Hypothetical 348 budget build options

[Tom Kochtanek]

There's been a great discussion about the length of the GM connecting rods on the stock 348 builds, and I think we resolved that issue. That said, it got me to thinking about what the original intent of the question was.

So I pose this hypothetical question:

What if you had a good clean standard bore 348 truck block from 1965 (the ones with the ArmaSteel caps and the 409 truck oil pan). Let's say you had the original 348 crank, rods and pistons, all in decent shape. Your objective is to build a bottom end that is stout but doesn't break the bank, something you might use for street driving and occasional lead-foot situations. Call it a budget build.

Clearly the least expensive option would be to fit the original pistons on the original con rods with new rings, new bearings for the rods and crank (assuming the standard bores are still within spec). Let's veto that for now, since those cast truck pistons are so low on the performance scale (and heavy!)...

Would you go with the 348 crank and original (but R&R'd) con rods and those new pistons?

Or would you go with the 348 crank and new BBC rods connecting the forged pistons?

Or would you stick a 409 crank in place, go with BBC rods and those new forged (now custom) pistons?

Assume all new bearings, etc. and standard machine shop costs. Forget about the top end and valve train for now, those are separate choices.

Your insights? What are the pros and cons of these various options? Are there other options? Remember, you are trying not to break the bank!

Cheers!
TomK

 

[1961BelAir427]

Would you go with the 348 crank and original (but R&R'd) con rods and those new pistons? Since this is option #1 (or 1B) I'm just looking at the cost to move up from here. I figure you'll have to have it balanced either way, so not counting that. New Forged pistons from KB are about $550 right? You already have the crank......R & R the rods will be at least $100..... so $650+ here.

Or would you go with the 348 crank and new BBC rods connecting the forged pistons? Same price for pistons plus another $50 or so for a set of bbc rod cores to R & R. Or $300 for quality BBC rods that are good to over 700 HP. So $700 to $900 for option #2 (Minus what you can get for the 348 rods on Ebay.)

Or would you stick a 409 crank in place, go with BBC rods and those new forged (now custom) pistons? Again, same price for pistons and BBC rods as above, plus around $300 for a good 409 crank.....so $1000 to $1200 for option #3 (less what you can get for your entire 348 rotating assembly since you won't be using any of it now.)

Cheers!
TomK

Tom,
The way I see it, you're only looking at an extra $350 to $550 to add about 27 cubic inches along with adding a whole lot of piece of mind from the stronger connecting rods. That's even if you don't sell any of the 348 rotating parts to recoup some of the cost.
I know how quickly stuff can snowball once you change something, but for me it would be a choice between your option #3 above......or just leaving the whole stock rotating assembly in it and just doing a basic hone, re-ring, & bearing rebuild with a cam that'll clear and give some extra fun. Don Jacks is building a nice 348 stroker using a 409 crank, 6.385" rods, and off the shelf KB pistons.....just like option #3. I got an email alert with a reply to this about it, but now it's gone? I'm sure others will have many other ideas on this. Like you, I'm looking forward to reading them!
Jason

 

[1958 delivery]

I'd buy a 409 block and crank

 

[Rickys61]

Tom,
I went with the option of 348 block, 409 crank and BBC stock rods... I know that there's probably better ways to do it, but my objective was to use parts I had collected over the last 15 years. I figured if I didn't use this stuff now, I never would. The longer I wait, the more obsolete the OEM stuff seems to become...
Rick

 

[Don Jacks]

Well Tom,I am using Kb forged pistons made for the 4in stroke[560 or so from Show Cars],6.385 rods from Competion products,about 260.00] and a 409 crank that I got a good deal on[200.00]This combo will give you about 10.5-1 on "car"heads,or about 10-1 on 333's,does not break the bank,uses the modern thin rings for reduced friction,and you can beat the tar out of it without fear.I'm about to the point that ,unless it's ashow piece than almost never gets run,that I would not use cast pistons.I've seen a couple of sets lately that,quite frankly ,the lack of quality scares me.I dont bthink that they're as good as the 1959 pistons I took out of my engine core.Others may disagree,and if I'm wrong,please someone tell me.These engines are tongetting too hard to replace to cheap out and blow up just someone dosent want to spend what it takes to do it correctly.And I'm cheap!

 

[Fathead Racing]

I don't know where the 348 got lost in this game but my little .060" over 348 with cast pistons a 268@ .050 hyd cam with three two's in my lead sled 60 Impala, 4250 lbs. turned solid mid 14.00s @ 95mph. On a budget if you didn't have a 409 crank the stock 348 crank would be just fine. Bumping the compression with a good set of forged pistons would be great but a set of cast pistons would fit the bill just fine and you can get those up to any comp ratio you want. The rods are plenty stout for a 5500 rpm engine and the three two's won't flow enough air to go much past that anyway. With a set of 4:11s in the rear with a four speed stick or a built 350 turbo and a 2400/2800 stall converter you got yourself a great street machine that will run with most of the muscle cars to date.

 

[Don Jacks]

I too,like the 348 engine,but parts were a lot better few years ago when you were running yours Ray.The new ones that I saw last week[cast pistons] were some sorry looking pieces.When I got the "Bug",about 4 years ago,one could find a rebuildable 348 for about 400 dollars,a 409 was around 1500-2000 dollars.Now days ,prices have over doubled,and 409's about 50 percent. Yes the 348 rod's ok when upgraded with good rod bolts,but by the time you have the machine work done,you're nearly in as deepas a stock,new,bigblock rod would cost.If one could find decent cast pistons,fine,but in all honestly,the market as a whole isnt there for that,so we're left with the cheap,weak stuff,or we can spend about twih as much on pistons,and be able to sleep nights,is the way I see it.

 

[Fathead Racing]

I thought we were talking about what he had on hand? He said he already had pistons etc.? Other than that I agree with you Don.

 

[Tom Kochtanek]

Great responses to date. My favorite is from 1958 Delivery ("I'd buy a 409 block and crank") .

Don makes a good point about the newer cast pistons being a potential problem, especially if you have the tendency to step on it once in a while. That's why I factored in the cost of a good set of forged pistons. That made it a "which crank and rod" question.

I have to think slipping a 409 crank and going with new BBC rods would have to be pretty inexpensive and maybe even have the most bang for the buck. You get a few more cubes with the stroke, a great set of rods and pistons and ring options. I bet that little bit of stroke wakes up the smaller 348 engine, although that would also have to take into account the top end. About the same amount of cost in terms of machine shop work for the bottom end, I suspect.

Best, TomK

 

[Rickys61]

Well Tom,I am using Kb forged pistons made for the 4in stroke[560 or so from Show Cars],6.385 rods from Competion products,about 260.00] and a 409 crank that I got a good deal on[200.00]This combo will give you about 10.5-1 on "car"heads,or about 10-1 on 333's,does not break the bank,uses the modern thin rings for reduced friction,and you can beat the tar out of it without fear.I'm about to the point that ,unless it's ashow piece than almost never gets run,that I would not use cast pistons.I've seen a couple of sets lately that,quite frankly ,the lack of quality scares me.I dont bthink that they're as good as the 1959 pistons I took out of my engine core.Others may disagree,and if I'm wrong,please someone tell me.These engines are tongetting too hard to replace to cheap out and blow up just someone dosent want to spend what it takes to do it correctly.And I'm cheap!

If I wouldn't have had the rods, I would have used the KB's and the 6.385 rods... I feel confident the combo I decided on would be reliable... With the factory tri power and 1147 heads, it should be plenty sturdy for what I'm doing...

 

[Don Jacks]

No doubt in my mind ,Ricky.Youre building a very nice,reliable,rather stought piece there.That ones gonna be sweet!

 

[LMBRJQ 60]

Tom, very interesting thread here.
I have the very block mentioned and crank, rods, pistons, no heads though.
I also have a 454 crank and a 396 crank and a set of BBC rods
I am following with interest, but i believe that i would have a lot of machining and balancing to do if i was to use the BBC cranks? and not just use a 409 crank.
Looking at cheap as i can but solid (i know they dont go together but there must be a compromise somewhere)


Steve

 

[jim_ss409]

Well Tom,I am using Kb forged pistons made for the 4in stroke[560 or so from Show Cars],6.385 rods from Competion products,about 260.00] and a 409 crank that I got a good deal on[200.00]This combo will give you about 10.5-1 on "car"heads,or about 10-1 on 333's,does not break the bank,uses the modern thin rings for reduced friction,and you can beat the tar out of it without fear.I'm about to the point that ,unless it's ashow piece than almost never gets run,that I would not use cast pistons.I've seen a couple of sets lately that,quite frankly ,the lack of quality scares me.I dont bthink that they're as good as the 1959 pistons I took out of my engine core.Others may disagree,and if I'm wrong,please someone tell me.These engines are tongetting too hard to replace to cheap out and blow up just someone dosent want to spend what it takes to do it correctly.And I'm cheap!

This sounds like a good plan for anyone wanting to build a 348 stroker.
It's nice that you can use off the shelf pistons and it should be virtually unbreakable even if you use a big cam and rev it to the moon.

 

[Don Jacks]

Steve,As I under stand it,with the 396 crank and an overbore of .040,you'll now have 409 cu.in.With an overbore of .030,and a modified 454 crank,it's 434 cu.in.As to the work involved,both cranks will have to have .250 ground from the main journals,the snout ground to the w and smallblock size,and the cranks counterweights cut down some to clear the block.Now,on the positive side,Aubrey loves the 396-427 stroke in an engine for all around revability,and he's done a bunch of them.The modified 454 crank will still be externally balanced.I think that if I were going to go 434,I'd get a ready made crank for the application such as an Eagle or Scat,that way I wouldnt have the external balance issues.

 

[Tom Kochtanek]

I think we're going to see a lot more of these as interest peaks and we run out of original castings. We've already seen that with the scarcity of good 409 blocks. As has been noted, the costs have risen with the 409 stuff, but one can still find 348 engines if you get lucky. And you can build a pretty stout engine out of a set of core 348 components. As new block castings from the likes of Bob Walla enter the market, we might see a change in demand, similar to what happened with the introduction of the newer aluminum cylinder heads.

Assuming one were to start with a good "Junior Varsity" block (348), basing the bottom end on a 409 crank seems to be a low cost option (as opposed to a modified BBC crank) . Choosing off the shelf BBC rods (readily available at good prices) and mating those to a good set of forged pistons made specifically for that application seems a solid approach. Not much machine work needed to slip the 409 crank in place, the cost of bearings and gasket sets are the same.

I bet we start to see more of these types of builds in the near term. Given the current pricing on a finished high performance 409, it seems possible to build a stout 348 look-alike for less than half the cost of the 409 build. Of course decisions related to top end components can influence final cost. Keep in mind the current inference is that you're playing at the JV level, and some of you guys are building All Star one-of-a-kinds at the Varsity level.

TomK

 

[303Radar]

This is definitely a good way to have Champagne dreams on a Budweiser budget!

 

[wally72974]

A stock BBC connecting rod should be good (safe) to 500hp. If you plan on going higher than that I would go aftermarket rods.
(You said you were trying to be cheap) that would save you $200 or so. I would definitely put a 409 crank in it. The extra 27 cubic inches
is always nice. How does that old saying go....... There's no replacement for displacement.

 

[Don Jacks]

It would really be a "wash ",Wally.The K-B pistond required to make to make this work are about 200 cheaper than the Ross piston,but then you could specificy the exact compression that you want.In order to use the K-B off the shelf piston thats readily availeable,you must use the aftermarket 6.385 rod.Yes the 409 crank in a 348 block is the best bang for the buck stroker for the 348,next would be the 4in stroke,434 package.

 

[jr.W]

With this timing cover http://www.show-cars.com/cgi-bin/commerce.cgi?preadd=action&key=7722 would the bbc crank work needed to make
it fit be quite a bit less?
I am guessing a bbc balancer could be used with out mods.

 

[Don Jacks]

I've heard that a large harmonic balancer interferes with the stock waterpump.Yes you wouldnt have to turn down the snout.Bob Walla can sell you the timing chain set you'd need.