freshen up 474 not good
- Thread starter MRHP
- Start date
That's interesting information, thanks for posting it.
It got me thinking about some of the stroker cranks that are used in some of the aftermarket big blocks. I tried the formula on the 4.5" crank from a 572 and got 22.4% That's exactly the same as a 4.25" stroke in a 409. I guess you can go as far as a 5" stroke on some blocks, if they use the regular big block bearing sizes that would work out to -026% or no overlap at all.:eek:
I'm a little like Ronnie, my crank is a stock GM steel crank cut down to 409 specs and my block has regular two bolt mains with ARP studs. It's been working fine for the past four years but my rev limiter is set at 6,400
I do have a spare truck block that I'd love to build as bulletproof as possible. I think 4 bolt mains and a crank with big block sized mains would be nice. And if I went that far I'd also keep the big block sized snout, Lamar makes a timing chain cover that works with the big block snout. I think a setup like that would be quite reliable to 7,500 or so.
It got me thinking about some of the stroker cranks that are used in some of the aftermarket big blocks. I tried the formula on the 4.5" crank from a 572 and got 22.4% That's exactly the same as a 4.25" stroke in a 409. I guess you can go as far as a 5" stroke on some blocks, if they use the regular big block bearing sizes that would work out to -026% or no overlap at all.:eek:
I'm a little like Ronnie, my crank is a stock GM steel crank cut down to 409 specs and my block has regular two bolt mains with ARP studs. It's been working fine for the past four years but my rev limiter is set at 6,400
I do have a spare truck block that I'd love to build as bulletproof as possible. I think 4 bolt mains and a crank with big block sized mains would be nice. And if I went that far I'd also keep the big block sized snout, Lamar makes a timing chain cover that works with the big block snout. I think a setup like that would be quite reliable to 7,500 or so.
I was thinking the same thing myself. If that can be done, how does that effect the connecting rod length, or wrist pin location, in the piston, and timing chain length. Skip
All that stuff should stay the same. When Lamar Walden was at the big convention he said he liked to use BBC sized mains. But keep in mind that Lamar specializes in race engines. I think he probably uses billet caps when he does this. Boring the stock caps out to big block size might weaken them.
I don't really know.
I think for most of us just getting a stroker kit that works with the stock two bolt mains is the easiest way to go. And it should last just fine as long as you keep the revs down to a reasonable level.
Couldn't you make your own timing cover for the big block crank by migging in a big block seal opening in the 409 cover? You could even fillet weld it in.
After turkey was consumed, I got to thinking about Gary's formula. Another tool for engine building. Spent an hour trying to figure out how best to use the formula. Nothing. Could not come up with one example of how this formula would aid in parts selection. The wider an arm swings, the more pressures exerted on the crank spine and block main bores. Didn't need a formula to know that. A bigger main journal is stronger than a smaller journal. Didn't need a formula for that. Pick a block, pick the size of engine you want and put it together. Where does the formula come in?? No, I don't get it. Lighter pistons? Everyone uses the lightest piston-rod combo they can for any performance engine. Stroker or non-stroker. Gary uses the word "must" instead of "in my opinion , you should"....... There are many 4 inch stroke 409s across the country that have been running for years very well with 409 size mains. Ross pistons and steel rods. Since I have experience only with GM cranks, I would like to know which aftermarket cranks have the center courterweights. Maybe all?? That would be a big asset. Well, thanks anyway Gary for the formula. It is interesting to play with, I just dont see how it translates into a benefit for picking w-head stroker parts.
Ah heck, what's wrong with building a "REAL 409" with a 3.5" stroke? I would sure like to build one that would get me in to the solid 11s and still be streetable! Think I can do it? Is it going to take a better intake, Bobs aluminum heads? I can start with the 62 block I have. I wonder if the new Edelbrock intake will flow better. I have to find that missing torque 
Tunnel ram Maybe put in that left peddle 
Is it going to take a better intake, Bobs aluminum heads? I can start with the 62 block I have. I wonder if the new Edelbrock intake will flow better. I have to find that missing torque Tunnel ram Maybe put in that left peddle 
CDNpontiac409guy
Banned
Ah heck, what's wrong with building a "REAL 409" with a 3.5" stroke? I would sure like to build one that would get me in to the solid 11s and still be streetable! Think I can do it?
Kind of what I was thinking, Fat
bang Heck, ya' put in a 4" crank, and it sure isn't a 409 anymore
. I think a real 10.5-10.75:1 ( using the right piston
), properly prepared, with some porting, 690 / 583 heads, a stout high-lift solid or solid roller cam, and a proper intake ( Lamar's or of course a tunnel ram ), with a pair of Holley's... and you're there. 1 5/8" tube tri-Y headers won't cut it either. Will require proper 1 7/8" tube.
GOSFAST
Well Known Member
Ronnie, I don't put this info here to "scare" anyone but to make you aware of certain conditions that need to be addressed on every build from a "builder's" standpoint. By having this formula AND the dyno results to reflect back on, we can determine ahead of time whether or not we will have any issues. That's all this is about, I cannot have "comebacks" for any reason, I barely have time to do these things once, let alone twice!
When you start upping the stroke you should be paying close attention to the details. Most especially the details that cover the all the reciprocating pieces. You want these to be as lightweight as possible but NOT sacrifice the integrity of the part. Light pins, pistons, rings, etc. should all be used if possible! The newer 2618 material for the pistons was a move in the right direction, as the material became stronger, the weight was able to come down some! It's only slight, but it helps.
You really need a piston in these strokers around 650 grams. Remember, this is a fairly large bore to support that weight piston when you factor in the "dome". We are using 600/650 grams, with medium domes, in the BB 540" platform.
With these "W" units you are battling a heavy piston in most part due to the inherent design of the unit itself. You cannot redesign that area, or are very limited!
The "rod overlap percentage" number to us is only used to make us aware of a reasonable expectation of how much stress/power the unit can withstand. If you stay around the 40% area you should be comfortable. Installing "steel" main caps is a "plus", but should be tied into the pan rail area (splayed) to "tie" the block together.
It all comes down to how much power will be made before the 'lower" percentages come into play and cause damage.
Chevrolet became aware of this when they drew up the plans for the BB as we know it today. They needed larger mains to support the "numbers". We have found through extensive testing that the really long strokes (4.750") in these "standard BB" blocks need the center counterweights, we've had some units without them that would not even get past the dyno tests. If you keep the stroke "reasonable", at/under 4.000", you can get by without them, but as I said, you really do need light pieces on top.
I would go one note more here and state this: these should NOT be externally balanced, they should be "internal" only, even with the 4.000" stroke and also with NO "tungsten" (heavy-metal). This is easy to accomplish with "aftermarket" cranks. The 454" (4.000") shafts we use here, not G.M.'s, will "zero-balance" with a "target" bobweight of 2350 grams. No "external" damper/flywheel!! This allows the use of the "standard" 409" components if required.
(Add) One other VERY important item to remember here with respect to "RPM limits", just as a general "rule-of-thumb", as you do go up on the stroke you tend to actually lower the power band that peak power occurs. I have some 540" BB's (4.250" strokes) coming off the dyno with 740+ HP occuring at 6200/6300 RPM. This is an extremely reasonable range for almost any BB, "W" or otherwise.
Thanks, Gary in N.Y.
P.S. When laying out the platform with the 348"/409", we try to "prefigure" if you will, the "bobweight" that we will be using on the build. If the numbers don't "look" good on paper we try to alter/adjust them to make it happen. For arguments sake here, if you said you wanted a 4.000" stroker I would try my best to come in with a 2250 (nominal) gram weight, staying with the "steel" rods. Going back through years of dynoing different combos we can draw a parallel drawing on previous "rod overlap percentages" that have NOT presented an issue.
Thanks Gary for the input, Current build is 752 gram piston and a 2426 bobweight. If a lighter 409-4in stroke piston is out there , I would like to find it. As far as external balance goes, maybe you missed the " 1,000+ runs" on the dragstrip, with external balance engines. Would you mind answering my question about the aftermarket cranks? Are they all center counterweights, or just a particular brand? Thanks,
Thanks quick9er, that was the answer I was lookin for.
GOSFAST
Well Known Member
Hi Ron, the counterweights are on the Eagle's, as stated above, they start at the 4.250" stroke and are on the larger ones.
With respect to internal vs. external balancing, you would have to have some background in both the dyno area AND the balancing of units to fully understand the advantages of the "internal" deal.
Let me see if I can make it somewhat clearer.
When the rotating assembly is mounted on the balancing equipment, you can get the shaft "up-to-speed" much quicker WITHOUT all the "external" components along for the ride. These "weighted" damper's and flywheels/flexplates do nothing but "slow" the entire time it takes for it to "come up to speed".
Now having said that, it's exactly the same on the dyno, it takes "X" amount of power AND time for the unit to "rev" for lack of a better term. In other words the unit is taking some of the available power to literally "spin" these external components up. It's exactly the same scenario with the lightweight parts and the HP gains from even the ring-packs we choose.
It's for this reason I would most likely NOT do an "external" balanced unit if I can avoid it. The only time I've done them is on some units that HAD to be 100% correct appearance-wise, where they HAD to use both the 454" damper and/or flywheel. I've done dozens of these 496's "external", but I've also done most internal. Not even sure on the BB's anymore you can purchase an "external" steel 4.250" stroker. I believe they've been discontinued for the most part.
Before I would use a 400" damper OR flywheel on a "W" stroker (4.000"), I would "fill" the shaft with the "tungsten". On the "4340 steel" Eagle's this isn't even necessary!
Of the few 4.000" '09's I have done, my guy's wanted to retain the '09 damper and flywheel. Easy, no problem!
As I stated, the Eagle 454" crank's make a 2350 gram "target" even without the center weights. I'd have no problem making a 2350 B/W (internal) on an '09 with the 4.000" arm!
With respect to the amount of dragstrip runs, it would "hinge" entirely upon how much HP was available. The more power you produce the more "maintenance" you will incur and the less trips "down the strip" you'll make!!
Thanks, Gary in N.Y.
P.S. All the info above pertains to "steel" cranks, I use almost no "cast" cranks whatsoever.
I see that the new Eagle 4" crank for the 409 is designed for internal balance.
Here's a link, it's about a third of the way down the page.
http://www.eaglerod.com/Big_Block_Chevy.pdf
The sheet that came with my 10 1/2 to 1 Ross pistons says they weigh 675 grams. That seems light. They're for a 4" stroke with a 6.135 rod. Maybe a higher compression version of the same piston would weigh more.
Does anybody know if the pistons that take a 6.385 rod are any lighter?
I don't think I've seen pistons advertised with a compression ratio of more that 13 to 1, and of course you loose some of that with a truck block. Does anybody make a 14 or 15 to 1 piston?
Here's a link, it's about a third of the way down the page.
http://www.eaglerod.com/Big_Block_Chevy.pdf
The sheet that came with my 10 1/2 to 1 Ross pistons says they weigh 675 grams. That seems light. They're for a 4" stroke with a 6.135 rod. Maybe a higher compression version of the same piston would weigh more.
Does anybody know if the pistons that take a 6.385 rod are any lighter?
I don't think I've seen pistons advertised with a compression ratio of more that 13 to 1, and of course you loose some of that with a truck block. Does anybody make a 14 or 15 to 1 piston?
Ah heck, what's wrong with building a "REAL 409" with a 3.5" stroke? I would sure like to build one that would get me in to the solid 11s and still be streetable! Think I can do it?
This is an interesting thread.
bang We know that if you were to take two identical engines and give one a 3.5" stroke and the other a 4" stroke they would both make similar horsepower. The main difference would be that the shorter stroke engine would have to rev higher.
My guess is that a 474ci engine reving 6,000 rpm might last longer than a 409ci engine reving about 7,200 but it's just a guess. I think a 409 that reved about 8,000 rpm would really suit my 55
bang but then my converter and gearing would be all wrong, so I'll probably stick with the 4" stroke.What crank to use is always an interesting debate. Do you go with the fast reving 3.5 inch stroke or the big torque of the 4" stroke,,, or do you split the difference and use the 3.76 inch stroke.
Jim, The 2 spec sheets I have show 796 grams and 818 grams. I want some like yours !!! I have used a set of Ross that were 13 1/2 cr. Don't see why they can't offer 14 or 15 to 1.
I may have missed this somewhere , did anybody address this question ?
Rusty, The larger crank diamiter is stronger. How much is "strong enough". Guess it comes down to money again. Spend a lot of money to build a stroker with 409 main size or spend a whole lot of money to use BB size mains. BB size mains have more problems to solve. Main caps, timing cover, etc. All adressable, but takes more money. Maybe a simple way to look at it would be rpm desired. 6,200 or 7,200?? But then those with funds would prefer BB size even for 6,200. No easy answer, it all depends on how safe one wants to feel.
I have been working at a machine shop that builds pulling engines for pickups and tractors. These are mostly supercharged engines but when the engine is on the dyno and the rpms get to a certain point the HP really takes a nose dive. The point I'm making is that sometimes we push our engines way past making any more power just because they will. The heads and intake are what makes an engine breath and with the new heads out we should see some major power increases without 7000 and 8000 rpms. You get into all kinds of trouble with valves, springs and lifters at these rpms. If your horsepower is starting to drop at 6500 why push it to 7500? My cousin had a Vega with a 454 in it. He always went to 7500 and shifted, I drove it a few times and I had a better et and about 2 mph faster than him. He wanted to know what I was doing different than him. I said I shifted at 6500 rpm. Roy
Roy
Roy, Anything new on the 6 cyl plans???