4u 429 crank and cj rod strength

hello everyone. I have a couple questions. I want to put together another boss 9 engine with a d1ve block I bought 3 sets of pistons at the ford Carlisle nationals. they are all arias the set i'm gonna use are 4.375 bore and was wondering if the set of scj rods I have and 429 cast crank I found will survive 10 to 15lbs of boost? I understand the tune is the biggest variable. if the crank is strong enough i'll just get some H beam rods...  my intended use is to go in my 69 mustang tube chassis drag car I'm building..... second question is there a way to figure out rod length and stoke of a piston. the 2 other sets of pistons only have limited info with them.  one set is 4.629 bore and the second set is 4.43 bore. smaller set the wrist pin isn't into the oil rail. the big bore set has the wrist pin all the way through the oil ring land and they have Jon kaase written with the job # but they are older. I can provide pictures if it helps. thanks for any replies....... joe

Given the journal diameter and journal overlap of a 429 crank, I don't know that they can be broken. Probably take four figure HP for sure.

On the pistons, take the compression distance (distance from the top of the piston to the center of the pin bore), and figure it out from there. 1/2 stroke + rod length + compression distance - deck hieght, will give you the theoretical piston/deck.


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thank you for the reply Carl that's what i was hoping to hear..... i am shooting for 4 digit hp. there are a lot of LS turbo stuff around where i live and i want to show them  what happens when they run into a boosted 40 year old bbf lol..... thanks again

Watch the rod length on the Pistons real boss 9's can have different length rods than a regular 429/460.

The crank will take anything you can throw at it the rods are not as good. Shooting for 4 digit Hp you better put some decent rods in it

thanks for the reply!... i think I'm gonna go with a good set of H beams and some L19 rod bolts just to be on the safe side. the pistons i am using are for standard 6.605 rods not the nascar rods.

+1 - H beam rods , SCJ's won't cut it.

L19 bolts are a pain in the butt. 2000's would be my choice.

Carl wrote:L19 bolts are a pain in the butt.  2000's would be my choice.

2000 should be plenty.

You should also step up to a Ford Racing A460 block, or an Eliminator block instead of a D1VE production block.
Although there is debate as to the ability of the factory block being able to handle it....its a 50/50 shot.
It may handle the power and come back for more....or it may grenade and take out your whole project.

The 4U 429 crankshaft has proven itself to over 1700 hp on dynamometers and faster than 7 seconds down the track.  Obviously, the more you push it the shorter it's life and the greater the risk. Assuming ~1000+\- hp you should be fine. Mag check the crank each freshening (that shouldn't alarm you--it's simply a prudent part of a racing program).

Definitely change your rods. Most brand name H-beam rods will suffice past 1000 hp. As this is a drag car you might also consider aluminum rods if the pistons you are using dictate a custom rod length.  Aluminum will also be easier on the crank and cylinder block.

With your 4.375" bore pistons, you should have no problems with the OEM passenger car block.  This holds true provided you stay with the OEM main bolts.  Once you step up to aftermarket studs or bolts all bets are off and risk of of block failure increases big time...in my opinion doing so almost a guarantees block failure.

Laslty, build such an engine intentionally loose and let things move around.

BBFTorino wrote:...there is debate as to the ability of the factory block being able to handle it....its a 50/50 shot...

^^^False.^^^

50% of passenger car blocked blower builds do not fail.  In fact when built and operated properly I estimate that greater than 90% provide reliable service or the life of the build. Furthermore of the last 10 percent, perhaps half of those that break are due to either user error or another engine component (ie, con rod, etc) taking out the block, not the other way around.

Paul Kane wrote:

BBFTorino wrote:...there is debate as to the ability of the factory block being able to handle it....its a 50/50 shot...

^^^False.^^^

50% of passenger car blocked blower builds do not fail.  In fact when built and operated properly I estimate that greater than 90% provide reliable service or the life of the build.  Furthermore of the last 10 percent, perhaps half of those that break are due to either user error or another engine component (ie, con rod, etc) taking out the block, not the other way around.

If that's true, then 50% DO fail, so you're agreeing with the 50/50 shot...
Doesn't matter why they fail.
So your ^^^False.^^^ is False.

32.7% of all statistics are made up.

Scott, I think Paul meant to say that those builds DO NOT HAVE A 50% FAILURE RATE....not that 50% of them do not fail.

Just for clarification...um, I think...

Re-read Post #11 again, Foxwell; your allegations are not at all what I said.

The statement of mine that you highlighted in bold is a not a stand-alone statement from me that "50% of passenger car blocked bower builds do not fail," it is a rebuttal to another individual’s statement who himself said that there’s a 50/50 chance (ie, 50%) that big-powered, OEM-blocked blower engines cannot handle their own power output.  I quoted his statement, and even pointed up to it via arrows straddling the word "False."

Are you able to determine what percentage of OEM blocks I suggested (above) are likely to fail unto themselves?  (By the way, based on personal experience and other feedback loops on such builds, even my posted percentage of stand-alone block failure rate is generous).

Thanks for the reply Paul Kane.... I also have a d9 block is there any advantage one block has over the other?

Paul Kane wrote:Re-read Post #11 again, Foxwell; your allegations are not at all what I said.

The statement of mine that you highlighted in bold is a not a stand-alone statement from me that "50% of passenger car blocked bower builds do not fail," it is a rebuttal to another individual’s statement who himself said that there’s a 50/50 chance (ie, 50%) that big-powered, OEM-blocked blower engines cannot handle their own power output.  I quoted his statement, and even pointed up to it via arrows straddling the word "False."

Are you able to determine what percentage of OEM blocks I suggested (above) are likely to fail unto themselves?  (By the way, based on personal experience and other feedback loops on such builds, even my posted percentage of stand-alone block failure rate is generous).

LOL... "BAZINGA".

Bosskk1786 wrote:Thanks for the reply Paul Kane.... I also have a d9 block is there any advantage one block has over the other?

I like D9 blocks, and not only for the slightly longer cylinders that most people point to.  It's been my experience that the D9's show more consistent sonic check wall thickness from cylinder-to-cylinder within a block compared to earlier engineering revision blocks.  But for your build as far as "advantage over the other," no, I would not say any particular engineering revision has an advantage for your build, it's more about selecting a block well suited for the application.

Since you haven't built it yet there's one last thing to consider and that's 4-bolting the block with aftermarket caps.  It will increase reliability and minimize maintenance, particularly in the area of bearing life.  Also, in blower engines on occasion some people have cracked their cast #2 main cap--the blower belt tugs upward on the snout and the crankshaft pivots or "see-saws" on the #1 main web, thereby pushing downward on #2 cap and breaking it.  This is not a common failure but it's something to consider.  Locate the lower blower pulley as close to the timing cover as possible so as to minimize leverage on the crankshaft.

You ought not feel alarmed by this last statement, and 2-bolt blocks below 1000 hp can work well if set up and operated reasonably and wisely...but hey if it's still apart then billet main caps are just $100 + installation.  If you do 4-bolt the block, stick with the OEM main bolts, use common grade 8 fasteners for the outer bolts as well, and those outer bolts should extend 1-1.25" beyond the underside of the main caps.  If you don't 4-bolt the block, you'll likely be fine but have more teardown maintenance.

Thank you for your knowledge Paul!.... I will 4 bolt main it. I'm planning on twin turbos. Something that will give me room to grow in case I want to go bigger on the cubes. I figure the my extra set of boss heads should make power pretty easily, Ohio George had great success doing it!

Paul Kane wrote:The 4U 429 crankshaft has proven itself to over 1700 hp on dynamometers and faster than 7 seconds down the track.  Obviously, the more you push it the shorter it's life and the greater the risk. Assuming ~1000+\- hp you should be fine. Mag check the crank each freshening (that shouldn't alarm you--it's simply a prudent part of a racing program).

Definitely change your rods. Most brand name H-beam rods will suffice past 1000 hp. As this is a drag car you might also consider aluminum rods if the pistons you are using dictate a custom rod length.  Aluminum will also be easier on the crank and cylinder block.

With your 4.375" bore pistons, you should have no problems with the OEM passenger car block.  This holds true provided you stay with the OEM main bolts.  Once you step up to aftermarket studs or bolts all bets are off and risk of of block failure increases big time...in my opinion doing so almost a guarantees block failure.

Laslty, build such an engine intentionally loose and let things move around.

Hi Paul, so your saying if ya Got a dove block with Boss bulk heads with Milodon  Splayed caps with Studs That I should go back factory bolts? I seen and read the factory bolts are bigger and fit better in the caps then studs. With the splayed bolts wouldn't that under normal circumstances keep caps from floating around even with stock bolts? I would love to build a 429 one day and spray it heavy a few times while having a decent street motor that can get over ten MPG. Be about a 600 hp 10.5 to one motor , street roller custom cam. TFS streets that flow 380/ 260+. Would want 1000-1100 on hose. I would us a duel stage 200 then 200 to ease the load of the hit. Got my Son hooked now, Hope it can be a father and son project one day. Please advise on the Bolts. P.S. I always liked 3.25-3.5  on the cranks mains. Don't think the factory studded bolts would hold my canton tray high enough, guess I can use the long extension nuts and use bolts to hold down. Thanks for any advice, gotta keep dreaming or just lie down and never get up!

Actually, there are two distinctly different type main bolts which are O.E.M. with a big block Ford block. Some bolts are straight shanked and some have most of the shank diameter decreased so all their stretch is not all happening within the root diameter of the threads on the bolt.  The straight shank bolts are stronger but, the cut down shank bolts are more forgiving to any detonation and possibly saving the production cast caps from cracking.

In lieu of 4 bolting, I have had great success with steel strapping across the machined flat stock caps, (now you do need longer bolts), or using the "Program Engineering" front, steel, 2 bolt cap on all the first four places.

I looked up the $100 billet caps and found they are splayed not like stock 4 bolt setup. Thats why I asked about my Milodon caps. I doubt in good tune it make a difference with what I would make, but will look into those stock bolts. Wonder if they make the studded oilpump pickup bolt in the GOOD Stepped design. I know with 351w, they let the caps walk around and alot push close to 1000 hp with power adders regularly with stock 69-74 block. This theory is sound, metal fatigue is not a good thing in the main Web 

IMHO, one thing you might want to consider for reliability is the 8/2 firing order swap. I do remember at one of the Winter Tech Seminars that Charlie Evans hosted, Jon Kaase touch on that subject. He stated that in his research it was not so much for power gains but was easier on the bearings and crankshaft. This has been discussed on here before with much controversy about the benefits. Okay, let her rip guys.

ED468 wrote:

Paul Kane wrote:With your 4.375" bore pistons, you should have no problems with the OEM passenger car block.  This holds true provided you stay with the OEM main bolts.  Once you step up to aftermarket studs or bolts all bets are off and risk of of block failure increases big time...in my opinion doing so almost a guarantees block failure.

Lastly, build such an engine intentionally loose and let things move around.

Hi Paul, so your saying if ya Got a dove block with Boss bulk heads with Milodon  Splayed caps with Studs That I should go back factory bolts?

If I came into a 4-bolted block that was already machined and set up with aftermarket studs, then whether or not I would use it that way would depend on its application.  The less power generated by the build, the more likely I'd use the block as-is (with the studs).  Which is ironic because the point at which I'd use a passenger car block with main studs in it is essentially the point where most people (including myself) would feel main studs aren't needed in the first place.  

ED468 wrote:I seen and read the factory bolts are bigger and fit better in the caps then studs. With the splayed bolts wouldn't that under normal circumstances keep caps from floating around even with stock bolts?

When it comes to main cap movement I never paid much attention to bolt shank diameter vs main cap bolt hole diameter.  With the aftermarket splayed caps I think the main cap registers in the block's webbing are what minimize the lateral movement (X-axis), while the primary main bolt fasteners are what minimize the up-and-down movement (Y-axis), and the outer splayed main bolts with their angled position triangulate and thereby tie it all together (supporting loads of both X+Y). So the primary main bolts essentially need to be just strong enough to do their job via clamping force for Y, but the clamping force I personally envision is not one which stops cap walk; it's one which does its part relative to the overall engine package.  There will be some cap movement while the OEM bolts absorb some of the load from the high power build.  You need to accept that and the additional maintenance that comes with it--but you also get increased block reliability in exchange.  If you cannot wrap your head around letting the caps move a bit, then get yourself a nice strong aftermarket block with nice strong aftermarket studs...your caps may walk a lot less but the overall maintenance level will be pretty close to similar anyway. And you'll be out a couple thousand dollars.

ED468 wrote:Be about a 600 hp 10.5 to one motor...

I'd run the block as-is, with the studs.

ED468 wrote:Would want 1000-1100 on hose.

In this case I'd definitely ditch the studs and install OEM bolts with regular Grade 8 outer fasteners as described above.

Paul Kane wrote:The 4U 429 crankshaft has proven itself to over 1700 hp on dynamometers and faster than 7 seconds down the track.  Obviously, the more you push it the shorter it's life and the greater the risk. Assuming ~1000+\- hp you should be fine. Mag check the crank each freshening (that shouldn't alarm you--it's simply a prudent part of a racing program).

Definitely change your rods. Most brand name H-beam rods will suffice past 1000 hp. As this is a drag car you might also consider aluminum rods if the pistons you are using dictate a custom rod length.  Aluminum will also be easier on the crank and cylinder block.

With your 4.375" bore pistons, you should have no problems with the OEM passenger car block.  This holds true provided you stay with the OEM main bolts.  Once you step up to aftermarket studs or bolts all bets are off and risk of of block failure increases big time...in my opinion doing so almost a guarantees block failure.

Laslty, build such an engine intentionally loose and let things move around.

Paul Kane wrote:

Bosskk1786 wrote:Thanks for the reply Paul Kane.... I also have a d9 block is there any advantage one block has over the other?

I like D9 blocks, and not only for the slightly longer cylinders that most people point to.  It's been my experience that the D9's show more consistent sonic check wall thickness from cylinder-to-cylinder within a block compared to earlier engineering revision blocks.  But for your build as far as "advantage over the other," no, I would not say any particular engineering revision has an advantage for your build, it's more about selecting a block well suited for the application.

Since you haven't built it yet there's one last thing to consider and that's 4-bolting the block with aftermarket caps.  It will increase reliability and minimize maintenance, particularly in the area of bearing life.  Also, in blower engines on occasion some people have cracked their cast #2 main cap--the blower belt tugs upward on the snout and the crankshaft pivots or "see-saws" on the #1 main web, thereby pushing downward on #2 cap and breaking it.  This is not a common failure but it's something to consider.  Locate the lower blower pulley as close to the timing cover as possible so as to minimize leverage on the crankshaft.

You ought not feel alarmed by this last statement, and 2-bolt blocks below 1000 hp can work well if set up and operated reasonably and wisely...but hey if it's still apart then billet main caps are just $100 + installation.  If you do 4-bolt the block, stick with the OEM main bolts, use common grade 8 fasteners for the outer bolts as well, and those outer bolts should extend 1-1.25" beyond the underside of the main caps.  If you don't 4-bolt the block, you'll likely be fine but have more teardown maintenance.

Paul Kane wrote:

ED468 wrote:

Paul Kane wrote:With your 4.375" bore pistons, you should have no problems with the OEM passenger car block.  This holds true provided you stay with the OEM main bolts.  Once you step up to aftermarket studs or bolts all bets are off and risk of of block failure increases big time...in my opinion doing so almost a guarantees block failure.

Lastly, build such an engine intentionally loose and let things move around.

Hi Paul, so your saying if ya Got a dove block with Boss bulk heads with Milodon  Splayed caps with Studs That I should go back factory bolts?

If I came into a 4-bolted block that was already machined and set up with aftermarket studs, then whether or not I would use it that way would depend on its application.  The less power generated by the build, the more likely I'd use the block as-is (with the studs).  Which is ironic because the point at which I'd use a passenger car block with main studs in it is essentially the point where most people (including myself) would feel main studs aren't needed in the first place.  

ED468 wrote:I seen and read the factory bolts are bigger and fit better in the caps then studs. With the splayed bolts wouldn't that under normal circumstances keep caps from floating around even with stock bolts?

When it comes to main cap movement I never paid much attention to bolt shank diameter vs main cap bolt hole diameter.  With the aftermarket splayed caps I think the main cap registers in the block's webbing are what minimize the lateral movement (X-axis), while the primary main bolt fasteners are what minimize the up-and-down movement (Y-axis), and the outer splayed main bolts with their angled position triangulate and thereby tie it all together (supporting loads of both X+Y). So the primary main bolts essentially need to be just strong enough to do their job via clamping force for Y, but the clamping force I personally envision is not one which stops cap walk; it's one which does its part relative to the overall engine package.  There will be some cap movement while the OEM bolts absorb some of the load from the high power build.  You need to accept that and the additional maintenance that comes with it--but you also get increased block reliability in exchange.  If you cannot wrap your head around letting the caps move a bit, then get yourself a nice strong aftermarket block with nice strong aftermarket studs...your caps may walk a lot less but the overall maintenance level will be pretty close to similar anyway. And you'll be out a couple thousand dollars.

ED468 wrote:Be about a 600 hp 10.5 to one motor...

I'd run the block as-is, with the studs.

ED468 wrote:Would want 1000-1100 on hose.

In this case I'd definitely ditch the studs and install OEM bolts with regular Grade 8 outer fasteners as described above.

So, Paul If you already answered this I apologize for missing it. What part exactly will fail if using the stronger studs in a production block? Are you saying that the extra rigidity of the studs will cause the main webs to crack? Where in contrast the same engine with factory bolts installed the main caps would just walk around a little and wear the bearings??

On another note, a lot of guys refer to a D1 block as if it's a one of a kind. It is not. The earlier blocks do have thicker webs that are machined flush with the pan rails. The later D1 blocks are significantly thinner and rough cast about an 1/8 inch below the pan rail.

stanger68 wrote:

On another note, a lot of guys refer to a D1 block as if it's a one of a kind. It is not. The earlier blocks do have thicker webs that are machined flush with the pan rails. The later D1 blocks are significantly thinner and rough cast about an 1/8 inch below the pan rail.

There are a some "D0" Cobra Jet blocks having 2 bolt mains which made it into the early mix during O.E.M. production but, they are certainly not the norm for most early blocks.
Other than  having the main-web be flat to the oil pan rails there is no difference in the main-web thickness between regular early and late blocks ... the later blocks do have longer cylinders, (allowing for a slightly shorter main-web), and a much stronger, full width circumferential oil pan rail where as the early blocks have scalloped oil pan rails.

I take Paul's meaning to allow other things to absorb some of the loading and vibration to not transfer all of it to the webbing of the block.