Standard Stroke 3.85 cast crank Viability??

I have heard an engine built for N2O usage needs forged rods & cranks.

If an engine builder built a mild FMS SCJ headed(forged 6.8 inch rods but cast stock crank) 468 CID BBF with a 9-9.7:1 CR, mild hydraulic roller cam, for sake of argument lets say this engine running on 91 octane pump gas makes 520 HP at 6100 rpm with 540 lb. ft. of torque at 4800 rpm.

The end user installs a 250 HP Cheater N2O system(110 octane leaded gas aux fuel system) for engagement in second gear from 3800-6000 rpm is this engine a disaster waiting to happen?

It will work fine as long as your on top of the tune .

 I don't build any hyd cam engines anymore and i've never messed w/nos,so I was wondering IF they would be a good marriage?  

Here's my combo

Frpp scj heads

Solid roller cam

Stock crank with h beam rods and forged pistons 7,000 rpm with direct port nitrous (a lot)

10.8 pump gas compression.

This is new combo my old combo lived a long time on the same nitrous shot and it was box stock ford parts.

gmsmkr wrote:Here's my combo

Frpp scj heads

Solid roller cam

Stock crank with h beam rods and forged pistons 7,000 rpm with direct port nitrous (a lot)

10.8 pump gas compression.

This is new combo my old combo lived a long time on the same nitrous shot and it was box stock ford parts.

Like Dave said, use your head on the tuneup. Some guys could break a cannonball in a sandbox, but that stock crank is a pretty damned tough piece for the money.  The cast China cranks probably won't take the abuse a stocker will, IMO.

Dark Horse of Apocalypse wrote:If an engine builder built a mild...468 CID BBF with a 9-9.7:1 CR, mild hydraulic roller cam, for sake of argument lets say ... 520 HP at 6100 rpm with 540 lb. ft. of torque at 4800 rpm.

The end user installs a 250 HP Cheater N2O system(110 octane leaded gas aux fuel system) for engagement in second gear from 3800-6000 rpm is this engine a disaster waiting to happen?

That's all?  Ford production cast crankshafts have been thus far dyno-proven to over 1700 hp (not that I recommend you try to push one that far).

gmsmkr wrote:Here's my combo

Frpp scj heads

Solid roller cam

Stock crank with h beam rods and forged pistons 7,000 rpm with direct port nitrous (a lot)

10.8 pump gas compression.

This is new combo my old combo lived a long time on the same nitrous shot and it was box stock ford parts.

maverick wrote:

gmsmkr wrote:Here's my combo

Frpp scj heads

Solid roller cam

Stock crank with h beam rods and forged pistons 7,000 rpm with direct port nitrous (a lot)

10.8 pump gas compression.

This is new combo my old combo lived a long time on the same nitrous shot and it was box stock ford parts.

Like Dave said, use your head on the tuneup.  Some guys could break a cannonball in a sandbox, but that stock crank is a pretty damned tough piece for the money.  The cast China cranks probably won't take the abuse a stocker will, IMO.

Paul Kane wrote:

Dark Horse of Apocalypse wrote:If an engine builder built a mild...468 CID BBF with a 9-9.7:1 CR, mild hydraulic roller cam, for sake of argument lets say ... 520 HP at 6100 rpm with 540 lb. ft. of torque at 4800 rpm.

The end user installs a 250 HP Cheater N2O system(110 octane leaded gas aux fuel system) for engagement in second gear from 3800-6000 rpm is this engine a disaster waiting to happen?

That's all?  Ford production cast crankshafts have been thus far dyno-proven to over 1700 hp (not that I recommend you try to push one that far).

Great to know I usually end up debating Chebbie guys( usually family) so fore warned is forearmed.

I ran a flat topped 466 with h-beam rods and stock cast crank for several years in my mud truck and had numerous 250-300 shot hits of the spray until the 1 day I got laxed and didnt watch the tune. Melted a couple pistons, but the rods and crank were in great shape. So much so I had that crank offset ground for my 488ci deal to keep me in the 500ci and under classes.

Unless it is an all out race version ... I wouldn't use a hydraulic roller camshaft and valve train.

Since CAT went out of business, I am not aware of any company who now offers a 6.8" long rod with a Big Block Ford crankshaft journal size.

Looks like Eagle and Lunati (that is if I didn't misread the charts on their sites). I am NO engine builder just a guy trying to learn from you guys who have built it broke it and rebuilt it with the T-Shirt to prove it.  

IMO there are other factors here to be looked at, I would have to assume the stock rods and crank were prepped/checked (likely balanced too) at the machine shop, but I would also ask if the stock rods are using press fit wrist pins or full floating as in my experience press in pins don't appreciate nitrous. The FOMOCO rods and cranks can handle it to a fairly high degree with proper tuning/timing, I have seen the pins pulled on more nitrous grenades due to things like poor tuning, leaving with nitrous on the rev limiter, over reving (floating), even a few leaky systems blowing the intakes off at start up...I prefer to run the better rods and cranks, however the budget doesn't always allow, so if it doesn't I prefer to check it regularly and listen carefully...especially when its 2x the cheater plates...hehehe

I am still learning about the wonders of the BBF. In my head depending on 2 things vehicle weight and bank account will determine whether it is a 468,532 or 547.

Dark Horse of Apocalypse wrote:I am still learning about the wonders of the BBF. In my head depending on 2 things vehicle weight and bank account will determine whether it is a 468,532 or 547.

"bank account" then you forgot stock 429/460' s

DanH wrote:

Dark Horse of Apocalypse wrote:I am still learning about the wonders of the BBF. In my head depending on 2 things vehicle weight and bank account will determine whether it is a 468,532 or 547.

"bank account"  then you forgot stock 429/460' s

I heard an old adage "Speed costs $$$ how fast ya wanna go?"

Not that its right but I have sprayed my 472 a lot but only with a 65 nitrous jet some say 125hp other 150hp... stock bottom end with cast hyper pistons. Haven't had any problems the tune is from Monty Smith the key is the right ring gap on the KB pistons and don't get greedy with the

Dark Horse of Apocalypse wrote:

DanH wrote:

Dark Horse of Apocalypse wrote:I am still learning about the wonders of the BBF. In my head depending on 2 things vehicle weight and bank account will determine whether it is a 468,532 or 547.

"bank account"  then you forgot stock 429/460' s

I heard an old adage "Speed costs $$$ how fast ya wanna go?"

That should be, "Speed costs $$$, how fast ya wanna SPEND?".

cletus66 wrote:

Dark Horse of Apocalypse wrote:

DanH wrote:

Dark Horse of Apocalypse wrote:I am still learning about the wonders of the BBF. In my head depending on 2 things vehicle weight and bank account will determine whether it is a 468,532 or 547.

"bank account"  then you forgot stock 429/460' s

I heard an old adage "Speed costs $$$ how fast ya wanna go?"

That should be, "Speed costs $$$, how fast ya wanna SPEND?".  

Ouch ain't that the truth there!!?