348 head/block compatibility

[boxerdog]

As to your original question,Stan b,you can use the block and heads together.For the power that you want,10.5 pistons,a good valve job with stainless valves and a bowl blend,an 0949 flat tappet cam,an intake manifold from a 340 horse 409 and a small afb and you're there.

Just wait a couple of days, then everyone will start with the 409 cranks and other stroker options will be laid out and you won't be able to resist. After all, the costs are so incremental that it's almost painless. Happens every time. Don's plan is a good one if you want to stay 348, but it's one of those "slippery slope" deals.

 

[Don Jacks]

Yes,Dave,I personally like the "380" combo.You know,the 409 crank in a 30 over 348 as a "bang for the buck" combo.Add to this reworked 333 heads and headers and the fun really starts.

 

[fourzeronine]

Yes,Dave,I personally like the "380" combo.You know,the 409 crank in a 30 over 348 as a "bang for the buck" combo.Add to this reworked 333 heads and headers and the fun really starts.

That's what I have going together right now, except .060" over for a 385. Early '58 block with 333 heads that have bowl blend and bigger valves. Of course, I already had the 409 crankshaft collecting dust. Unless doing a bone-stock rebuild, doing what's required for such a "mini" stroker would need to be done with the stock 348 stroke anyway (better rods, pistons, machine work, etc).

 

[stan b]

Ok, here is what I have found. Contrary to what I have read, my late 1958 block (1872 casting) does not have cooling holes around the spark plug as you can see in the photo of the clean block. Neither do the heads (casting 2791) as seen in the photos of the dirty heads that came off the 1872 block. I have included a photo of a 409 head that does have the cooling holes just for reference. Against some advise, I plan to use the head and block combination of 1872 block and 2791 heads. It ran this way before disassembly and should run again. I will let you all know how it turns out.

 

[Don Jacks]

For the power level that you've said that you want,that combo will work fine.If during clean up you find that one of the heads is cracked,that block CAN be drilled for the spark plug cooling,allowing the use of any of the later heads.

 

[Phil Reed]

Get a head gasket and drill the cooling holes!!!! Chevrolet did that for a REASON!!!!!
You have the first revision block
Cooling pads were added but not drilled yet. Get a set of later heads and go for it!!!!!

 

[fourzeronine]

Get a head gasket and drill the cooling holes!!!!

Only if he uses a later head that has the coolant passage around the spark plug. His 791 head(s) don't have that, and it appears he would like to re-use them. If he drills the block, he'll create a leak.

Two combinations will cause leaks:

1. Using an early head (without the additional water passage around the spark plug) on a block with the cast (or drilled) coolant hole.
2. Using a later head (with the water passage and hole) on an early block that is missing the extra boss material for the coolant hole.

I suspect he posted the last photo (the head sans valves) as a reference to show a head with the water passage and coolant hole, and that is not one of the heads used on his engine. If I'm mistaken and that was one of his heads, then his engine had a mis-matched pair.

 

[stan b]

You are correct-the last photo is a later 409 head with the factory cooling holes. At this point the block cleaned up well and if the heads are usable as well, then I intend to use them as is. They ran for fifty years that way so I’m gonna run em that way again.

 

[Tom Kochtanek]

Keeping it all original is a valid option. If it worked in 1958, it should be OK in 2019.

We warned you we might give you a range of options for a rebuild, but staying bone stock is just fine .

Good luck!
TomK

 

[427John]

Stan I think all the recommendations that you got to use the later heads was mostly due to their higher performance potential and not so much because of any incompatibility.From what I understand from most of the comments with the exception of the 379 heads most of the later small port heads have superior porting as cast to the the 791 and 379 heads.As to your power goals the earlier heads like yours were used in engines with power ratings up into the low 300's,while engines with power ratings up into the mid 300's used the later superior port cylinder heads.But with a bigger cam as Don suggests you should still be able to reach your goal.Provided your build is a 1 and done with no possible future power upgrades you should be good,but if you're like most and want to be able to step up the power down the road you may want to consider the later heads.

 

[stan b]

Valid points. I will update you guys as I progress

Stan

 

[Phil Reed]

Stan......PLEASE use heads with cooling holes!!!!!!!!!! Chevrolet did that for a reason!!!!!!

 

[rstreet]

Stan......PLEASE use heads with cooling holes!!!!!!!!!! Chevrolet did that for a reason!!!!!!

I have to agree with Phil on this one
Robert

 

[Iowa 409 Guy]

Ok, I respect everyone's opinions/experience here. So far I have rebuilt 1 W motor so I really have none.
Stan been using this set up for quite some time without any problems, so why change? Just curious. Does the old saying of "there's never time (or money)to do it right, but there's always time to do it over" apply here?

 

[Don Jacks]

Why spend more money than needed? I gave him a simple,inexpensive[for a W] plan that will meet his projected goals.I could see it if he's planning on running it hard or over 5500 rpm,but he's not.Cast 10.5 pistons,a little bowl work[you're already there for the valve job,so why not],a 340horse intake[the 250 horse or truck intakes suck],an 0949[smooth idle] or an 0950[sight "attitude"at idle] and a 625 Street Demon or a 650 AVSII Edelbrock,and 2 1/2 manifolds and he's where he wants to be.

 

[Greg Reimer]

That is a service replacement block,apparently. Any head would bolt on without issues. No real need for the spark plug water cooling holes, but using a replacement head gasket as a pattern and drilling holes in the block deck wouldn't hurt, but you wouldn't be able to ever use the '58 heads again on that block without blocking the holes you just drilled.Your call on what you want to do.

 

[boxerdog]

I'm kinda with Don in the "it ain't broke..." camp. If I had reason to keep the heads, I'd run them as-is.

Phil, I hear you, but I was only 10 in 1958 so I don't know if it was a big deal or not. Remember, the same GM engineers gave you those squared-off intake runners and some other crazy stuff so I'm not sure they were infallible.

 

[oldskydog]

It was to save spark plugs. Plenty of 58 791 heads running for years without problems.

 

[stan b]

The TSB solved my dilemma-THANKS!!! I got my engine back from the Machine shop and its going back together with the original block and heads without the newer spark plug water cooling holes. I went with stock 9.5 pistons and a 340 hp 409 Isky cam from Show Cars. I will use the stock intake with an Edelbrock carb and spacer for now. I encountered an issue I posted on another thread about a spacer between the oil slinger and the harmonic balancer. The exploded engine diagram shows a spacer but there wasnt one upon disassembly. Anyone familiar with this part and is it necessary?

Stan

 

[Don Jacks]

I've seen many engines where that part was left out that had no issues.It's primary function was to help prevent oil leaks or so I was told.I wouldn't worry about it.