WOW! 4.25" Stroke Small Block Cranks now availavbe from BPE!

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DJVCUDA said:
Somehow this turned into my engine build thread - so here is the update...


well just a quick update- the deck was a mess when we put it on the ROTTLER CNC machine - 12 thousands off on the drivers side and 10 thousands off on the passenger side.

While the deck was flat - and this block was machined at a very reputable shop in the 80's the machinery of today has brought inconsistencies like this to the forefront of modern engine building.

so I had a flat, crooked deck on this sucker. But it will clean up within spec for the rotating assembly.
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Speaking about the rotating assembly - It measured out to 1794.6 grams for the bobweight - nice and light!

Weights were consistent for everything :

Rods: +/- 2 grams - 599-601
pistons - +/- 1 gram - 471-472

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Just out of curiosity - does anyone know the stock 340 rotating assembly bobweight?


The TCI Rattler had to be fitted to the crank which was 1.532" and the balancer was 2 1/2 thousands smaller - It was honed to fit with a 1 1/2 thou press fit.

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so we're gettin there - slowly but surely.
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I sent a reply to your pm and said your box is full.
 
kielbasa said:
heck, i was at a reputable shop last year while they were decking a block - all they did was follow the existing deck surface and "cleaned 'er up"......after my brother put the block in a Rottler, neither decks weren't parallel to crank, along with different deck heights! the mentality of some machinists just makes me shake my head.......
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I look at it this way: 40 yrs ago manual drum brakes and bias ply tires were what was considered acceptable for a factory produced car. Perfectly safe, and performing well enough for even the highest powered cars. A modern base model car will come with power assisted disc brakes and all weather radial tires usually with short sidewalls for stability. It's just called progress. If I brought in my Neon, and a guy wanted to put front drum brakes on it I wouldn't accept it. The fact that "good enough" back then was fine does not mean it's good enough now. But modern stuff costs more, and I think we all price shop first, then ask what the differences are. Some shops don't have the equipment to properly sqaure deck. Some have the erquipment but are still stuck with using a miller that can't cut flat or smooth enough even when run by the best guy on the planet. Some have the best equipment and then "all the options" are simply part of thier standard job that costs more than other's base operation.

Sorry Dave... Got off topic there. I'll shut up now...
 
The shop that did my short block line honed it first and used the crank center line to measure where to cut the deck. They had the right equipment and knew how to use it.
 
Got the block bored and decked last night - the cylinder to cylinder center to centers were not off too bad - the worst was 2 thousands - there were a couple exact ( .0000 ) so thats cool

The Rottler CNC will bore the exact centers for all the new pistons and have the bores exactly where they are supposed to be.

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After all the cylinders were punched out we decked the block.
Remember I said earlier that the deck was flat - but not square to the deck? well after the first cut you can actually see the difference in out of square...

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This shot was taken as the second pass was being made on the deck. - you can clearly see the top of the deck was taller then the bottom, and not it is square to the cylinders.

Like I said before the block was built at a very reputable shop - imagine what it would look like if it was not...lol
 
very kool build... Would it be acceptable to use a standard 360 block say, with a Hughes main stud girdle? I want to build one now...
 
I'd cap and stud it before I did the girdle, personally with a stock block.
 
eventually ported eddy heads - the block was already tubed so I am leaning towards a solid roller
 
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Mocked up the rod, piston and bearing - the counterweight needs to be .060 away from the skirt - we have that by a mile

This is something brand x guys would think of and the mopar guys take for granted with the tall deck.
 
I've been out of Mopars for a few years but have really been following this thread. I like the idea of the 4.25 stroke and the extra cubic inches but it seems like most people will run this setup with aftermarket heads. That's great if you got the bucks but if I spend this kind of money on the block I won't be able to afford new heads, too. I have a set of "X" heads that were ported in the late 70s that have been sitting on the shelf for the last 30 years. They were on a standard bore 69 340 with 12.5-1 pistons that ran pretty well back in the day. :mrgreen: Do you think these would choke off an engine like this and you'd almost need to run modified RHS, W2 (etc.), or aluminum heads? Don't beat up on me too bad - I'm just getting back into this and I'm sure I'm not the only guy here wondering this. :toothy9:
 
All depends on your usage. A big stroke needs enough port to feed it without it wheezing. RPM will determine when it wheezes. If you are building a lower rpm engine, a smaller head will work. If you need more rpms, you have to give it port volume to get it to work. What IMO will hurt you more are the open chambers. I use modern heads for the benefits of squish on pump fuel more than any other reason.
 
Well, I gotta kind of run what I got. :toothy9: I have 5 sets of 340-360 heads collecting dust. I could probably pick up a set of the newer "swirl port" (?) or whatever they're called heads pretty cheap, though, if those would run better and keep the old stuff for a more stock engine, I suppose. I haven't really checked into Magnum heads much yet - all my stuff is pretty old (like me). :glasses8: So . . . can a stroker like this make good power with stockish iron heads or do you pretty much have to go the aftermarket route? I guess I should wait until somebody's built a few of these, huh? :???:
 
AMC PackRat said:
Well, I gotta kind of run what I got. :toothy9: I have 5 sets of 340-360 heads collecting dust. I could probably pick up a set of the newer "swirl port" (?) or whatever they're called heads pretty cheap, though, if those would run better and keep the old stuff for a more stock engine, I suppose. I haven't really checked into Magnum heads much yet - all my stuff is pretty old (like me). :glasses8: So . . . can a stroker like this make good power with stockish iron heads or do you pretty much have to go the aftermarket route? I guess I should wait until somebody's built a few of these, huh? :???:
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fvor sure the x heads will hurt the power
improve of stroker like that but it depend
on what kind of power you wanna make
you can built a torque monster with that stroke
and x heads but can do better with after market
heads
 
crazy 340 said:
fvor sure the x heads will hurt the power
improve of stroker like that but it depend
on what kind of power you wanna make
you can built a torque monster with that stroke
and x heads but can do better with after market
heads
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What the hell are you trying to say?

I have read what you wrote a few times but I can't figure out what you are talking about.

Kind of early to be drinking.
 
fcm42000 said:
What the hell are you trying to say?

I have read what you wrote a few times but I can't figure out what you are talking about.

Kind of early to be drinking.
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Hell I thought it was my eyes going bad but like you said,,WHAT?
 
65TerrorCuda said:
Now that sounds like a fun ride. 440 through spitfire headers? Hmmmm
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Your joking, right? Maybe Hedman 2" W2's with an LA flange. You could run a chevy 6.00 rod and get away with a chevy 4.00 piston too, probably close to working off the shelf as they have chevy journals anyway. 6.123 Mopar rod = 6.00 rod with a .125 higher throw 4.250 stroker crank= +.002 deck height on a stock block, right??
 
got the caps fitted and drilled today.

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I was curious about the stroke of the crank so we mocked up a piston and it's not out of the hole as anticipated - the fixture or indicator was off regarding measuring stroke and it's dead on 4.125 as advertised - not 4.133 as measured a few weeks ago - always good to double check.
 
and man - now I know why they charge so much to fit main caps - trying to get the air gap set for the .0015 to .0002 clear under the splayed portion of the cap a little at a time as you get closer and closer is alot of time, and time is money!


There is a pretty significant size difference between the two - so it should hold up to the power i * could * make if I ever upgrade to a race head...
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Like I said - it was mocked up today and there is a ton of room from the last clearance job - the 2" journals certainly help the situation!
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From left to right :

4.125" Stroke setup - BPE Piston - .927 pin - Compstar 6.200 Rod w/ 2" journal - total weight - 1186g - Total Bobweight - 1749g

4" Cast Stroke setup - KB Piston - .984 pin - SCAT 6.125 rod w/ 2.125" journal - total weight - 1216g - Total Bobweight - 1799 G

3.31" Stroke Setup - Stock Piston - .984 pin - Stock rod - total weight - 1508 - Total Bobweight? over 2000 G I assume?

Anyone know?

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I wonder if you could use the rods and pistons for a 4" stroke with 4.125 stroke crank in a tall deck R3 block. Anyone know?
Those BPE pistons have a skinny oil ring and the rings are close together. Also seems like they would rock more. I think the bob weight on my scat h beams with those KB pistons for my stroker was 1769. That was before I had .040 milled off the step of the pistons, so may have been slightly less.
 
OK - a few updates - the heads are at Shady Dell Speed Shop to get the port work done.


The cam selected will require a 954 spring ( double with damper ). This required a tool steel retainer and super 10 degree lock.

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The lifters are the COMP 8043 lifters that have the link bars in the front as opposed to the older style 828 lifters. These should require no grinding on the block and since the block is tubed the ability of the lifter to pushrod oil is not going to be used.


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Side shot of the lifters.
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