Wanna build a 409 a little different way?

[Greg Reimer]

OK,guys, it's the lull between the storms, between either Christmas and New Years, or between the World Finals and the Winternationals, but I got curious. How do you turn a 348 into a 409?
First, find a 59-61 348 block, crack check it, sonic it, all that stuff, and determine that it would clean up at.040". Those might be hard to find,however.
4.125"plus.040=4.165. X r squared is 4.336X Pi =13.62" X 3.76stroke( 396 crank),=51.21 cu. in. disp. per cylinder,times 8= 409.69 final cubic inches. That produces a 409 that is dimensionally different by way of the smaller bore and the longer stroke. You would have an advantage of the longer stroke and with the smaller bore, the piston could be made scads lighter than an OEM 409 piston was. To use the 6.125" rod, better yet, see if a 6.250 rod could be made to work, you would deck the piston at least 1/8th inch,and move the pin bore up as well. This could result in moving the rings higher up on the piston, improving ring seal. Put some godzilla steel main caps on this thing, of course, you filled the block to the bottom of the freeze plug bores, and your short block is done. Advantages would also include having more deck area around the cylinder bores for gasket sealing surface to be wider and therefore, more stable,then use your choice of camshaft and heads. Just make sure you have adequate clearance between the valve heads and the cylinder walls. No reason that this wouldn't work,especially since the overbore isn't so great that the block was weakened by being overbored. Just a thought,guys, we're not snowed in here, it's sunny and 75 degrees. I thought of this,figured it out, and had to write this down while the idea was still fresh.Has anybody built one of these yet? Love to see a response to it, why it would work,or why not.

 

[Don Jacks]

Well Greg,I think that your combo would work,but you're overthinking it a bit.You can buy from Show Cars,a set of Ross pistons made for this combo using the 6.385 big block rod and a 3.76 crank.Most of the 6.250 length are made for a small journal small block crank.While it could be done,the bottom end would be weaker since these rods are made for the 2bbl.,lightweight piston combos up to about 450 hp.Joe Sherman built a 434 or so cu.in engine using no 4bolt caps or "hardblock",using an early 58 348 block.It made 650 hp,and one of the jims ran it for a year using a peak rpm of 72-7300 rpm until the "trick" roller cam failed and screwed up one of the lifter bores.Jim posted that there was no sign of cap walk.He was using the 6.385 rods and a custom piston with trick rings.Yes what you propose could ,cu.in. wise could be,and has been done.The problem would be keeping the valvetrain alive at 7500 rpm,not this short block.

 

[Greg Reimer]

I know Ross made all kinds of pistons for just about anything, they make Super Stock pistons for other Chevy applications, so this wouldn't be the problem. The 396/427 Chevy big block combo makes all kinds of power with OEM length rods, so rod length increases might not even be worth the problems and trouble. No way do you want to compromise rod construction,strength,or big end dimension. Also,7200-7800 is above the RPM limits I was even considering, in fact, I hadn't considered it. The cam and valve train operate inconsequential of the crank RPM,until something fails and breaks it, so the before mentioned valve train issues have nothing to do with it. also, unbenounced to many, the roller lifters in most applications need periodic rebuilding with needle bearing replacement every 60-80 runs,this is basic Super Stock maintenance.It is essential to have a roller lifter with an out of the box type of application so that replacements are readily available. That way, when lifter maintenance time comes, a new set can be installed and the used set can be sent out for rebuilding and the car isn't subject to down time. That could have been the problem with the Sherman power plant, I am only speculating,I didn't see it.
We did have a 409 CCA member back in the day that had a 348+1/8th plus a 3.76 stroke crank in a Super Gas 55 Chevy, with a Powerglide and a trans brake and whatever 9 inchFord gears he had, it went 9.90's at over 135 or so. He went rounds with it, and it was a pretty remarkable 427 inch 348. This was about 25 years ago or so, so the development of W motors was nowhere near like it is now.

 

[Tom Kochtanek]

That could be interesting, as most of us can locate a usable 348 block at an affordable price, as opposed to a good 409 block.

We have a 396/427 stroked 409 block currently set up in my '62 SS car, but I went with a 409 crank in my 348 tripower build.

TomK

 

[Travis Horton]

That's exactly what our W engine is. 380HP intake, no compression, small solid roller, and the wrong converter spec'd for a high winding 461 bbc. It's run a best of 11.00 at 121mph and shifts at 6500. The 60ft. is only 1.60 with the wrong converter. The right conveter should get it around 1.45 to 1.48 making it a full time 10 second ride.

 

[boxerdog]

I've got one of these too, I built it several years ago as a mild cruiser combo for my '37 Chevy truck project. The short block is solid, 655 block, BBC crank, scat 6.135 rods, Ross pistons, etc. Comparing balance cards, it is VERY much lighter than a 409. So I have a mild hydraulic cam in it, small port heads, Offy intake...etc.

But then the '37 project stalled a bit and I got looking at that engine. Right now the plan is to put on a set of BWRs, an Edelbrock intake which I have with 2 Demons and a much more serious cam. I've got all of the pieces sitting here. Then I might put this combo into my '63 Nova and put a 348 in the truck.

So, I do like the overall combination and I appreciate all of the info you guys are posting.

 

[303Radar]

OK,guys, it's the lull between the storms, between either Christmas and New Years, or between the World Finals and the Winternationals, but I got curious. How do you turn a 348 into a 409?
First, find a 59-61 348 block, crack check it, sonic it, all that stuff, and determine that it would clean up at.040". Those might be hard to find,however.
4.125"plus.040=4.165. X r squared is 4.336X Pi =13.62" X 3.76stroke( 396 crank),=51.21 cu. in. disp. per cylinder,times 8= 409.69 final cubic inches. That produces a 409 that is dimensionally different by way of the smaller bore and the longer stroke. You would have an advantage of the longer stroke and with the smaller bore, the piston could be made scads lighter than an OEM 409 piston was. To use the 6.125" rod, better yet, see if a 6.250 rod could be made to work, you would deck the piston at least 1/8th inch,and move the pin bore up as well. This could result in moving the rings higher up on the piston, improving ring seal. Put some godzilla steel main caps on this thing, of course, you filled the block to the bottom of the freeze plug bores, and your short block is done. Advantages would also include having more deck area around the cylinder bores for gasket sealing surface to be wider and therefore, more stable,then use your choice of camshaft and heads. Just make sure you have adequate clearance between the valve heads and the cylinder walls. No reason that this wouldn't work,especially since the overbore isn't so great that the block was weakened by being overbored. Just a thought,guys, we're not snowed in here, it's sunny and 75 degrees. I thought of this,figured it out, and had to write this down while the idea was still fresh.Has anybody built one of these yet? Love to see a response to it, why it would work,or why not.

What need to fill the block is there? Several 348s have been turned into 430+ using a 454/4.00 crank with no problem.

 

[Don Jacks]

To my way of thinking,Hardblock would only be necessary in a severly overbored[.080-up] block that was heavily boosted,or very high compression,and intended for the stresses of high rpm racing.I could be wrong.

 

[Greg Reimer]

Hardblocking a .040-060" over motor wouldn't be necessary,but anything over that that gets seriously romped on would definitely be a good idea. Hardblok stabilizes the entire bottom half of the block and stiffens the main saddles as well. The 409 crank in the 348 isn't a bad idea, comes out to 374 with a standard bore,(4.125")and would make good torque.
How easy is it to find standard 348 blocks that would clean up at .040"?

 

[Tom Kochtanek]

Greg asks: "How easy is it to find standard 348 blocks that would clean up at .040"?"

I used to run into these a few times each year, generally at swap meets or via Craigslist ads. For a while there I was following up on nearly every "W" within easy driving distance. I purchased a fairly complete but disassembled standard bore 250 horse 348 about three years ago for $300 at a local swap meet. I gave $500 for a complete 1965 "655" block with 333 heads and a "409" truck oil pan around that same time (also standard bore). I passed those along to others since acquiring them. Haven't seen any lately that spark my interest. Seems everyone thinks they are as desirable as 409s and are asking high dollar ($1K-$2K).

I try to focus 348s that have interesting date codes (I like the 1961s) or lead a high performance life (FH and FA blocks). I also prefer those service replacement 962 casting and of course the 655 castings from around 1965.
These are the ones with the ArmaSteel main caps.

TomK

 

[oldskydog]

The mistakenly maligned 58 872 blocks cast after March 27 for trucks and after May 21 for cars had spark plug cooling provisions and also had thicker cylinder walls possibly sufficient for boring out to 409 specs. I have one in my possession which I someday plan to build to 409 specs. I believe that it is possibly the best of the 348 blocks for building because of the popular misconception and resultant price advantage and the thicker cylinder walls.

 

[Tom Kochtanek]

Thanks for noting that Cecil!

I have one of those 872 blocks from 1958 that I was going to use for my mailbox for the new Manshed . I guess I'm going to look for a cracked 348 block instead, pretty sure I have one or two of those laying about.

TomK

 

[Greg Reimer]

Ok, guys, what if you found some giant overboard block with shaggy cylinder walls that you definitely couldn't overbore another time and have anything left stable enough to use? Like a 409 block with BBC mains, steel caps, and the usual race work done to it? Why could you not install 8 sleeves in it and bring it back to a 4.165" final bore? The cost of obtaining a block like that that had the time consuming and expensive work already done to it would be a cost saver in the long run.That would be a solid engine with good cylinder rigidity and it would retain its roundness for a long time .Just another thought.

 

[poison ivy]

i would be interested in how many machine shop people on this site, would install eight sleeves, aprox cost, and insure no leaks, or advise to insure long life.as well as cost to get block ready for assembly.

 

[Don Jacks]

I can think of about 1600 reasons ,which is about what it would cost to have that done.If said block could be bought cheap enough,absolutely! Save another 409! If it were mine,my call would be to Tony Schaffer at Day automotive.

 

[MRHP]

If it were a decent block, with other upgrades, I would sleeve 8,but shoot for 4.312 bore. I never was much for schoolin' though.

 

[scott hall]

Doubt you'd find a shop willing to do all eight. Way to much taking out of block to put in that many sleeves.

 

[Tom Kochtanek]

I have a 1963 814 QB block that I picked up in a barn and found to be .100" over with no room for an overbore. Putting 8 sleeves in that block might be doable, but you have to think there might be some distortion there or something that might compromise the final effort. Plus there's that cost to resleeve. Right now it's a decoration .

TomK

 

[Greg Reimer]

I understand your initial reactions to all this,but we're not going for a maximum overbore here. I never would have considered such a thing, but I learned that the way to build a Stock Eliminator 396 for a Camaro or Chevelle or whatever, is to get an ordinary garden variety 454 2 bolt main block, make sure it's dimensionally within reason, and put 8 sleeves in it. Next,fill it to the bottom of the freeze plug holes with Hardblok,then line hone it after a week or two of cure time. At that point,bore and power hone,making all 8 cylinders round and very straight. Doing any corrective machine work after all this would also remove any distortion caused by the subsequent work. On the 396, you eliminate that little cut out on the cylinder wall at the top for a valve relief,gaining a little compression in the process. Now, this thread started to discuss a way to build a 409 out of a 348 while taking advantage of a longer stroke,better rods,and lighter pistons. We have come a ways since then,however, you guys like to think outside the box also.That's great.I do agree,that would be a costly endeavor,but what do aftermarket blocks cost?Might be nice to own a machine shop!