Early 58 block advise

[Jens]

I have a 348 engine with the following codes (below). The engine seems to run fine. But I was wondering if this non water cooled version is going to be problematic and cause me trouble down the road ?
Would I be better off building the later version. (I have a later block # 3755011 and heads #3732791 that I could use, if need be).
Thanks.

Block:
T612G
F258
3751872

Heads:
3731291
F1058

[models916]

The 872 block should have the pad for the later water heads. Just drill the holes to match the head gasket, or use the later block.

[Bungy]

Your early 872 block may or may not have the pad for the water cooled heads. If it doesn't, just use it with the 3732791 heads and you'll be fine. The 791 heads don't have the water cooled plugs and can't be used with the later block. Are you sure of the casting number 3731291 on the set of heads listed? I'm not familiar with those. Don't know if they have the water cooled plugs or not.

[Jens]

Yes, the heads on it are #3732791.
The block is dated June '58. And I think the pad is on the block. I'll try & post a pic tomorrow . Thanks.

[bowtieollie]

Hi Jens,

The purpose of the supercession on the heads was to maintain spark plug temperature.

In HD applications (police cars) the spark plug temperature was high causing errosion issues. Hence the updated head/block.

For what you are doing - its a great engine. :love

[Jens]

Thanks for the info Ollie. Like I said, the engine seems to run fine & the compression is between 125-150 in all cyls. Maybe I would be better off to run it like it is & see how I get along for awhile. I just didn't want to take off & get halfway to Pennsylvania or something and have someone say "I told you so"!. :dunno
...So what's the best plug to run in it?

[bowtieollie]

Hi Jens,

Coming to Pennsylvania, heh?! :)

The only spark plug I would consider is the NGK XR4. (stock number 5858 - how's that for coincidence)

Although the AC version would be technically correct, I do not care for how the steel casing on the AC rusts over time. Also the heat range on the AC is not as exact as the NGK.

Its what I run on my '58 and it performs flawlessly.

If you are modifying the engine for more performance and want a spark plug that will go 100,000 miles - then I would recommend the NGK XR4ix. Its an iridium version of the standard plug. Lower firing voltage and no electrode errosion issues to contend with. (stock number 7189) (nice for a very lumpy cam) :brow

You will have to order these plugs (most likely) since most vendors do not stock them. I provided the stock number because it seems that parts houses like the four digits over the alphanumeric config (that we all grew up with!)

Have fun with that new project.... the water cooled heads were a TSB from July of 1958 (going from memory on the date). It was first intro'd on the high HP versions of the 348 - which found themselves in Police cars or as the high performance option chosen by the customer. By the '59 model year they were used across the entire 348 engine family.

[bobs409]

,I do not care for how the steel casing on the AC rusts over time.

Ain't that the truth! And it doesnt' take long either. I started painting mine with semi-flat black because of the rust problem.

[Tman]

FWIW, as I mentioned in another post, I am running an early block with NO pad by the plugs and later heads with the spark plug cooling. I welded the holes in the head so that the bead stayed UNDER the deck surface then sealed it with JB Weld in case of porosity. I went this route due to the heads being already done when I found out the compatibility problem. If I was starting over with fresh heads, I would get more aggressive with the weld and then have the heads decked.

What I am doing is not perfect but my plugs at least have a LITTLE coolant running around them.

BTW, thanks for the info on the plugs. I will see how my ACs run and maybe try the NGKs?

[bowtieollie]

Hi Tman,

Since you have water cooled heads (later countermeasure config) the spark plug numbers I mentioned do not apply to the later head.

The early head had a 3/8" reach - the later head the plug reach is 3/4"
The correct NGK spark plug for the later head (water cooled) or late 1958 and newer, is GR4 (stock number 2635)

The iridium version would be GR4ix (stock number 7149)

[fatride]

If you are modifying the engine for more performance and want a spark plug that will go 100,000 miles - then I would recommend the NGK XR4ix. Its an iridium version of the standard plug. Lower firing voltage and no electrode errosion issues to contend with. (stock number 7189) (nice for a very lumpy cam) :brow
Ollie


Would this plug be suitable for a CD type ignition? I run an Accel + 300 CD ignition with a MSD dist.

[bowtieollie]

Absolutely - this would be the plug of choice.

You can even open up the gap to .045 with that ignition.

[tripowerguy]

Fatride, if you run a set of these at the track let us know how they pan out. I won't be ging to thetrack until late June because of my Shoulder but I will be waiting to see how you do at the wars. :beerbang Roy