I'm gonna be doing my first stroker build and have some questions on the rotating assembly. The car is a street car with a little strip action, i have a stick and 4.11s. I have a good 350 block waiting for machine shop and have to order rotating assembly next. I really want to do a 3.875" stroke instead of a 3.75".

I priced out a few kits made by scat and sold by flatlanderracing.com. It seems i could get 3.875" forged 4340 crank, 6" H-beam or I beam forged rods, and forged mahl pistons with bearings for $1,400.

I could do a 3.75" stroke much cheaper and stay with scat 9000 cast crank, 6" I beam forged rods, forged flat tops for around $800.


questions:


Do i really need a forged crank for a street motor, or should i cheap out and go cast?
Unsure about I-beam rods or H-beam rods?
Is the extra cubics from 383ci to 396ci worth the extra $600 in cost?
Can Cast crank handle 6,500rpm shifts?

I'm on a budget here but if the forged stuff is really alot stronger and i need it then I'll go that route. but at the same time that extra 600 bucks could go towards machine work.



this is my first real High Perf. small block so I'm still learning. I already have some protopline 200cc, 2.02, 64cc alum heads, and xs282s solid comp cam, 1.6 roller rockers, 750cfm speed demon, 1 7/8 headers. I want keep compression at or just under 11.1 and run a single plane intake.

Thanks for help

 

I would just get a cast kit to complement the rest of the parts you already have and shift at a lower RPM

I have had cast crank motors up to 6500RPM but I wouldn't be doing that all the time, if you want to take it to the track and shift there then you need forged assembly and new heads because you won't be making any more power than at 5500RPM with those heads

 

Unless you plan on hitting it with nitrous or forced induction, you don't need forged materials. They are only more tightly compact on a molecular scale. While that makes them a little harder and more resistance to breakage when they do break they shatter.
But they are no more prone to breakage than a cast part in a naturally aspirated engine. Meaning if it is just PURE street, you're throwing money away and you could use the extra $600.00 on some other goodies.

 

Plus you might take into account that some guys like to use cast cranks on their high performance build due to the little extra give it has over a forged part.

 

The car is mostly street but I do drive it hard and have taken it to the strip a few times before. I have a cast crank in my current 350 and I shift it between 5800-6000rpm when racing, was hoping to rev new motor about 500rpm higher with the solid lifers. my cam is rated at 2400-6800rpm.

nitrous has crossed my mind because i have a few buddies use it on their mustangs and haven't had any problems yet. Maybe if i did go forged then i would consider trying a small shot of nitrous.

 

I wanted some AFR cnc ported 210cc heads but I've had these protoplines for 4 years brand new sitting under my bed. I was gonna use the protoplines on a 355 but plans changed and heads are still untouched.

I got them because they were about 300 bucks cheaper then AFR heads and was told they were decent heads able to make 450hp and had similar flow numbers as Dart Pro I heads.

not too many people i've talked too have heard of pro topline, have you? Maybe I should consider having them ported and put on flow bench? i wish i could go back in time and order a better head for a stroker motor, i could of got Dart PRO 1 heads, canfields, or even a 220cc Pro topline all for the same cost. at the last min i was talked into the 200cc pro-topline, the salesman told me they were the best deal and flowed like a wind thunnel

 

It isnt all just about flow numbers. You can put 220cc intake runner heads on there, but you are going to lose velocity unless you have a lot of cam, and a lot of compression, along with the right gears out back.
And if you don't have velocity, the motor is going to be sluggish and underperform.
A properly blueprinted engine with 180cc heads will outrun a engine that was just slapped together with 220cc heads on it I guarantee you.

However, your selection of parts doesn't seem to be bad at all. Not sure what octane you have out there, but you are pushing the limits of pump gas under load at 11.1:1 compression. Even with aluminum heads and backed off timing. Then if you hit that combination with nitrous you are just asking for trouble if you dont have some higher than pump gas octane in there.

 

A couple of quick thoughts:

First, buy your rotating ***'y *as an assembly* - don't make one up out of parts from different vendors. This will save you significant money in balancing.

Second, IMHO the 396, and especially with 6" rods, is problematic. Block clearancing gets more difficult (most 383s any more require little or no clearancing with the right rods) and you need to be VERY dilligent about cam clearance. The $/CID ratio isn't very good here IMHO for 13 cubes.

Quality cast cranks are good to about 1.1 HP/CID, and 6K RPM...and if you're even considering NOS now would be the time to build it to take it.

Other thoughts available if you want them

If you've already got your mind made up, go for it - just wanted to share some experience.

 

Respectfully, I disagree that cast offers any extra give over a forged part.

I suggest just the opposite is true; that forged will give or flex a bit more while cast is usually more brittle than forged. And that applies to both cranks & pistons.

However, in the long view, I think a cast crank will be fine for OP's proposed app. Also, I believe it's best to use a local shop to balance RA as budget stuff often has flaws only an expert may find as he handles it. I also like to buy parts separately & not as a kit; but one needs experience to be successful thus a kit may be best for less-experienced. Me thinks future gas availability for 11:1 carb motor is iffy; suggest a lower CR ceiling. So ... maybe a scat cast 383 crank & scat rods are good choice here ... suggest scat cast 383 crank for 6" rod that can be Internal balanced ... there were 2 ... one was for internal ... you still must have it balanced but Internal's Not balanced with a counterweighted flexplate&damper hanging off ends of (external) crank ... internal uses gen 1 350 flexplate&damper ... external uses gen 1 400 flexplate&damper. Flatlander OK but there are other discounters too ... one was cnc motorsports. Suggest I-beam rod ... scat has good ones w/ good capscrews ... get the version w/ 3/8" capscrews not 7/16 ... get the bushed rods otherwise you will pay to have pistons pressed onto rods. Good luck!

 

I've read and heard that about cast cranks many times.
As for MY train of thought, if it is going to be a race anything then I would definately put forged internals in there.

 

Before you go order all this stuff....give me a shout.I am pretty sure that I can beat all these other places prices,and I carry everything that you could ever want for your engine,and all the best companies.

 

I went with SCAT 9000 crank and 4340 I Beam rods and KB flat top forged pistons.in my recent 383. RA came it at ~900.00 balanced. The gentlemen who built my engine told me he uses the SCAT 9K stuff in many injected sprint car motors and spins them to 7k all the time.. i have 1k miles on the motor but have only but have only spun up to 6k once are twice...and breifly...but to date she's rock solid! .

 

contact cnc motor sports and look what they have to offer.
I recently purchaced there eagle stroker kit #ESP-12008 had optional ARP L-19/2000 bolts
with 11.0:1 SRP pistons and H beam rods balanced and out the door for$ 1,669.95
When i recieved it i had my local machine shop recheck the balance job and it was right on the mark.
That included rings and bearings Good luck

 

Scat 9000 crank is one of the best cast cranks. You must take it and the rest of the rotating assembly to a machine shop that knows their stuff, and have everything, I mean everything checked, then balanced.

I had to have a brand new set of 4340 stroker rods resized right out of the box because they were not round. I sent a 4340 crank back because it was not straight and bought another brand, don't want to mention the name of the manufacturer but it is a very big, common one, which I will never buy from again

 

I would be most concerned with piston selection..use a quality forged set..the crank will be more than adequate,whenever these engines fail it,s ALMOST always a piston issue not a crank or rod issue,However if you go with a forged assembly then you know it,s pretty much bullit proof...now your week point will be the factory block! As for displacement go with the 383 too much hassle /money for only a few cubes.Your protopline heads ..aren,t those the same as the RHS heads ..comp cams bought the company?!!! If so these are a really decent head,and on a 383 should make for a great street /light strip motor..

 

you are correct, protopline was bought out and are now RHS heads, not sure if they are the same exact casting or not.