[JLMounce]

I'm starting to accumulate parts for a rebuild on my engine. It's an XJ code 455. It's in good condition, but it was built in the late 90's and has a lot of old era parts, including the factory N crank and factory rods.

It's currently topped with a set of KRE D-ports, as cast and a mild roller cam. For what it is, it runs pretty decent. However the factory rods are a limitation on what I can do with it at this point.

I've had the engine open this past year as some of you may know and everything actually looked great. That's where my question comes in to play. At what point is it necessary to start looking at replacing the factory crankshaft?

The goal with this refresh will be to lighten and strengthen the rotating assembly, while adding some flow to the top end and more cam. Going from the as cast ports to around 290-300cfm or so and something in the 240/250 range on a hydraulic roller...probably something from bullet. Target around 570ish hp with a shift point around 6000 rpm.

The block has 2 bolt caps and is drilled for 4 bolt caps.

This engine is .030 over now and I'm assuming the crank is likely 10/10, but I have no real way to verify that without removal. At the power and rpm levels discussed, assuming the crank checks out, is there even need to spend money on a replacement?

Likewise, what's the need to step up to a 4 bolt cap? I'm leaning towards a simple main stud upgrade. Is that even necessary?

The engine is backed up by a moderately built 4l80e. Has a 3000rpm stall TSP converter with a triple disc lockup clutch. Moser 12 bolt with 3.36's on a TrueTrac. The drivetrain is good to 600whp.

I'm making an assumption the bores will clean up at .040.

I'm just looking at cost savings anywhere that I don't have to spend it, without cutting corners. As a result I'm thinking if I do need a crank, it's likely best to blow past the cast aftermarket stuff and go straight to a forged crank.

Just looking for your thoughts here. This will be the first engine rebuild I undertake.

[b-man]

I would leave the N crank in it if it’s looking as good as you say.

That crank is more than adequate for what you’re doing, with a lighter set of rods and pistons it’ll be even better than before. Stock 2-bolt mains and bolts should be fine as well.

You’re kinda on the edge of where using a forged crank would be better but if budget is a big concern you’re probably fine keeping the N crank. If you do change the crank then some studs for the main caps along with an align hone would be a good idea since you’re spending all that dough. An aftermarket cast crank shouldn’t even be a consideration.

It’s up to you whether or not it’s worth throwing another $1500 into the build to upgrade the bottom end and that’s keeping the stock 2-bolt caps.

[Tim Corcoran]

Depends on how you drive the car, if you're constantly hammering it or taking it to the drag strip on a regular basis then upgrade the rods and crank. If your just cruising around and hammering it on occasion put in your bigger cam and leave the rest alone. I know everyone says aftermarket rods are cheap so get rid of the factory rods, but if the factory rods were checked for size and new bolts installed then they will last.

[mysticmissle]

if everything is working fine, i would say nice set of rods and go have fun. The N cranks have held up to plenty of abuse.
Also if you really think you want a forged crank and i wouldnt blame you if you wanted the added insurance, i would build a 400 based stroker with the forged crank and sell your running short block when you're ready to install it. I just dont think the smaller rod and main bearings of a 400 block and bbc rods, should be over looked when considering a clean slate type stock block build.

[JLMounce]

Based on what I saw in the engine this past summer, I do know that the rods are using at least factory type bolts. They have not been upgraded to ARP for instance. The previous owner built this engine in the late 90's so I don't know if the original bolts were re-used or not. The factory rods kind of look like they may have been shot peened, but I'm not certain on this or if the factory rods have that type of surface to them. The parting lines have not been ground down. It has the old TRW pistons on top of the rods. My understanding is that these are strong, but may actually be heavier than the factory pistons.

The current crank may get by with just a polish. I had the #3 main cap off to pound in a new dipstick tube and both the journal and the bearing looked terrific. No edges that I could catch with a fingernail and only minimal wear with no copper showing on the bearings.

The car gets run pretty hard. It's 95% street car, but It gets run through the gears almost every time I take it out. It sees some drag strip runs on occasion (none now that Bandimere is closed).

[Skip Fix]

Might hit the 570 mark but my pump gas 455 in the 78 TA with a HFT about that and 320 E heads I am probably at 550 based on wt/mph. Stingy dyno was only 525. But an N crank and SCAT rods 2 bolt main. Same short block with a click smaller 288/296 UC HFT cam and my RAIV heads on it buzzed 6000-6500 autocrossing and drag racing.

[JLMounce]

Originally Posted by mysticmissle

if everything is working fine, i would say nice set of rods and go have fun. The N cranks have held up to plenty of abuse.
Also if you really think you want a forged crank and i wouldnt blame you if you wanted the added insurance, i would build a 400 based stroker with the forged crank and sell your running short block when you're ready to install it. I just dont think the smaller rod and main bearings of a 400 block and bbc rods, should be over looked when considering a clean slate type stock block build.

I have thought about doing a 400 based build as well for those reasons. Ultimately it may come down difference in cost. This isn't a budget build, I don't want to cut corners, but I don't want to spend a fortune either.

Originally Posted by Skip Fix

Might hit the 570 mark but my pump gas 455 in the 78 TA with a HFT about that and 320 E heads I am probably at 550 based on wt/mph. Stingy dyno was only 525. But an N crank and SCAT rods 2 bolt main. Same short block with a click smaller 288/296 UC HFT cam and my RAIV heads on it buzzed 6000-6500 autocrossing and drag racing.

Yeah that was just a number I really kind of threw out. More so after initially talking with Dave at SD way back when I did my top end, it was his estimate at the time. I'm really just after what I can get as a max level streetable combination with what I currently have. I could certainly go further with round ports or RAV stuff, but I don't want to redo the headers etc.

Along with some work to the heads I'll either have the torker II sitting on top ported and matched, or may need to go with something like a northwind. I still need this under the factory 69 bird hood.

[Johnny406]

A nodular crank and 2 bolt block are really quite strong! I've been running my 455 since 2010 with the factory bolts in my block (a shortage at the time). My car is in the 11.60's on motor in Pueblo (see signature). You're right about the rods, I'm running Scat H-beams in mine. I rushed my motor a bit so I could race Pinks All Out at Bandimere in 2010 or I would have main studs as well.

Here's another idea, have Mile High Crankshaft in Denver turn down your main journals to 2.20 and buy a new set of Molnar 6.625 rods. He produced them to fit his 4" stroke 2.20 rod journal 428 cranks. There are far more and better choices of BBC bearings than Pontiac. Otherwise, Eagle still produces a I beam replacement rod and from time to time you'll see a set of CAT or RPM rods pop up here.

[JLMounce]

Originally Posted by Johnny406

A nodular crank and 2 bolt block are really quite strong! I've been running my 455 since 2010 with the factory bolts in my block (a shortage at the time). My car is in the 11.60's on motor in Pueblo (see signature). You're right about the rods, I'm running Scat H-beams in mine. I rushed my motor a bit so I could race Pinks All Out at Bandimere in 2010 or I would have main studs as well.

Here's another idea, have Mile High Crankshaft in Denver turn down your main journals to 2.20 and buy a new set of Molnar 6.625 rods. He produced them to fit his 4" stroke 2.20 rod journal 428 cranks. There are far more and better choices of BBC bearings than Pontiac. Otherwise, Eagle still produces a I beam replacement rod and from time to time you'll see a set of CAT or RPM rods pop up here.

That's not a bad idea. I've heard the Molnar pieces are top notch. I may have to look at cost and availability of bearings and make a decision. I was going to go with the standard eagle H-beams.

[PunchT37]

That 455 crank isn`t just any cast crank. It`s a huge 3.25 main unit. So, if any cast crank will stand up to abuse, the large main factory cranks will when compared to the 3 inch.


I used my factory crank with 4340 rods, ross pistons, and 2 bolt mains[arp studs] in my 600`ish hp 463.


Granted, those rods, pistons, and pins are way lighter than the old cast rods and old school TRW pistons.

[Gach]

The killer for the cast crank, is rpms. 625-650 hp at 5500 rpm Will live a long Life. But not something making that kind of hp shifting at 6500. Back in the 80’s early 90’s when we were pushing the hp limits which meant raising rpm levels. To get past that 650 hp. The stock cast cranks wouldn’t live very long. So back to a safe level of 625-650 hp keeping rpms at 5500 rpms. In the 80’s bracket racing running 10.30’s shifting at 5500 over 200 passes. It lived. Of course those were 12.1 compression motors.

Today building a 500-600 hp motor on pump gas and aluminum heads with at most 11.00 compression Iron heads 9.5 compression. Keeping peak power at 5500-5800. Cast crank has a much better chance of living a good life. But the killer is ( and I know most are automatics now ) is the 4 speeds and missing a shift and the motor going to the moon. And of course donation especially the definition that you don’t hear. The 2 biggest killers of cast cranks. Before you know it you’re riding around doing burnouts quarter mile passes with a cracked crank but you don’t know it. Especially with today’s gas which is critical not having any detonation. I’ve just seen it happen so many times.

Difference is with good steel crank and rods 6500 or going to the moon 7-8000 isn’t going to hurt anything. The experiences haven’t been through all this, and learning the hard way. So in the end what did you save. Of course there are combos making 500 hp that just die at 6000 rpms. So those are kind of safe.

[PunchT37]

Originally Posted by Gach

The killer for the cast crank, is rpms. 625-650 hp at 5500 rpm Will live a long Life. But not something making that kind of hp shifting at 6500. Back in the 80’s early 90’s when we were pushing the hp limits which meant raising rpm levels. To get past that 650 hp. The stock cast cranks wouldn’t live very long. So back to a safe level of 625-650 hp keeping rpms at 5500 rpms. In the 80’s bracket racing running 10.30’s shifting at 5500 over 200 passes. It lived. Of course those were 12.1 compression motors.

Today building a 500-600 hp motor on pump gas and aluminum heads with at most 11.00 compression Iron heads 9.5 compression. Keeping peak power at 5500-5800. Cast crank has a much better chance of living a good life. But the killer is ( and I know most are automatics now ) is the 4 speeds and missing a shift and the motor going to the moon. And of course donation especially the definition that you don’t hear. The 2 biggest killers of cast cranks. Before you know it you’re riding around doing burnouts quarter mile passes with a cracked crank but you don’t know it. Especially with today’s gas which is critical not having any detonation. I’ve just seen it happen so many times.

Difference is with good steel crank and rods 6500 or going to the moon 7-8000 isn’t going to hurt anything. The experiences haven’t been through all this, and learning the hard way. So in the end what did you save. Of course there are combos making 500 hp that just die at 6000 rpms. So those are kind of safe.

I agree. RPM`s and detonation are killers. But, I also believe that to be true with the block too. So, I believe if one builds a 455 combo to break a factory crank, he will most likely start to crack main webs as well.


I don`t see putting a forged crank in a factory block if the original crank is good. I won`t use a china cast crank. I think a forged crank IS a good idea in a 400 type build at 550 hp and up with 6200 plus rpm`s.

[Gach]

Originally Posted by PunchT37

I agree. RPM`s and detonation are killers. But, I also believe that to be true with the block too. So, I believe if one builds a 455 combo to break a factory crank, he will most likely start to crack main webs as well.


I don`t see putting a forged crank in a factory block if the original crank is good. I won`t use a china cast crank. I think a forged crank IS a good idea in a 400 type build at 550 hp and up with 6200 plus rpm`s.

I agree with you 100%. Thanks for pointing out about factory blocks.

[Johnny406]

Originally Posted by JLMounce

That's not a bad idea. I've heard the Molnar pieces are top notch. I may have to look at cost and availability of bearings and make a decision. I was going to go with the standard eagle H-beams.

The Molnar stuff is VERY NICE/PRECISE

Dave Olsen
Mile High Crankshaft
www.milehighcranks.com
(303)781-6762

I just had Dave turn down a 428 crank for me to use a set of 6.660 BBC rods and some old Venolia blower pistons. He only charged me $125.00 to do it. Gotta be patient, took about 7 weeks to get it back. He's a super nice man and has hundreds of cranks in his shop at any given time.

[mgarblik]

We ran properly prepped 455 N crankshafts with aluminum connecting rods to a little over 1000 HP for years. Never broke or cracked one. Cracked a couple blocks, the crankshafts were fine. I think they are pretty darn tough. Not to say a beautiful new Molnar forging wouldn't be even better. But IMO, of all the things that can break in an engine, a Pontiac N crank would be pretty low on my list. FWIW.

[mgarblik]

Originally Posted by Johnny406

The Molnar stuff is VERY NICE/PRECISE

Dave Olsen
Mile High Crankshaft
www.milehighcranks.com
(303)781-6762

I just had Dave turn down a 428 crank for me to use a set of 6.660 BBC rods and some old Venolia blower pistons. He only charged me $125.00 to do it. Gotta be patient, took about 7 weeks to get it back. He's a super nice man and has hundreds of cranks in his shop at any given time.

If you have access to his shop, Mile High Crankshaft is the best in the country, IMO. Dave is a craftsman and nothing leaves there that isn't perfect. It cost me $300.00 round trip to send a crankshaft there. But I do it because it's perfect every time. Last thing I had done there was weld up all 5 mains on a Crower Billet Pontiac crank. Welded up, straightened, ground, nitrided and it's as good as new for $1100.00. That's a 5K crankshaft new now.

[Gach]

Originally Posted by mgarblik

We ran properly prepped 455 N crankshafts with aluminum connecting rods to a little over 1000 HP for years. Never broke or cracked one. Cracked a couple blocks, the crankshafts were fine. I think they are pretty darn tough. Not to say a beautiful new Molnar forging wouldn't be even better. But IMO, of all the things that can break in an engine, a Pontiac N crank would be pretty low on my list. FWIW.

LOL you think running aluminum rods help. Crank flexing doesn’t help stock blocks from cracking. Still that’s quite an achievement.

[Gach]

I tired calling that number, says no longer in service.

[Gach]

Ok went to his web site, johnny posted wrong number. The one on web site works. Thanks guys.

[mgarblik]

Originally Posted by Gach

LOL you think running aluminum rods help. Crank flexing doesn’t help stock blocks from cracking. Still that’s quite an achievement.

Certainly a light rotating assembly is a help. We did this out of necessity and budget. No aftermarket forgings were available, only an old 990 crank if you could find one. Billet crankshafts were not an option for us in those early days. We ran what we had and we had 3-4 N cranks. With all the options we have today, I would never run a cast N crank to 1000 HP. But I wouldn't be at all concerned running one to 600-650 HP with nice steel rods and modern pistons.