12 replies to this topic

[mr5000]

just been getting some prices on stroker kits and the scat cranks are about half the price of the come cranks just wondering if theres a difference in quality have scat cheapend up is come just trying to bend me over i want something that will hang in there with up to the 500-550hp mark atleast

[rexy]

The prostroke 355 crank I had years ago was crud. So was Hernes apparently.
Certainly cant complain about the COME 383 crank in the sedan. Its copped a flogging for a decade now without drama. Darren Parkers commodore ran hundreds of passes on his.
You pays your money and you takes your chances. Personally I would stay away from the cheapest options and at least hunt around in the middle ground if you cant afford the top shelf stuff.

[ACJ]

Both are good I think. I went scat. Eng billed was more than happy to use it, in fact give then a good rap. I think both are rated to 500HP and 7000RPM but people are going way past this. I think you must put some thought into the other parts as well. The weight of your pistons and rod can make or brake your crank. 100 grams x 8 at 7000RPM will add up to lots of kg spinning off your crank.

[mr5000]

ive heard from a lot of people the scat and come crank are coming out of the same factory now in china then being sent to there respective factorys for machining up i think its just the case of us prices vs aus im going h beams with forged flat tops

[Struggler]

FWIW Scat have revised their 308/355 casting about 4 times.

In my experience the only cranks I have seen fail have been LJ SBC journalled. The Chev rod is wider and smaller diameter than the 308 rod. The Chinese must have copied a Holden journalled crank and then machined the journals wider and smaller to accomodate the Chev rod. This then weakened the crank, particularly it would seem at the most forward journal where it meets the counterweight. This is where they all broke. The problem got worse when heavy H beam rods and chev 383 pistons were used as in order to balance it properly heaps of metal had to be removed in areas that were already weak.

Here are some pics of the last one I saw, a couple of months ago.

 IMAG0044.jpg   427.4K   12 downloads

 IMAG0045.jpg   434.18K   5 downloads

To their credit both Scat and COME developed a 5.700" rod with a Holden sized big end to avoid having to use the SBC sized rod, thus maintaining the structural integrity of their cranks while still allowing the use of the common 383 pin height piston.

I guess what I'm trying to say is if you purchase a crank get one with Holden sized journals and either use the Holden A9L rod and the right piston or the 5.7" aftermarket rod with Holden big end.

This is my opinion only, I'm sure there are others out there that disagree but for a year or 2 now I have avoided stroker cranks with Chev rod journals.

Hope this makes sense.

Also I might add the above crank failure resulted in the manufacturer providing a new crank under warranty. Unfortunately they didn't provide anything else. The engine was pretty much ruined. Valves hit pistons, cam and lifters were damaged, the block main tunnel was damaged, the timing case and balancer were damaged and the list goes on. Suffice to say repairs were expensive.

End of rant....

[mr5000]

that looks like the exact same spot the eagle cranks snap

[Struggler]

that looks like the exact same spot the eagle cranks snap

Yes, and for the same reason.

[Struggler]

At what sort of power level do those SBC journal cranks snap? and when did they update to Holden style ones?

Ive got a Eagle crank with Scat rods in my 355 so now you got me worried!

I don't think it is power related. It's just a bit of a lottery.

Not every SBC journalled crank made has broken, only a very small percentage.

Some brands seem to fail more than others.

Holden journalled stroker cranks have always been available, in Scat anyway. All the original Harrop and COME cranks had Holden journals.

As an aside, a friend of mine was at the SEMA show last year. He approached both Eagle and Scat and asked them what they were doing about the high number of failures and poor machining on the 308 stroker cranks. They were shocked ! Appears that the Australian distributors never let them know of the issues. It has only been since then that they have been replacing the cranks. Before then the Aust. distributors were basically laughing at you. Unfortunately the engine builder gets caught in the middle and cops the shaft. You can imagine how depressing it is when a customer brings back an engine that is pretty much totally destroyed through no fault of their own and the crank manufacturer cheerfully gives you a fresh crank and waves goodbye.

[ozyozyozy]

The big question is what are you planning on doing with engine? Street driving, drags, track work.
Most of the cranks will be fine for street, bit of drag work and some odd track days. Iv heard stories for just about every crank for the holdens
As said weight is the killer a heavy crank dosent like lots of constant rpm.
If you are going to lean on it lots, only one choice for company, crankshaft rebuilders.

[TempesT]

THREAD DIG

 

is this crank snapping of chev rods on the chev journal cranks still relivant?

 

Scat do a holden width rod to fit their holden journal crank but there are alot of places pushing chev rod journal cranks. The come is also chev and good for 600bhp and 7000 rpm but hevier ?

 

understand that struggler and tk383 dont get on here much these days.

 

cheers

James

[TK383]

I've run the scat chev journal cranks at 580+hp with no issues.
I'd call them good to 550hp/7500rpm.
Come cranks I've turned past 8000 & over 600hp.