve would have fixed a lot of things, for sure. Also, the large port intake with its square turns between the plenum and the intake surface of the cylinder heads left room for improvement. For an example of a BAD intake port, look at the intake port at the flange with the head on a cast iron 340 horse intake for the #6 cylinder. Also, the 327 factory hi po aluminum intakes seem to have square turns between the intake gasket surface and the plenum. Obviously, the factory released small block intakes that were far better horsepower makers later on with the mid '60's hi po 327's.

 

[Don Jacks]

All true enough but it's been well proven that the s mall port 333,817,1147 head can be worked to support over 500 hp,n.a. at 6,000 rpm.It just depends upon what you want the engine to do and how much money you're willing to spend.

 

[region rat]

The small port heads on the W motor look to be ample, and for street use and cruise nights they work fine.The main reason that the 690 and the 583 head make much more power has not so much to do with the port size, but the fact that the roof of the port has been raised a lot. The floor of the port is curved upward on both series heads, it is pretty dead on air flow, leaving the top 2/3 of the port left to accomplish all the air flow. The reason the Z-11 cranked it on pretty well is that the entire intake side of the head was raised and straightened, and so were the intake ports. The intake on the Z-ll was a dual plane, not good, but the entry angles and the air flow was straightened out considerably. The port entry angle on the small port W motors was so low that the roof of the ports was right about on the center line of where the center of the port should have been. Raising the roof of the port and filling in the floor to effectively straighten it out and reduce the changes in angles between the plenum of the intake and the bowl around the intake valve would have fixed a lot of things, for sure. Also, the large port intake with its square turns between the plenum and the intake surface of the cylinder heads left room for improvement. For an example of a BAD intake port, look at the intake port at the flange with the head on a cast iron 340 horse intake for the #6 cylinder. Also, the 327 factory hi po aluminum intakes seem to have square turns between the intake gasket surface and the plenum. Obviously, the factory released small block intakes that were far better horsepower makers later on with the mid '60's hi po 327's.

Greg, You're correct about nothing happening on the floor of those ports. That was one of the reasons we made the raised port head. Floor is filled in and roof is raised. We also added extra material so less welding would be needed if you wanted to go above the valve cover rail.