526 SOHC rotating assembly

[338Raptor]

Based on input from FE Power members I have fine tuned my specs for the SOHC I will soon begin to build for my ‘67 fastback.  The specs for the chassis are listed below in my Signature.  My next step is to determine which crank/rods/pistons will best suit my needs.  Before I get to the questions I’ll list the specific details of the engine.

Shelby large bore aluminum FE block (4.375 bore)
4.375” (526 cid) or 4.5” (541 cid) 4340 forged crankshaft
Pond SOHC heads
Jay Brown SOHC rocker arms
11:1 static compression ratio
93 octane pump gas
Hilborn EFI
Holly HP EFI system
Custom 2” headers
Cam specs are still undecided but they will need to be big
Car use: 90% street, 5% drag, 5% autocross
Curb weight is unknown but I would estimate it to be a couple hundred pounds less than stock.

Target horsepower and torque:  800 hp @ 7000 rpm and 700 Torque @ .

I want to focus on utilizing relatively light weight internals without compromising too much in strength. I’m running an aluminum flywheel and drive shaft. I figure with such large hemi pistons and a heavy crankshaft my internals are going to be heavy relative to most other builds.  I just want to minimize how heavy. That leads me to my questions:

1. Am I wrong to focus on internal weight?  Are the small weight savings of these parts just not noticeable in a 500+ cid engine?

2.  Trying to minimize weight, would I be sacrificing too much strength by utilizing K1 or Molnar connecting rods.  Respectively 781 & 797 grams vs. 860 grams for Crower sportsman’s. Is this enough weight savings to be able to “feel”?  Or should I look at another rod option?

3.   Is the RPM forged 4.375” crankshaft strong enough for my build?  And if so, is it worth the effort to lighten it or should I look at a custom light weight crankshaft?  Which crankshaft do you guys recommend? 

4.   Which 4.375” piston (11:1 compression) would you recommend?  Does anyone have weights for different SOHC pistons?

Thanks in advance for sharing your knowledge and experience.

[e philpott]

I would think the parts you have chosen will be fine on a 800 HP build including the Molnar rods

[blykins]

No RPM cranks available at this time.  I would do a custom Scat.

You will not feel any differences in weight that you have outlined but a lighter rod and piston would make balancing a shelf crank easier.

Almost any piston manufacturer could make that piston for you.  Diamond, Racetec, CP, you name it.

[338Raptor]

Has anyone heard of strength issues with the K1 H-beam Rods?  They only weigh 781 grams.
I e-mailed them my specs and asked them the horsepower capacity at 7500 rpm with a heavy Hemi piston and they replied 1600 hp.  That seems a little exaggerated.

[blykins]

K1 and Molnar are essentially one in the same.  Tom Molnar used to work for K1. 

I've never used K1 rods but with these situations, I would be reaching for a Crower/Oliver/Carrillo. 

[Dumpling]

JMO, but 11:1 on 93 octane is optimistic/hopeful/unrealistic...again, JMO.

[blykins]

JMO, but 11:1 on 93 octane is optimistic/hopeful/unrealistic...again, JMO.

The right combo will run on 93 octane, but the overall package has to work together.

[machoneman]

Is a 2" primary tube big enough for a 500+ CID SOHC?

Maybe Werby can run his magical program.

[Dumpling]

Is a 2" primary tube big enough for a 500+ CID SOHC?

Maybe Werby can run his magical program.

Thinking about it, the Hilborn is IR;. its runners may not be big enough to supply a 500+ cubic inch engine.  I think Hilborn offers (offered?) a larger runner version (58mm?) once upon a time.

[338Raptor]

Hilborn quoted me 2-7/16” butterflies and 65# injectors based on my combo.  It’s my understanding 2” primaries can support 850hp. Does anyone have a different opinion?

[Dumpling]

So, 64.5 mm...
Way beyond "normal"

[338Raptor]

Keep in mind it’s a SOHC manifold not a standard FE manifold.

[hwoods]

Crower custom billet crank only $4K now
Ford 352-427-428 Custom Billet Crankshaft
Part Number: 95191C
Be the first to review this product

Ford 352-427-428 Custom 4340 Billet Crankshaft
$3,977.89

you could be the first to review this product

[338Raptor]

I understand $4000 for a crankshaft in a high horsepower race engine is justified. But it seems a little excessive for a 800 hp engine.  I want good reliable parts but I would think there has to be a crank that would handle 800 hp at 7500 rpm for less than $2k.

[wcbrowning]

The problem is the long stroke you want.  As far as I know, the only way to get anything more than 4.375" is to go billet.  I don't think there are any forged units available with a longer stroke than that.

I understand $4000 for a crankshaft in a high horsepower race engine is justified. But it seems a little excessive for a 800 hp engine.  I want good reliable parts but I would think there has to be a crank that would handle 800 hp at 7500 rpm for less than $2k.

[338Raptor]

That’s good to know.
If that’s the case I will stick to 4.375 to save $2000.

[blykins]

That’s good to know.
If that’s the case I will stick to 4.375 to save $2000.

If you're wanting to go with a 4.375" RPM crank, you may want to pick up the phone and start asking around to see who has one.  A few months ago, I was ordering cranks and couldn't find squat from RPM.  His viewpoint at the time was that he didn't know what the tariffs were going to bring, so he wasn't placing orders with the factory in China.  As of then, he had little to zero FE cranks on the shelf to sell.

I don't feel that you need a billet crankshaft.  You do need a forged crank.  I order custom forged cranks from Scat and they will pretty much make anything you want.  I know they will make 4.375" stroke pieces and I don't see why they can't cut you something a little longer.  The price would be a couple hairs under the $2k mark if you're going through an engine builder that's direct with Scat.

[mbrunson427]

IF I were in your shoes....

Call Joe at Denbeste Motorsports/Shelby Engine Company, have him build up the whole bottom end. He'll get the rods, he'll get the pistons, he'll get the crank. As long as you're going with the Shelby block, may as well keep that stuff under one roof. They'll do all the prep work on the block and you'll be ready to go.

We did this 5-6 years back with our drag car engine. Called just to buy a block and ended up having them do the bottom end. After you source the rods, source the pistons, source the crank, find a local machine shop to do all the final prep work etc etc..... I think you'll find it's faster/cheaper/less brain damage to have Joe do it.

I'm headed to the shop tomorrow to do some bead blasting, I'll try and pull the Shelby SOHC block off the rack and get you some pictures of what they look like. Give you some motorvation.

[blykins]

IF I were in your shoes....

Call Joe at Denbeste Motorsports/Shelby Engine Company, have him build up the whole bottom end. He'll get the rods, he'll get the pistons, he'll get the crank. As long as you're going with the Shelby block, may as well keep that stuff under one roof. They'll do all the prep work on the block and you'll be ready to go.

We did this 5-6 years back with our drag car engine. Called just to buy a block and ended up having them do the bottom end. After you source the rods, source the pistons, source the crank, find a local machine shop to do all the final prep work etc etc..... I think you'll find it's faster/cheaper/less brain damage to have Joe do it.

I'm headed to the shop tomorrow to do some bead blasting, I'll try and pull the Shelby SOHC block off the rack and get you some pictures of what they look like. Give you some motorvation.

That's a good idea....let someone else carry the hassle. 

I would even venture to suggest letting one of the builders on this forum get the bid since information has been passed freely here.   I'm not in the mood to do any aluminum stuff but I'm sure Barry and Blair would do an excellent job.

[338Raptor]

I’m still about 6 months from starting the build. But when I do I will definitely be talking to the builders in this forum.  And I’m going to take mbrunson427’s advise and have a builder familiar with aluminum FE’s inspect/machine/balance/setup the bottom end.